Genetic diversity and phylogenetic relationships of Clostridium perfringens strains isolated from mastitis and enteritis in Egyptian dairy farms.

BACKGROUND: Clostridium perfringens, a common environmental bacterium, is responsible for a variety of serious illnesses including food poisoning, digestive disorders, and soft tissue infections. Mastitis in lactating cattle and sudden death losses in baby calves are major problems for producers raising calves on dairy farms. The pathogenicity of this bacterium is largely mediated by its production of various toxins. RESULTS: The study revealed that Among the examined lactating animals with a history of mastitis, diarrheal baby calves, and acute sudden death cases in calves, C. perfringens was isolated in 23.5% (93/395) of the total tested samples. Eighteen isolates were obtained from mastitic milk, 59 from rectal swabs, and 16 from the intestinal contents of dead calves. Most of the recovered C. perfringens isolates (95.6%) were identified as type A by molecular toxinotyping, except for four isolates from sudden death cases (type C). Notably, C. perfringens was recovered in 100% of sudden death cases compared with 32.9% of rectal swabs and 9% of milk samples. This study analyzed the phylogeny of C. perfringens using the plc region and identified the plc region in five Egyptian bovine isolates (milk and fecal origins). Importantly, this finding expands the known data on C. perfringens phospholipase C beyond reference strains in GenBank from various animal and environmental sources. CONCLUSION: Phylogenetic analyses of nucleotide sequence data differentiated between strains of different origins. The plc sequences of Egyptian C. perfringens strains acquired in the present study differed from those reported globally and constituted a distinct genetic ancestor.

Impacts of intake of trichothecenes (Fusarium sporotrichioides) for dairy calves: Effects on animal growth, oxidative and inflammatory response.

The objective of the present study was to evaluate the impacts of trichothecenes (Fusarium sporotrichioides) for dairy calves on animal growth, oxidative and inflammatory responses in the presence or absence of essential oils. Twelve calves weaned at 70 days of age were divided into 2 groups: T-C (control) and T-EO (essential oils - oregano, thyme, basil and rosemary) in the period of 40 days consuming ration contaminated by trichothecenes (500 ppb). The animals in the T-EO group received a mixture of EOs via feed at a dosage of 0.75 mL per/kg of feed. Blood collections were performed on days 1, 20 and 40 for hematological and biochemical analyses; the fecal score was performed every 2 days on a scale of 1-5 and clinical examinations were performed 3 times during the experiment period. The animals were weighed at the beginning and at the end of the experiment; euthanasia of two calves per group for macroscopic and microscopic evaluation of several tissues (spleen, liver, duodenum, jejunum, ilium, cecum and colon) was performed at the end of the experiment. The calves in the T-EO group had a tendency (P = 0.07) of higher body weight when compared to the T-C. Treatment effect and treatment vs day interaction was detected for leukocytes and granulocytes variables, demonstrating a higher count of these cells in the T-EO group on both days (20 and 40), and the same behavior occurred for the distribution amplitude of erythrocytes (RDW). The enzymes alanine transferase (ALT), aspartate transferase (AST) and gamma glutamyl-transferase (GGT) showed higher serum activity in the T-C group (days 20 and 40). The levels of thiobarbituric acid reactive substances (TBARS) were lower in the serum of animals in the T-EO group. For calves in the T-EO group, glutathione S-transferase activity was higher in serum. Haptoglobulin and C-reactive protein levels were lower on days 20 and 40 in T-EO animals when compared to the T-C group. In the macroscopic and microscopic evaluations, which were collected at the end of the experiment after slaughtering the animals, liver and intestine did not show changes for the animals in the T-EO group, unlike the animals in the T-C group, which had moderately firm diffuse consistency of the liver and edema in the mesentery, as well as oxidative stress in tissues (liver, duodenum, jejunum, ileum, cecum and colon). The results concluded that the consumption of a mixture of EOs (essential oils - oregano, thyme, basil and rosemary) minimized the negative effects caused by trichothecenes in dairy calves, thus being an alternative to improving the immunological and antioxidant condition, as well as a possible adsorbent alternative.

Antibiotic resistance profiling and phylotyping of human-diarrheagenic Escherichia coli pathotypes detected from diarrheic and non-diarrheic calves in Iran.

BACKGROUND: Escherichia coli (E. coli) serves as a common indicator of gut microbiota and is utilized for monitoring antimicrobial resistance determinants in food-producing animals. This study aimed to investigate antimicrobial resistance patterns in virulence gene-positive E. coli isolates obtained from 340 healthy and diarrheic calves. METHODS AND RESULTS: A total of 340 fecal swab samples were obtained from diarrheic (n = 170) and healthy (n = 170) calves for 12 months from different farms in Kerman, Iran. The samples were phenotypically analyzed to detect E. coli isolates and antibiotic resistance. Also, antimicrobial resistance genes, diarrheagenic E. coli pathotypes, and phylogenetic background were screened by PCR. Fifteen percent (51/340) of E. coli isolates were positive for at least one of the examined virulence genes (VGs); the prevalence of VGs in E. coli isolates from healthy calves (36/170; 21.17%) was higher than that in diarrheic cases (15/170; 8.82%). Out of the 51 VG-positive isolates, six pathotypes including Shiga toxin-producing E. coli (STEC; 27.45%), enterotoxigenic E. coli (ETEC; 23.52%), enterohemorrhagic E. coli (EHEC; 19.6%), necrotoxigenic E. coli (NTEC; 19.6%), enteropathogenic E. coli (EPEC; 15.68%), enteroinvasive E. coli (EIEC; 1.96%) and three hybrid pathotypes including ETEC/STEC, ETEC/EHEC, and STEC/EIEC were detected among the strains. Antimicrobial resistance (AR) was observed in 98.03% of the VG-positive isolates, which was the same for both healthy and diarrheic calves. The maximum prevalence rate of AR was found against trimethoprim/sulfamethoxazole (49.01%; 3/51), while the minimum prevalence rate was against gentamycin (5.88%; 25/51). Among the VG-positives, phylotype A was found to be the most prevalent followed by B1 and D phylotypes. CONCLUSIONS: The prevalence of VG-positive E. coli isolates was higher in healthy calves compared to diarrheic cases. AR was widespread among VG-positive isolates. These findings suggest that calves may serve as potential reservoirs of antimicrobial-resistant hybrid pathotypes of E. coli.

Comparison of plasma substance P concentrations in the blood of healthy male and female German Simmental calves.

BACKGROUND: The recognition of pain is a major problem in cattle, as they are stoic animals which strongly mask their pain. Among objective parameters to assess pain in cattle is substance P (SP), a neurotransmitter which is involved in the pain pathways. Research about SP concentration in calves focus on painful procedures, such as castration and dehorning. Basic research work is lacking; evaluation of SP concentrations in healthy calves and possible differences between sexes have not been published yet. The objectives of this study were to (1) describe SP concentrations in healthy male and female calves of the German Simmental breed to establish benchmarks of orientation, (2) compare SP concentrations between male and female calves, and (3) assess differences in SP concentrations between calves and adult cows. A total of 44 male and 49 female calves aged 14 to 21 days (17.1 ± 2.2 days) were included in this study. Blood samples were taken at 06:00 a.m. from the jugular vein, followed by a clinical examination. SP concentrations were analyzed using a commercial ELISA kit. Differences in SP concentrations according to laboratory parameters, and correlation of SP concentrations with different parameters were assessed. RESULTS: Median SP concentrations in the blood plasma were 516 pg/ml (Interquartile Range 320 pg/ml, range 229-1615 pg/ml) in calves. Median SP concentrations differed significantly between male and female calves (554 pg/ml for male, and 489 pg/ml for female calves, respectively). There was no significant difference in animals with laboratory findings within reference ranges and those with mild deviations from reference ranges. There was a positive correlation between SP concentrations and leucocyte count, which was significant. SP concentrations were significantly lower in calves compared with a dataset of adult cows, which has been published previously. CONCLUSION: Due to the high interindividual differences in SP concentrations, it is hard to establish benchmarks for orientation. Sex has a significant influence on SP concentrations. Research work should preferably be done in animals of the same sex. Also, animals should be within the same age range (adults or calves), as age seems to have an influence on SP concentrations.

Effect of parenteral micronutrient supplementation at birth on immunity, growth, and health in preweaning dairy heifers.

This randomized clinical trial aimed to determine the extent to which injectable micronutrient supplementation at birth can improve intranasal vaccine response by ameliorating oxidative stress in dairy calves from birth to weaning. For this, 120 Holstein heifer calves were enrolled at birth and randomly allocated into one of 4 groups. The 4 groups included 3 commercially available micronutrient supplements (selenium, copper, zinc, and manganese; selenium and vitamin E; and vitamins E, A, and D) and one control (saline). Calves received an intranasal vaccine against the respiratory viruses parainfluenza 3, bovine herpesvirus type 1 (BHV-1), and bovine respiratory syncytial virus (BRSV) within the first week of life. Body weight and hip height (HH) were recorded, and a blood sample and nasal secretion sample were collected at birth before treatment and vaccine administration, as well as weekly until weaning at 8 wk. Health scores, including thoracic ultrasound assessment, were recorded weekly from wk 1 to wk 8. Farm treatment records were collected after the completion of the study. Serum micronutrient concentrations were determined from birth to weaning to identify micronutrient status, and serum blood metabolites were analyzed as markers of nutrient utilization. Redox balance was determined in serum as a ratio of reactive oxygen and nitrogen species to antioxidant capacity, known as the oxidant status index (OSi). Intranasal vaccine response was quantified as anti-BRSV and anti-BHV-1 IgA concentrations in nasal secretions. Linear mixed models with repeated measures were built for micronutrient concentrations, blood metabolites, redox balance, IgA concentrations, BW, and HH. Pre-planned contrasts of the control and supplemented groups were also built for the primary outcome of IgA concentrations. A logistic regression mixed model was built for health events and treatment of disease. Serum selenium concentrations were greater in calves receiving supplements containing Se throughout the first 4 wk of life. However, we did not observe any consistent differences in the other micronutrients. The metabolic biomarkers indicate that supplemented calves had better energy status, as suggested by lower BHB and nonesterified fatty acids concentrations. Supplemented calves showed improved redox balance, as indicated by lower OSi throughout the first week of life. Calves supplemented with antioxidants at birth had higher anti-BRSV IgA than control calves. Our results indicate an improved immune response to vaccines in calves supplemented with antioxidants at birth. However, this did not translate to growth and health performance, as we did not find any differences in average daily gain or incidence of health events throughout the preweaning period. This study provides evidence that improving the antioxidant capacity might improve vaccine response, and further research is required to investigate the appropriate frequency and dose of supplementation to improve calf growth and health.

Exploring the effects of transport duration on the fecal microbial communities of surplus dairy calves.

Transportation significantly affects the health and welfare of surplus dairy calves, largely due to the various stressors and pathogen exposures encountered during the process. Concurrently, an animal's microbiome is known to correlate with its health status, with stress-induced alterations in the microbiota potentially precipitating various diseases. This study aimed to compare the effects of transportation durations of 6, 12, or 16 h on the fecal microbiota in young surplus dairy calves. We used a randomized controlled design in which surplus dairy calves aged 1 to 19 d from 5 commercial dairy farms in Ontario were allocated into 1 of 3 transportation groups (6, 12, and 16 h of continuous transportation). Health assessments were conducted before, immediately after, and for 2 wk following transportation. Fecal samples were collected before, immediately after, and at 24 and 72 h after transportation and subjected to 16S rRNA sequencing. Alpha diversity metrics showed no significant differences between the 3 transportation groups at any of the sampling time points. Although ß diversity metrics revealed no clustering by transportation groups, they indicated significant differences across sampling time points within each group. The overall analysis revealed a total of 22 phyla and 353 genera, with Firmicutes, Bacteroidetes, Proteobacteria, Actinobacteria, and Fusobacteria being the most abundant phyla. Bacteroides, Escherichia/Shigella, Lactobacillus, Collinsella, and Bifidobacterium were the most abundant genera. The reduction in Fusobacteria abundance before and after transport was significantly larger in the 16-h transportation group when compared with the 6-h transportation group. We also identified several genus-level and amplicon sequence variation-level taxa that displayed significant differences in their abundances across various transportation groups, observed at all sampling time points investigated. This research identifies microbiota changes due to varying transportation durations in surplus dairy calves, providing a broad understanding of the microbial shifts in surplus dairy calves after transportation across varying durations. Although these variations may not directly correlate with overall calf health or indicate dysbiosis, these results emphasize the importance of further investigating transportation practices to enhance calf health and well-being. Further studies are warranted to elucidate the relationship between microbiota and calf health.

Retrospective cohort study investigating the relationship between diarrhea during the preweaning period and subsequent survival, health and production in dairy cows.

The primary objective of this study was to evaluate the association between preweaning diarrhea and measures of survival, health and production. The measures of interest included survival (mortality before first calving and time to removal from the herd), health (retained fetal membranes, metritis, mastitis and somatic cell count), and production (305d mature equivalent milk yield and time to first calving). A secondary objective was to investigate if these associations varied according to the age of the calf when the case of diarrhea occurred. Herd records from a farm located in Southern Australia were used to conduct a retrospective cohort study where subjects (calves) with diarrhea were enrolled at the time of their first case along with 2 subjects without diarrhea, matched for age (±3 d) and date of birth (±15 d), amounting to 9833 calves in the data set. Survival analysis was conducted to determine if preweaning diarrhea was associated with death in the short term (first 20 d after enrollment), medium term (21 to 100 d after enrollment) and long-term (101 d after enrollment to first calving). Crude incidence rate ratios, Kaplan-Meier curves and hazard ratios (HR, Cox regression) were derived for each event-based outcome (e.g., death, calving, mastitis). Multivariable linear models were used for continuous outcomes. Calves with preweaning diarrhea had greater mortality rates in the short term (hazard ratio, HR = 2.48, 95% CI: 1.87-3.29) and medium term (HR = 1.89, 95% CI: 1.41-2.55) but not in the long term (HR = 0.98, 95% CI: 0.79-1.22). A small negative association between preweaning diarrhea and time to first calving was found, with calves with diarrhea calving 4 d later than calves without diarrhea (HR = 0.95, 95% CI: 0.91-1.00). Rates of post-calving removal from the herd (death or culling) were higher in calves with a history of preweaning diarrhea (HR = 1.13, 95% CI: 1.01 to 1.26), as were peak lactation log somatic cell count (+0.08, 95% CI: 0.02 to 0.14). Further research is needed to replicate these novel findings as they are based on exploratory analyses and could be spurious findings. No substantial associations were observed for the other measures of interest. Our study findings support existing research demonstrating the significance of preweaning diarrhea as a significant cause of calf mortality, and raises new hypotheses about other potential impacts during lactation.

Graduate Student Literature Review: Social and feeding behavior of group-housed dairy calves in automated milk feeding systems.

Automated milk feeders (AMF) allow farmers to raise calves in groups while generating individual records on milk consumption, drinking speed, and frequency of visits. Calves raised in groups benefit from social interaction, which facilitates learning and adapting to novelty. However, calves in large groups (>12 calves/feeder) experience a higher risk of disease transmission and competition than those housed individually or in smaller groups. Therefore, if group size, grouping strategy, and disease detection are not optimal, the health and performance of calves can be compromised. The objectives of this narrative literature review, from publications available as of February 2023, are to (1) describe the use of AMF in group housing systems for calves and the associated feeding behavior variables they automatically collect, (2) linking feeding behavior collected from AMF to disease risk in calves, (3) describe research on social behavior in AMF systems, and (4) introduce social networks as a promising tool for the study of social behavior and disease transmission in group-housed AMF-fed calves. Existing research suggests that feeding behavior measures from AMF can assist in detecting bovine respiratory disease and enteric disease, which are common causes of morbidity and mortality for preweaning dairy heifers. Automated milk feeder records show reduced milk intake, drinking speed, or frequency of visits when calves are sick. However, discrepancies exist among published research about the sensitivity of feeding behavior measures as indicators of sickness, likely due to differences in feeding plans and disease-detection protocols. Therefore, considering the influence of milk allowance, group density, and individual variation on the analysis of AMF data is essential to derive meaningful information used to inform management decisions. Research using dynamic social networks derived from precision data show potential for the use of social network analysis to understand disease transmission and the effect of disease on social behavior of group-housed calves.

Producer perceptions of dairy calf management, behavior, and welfare.

Approaches for raising calves vary across commercial dairy farms and relate to behavioral opportunities and animal welfare. The objectives of this study were to evaluate how US dairy producers and calf managers perceive 1) welfare implications of varying management practices (including social housing and milk allowance) and behaviors in dairy calves, and 2) aspects of the human-animal relationship in calf rearing and relationships with on-farm management and personal calf handling habits. Survey questions were primarily quantitative (e.g., Likert scales) and addressed how common calf management practices and observed calf behaviors were related to aspects of welfare, including calf health and comfort. We additionally posed questions addressing respondent habits, management protocols, and perceptions related to human-animal interaction. Responses from 93 dairy producers and calf managers were collected via digital surveys. Social housing was viewed as being generally positive for both calf comfort and health, although this view was stronger with respect to calf comfort. Respondents from farms using social housing (56%) had more positive perceptions of social housing, viewed social play as being associated with better calf comfort and health, and considered access to other calves and "freedom to express natural behavior" as being more important for calves, compared with respondents from farms not providing social housing. Providing greater milk allowances (>7.6 L/d) was viewed as being good for both calf comfort and health, although respondents from farms providing these milk allowances (59%) had more positive perceptions than those who provided lesser allowances. Abnormal oral behaviors were viewed as being associated with both poor calf comfort and health. The welfare importance of various resources which may reduce abnormal oral behaviors (including hay and brushes) was perceived more ambiguously, although respondents from farms providing these resources, compared with those who do not, generally viewed them as more preferred by calves. We observed a positive relationship between how respondents perceived the human-animal bond (i.e., that calves enjoy contact with humans) and stated personal behavior related to calf contact (frequency of contacting calves to scratch or pet them). Respondent demographics were not related to perceptions of the human-animal relationship, but respondents identifying as female described more frequent positive calf interactions. Described aspects of human-animal interactions were not related to implementation of social housing on-farm. Job satisfaction was positively related to perception of the human-animal relationship. Overall, these results suggest that most calf management personnel place a high value on calf welfare, although farms implementing social housing appear to place a greater value on subjective calf well-being and individual perceptions of animal welfare may depend on practical experience.

Growth and body composition of dairy calves fed only milk replacer at 3 intakes.

Determination of energy requirements for growth depends on measuring the composition of body weight (BW) gain. Previous studies have shown that the composition of gain can be altered in young dairy calves by composition of the milk replacer diet. Here, our objective was to determine body composition and the composition of empty body gain in young calves fed increasing amounts of a milk replacer containing adequate CP. Male Holstein calves underwent an adjustment period of 14 d after birth in which they were fed whole waste milk at 10% of BW. Calves were then stratified by BW and randomly assigned to either an initial harvest group (n = 11) or to groups fed 1 of 3 milk replacer amounts and harvested after 35 d of growth. All treatments consumed the same milk replacer containing 24.8% CP (dry matter [DM] basis; from all milk proteins) and 18.9% fat, reconstituted to 12.5% solids. Treatments were milk replacer fed at 1.25% of BW (DM basis; n = 6), 1.75% of BW (n = 6), or 2.25% of BW (n = 8), adjusted weekly as calves grew. Calves fed at 1.25% or 1.75% of BW were fed twice daily and those fed 2.25% of BW were fed 3 times daily. No starter was offered. Post harvest, the bodies of calves were separated into 4 fractions: carcass; total viscera minus digesta; head, hide, feet, and tail; and blood. The sum of those 4 fractions was empty BW, which increased linearly as amount of milk replacer increased. Final heart girth and body length, but not withers height, increased linearly as intake increased. Gain:feed increased linearly with increasing milk replacer. Feeding more milk replacer increased the amounts of lean tissue and fat in the body. The percentages of water and protein in the final body decreased linearly, whereas fat percentage and energy content increased linearly as intake increased. As gain increased, the percentage of protein in gain decreased and the percentage of fat increased, resulting in an increase of energy content of EBW gain. Efficiency of energy use (retained energy:gross energy intake) increased linearly but retained energy:metabolizable energy available for growth was not different among treatments. Efficiency of protein use increased quadratically as feeding rate increased; there was no further increase at 2.25% of BW. Plasma insulin-like growth factor 1, insulin, and glucose increased linearly, whereas urea-N decreased linearly, as milk replacer intake increased. Our data document changes in body composition that affect estimates of retained energy in the bodies of calves harvested at a common age. These data are important for calculations of energy requirements for young calves.

Relative merits of offering a milk replacer, glucose-electrolyte or whey-based diet on the blood composition and health of unweaned calves after transport.

The objective of this randomized controlled trial was to assess the relative merits of offering unweaned calves 3 different types of diets to meet energy and water deficits that can occur during journeys. Six young unweaned male Holstein calves were randomly selected from within 2 body weight ranges (median 48 and 42 kg) from each of 29 loads (total n = 174 calves) transported from an auction market or a collection center to a calf sorting center before transport to a veal unit. The calves were then randomly allocated to one of 3 dietary treatments (n = 58 calves/dietary treatment). They were offered either a milk replacer diet (M), a glucose-electrolyte diet (G) or a whey-based diet with added electrolytes (W). The ability of these diets to provide sufficient nutrient energy to restore vigor, avoid hypoglycaemia and clinical signs of dehydration without increasing the risk of diarrhea was assessed. A clinical assessment of dehydration, health and vigor was made, and the calves were blood sampled before feeding, then 2 h and 4 h after feeding. The plasma glucose concentration was increased 2 h and 4 h after feeding the M and W diets. The increases in plasma glucose concentration were greater 2 and 4 h after (a) feeding the M than after the W diet and (b) feeding the M and W diets than after the G diet. Back-transformed means and 95% Confidence Intervals (CI) for the ratio of the plasma glucose concentration at 4 h compared with 0 h for the milk replacer, glucose-electrolytes and whey-based diets were 1.2 mM CI 1.21, 1.35; 0.95 mM CI 0.92, 0.97; and 1.09 mM CI 1.06, 1.14, respectively. There was no effect of diet on the change in serum total protein concentration between before feeding and 2 and 4 h after feeding. The serum osmolality was lower 2 h after feeding the G diet. The fall in serum osmolality was greater 2 h after feeding the G diet than after feeding the M and W diets. The changes in the serum osmolality between before feeding and 2 h after feeding for the milk replacer, glucose-electrolytes and whey-based diets were -0.68 mosmol CI -3.27, 1.91; -5.23 mosmol CI -7.82, and -2.64; -0.13 mosmol CI -2.77, 2.51, respectively. The diet offered at the sorting center had no effect on subsequent growth on the veal rearing farm between arrival and slaughter (milk replacer 1.22 kg/d, CI 1.17, 1.28; glucose-electrolyte diet 1.23 kg/d. CI 1.18, 1.28; whey-based diet 1.28 kg/d CI 1.23, 1.33). The M diet provided the calves with nutrients and water to replace energy and water deficits that had accumulated before arrival at the sorting center, and these dietary benefits were still apparent 4 h after feeding. The benefits of the W diet were similar to those of the M diet, but the M diet was better able to assist the calves in maintaining their plasma glucose concentration 4 h after feeding than the W diet. The G diet had some short-term benefits in providing energy and assistance to the calves to recover from dehydration, as indicated by a decrease in serum osmolality. However, the G diet was clearly inferior to the M and W diets in providing sufficient energy to assist the calves in recovering from the effects of transport and fasting. During the 4-h after feeding, no adverse effects of offering the calves the M or W diets were observed. The benefits of the W diet in replacing energy and water deficits were similar to those of the M diet, but the M diet was better able to assist the calves in maintaining their blood glucose concentration 4 h after feeding than the W diet.

Effects of castration and eucalyptus oil supplementation on growth performance, nutrient digestibility, and blood-immunity indicators of male Holstein calves.

The purpose of this study was to investigate the effects of early castration and eucalyptus oil (EUC) supplementation on dry matter intake (DMI), growth performance, and immune response of Holstein calves. Fifty-six male Holstein calves 52 d old and with an initial body weight (BW) of 63.5 ± 5.27 kg were used. The animals were blocked by BW and randomly assigned into 1 of the 4 treatment groups in a randomized complete block design with a 2 (no castration vs. castration) × 2 (without vs. with EUC) factorial arrangement of treatments. The treatments were (1) uncastrated calves fed without EUC, (2) uncastrated calves fed 0.5 g/d EUC (EUC group), (3) castrated calves (steers) fed without EUC (castrated group), and (4) steers fed with 0.5 g/d EUC (castrated + EUC). The experiment was 8 wk long, including pre- and postweaning (weaned at 72 d). The EUC × castrated interactions were not significant for DMI, growth performance, nutrient digestibility, and immune response. Castration did not affect the DMI, final BW, average daily gain (ADG), or feed efficiency, except that the ADG was greater for bull calves than for steers at postweaning. Supplementation with EUC increased DMI pre- and postweaning and increased the ADG of weaned calves. Digestibility in the total digestive tract was not affected by castration (except for organic matter digestibility), whereas adding EUC improved the digestibility of dry matter, acid detergent fiber, and crude protein. Blood concentration of IL-6 at d 94 was decreased by feeding EUC. These results indicate that the EUC could be fed to either intact or castrated dairy calves to promote growth and health postweaning; castration before weaning may reduce ADG and cause inflammatory stress without affecting feed intake or feed efficiency.

Residual feed intake is related to metabolic and inflammatory response during the preweaning period in Italian Simmental calves.

Residual Feed Intake (RFI) is defined as the difference between measured and predicted intake. Understanding its biological regulators could benefit farm profit margins. The most-efficient animals (M-Eff) have observed intake smaller than predicted resulting in negative RFI, whereas the least-efficient (L-Eff) animals have positive RFI. Hence, this observational study aimed at retrospectively comparing the blood immunometabolic profile in calves with divergent RFI during the preweaning period. Twenty-two Italian Simmental calves were monitored from birth through 60 d of age. Calves received 3 L of colostrum from their respective dams. From 2 to 53 d of age, calves were fed a milk replacer twice daily, whereas from 54 to 60 d (i.e., weaning) calves were stepped down to only one meal in the morning. Calves had ad libitum access to concentrate and intakes were recorded daily. The measurement of BW and blood samples were performed at 0, 1, 7, 14, 21, 28, 35, 45, 54, and 60 d of age. Calves were ranked and categorized as M-Eff or L-Eff according to the median RFI value. Median RFI was -0.06 and 0.04 kg of DMI/d for M-Eff and L-Eff, respectively. No evidence for group differences was noted for colostrum and plasma IgG concentrations. Although growth rate was not different, as expected, (0.67 kg/d [95% CI = 0.57-0.76] for both L-Eff and M-Eff) throughout the entire preweaning period (0-60 d), starter intake was greater in L-Eff compared with M-Eff calves (+36%). Overall, M-Eff calves had a greater gain-to-feed ratio compared with L-Eff calves (+16%). Plasma ceruloplasmin, myeloperoxidase, and reactive oxygen metabolites concentrations were greater in L-Eff compared with M-Eff calves. Compared with L-Eff, M-Eff calves had an overall greater plasma concentration of globulin, and γ-glutamyl transferase (indicating a better colostrum uptake) and Zn at 1 d. Retinol and urea were overall greater in L-Eff. The improved efficiency in nutrient utilization observed in M-Eff was paired with a lower grade of oxidative stress and systemic inflammation. L-Eff may have had greater energy expenditure to support the activation of the immune system.

Schizochytrium sp. and lactoferrin supplementation alleviates Escherichia coli K99-induced diarrhea in preweaning dairy calves.

Calf diarrhea, a common disease mainly induced by Escherichia coli infection, is one of the main reasons for nonpredator losses. Hence, an effective nonantibacterial approach to prevent calf diarrhea has become an emerging requirement. This study evaluated the microalgae Schizochytrium sp. (SZ) and lactoferrin (LF) as a nutrient intervention approach against E. coli O101:K99-induced preweaning calve diarrhea. Fifty 1-d-old male Holstein calves were randomly divided into 5 groups (n = 10): (1) control, (2) blank (no supplement or challenge), (3) 1 g/d LF, (4) 20 g/d SZ, or (5) 1 g/d LF plus 20 g/d SZ (LFSZ). The experimental period lasted 14 d. On the morning of d 7, calves were challenged with 1 × 1011 cfu of E. coli O101:K99, and rectum feces were collected on 3, 12, 24, and 168 h postchallenge for the control, LF, SZ, and LFSZ groups. The rectal feces of the blank group were collected on d 14. Data were analyzed using the mixed procedure of SAS (version 9.4; SAS Institute Inc.). The E. coli K99 challenge decreased the average daily gain (ADG) and increased feed-to-gain ratio (F:G) and diarrhea frequency (control vs. blank). Compared with the control group, the LFSZ group had a higher ADG and lower F:G, and the LFSZ and SZ groups had lower diarrhea frequency compared with the control group. In addition, the LFSZ and SZ groups have no differences in diarrhea frequency compared with the blank group. Compared with the control group, the blank group had lower serum nitric oxide (NO), endothelin-1, d-lactic acid (D-LA), and lipopolysaccharide (LPS) concentrations, as well as serum IgG, IL-1ß, IL-6, IL-10, and TNF-α levels on d 7 and 14. On d 7, compared with the control group, all treatment groups had lower serum NO level, the SZ group had a lower serum D-LA concentration, and the LF and LFSZ groups had lower serum LPS concentration. On d 14, compared with the control group, the fecal microbiota of the blank group had lower Shannon, Simpson, Chao1, and ACE indexes, the LFSZ group had lower Shannon and Simpson indexes, the SZ and LFSZ groups had a higher Chao1 index, and all treatment groups had a higher ACE index. In fecal microbiota, Bifidobacterium and Actinobacteria were negatively associated with IL-10 and d-lactate, while Akkermansia was negatively associated with endothelin-1 and positively correlated with LPS, fecal scores, and d-lactate levels. Our results indicated that LF and SZ supplements could alleviate E. coli O101:K99-induced calf diarrhea individually or in combination. Supplementing 1 g/d LF and 20 g/d SZ could be a potential nutrient intervention approach to prevent bacterial diarrhea in calves.

Apparent prevalence of hemotropic mycoplasma in dairy calves and replacement heifers on Michigan farms.

The bovine hemoplasmas include Mycoplasma wenyonii and Candidatus Mycoplasma haemobos, which are increasingly recognized as infecting cattle throughout the world. Infection with hemotropic mycoplasma has been reported to be widespread in mature dairy cows, but little is known about its prevalence in calves and heifers. The objective of this study was to investigate the prevalence and dynamics of infection with M. wenyonii and C. M. haemobos in calves and replacement heifers on Michigan dairy farms and assess the potential associations between infection status and hematological values. The study was designed as a prospective cross-sectional study with a longitudinal component. A convenience sample of 11 farms agreed to participate and were visited twice between March and September 2022. During the first farm visit, researchers collected blood samples from up to 94 animals per farm distributed among newborn and preweaning calves (n ≤ 31), weaned calves (n = 21), pre-breeding heifers (n = 21), and pregnant heifers (n = 21). During the first visit, blood samples (n = 174) were also collected from a convenience sample of mature cows to confirm the herd infection status. The same calves and heifers were sampled again ∼95 d (±3.0) later. During the first visit, blood samples were collected from 797 calves and replacement heifers, whereas 675 samples were collected during the second visit due to the inability to locate some animals. Detection of M. wenyonii and C. M. haemobos was based on results of real-time PCR. The hematocrit was determined using microcentrifugation, and the concentration of leukocytes using an automated cell counter. In all herds, most mature cows that were sampled tested positive for infection. The within-herd apparent prevalence of hemoplasma in calves and replacement heifers was 100% for both M. wenyonii and C. M. haemobos. The apparent prevalence of hemoplasma in youngstock was associated with age. In calves that were 1 to 6 mo old, the prevalence of infection was 6% to 8% but sharply increased to 31% by 8 mo of age. In older animals, the prevalence remained high, and was almost 100% in animals greater than 17 mo of age. Based on calves and heifers sampled twice, the cumulative incidence varied widely among herds, ranging from 3.7% to 96.0%, and increased with the age of the animals. We found no difference in hematocrit or number of lymphocytes, monocytes, neutrophils, or total leukocytes based on infection status. The number of eosinophils was greater in infected animals. This is the first study to report the prevalence of hemoplasmas in calves and replacement heifers in the United States. It indicates that young calves can be infected with hemoplasmas, but the rate of infection is low. The likelihood of infection increases as animals age, with a notable rise in the proportion of infected heifers occurring by 8 mo old, and the prevalence eventually reaching nearly 100% in older animals. Once infected, heifers appear to remain chronic carriers. Hemoplasma infection alone does not usually lead to the development of clinical signs, and most of the animals remain apparently healthy.

Effects of weaning age and pace on blood metabolites, cortisol concentration, and mRNA abundance of inflammation-related genes in gastrointestinal, adipose, and liver tissue of Holstein dairy calves.

The objective of this study was to evaluate the effects of weaning age and pace on blood metabolites, cortisol concentration, and mRNA abundance of inflammation-related genes in Holstein dairy calves. A total of 70 1-d-old calves (38.8 ± 4.4 kg BW ± SD), blocked by sex and birth BW, were randomly assigned to a 2 × 2 factorial arrangement of treatments. The first factor was weaning age, which was either early (6 wk) or late (8 wk). The second factor was weaning pace, which was either abrupt (4 steps down over 3 d; the initial milk replacer was 7.6 L, which was reduced by 1.9 L in each step-down) or gradual (7 steps down over 14 d; the initial milk replacer was 7.6 L, which was reduced by 1.09 L in each step-down), generating early-abrupt (EA), early-gradual (EG), late-abrupt (LA), and late-gradual (LG) treatments. All treatments had 10 female and 8 male calves, except EA that had 1 fewer male calf. Milk replacer (24% CP, 17% fat) was bottle fed, up to 1,200 g/d, twice daily (0600 h and 1800 h). The EA and EG treatment calves received 46.2 kg of milk replacer, and the LA and LG treatment calves received 63 kg of milk replacer. The study had 2 cohorts (2020, n = 40; 2021, n = 31), and each cohort included all treatments. Blood was collected from the jugular vein at 0900 h at 3 and 7 d of age, and a day before starting and a day after weaning completion. Male calves were humanely killed a day after weaning. Rumen, jejunum, large intestine, liver, omental adipose and perirenal adipose tissues were sampled to determine the mRNA abundance of inflammation-related genes. Weaning pace, age, pace × age, birth BW, and sex were included as fixed and cohort was included as random effects in the model. Blood metabolites and cortisol were analyzed as repeated measures, and sampling day, pace × sampling day, and age × sampling day were also included as additional fixed effects. Significance was noted at P ≤ 0.05 and tendencies when 0.05

Effects of simplified group housing on behavior, welfare, growth performance, and health of preweaned dairy calves on a California dairy.

Most US dairy calves are raised in individual hutches for biocontainment purposes and to facilitate monitoring and handling of calves. However, individual hutches typically restrict calves' activity and social interactions. Previous studies showed that group housing (GH) is beneficial to calf welfare and is associated with social benefits. The adoption of GH on dairies is hindered by several concerns, with the primary concern being the potential for increased transmission of diseases due to heightened calf-to-calf contact. In light of this, our study aimed to compare the behavior, health, and growth outcomes of calves housed in groups of 3 to individually housed (IH) calves during the preweaning period. A total of 42 Holstein heifer calves on a commercial dairy in Northern California were enrolled in groups of 3 to different housing treatments; IH (n = 21) or GH (n = 21) between July and October 2020. Each treatment was composed of 7 groups of 3 calves each. Calves in the GH treatment were housed in groups of 3 from 6 to 10 d until 70 d of age. Individual pens consisted of one polyethylene hutch with a 1.5 m × 1.2 m outside exercise area. Group pens were constructed by assembling 3 polyethylene hutches with a 1.5 m × 3.6 m outside exercise area of wire panel fencing. Calves were weighed and measured for height at birth and weaning. Diarrhea and bovine respiratory disease (BRD) scores were recorded daily throughout the preweaning period. Cumulative incidence and hazard ratios were estimated for BRD and diarrhea for GH and IH. A mixed model with pen as a random effect was specified to evaluate the effect of treatment. Group-housed calves gained 0.64 ± 0.02 kg/d while IH calves gained 0.65 ± 0.02 kg/d. Similarly, there was no evidence for treatment differences in withers height gain in GH calves (0.22 ± 0.01 cm/d) compared with IH calves (0.21 ± 0.01 cm/d). The cumulative incidence of BRD based on the California scoring system in GH calves was 75 ± 9.68% compared with 66.66 ± 10.28% in IH calves. Group-housed calves had a BRD hazard of 1.14 times that of IH calves (95% CI: 1.21-2.40). The cumulative incidence of diarrhea (fecal score 3) in GH calves was 100% in comparison to 95.20% ± 4.66% in IH calves. The mean proportion of scan observations of calves feeding on concentrates was significantly higher in GH (0.145 ± 0.004/h) compared with IH calves (0.076 ± 0.003/h) during the preweaning period. The study results provide evidence that this simplified GH system provides benefits of GH without detrimental short-term effects on calf growth and health during the preweaning period.

Effects of Meloxicam on the Welfare of Holstein Calves from 6 Weeks to 6 Months Old Undergoing Amputation Dehorning.

Amputation dehorning (AD) is a common practice performed on calves, causing harmful effects such as pain, distress, anxiety, and fear. These effects extend to behavioral, physiological, and hematological responses, prompting serious ethical concerns regarding animal welfare, even when performed with local anesthesia. Meloxicam, a non-steroidal anti-inflammatory drug, has been widely used to mitigate the side effects of dehorning and disbudding in calves. However, there is a notable gap in research regarding the effects of meloxicam on calves aged 6 weeks to 6 mo undergoing AD procedures. This study was designed to assess the effectiveness of co-administering meloxicam with lidocaine, a cornual nerve anesthetic, in alleviating the adverse effects caused by the AD procedure in calves within this age range, compared with the use of lidocaine alone. Thirty Holstein calves were enrolled and randomly divided into 2 groups. The first group (Placebo) received a subcutaneous injection of 5 mL of lidocaine in the horn area and a subcutaneous injection of 0.9% saline at a dose of 0.025 mL/kg in the neck, administered 10 min before the AD procedure. The second group (MX) received a combination of lidocaine and meloxicam: a subcutaneous injection of 5 mL of lidocaine in the horn area and a subcutaneous injection of 20 mg/mL meloxicam at a dose of 0.025 mL/kg in the neck, also administered 10 min before the AD procedure. To avoid subjective bias, the researchers were blinded to the treatment groups. Pain-related behaviors, including tail flicking, head shaking, ear flicking, head rubbing, head crossing bar, and kicking, were observed, and physiological parameters, including heart rate, rectal temperature, respiration rate, mechanical nociceptive threshold (MNT), daily active steps, and food intake were monitored. Hematological conditions were determined using enzyme-linked immunosorbent assays and routine blood tests. The data were processed using a generalized linear mixed model (GLMM). The outcomes demonstrated that the AD procedure increased the frequencies of ear flicking and resulted in rises in the respiration rate, heart rate, rectal temperature, and daily active steps. It also led to decreases in total food intake, forage intake, hay intake, MNT, and increased concentrations of prostaglandin E2 (PgE2), interleukin-1ß (IL-1ß), tumor necrosis factor-α (TNF-α), nitric oxide (NO), and malondialdehyde, as well as glutathione peroxidase activity. However, calves that received meloxicam treatment showed significant improvements in response to the AD procedure, including lower respiration rates, heart rates, and rectal temperatures; higher MNTs; and lower intermediate cell ratio. They also had higher red blood counts, hemoglobin levels, hematocrit values; larger mean platelet volumes; and lower concentrations of PgE2, IL-1ß, TNF-α, and NO. These results suggest that co-administration of lidocaine and meloxicam may aid in mitigating the adverse impacts induced by the AD procedure on these calves, thereby supporting the use of meloxicam in conjunction with a local anesthetic in AD procedures for calves aged 6 weeks to 6 mo.

Effects of supplementing direct-fed microbials on health and growth of pre-weaning Gyr × Holstein dairy calves.

This study aimed to evaluate the effects of direct-fed microbials (DFM) on health and growth responses of pre-weaning Bos indicus × B. taurus (Gyr × Holstein) crossbred calves. Ninety newborn heifer calves [initial body weight (BW) 35 ± 4.0 kg] were used. At birth, calves were ranked by initial BW and parity of the dam and assigned to: 1) whole milk without DFM supplementation (CON; n = 30), 2) whole milk with the addition of 1.0 g/calf per day of a Bacillus-based DFM (BAC; n = 30), or 3) whole milk with the addition of 1.0 g/calf per day of BAC and 1.2 g/calf per day of Enterococcus faecium 669 (MIX; n = 30). Milk was fed individually during the study (77 d) and the BAC and MIX treatments were offered daily throughout the 77-d pre-weaning period. All calves were offered a starter supplement and corn silage starting on d 1 and 60 of age, respectively. Milk and starter supplement intake were evaluated daily, and BW was recorded on d 0 and at weaning (d 77). Diarrhea and pneumonia were assessed daily, and fecal samples were collected on d 0, 7, 14, 21, and at weaning (d 77) for assessment of the presence of bacterial and protozoal pathogens via qPCR. All data were analyzed using SAS (v. 9.4) with calf as the experimental unit and using single-df orthogonal contrasts (BAC + MIX vs. CON; BAC vs. MIX). Daily feeding of DFM, regardless of type, improved weaning BW. Odds ratio for occurrence of pneumonia was lower for DFM-supplemented calves, but occurrence of both did not differ between BAC and MIX calves. No Salmonella spp. or E. coli F41 were detected in any of the calves. The proportion of calves positive for E. coli F17 was greater for DFM calves on d 7 (92 and 96% vs. 81% for BAC, MIX, and CON, respectively), 21 (13 and 26% vs. 7% for BAC, MIX, and CON, respectively), and at weaning (48 and 35% vs. 22% for BAC, MIX, and CON, respectively). For C. difficile, more DFM calves were positive on d 7 (65 and 30% vs. 35% for BAC, MIX, and CON, respectively) and 14 (20 and 28% vs. 7% for BAC, MIX, and CON, respectively), but also greater for BAC vs. MIX on d 7. More CON calves were positive for C. perfringens on d 14 (14% vs. 3 and 8% for CON, BAC, and MIX, respectively) compared with DFM-fed calves. Incidence of calves positive for C. perfringens was greater in BAC vs. MIX on d 7 (50 vs. 18%), and greater for MIX vs. BAC at weaning (9 vs. 0%). For protozoa occurrence, a lower proportion of DFM calves were positive for Cryptosporidium spp. on d 7 (58 and 48% vs. 76% for BAC, MIX, and CON, respectively), but opposite results were observed on d 21 for Cryptosporidium spp. (3 and 11% vs. 0% for BAC, MIX, and CON, respectively) and Eimeria spp. on d 14 (7 and 8% vs. 0% for BAC, MIX, and CON, respectively) and 21 (50 and 59% vs. 38% for BAC, MIX, and CON, respectively). In summary, DFM feeding alleviated the occurrence of pneumonia, improved growth rates, while also modulating the prevalence of bacteria and protozoa in pre-weaning Gyr × Holstein calves.

Dairy producers' colostrum practices, marketing, and attitudes toward male dairy calves.

Optimal early-life care of surplus calves born on dairy farms is critical for health and welfare. This cross-sectional study aimed to describe the marketing practices of male dairy calves, differences in the colostrum management between male and female calves on dairy farms, and the relationship between discrepant colostrum practices and dairy producers' attitudes toward male calf care. United States dairy producers (n = 1,000) in the states of Florida, Michigan, Ohio, Vermont, and Wisconsin were selected using stratified random sampling. A questionnaire containing questions about farm demographics, colostrum management (including quantity and timeliness of colostrum delivery), and producers' attitudes toward male calf care was mailed in February 2021. Attitudes toward male calf care were assessed using 5-point Likert scales for 10 statements regarding perceptions of the value of male calves and barriers in providing optimal care. Producer responses to questions about the quantity and timeliness of colostrum delivery between male and female calves were compared using a nonparametric Wilcoxon rank-sum test. Multivariable logistic regression models were used to investigate the association between differences in colostrum management and producers' attitudes. By May 2021, 953 surveys were delivered and 315 (33.1%) were returned with complete responses. Most producers (>90%) reported feeding equal volumes of colostrum and performing the first postbirth feeding within a similar time frame for male and female calves. However, compared with females, male calves had a longer delay to the first colostrum feeding. Approximately 40% of producers marketed their male calves through auctions, and over half (54.6%) of farms sold the male calves between 3 and 10 d of age. Large farms (≥500 lactating cows) were found to market male calves at a younger age (≤3 d of age). Most producers (>78%) believed their male calves were receiving optimal care and did not consider the workload and financial costs as obstacles to providing good care to male calves. However, those who viewed the workload as an obstacle to good care and produced organic products were marginally more likely to feed a lower volume of colostrum to male calves in the first feeding after birth. These findings suggest that interventions to improve colostrum practices should be more broadly targeted to all calves born on dairy farms, and that age at transport is markedly different between large and small farms.