Dexamethasone administration restored growth in dairy calves exposed to heat stress.

Recent evidence indicates that the heat stress loss on the growth performance of calves is associated with the diversion of nutrients to control enteritis and systemic inflammation. In this study, we investigated the impact of heat stress on markers of inflammation, feed use-efficiency, and growth of dairy calves. We hypothesized that dexamethasone, which is known for its immunosuppressive and anti-inflammatory properties, would reduce inflammation and restore the growth of calves exposed to heat stress. Thirty-two Holstein bull calves (body weight (BW) 68.5 ± 1.37 kg; age 3.5 ± 0.5-week-old; mean ± SD) were housed in individual pens in climate-controlled rooms at constant ambient temperature and allowed to adjust to facilities for 5 d before the start of treatments. Calves were randomly assigned to one of 4 treatments (n = 8/treatment) in a 2 × 2 factorial arrangement of environment (ENV, thermoneutral or heat stress) and intervention (INT, saline or dexamethasone) imposed for 5 d as follow: 1) thermoneutral (constant ambient temperature of 20°C 24 h/d) and administration of saline, 2) thermoneutral (constant ambient temperature of 20°C 24 h/d) and administration of dexamethasone, 3) cyclic heat stress (40°C ambient temperature, from 0800 to 1900 h/d) and administration of saline, 4) cyclic heat stress (40°C ambient temperature, from 0800 to 1900 h/d) and administration of dexamethasone. Dexamethasone (0.05 mg/kg BW), or saline (1.2 mL) was administered intramuscularly on d 1 and 3. Upon completion of treatments, calves were euthanized on d 5 to obtain jejunum mucosa samples. Commercial milk replacer, starter grain, and water were offered, and intake was monitored daily. Rectal temperature and respiratory rate were monitored 3 times daily. Blood samples were collected on d 1, 3, and 5 to determine serum pro-inflammatory cytokine concentrations. A section of the jejunum was collected and snap-frozen to determine the concentration of pro-inflammatory markers. Statistical analyses included a mixed model, fixed effects of ENV, INT, consecutive measurements taken over time (d, h, or both), replica, and random effects of calf and error (SAS version 9.4, SAS Institute Inc., Cary, NC). The measurements collected immediately before treatment allocation were included as covariates in the model. An ENV effect showed that heat stress increased rectal temperature (38.72 vs. 39.21°C), respiratory rate (36 vs. 108 breaths/min), and water intake (3.2 vs. 6.6 L/d). The treatments did not affect dry matter intake. An ENV × INT interaction showed that heat stress with saline decreased average daily gain (ADG) by 35% and tended to decrease feed use-efficiency by 36%, but the use of dexamethasone to treat heat stress restored ADG and feed use-efficiency comparable to their basal levels. An ENV × INT interaction revealed that heat stress with saline increased jejunal interleukin (IL)-6 concentration 2-fold, but dexamethasone treatment of heat stress restored jejunal IL-6 concentration to basal levels. The bioenergetic cost of the heat stress-immune pro-inflammatory response ranged between 1.18 and 1.50 Mcal of ME. Overall, the administration of dexamethasone reduced the jejunal concentration of a pro-inflammatory marker and restored the heat stress-associated reduction in growth and feed use-efficiency. The immunomodulation and anti-inflammatory effects of dexamethasone could be part of a homeorhetic change that results in a shift from maintenance functions to support growth on calves exposed to heat stress.

Molecular Detection and Characterization of Cryptosporidium spp. and Giardia duodenalis in Dairy Calves from Ningxia, China.

PURPOSE: Cryptosporidium spp. and Giardia duodenalis are two important foodborne human and animal parasites that can be disseminated through both food and water, leading to diarrheal disease. Nevertheless, available information on the circumstances of Cryptosporidium and Giardia duodenalis from Ningxia is limited. METHODS: A total of 208 stool samples of dairy calves derived from large-scale farms (> 1000 heads) of five cities randomly in Ningxia were gathered randomly, were amplified and analyzed by nested PCR based on the three target genes (18S rRNA, gp60 and tpi)and phylogenetic systematics. RESULTS: The prevalence of cryptosporidiosis and giardiasis in dairy calves in Ningxia were 13.0% (27/208 samples, 95% CI 9.1-18.2%) and 1.9% (4/208, 95% CI 0.8-4.9%) respectively. Three Cryptosporidium species appeared in this study which are Cryptosporidium parvum (C. parvum), Cryptosporidium andersoni (C. andersoni) and Cryptosporidium ryanae (C. ryanae) based on the 18S rRNA gene sequence. IIdA15G1 and IIdA13G1 belonging to the subtypes of Cryptosporidium were detected by the gp60 PCR. The genotypes of Giardia duodenalis were only assemblage E through the amplification of the triosephosphate-isomerase gene (tpi gene). CONCLUSION: There is a risk of transmission to humans in Ningxia because of zoonotic genotypes (C. parvum, C. andersoni, assemblage E) and subtypes (IId) of Cryptosporidium spp. and G. duodenalis in dairy calves, and it is necessary to pay attention to the disease to prevent a widespread epidemic of the disease with the purpose to protect human and livestock health.

Evaluation of a data-driven youngstock rearing quality system in Dutch dairy herds (2019-2022).

In recent years, the Netherlands exhibited an increased focus on improving youngstock rearing. Several data-driven tools were developed to assess and benchmark calf rearing practices based on key indicators, stimulate farmers to improve their youngstock rearing and reduce calf mortality. KalfOK is such a data-driven tool in which a farm-level overview with 15 indicators of youngstock rearing quality is communicated to participating farmers. In this study we assessed which farm characteristics are associated with A) a continuously high or low KalfOK score and B) frequent usage of KalfOK. Data from KalfOK and the identification and registration system were available for all participating herds over a period between 2019 and 2022 (Dataset A). Additionally, a sample of 324 dairy farmers, randomly selected from the entire Dutch dairy population (Dataset B), participated in a voluntary survey. Multivariable (logistic) regression models were used to A) identify differences in characteristics between farms with a continuously high- and farms with a continuously low KalfOK score and B) assess which farm characteristics were associated with frequent use of the KalfOK report. The results of analysis A showed multiple factors associated with having a low or high KalfOK score, including replacement rate, closed farming system, limited growth in herd size and the region where a farm was located. Sociological factors might also partly explain the difference between high and low scoring farms. Analysis B showed that approximately half of the surveyed farmers indicated that they do not frequently use their KalfOK overview in their calf rearing management. The KalfOK score of farmers who regularly use their KalfOK report was higher - and consequently better - compared to the KalfOK score of farmers who sometimes or never use KalfOK. Additionally, farmers using a milk robot and those discussing KalfOK regularly with their veterinarian, used KalfOK more often. Thirty four percent of the surveyed farmers made adjustments to their youngstock rearing management since the start of participation. The study's insights into patterns in KalfOK utilization and associations with farm characteristics provide valuable information for ongoing efforts to enhance calf rearing practices via the use of KalfOK. It is important to consider what is needed to convince farmers that do not use the KalfOK tool to frequently start using their KalfOK report. Future research incorporating sociological aspects can provide a more comprehensive understanding of other dynamics influencing calf rearing and contribute valuable insights for enhancing the effectiveness of programs like KalfOK in promoting calf health and welfare.

Predicting Body Weight in Pre-Weaned Holstein-Friesian Calves Using Morphometric Measurements.

Regularly weighing calves helps to assess the efficiency of the rearing period and contributes to animal welfare by allowing more precise feeding and medication application in dairy farming, but many farmers do not weigh their calves regularly. Improving the feasibility of this process is, therefore, important. The use of morphometric measurements has been used to estimate the weight of cattle. However, many studies have focused on adult animals or used a wide age range. As calves experience allometric tissue growth, specific models for certain ranges might be more accurate. Therefore, the aim of this work was to develop a weight estimation model specific for pre-weaned Holstein-Friesian calves using morphometric measurements and to compare the model with another equation previously validated for the same breed with young and adult animals. From four dairy farms, 237 measurements of body weight, heart girth, abdominal girth, hip height, withers height, and body length were taken from Holstein-Friesian male and female calves. Linear and non-linear regression analysis was used to test the relationship between body weight and morphometric measurements, with age, sex, and farm as possible explanatory variables. Selected models were compared with goodness of fit and agreement tests. The final model was able to accurately predict body weight (R2 = 0.96) with a mean difference of -1.4 ± 3.24 kg. Differences in the relationship between body weight and morphometric traits were observed between farms, but not between males and females. The genetics of the animal population at farm level may be responsible for this variability and further studies are needed to understand this variability and improve weight prediction models. The developed model was able to perform better in the agreement tests than the previously validated model for Holstein-Friesian animals, suggesting that different equations should be used depending on the growth phase the animal is in. In addition, a web application has been developed to facilitate the use of the developed model by farmers. This avoids the use of calibrated weight bands, which are usually calibrated for a broader age range or for beef cattle.

Microbial inoculum effects on the rumen epithelial transcriptome and rumen epimural metatranscriptome in calves.

Manipulation of the rumen microbial ecosystem in early life may affect ruminal fermentation and enhance the productive performance of dairy cows. The objective of this experiment was to evaluate the effects of dosing three different types of microbial inoculum on the rumen epithelium tissue (RE) transcriptome and the rumen epimural metatranscriptome (REM) in dairy calves. For this objective, 15 Holstein bull calves were enrolled in the study at birth and assigned to three different intraruminal inoculum treatments dosed orally once weekly from three to six weeks of age. The inoculum treatments were prepared from rumen contents collected from rumen fistulated lactating cows and were either autoclaved (control; ARF), processed by differential centrifugation to create the bacterial-enriched inoculum (BE), or through gravimetric separation to create the protozoal-enriched inoculum (PE). Calves were fed 2.5 L/d pasteurized waste milk 3x/d from 0 to 7 weeks of age and texturized starter until euthanasia at 9 weeks of age, when the RE tissues were collected for transcriptome and microbial metatranscriptome analyses, from four randomly selected calves from each treatment. The different types of inoculum altered the RE transcriptome and REM. Compared to ARF, 9 genes were upregulated in the RE of BE and 92 in PE, whereas between BE and PE there were 13 genes upregulated in BE and 114 in PE. Gene ontology analysis identified enriched GO terms in biological process category between PE and ARF, with no enrichment between BE and ARF. The RE functional signature showed different KEGG pathways related to BE and ARF, and no specific KEGG pathway for PE. We observed a lower alpha diversity index for RE microbiome in ARF (observed genera and Chao1 (p < 0.05)). Five microbial genera showed a significant correlation with the changes in host gene expression: Roseburia (25 genes), Entamoeba (two genes); Anaerosinus, Lachnospira, and Succiniclasticum were each related to one gene. sPLS-DA analysis showed that RE microbial communities differ among the treatments, although the taxonomic and functional microbial profiles show different distributions. Co-expression Differential Network Analysis indicated that both BE and PE had an impact on the abundance of KEGG modules related to acyl-CoA synthesis, type VI secretion, and methanogenesis, while PE had a significant impact on KEGGs related to ectoine biosynthesis and D-xylose transport. Our study indicated that artificial dosing with different microbial inocula in early life alters not only the RE transcriptome, but also affects the REM and its functions.

Beliefs, mindset and personality of farm managers working in large commercial dairy herds: Association with calf on-farm mortality.

This study aimed to describe the attitudes and personalities of farm managers (FMs) in large Estonian dairy herds and analyse the potential associations with calf mortality. The study included FMs from 114 free-stall farms with at least 100 cows. Each participant completed a questionnaire that comprised questions about the respondent and various statements to reveal their attitudes towards calves, calf mortality, and farming in general. A 7-point Likert scale was used to record the responses. The data on the number of live births and deaths and animal movement data were gathered from farm records and the Estonian Agricultural Registers and Information Board. The yearly calf mortality risk (%) during the first 21 days (YAG) and mortality rate between 22-90 days of age (OAG) adjusted for the animal time-at-risk were then calculated for each herd. Univariate negative binomial regression analysis was used to identify associations between calf mortality risk/rate, and the studied statements and variables with a p-value < 0.25 were included in a k-modes clustering analysis. The mean calf mortality risk was determined to be 5.9 % (range 0.0-26.8 %) during the first 21 days and mean calf mortality rate was 1.8 (range 0.0-9.2) deaths per 100 calf-months during 22-90 days of age. In both age group analyses, two FMs´ clusters formed based on 17 pre-selected statements. The FMs of the high-mortality cluster were found to be dissatisfied with the calf mortality levels. In the YAG analysis, FMs from high-mortality cluster gave lower priority to the issue of calf mortality, placed high importance on the influence of workers on calf mortality, and were more satisfied with the staff's performance compared to FMs of the cluster of herds with lower calf mortality. They were additionally less satisfied with their own performance and felt less recognized by the farm staff. They were also more inclined to try new products and practices on the farm and demonstrated greater empathy towards cattle. In the OAG analysis, the FMs from the higher-mortality cluster viewed reducing calf mortality more costly, had a less ambitious and target-driven management style, and rated their self-performance lower. This study determined that FMs working in herds with high calf mortality were dissatisfied and did not prioritize addressing calf mortality compared to managers working in farms with lower calf mortality. FMs' attitudes and management styles were associated with calf mortality, while the respondents' personality traits had little influence.

Summer scour syndrome in weaned dairy calves: case series.

BACKGROUND: Summer scour syndrome (SSS) is a recently identified pathological condition affecting weaned dairy and dairy-beef calves during their first grazing season in Ireland. The syndrome is characterised by diarrhoea, weight loss, weakness, and can ultimately lead to death in some calves. Oral and oesophageal ulcerations are present in some cases. This study aimed to characterise a series of SSS cases in weaned dairy-bred calves on Irish commercial farms. RESULTS: Five farms with calves having unexplained diarrhoea at grass were referred by private veterinary practitioners (PVP) following preliminary testing to exclude coccidiosis and parasitic gastroenteritis. Farms were visited within 2 to 5 days following PVP's referrals, or 2 days to 3 weeks relative to the onset of clinical signs. Farm management data, grass and concentrate samples, and biological samples from 46 calves (8 to 10 calves/farm) displaying clinical signs were collected. Two farms were subsequently found positive for coccidiosis and/or had chronic pneumonia problems after a thorough herd investigation and were designated as non-case farms (NCF). The remaining three farms were deemed typical SSS outbreaks (case farms; CF). Mean rumen fluid pH per farm ranged from 6.67 to 7.09 on CF, and 6.43-6.88 on NCF. Mean rumen fluid ammonia concentrations ranged from 17.6 to 29.6 mg/L and 17.2-45.0 mg/L on CF and NCF, respectively. Corresponding blood ammonia concentrations ranged from 129 to 223 µmol/L and 22-25 µmol/L. Mean blood copper and molybdenum concentrations were within normal range on all farms. Grass crude protein concentrations on the paddocks where the calves had grazed, and were currently grazing on the day of visit ranged from 137 to 148 g/kg DM and 106-177 g/kg DM, respectively on CF, and 160-200 g/kg DM and 151-186 g/kg DM, respectively on NCF. On CF, inorganic nitrogen fertiliser was applied 1 to 3 weeks pre-grazing, whereas on the two NCF, inorganic nitrogen fertiliser was applied 2 to 3 weeks pre-grazing on one farm and no fertiliser was applied on the other. CONCLUSION: These findings suggest that copper or molybdenum toxicity, and ruminal acidosis are not the primary causes of SSS. High blood ammonia concentrations and the timing and level of inorganic nitrogen fertiliser application to paddocks pre-grazing, warrant further investigation.

Impact of Parenteral Maternal Supplementation with Trace Minerals and Vitamins on Neonatal Calf Antioxidant System and Growth in a Dairy Herd.

Oxidative stress may affect new born calves due to high stress suffered around birth. We hypothesized that maternal supplementation with micronutrients and vitamins in late gestation enhance the neonatal calf's antioxidant system, decreasing the occurrence and duration of diarrhea, and improving growth from birth through weaning. To test this hypothesis, 80 multiparous cows were cluster-assigned to treatment groups. Treated group (TG) cows received mineral and vitamin supplementation while control group (CG) cows received saline solution. Feed intake and fecal score were measured daily until the ninth week. Weight and body measurements were registered weekly, and blood samples were collected from postpartum cows and calves after birth and at 7, 14, and 63 days of life. Although CG calves had greater fecal scores (p = 0.01), diarrhea characteristics did not differ. Calves in the TG showed greater starter intake (p = 0.04). Feed efficiency showed a trend with treatment-age interaction (p = 0.06). Calves in the CG had wider hips in the first week (p = 0.03), but not by the ninth week. Total antioxidant status, thiobarbituric acid reactive substances, and haptoglobin did not differ between treatment groups. Serum metabolites showed no differences. Supplementation did not impact calf antioxidant system or growth in the first two months.

Bacteria colonization and gene expression related to immune function in colon mucosa is associated with growth in neonatal calves regardless of live yeast supplementation.

BACKGROUND: As Holstein calves are susceptible to gastrointestinal disorders during the first week of life, understanding how intestinal immune function develops in neonatal calves is important to promote better intestinal health. Feeding probiotics in early life may contribute to host intestinal health by facilitating beneficial bacteria colonization and developing intestinal immune function. The objective of this study was to characterize the impact of early life yeast supplementation and growth on colon mucosa-attached bacteria and host immune function. RESULTS: Twenty Holstein bull calves received no supplementation (CON) or Saccharomyces cerevisiae boulardii (SCB) from birth to 5 d of life. Colon tissue biopsies were taken within 2 h of life (D0) before the first colostrum feeding and 3 h after the morning feeding at d 5 of age (D5) to analyze mucosa-attached bacteria and colon transcriptome. Metagenome sequencing showed that there was no difference in α and ß diversity of mucosa-attached bacteria between day and treatment, but bacteria related to diarrhea were more abundant in the colon mucosa on D0 compared to D5. In addition, qPCR indicated that the absolute abundance of Escherichia coli (E. coli) decreased in the colon mucosa on D5 compared to D0; however, that of Bifidobacterium, Lactobacillus, and Faecalibacterium prausnitzii, which could competitively exclude E. coli, increased in the colon mucosa on D5 compared to D0. RNA-sequencing showed that there were no differentially expressed genes between CON and SCB, but suggested that pathways related to viral infection such as "Interferon Signaling" were activated in the colon mucosa of D5 compared to D0. CONCLUSIONS: Growth affected mucosa-attached bacteria and host immune function in the colon mucosa during the first 5 d of life in dairy calves independently of SCB supplementation. During early life, opportunistic pathogens may decrease due to intestinal environmental changes by beneficial bacteria and/or host immune function. Predicted activation of immune function-related pathways may be the result of host immune function development or suggest other antigens in the intestine during early life. Further studies focusing on the other antigens and host immune function in the colon mucosa are required to better understand intestinal immune function development.

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.

TLR5 ligand induces the gene expression of antimicrobial peptides and CXCL8 through IL-1ß gene expression in cultured rumen epithelial cells.

High grain feeding or weaning, which could compromise the rumen epithelium by increasing ruminal short-chain fatty acid (SCFA) concentrations with pH reduction, is associated with high levels of ruminal toll-like receptor 5 (TLR5). This study aimed to determine the role of TLR5 in the rumen epithelium. Immunohistochemistry revealed that TLR5 was localized in cells on the basal side (i.e., basal and spinous layers) rather than in the granular layer in the rumen epithelium, where tight junctions are most potent, in pre- and post-weaning calves (n = 9). Primary bovine rumen epithelial cells (BRECs) obtained from Holstein cows (n = 3) were cultured to investigate the factors that upregulate TLR5; however, SCFA, low pH (pH 5.6), BHBA, L-lactate, D-lactate, and LPS did not upregulate TLR5 gene expression in BREC. Primary BREC treated with flagellin (TLR5 ligand) had higher expression of interleukin-1ß (IL-1ß) (P < 0.05) than BREC treated with vehicle. In addition, BREC treated with IL-1ß had higher expression of antimicrobial peptides and C-X-C motif chemokine ligand 8 than BREC treated with vehicle (P < 0.05). These results suggest that ruminal TLR5 may recognize epithelial disruption via flagellin and mediate the immune response via IL-1ß during high-grain feeding or weaning.

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.

Surveillance of Antimicrobial Resistance of Escherichia coli Isolates from Intestinal Contents of Dairy and Veal Calves in the Veneto Region, Northeaster Italy.

This surveillance study aimed to estimate the proportion of antimicrobial resistant strains and antimicrobial resistance (AMR) profiles of E. coli isolates detected from the intestinal contents of veal and dairy calves in the Veneto Region, Northeaster Italy. Additionally, we investigated the differences in AMR profiles between dairy and veal calves over the period 2017-2022. Overall 1150 E. coli isolates were tested from calves exhibiting enteric disease, with 868 from dairy and 282 from veal calves. The percentage of resistant isolates to nine antimicrobials was notably higher in veal calves compared to dairy calves, except for ampicillin. Throughout the study period, we observed a significant increase in the proportion of resistant isolates to florfenicol, gentamycin, paromomycin, tetracycline and trimethoprim/sulfamethoxazole in dairy calves, while we did not detect any significant increase in the proportion of resistant isolates among veal calves. A substantial proportion (75.9%) of the isolated E. coli exhibited multi-drug resistance (MDR). The proportion of multi-drug resistant isolates was significantly higher in veal calves (91.7%) compared to dairy calves (74.3%) all through the surveillance period (2017-2022), with no significant variation in MDR proportion among veal calves between 2017 and 2022 but a significant increase among dairy calves.

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

This study aimed to evaluate the effects of direct-fed microbials (DFM) on health and growth responses of preweaning Bos indicus × Bos taurus (Gyr × Holstein) crossbred calves. Ninety newborn heifer calves (initial BW of 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 preweaning 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 its occurrence did not differ between BAC and MIX calves. No Salmonella spp. or Escherichia 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), on d 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 Clostridium 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 proportion of positive calves was also greater for BAC versus MIX on d 7. More CON calves were positive for Clostridium 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 than MIX on d 7 (50% vs. 18%), and greater for MIX than 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 and improved growth rates, while also modulating the prevalence of bacteria and protozoa in preweaning Gyr × Holstein calves.

The addition of curcumin to the diet of post-weaning dairy calves: effects on ruminal fermentation, immunological, and oxidative responses.

Incorporating Curcumin into animal diets holds significant promise for enhancing both animal health and productivity, with demonstrated positive impacts on antioxidant activity, anti-microbial responses. Therefore, this study aimed to determine whether adding Curcumin to the diet of dairy calves would influence ruminal fermentation, hematologic, immunological, oxidative, and metabolism variables. Fourteen Jersey calves were divided into a control group (GCON) and a treatment group (GTRA). The animals in the GTRA received a diet containing 65.1 mg/kg of dry matter (DM) Curcumin (74% purity) for an experimental period of 90 days. Blood samples were collected on days 0, 15, 45, and 90. Serum levels of total protein and globulins were higher in the GTRA group (P < 0.05) than the GCON group. In the GTRA group, there was a reduction in pro-inflammatory cytokines (IL-1ß and IL-6) (P < 0.05) and an increase in IL-10 (which acts on anti-inflammatory responses) (P < 0.05) when compared to the GCON. There was a significantly higher (P < 0.05) concentration of immunoglobulin A (IgA) in the serum of the GTRA than the GCON. A Treatment × Day interaction was observed for haptoglobin levels, which were higher on day 90 in animals that consumed Curcumin than the GCON (P < 0.05). The catalase and superoxide dismutase activities were significantly higher (P < 0.05) in GTRA, reducing lipid peroxidation when compared to the GCONT. Hematologic variables did not differ significantly between groups. Among the metabolic variables, only urea was higher in the GTRA group when compared to the GCON. Body weight and feed efficiency did not differ between groups (meaning the percentage of apparent digestibility of dry matter, crude protein, and acid detergent fiber (ADF) and neutral detergent fiber (NDF). There was a tendency (P = 0.09) for treatment effect and a treatment x day interaction (P = 0.05) for levels of short-chain fatty acids in rumen fluid, being lower in animals that consumed curcumin. There was a treatment vs. day interaction (P < 0.05) for the concentration of acetate in the rumen fluid (i.e., on day 45, had a reduction in acetate; on day 90, values were higher in the GTRA group when compared to the GCON). We conclude that there was no evidence in the results from this preliminary trial that Curcumin in the diet of dairy calves interfered with feed digestibility. Curcumin may have potential antioxidant, anti-inflammatory, and immune effects that may be desirable for the production system of dairy calves.

Review: Opportunities and challenges for the genetic selection of dairy calf disease traits.

Interest in dairy cow health continues to grow as we better understand health's relationship with production potential and animal welfare. Over the past decade, efforts have been made to incorporate health traits into national genetic evaluations. However, they have focused on the mature cow, with calf health largely being neglected. Diarrhoea and respiratory disease comprise the main illnesses with regard to calf health. Conventional methods to control calf disease involve early separation of calves from the dam and housing calves individually. However, public concern regarding these methods, and growing evidence that these methods may negatively impact calf development, mean the dairy industry may move away from these practices. Genetic selection may be a promising tool to address these major disease issues. In this review, we examined current literature for enhancing calf health through genetics and discussed alternative approaches to improve calf health via the use of epidemiological modelling approaches, and the potential of indirectly selecting for improved calf health through improving colostrum quality. Heritability estimates on the observed scale for diarrhoea ranged from 0.03 to 0.20, while for respiratory disease, estimates ranged from 0.02 to 0.24. The breadth in these ranges is due, at least in part, to differences in disease prevalence, population structure, data editing and models, as well as data collection practices, which should be all considered when comparing literature values. Incorporation of epidemiological theory into quantitative genetics provides an opportunity to better determine the level of genetic variation in disease traits, as it accounts for disease transmission among contemporaries. Colostrum intake is a major determinant of whether a calf develops either respiratory disease or diarrhoea. Colostrum traits have the advantage of being measured and reported on a continuous scale, which removes the issues classically associated with binary disease traits. Overall, genetic selection for improved calf health is feasible. However, to ensure the maximum response, first steps by any industry members should focus efforts on standardising recording practices and encouragement of uploading information to genetic evaluation centres through herd management software, as high-quality phenotypes are the backbone of any successful breeding programme.

A retrospective study of thermal events on the mortality rate of hutch-reared dairy calves.

Introduction: Heat stress in hutch-reared dairy calves (Bos taurus) is highly relevant due to its adverse effects on animal welfare, health, growth, and economic outcomes. This study aimed to provide arguments for protecting calves against heat stress. It was hypothesized that the thermal stress caused by high ambient temperature in summer months negatively affects the survival rate in preweaning calves. Methods: In a retrospective study, we investigated how calf mortality varied by calendar month and between thermoneutral and heat stress periods on a large-scale Hungarian dairy farm (data of 46,899 calves between 1991 and 2015). Results: The daily mortality rate was higher in the summer (8.7-11.9 deaths per 10,000 calf days) and winter months (10.7-12.5 deaths per 10,000 calf-days) than in the spring (6.8-9.2 deaths per 10,000 calf-days) and autumn months (7.1-9.5 deaths per 10,000 calf-days). The distribution of calf deaths per calendar month differed between the 0-14-day and 15-60-day age groups. The mortality risk ratio was highest in July (6.92). The mortality risk in the 0-14-day age group was twice as high in periods with a daily mean temperature above 22°C than in periods with a daily mean of 5-18°C. Conclusions: Heat stress abatement is advised in outdoor calf rearing when the mean daily temperature reaches 22°C, which, due to global warming, will be a common characteristic of summer weather in a continental region.

Multidrug-Resistant Extended-Spectrum Beta-Lactamase (ESBL)-Producing Escherichia coli in a Dairy Herd: Distribution and Antimicrobial Resistance Profiles.

This study investigated the presence, distribution, and antimicrobial resistance profiles of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli in a dairy herd located in Northern Italy. The feces of clinically healthy calves, their mothers, and the cows treated for mastitis, as well as water, environmental samples, and waste milk were collected and subjected to bacteriological culture on CHROMagarTM ESBL plates. A questionnaire was administered to identify risk factors. The isolates were identified as E. coli by MALDI-TOF MS and subjected to the double-disk synergy test (DDST) and minimal inhibitory concentration (MIC) assay. As a result, ESBL E. coli was isolated from the feces of 28 of 37 (75.67%) calves, the feces of 2 of 3 (66.67%) treated cows, 8 of 14 (57.15%) environmental samples, and waste milk. All ESBL isolates showed multiple resistances and were categorized as multidrug-resistant (MDR). Several risk factors for ESBL E. coli selection and diffusion were identified, including lack of routine cleaning of calf feeding and housing equipment, administration of waste milk to male calves, and blanket dry cow therapy. In conclusion, this study highlighted the presence of MDR, ESBL E. coli in the feces of most dairy calves, and their association with different sample sources. Accordingly, adding to the prudent use of antibiotics, the adoption of adequate farm hygiene and biosecurity measures might also help prevent the spread and transmission of ESBL E. coli within the herd.

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.

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.