Prevalence of sex-chromosome aneuploidy estimated using SNP genotype intensity information in a large population of juvenile dairy and beef cattle.

Aneuploidy is a genetic condition characterized by the loss or gain of one or more chromosomes. Aneuploidy affecting the sex chromosomes can lead to infertility in otherwise externally phenotypically normal cattle. Early identification of cattle with sex chromosomal aneuploidy is important to minimize the costs associated with rearing infertile cattle and futile breeding attempts. As most livestock breeding programs routinely genotype their breeding populations using single nucleotide polymorphism (SNP) arrays, this study aimed to assess the feasibility of integrating an aneuploidy screening tool into the existing pipelines that handle dense SNP genotype data. A further objective was to estimate the prevalence of sex chromosome aneuploidy in a population of 146,431 juvenile cattle using available genotype intensity data. Three genotype intensity statistics were used: the LogR Ratio (LRR), R-value (the sum of X and Y SNP probe intensities), and B-allele frequency (BAF) measurements. Within the female-verified population of 124,958 individuals, the estimated prevalence rate was 0.0048% for XO, 0.0350% for XXX, and 0.0004% for XXY. The prevalence of XXY in the male-verified population was 0.0870% (i.e., 18 out of 20,670 males). Cytogenetic testing was used to verify 2 of the XXX females who were still alive. The proposed approach can be readily integrated into existing genomic pipelines, serving as an efficient, large-scale screening tool for aneuploidy. Its implementation could enable the early identification of infertile animals with sex-chromosome aneuploidy.

Farmers' knowledge of Johne's disease and opinions of the Irish Johne's Control Programme: results of an online survey answered mostly by young farmers.

A voluntary control programme for Johne's disease, the Irish Johne's Control Programme (IJCP) has been implemented in Ireland since 2017. The objective of this observational study was to assess Irish beef and dairy farmers' Johne's disease knowledge, implemented management practices and IJCP opinions. A questionnaire open to dairy and beef farmers was distributed via social media and email. In total 126 responses were used for this study; these responses came from mostly young farmers (18-25 years old) and represent a small proportion of the total number of dairy and beef farmers in Ireland whose average age is 55.Most respondents claimed to know what Johne's disease was (73%; 92/126) and associated the disease to loss of body condition (68%; 78/114) and diarrhoea (59%; 67/114). Twenty-eight respondents (mostly dairy farmers; 22/28) reported positive cases in their premises. And 38% reported to implement management practices to prevent Johne's disease transmission within or into their herd (i.e. management of milk for calf consumption and isolation of Johne's test-positive or newly purchased stock; 47/124).Eighteen percent (22/125) of respondents were, at the time of questionnaire or previously, members of the IJCP. The main benefits reported by some of the participating farmers were identification of positive cases (29%; 4/14), and management of milk for calf consumption (21%; 3/14). While the main disadvantage was inaccurate testing methods (50%; 10/20). The main reasons reported for the lack of participation in the IJCP were not being aware of the programme (52%; 53/102) and not having a Johne's disease problem on the farm (48%; 49/102).In conclusion, this study suggests that while young farmers are aware of Johne's disease, their participation in the IJCP is limited and could benefit from further promotion. Studies representing the wider farming community in Ireland are warranted to gather non-biased input and contribute to Johne's disease control in Ireland.

Association between quarter-level milk somatic cell count and intramammary bacterial infection in late-lactation Irish grazing dairy cows.

The objectives of our study were to describe quarter-level prevalence of intrammamary infection (IMI), to evaluate the performance of commonly used somatic cell count (SCC) thresholds for the diagnosis of quarter-level IMI, and to determine those with maximized sensitivity (Se) and specificity (Sp) for identifying quarter-level IMI as defined by positive aerobic culture in late-lactation grazing dairy cows. In this observational study, quarter milk samples were collected from all cows in 21 commercial spring-calving, pasture-based Irish dairy herds. Total SCC determination and aerobic bacterial culture were performed in 8,177 quarter milk samples obtained between 238 and 268 d in milk from 465 primiparous and 1,609 multiparous cows. The Se and Sp of SCC thresholds used for diagnosis of IMI were evaluated against the gold standard aerobic culture separately for all, primiparous, and multiparous cows. The overall prevalence of bacteriologically infected quarters was 6.3%, and it was higher among primiparous (11.3%) than multiparous cows (5.5%). However, considering all samples, quarter-level SCC was higher for multiparous than for primiparous cows (195,250 ± 21,422 vs. 115,940 ± 26,260 cells/mL). Associated Se and Sp for the 200,000 cells/mL threshold were 59.2% and 88.0% for all, 52.7% and 95.4% for primiparous, and 62.9% and 85.9% for multiparous cows, respectively. Receiver operating characteristic curve analyses determined the thresholds that optimized the Se and Sp of a positive bacterial culture: 101,000 cells/mL for all cows [Se = 80.0%; Sp = 76.4%; area under the curve (AUC) = 0.84], 61,000 cells/mL for primiparous (Se = 87.1%; Sp = 84.0%; AUC = 0.90), and 101,000 cells/mL for multiparous (Se = 80.9%; Sp = 72.6%; AUC = 0.83). The results indicate that the 200,000 cells/mL threshold was inefficient in identifying late-lactation quarter-level IMI (low Se) in the studied herds where the main etiological agent was Staphylococcus aureus. Suggested quarter-level SCC thresholds have the potential of serving as a supporting tool for dry cow therapy decisions and warrant further study in late-lactation cows from spring-calving, pasture-based herds with S. aureus as the main pathogen causing IMI.

Negative dietary cation-anion difference in prepartum dairy cow diets: a pragmatic study in two commercial dairy farms.

Pragmatic studies, evaluating the effectiveness of an intervention under its usual conditions, are less commonly reported than the explanatory trials. For instance, the effectiveness of prepartum negative dietary cation-anion difference (DCAD) diets on inducing a compensated metabolic acidosis that promotes a higher blood Ca concentration at calving has not been frequently described under commercial farm management conditions without researchers' interference. Thus, the objectives were to study cows under commercial farm management conditions to (1) describe the daily close-up dairy cows' urine pH and fed DCAD, and (2) evaluate the association between urine pH and fed DCAD, and preceding urine pH and blood Ca at calving. A total of 129 close-up Jersey cows about to commence their ≥2nd lactation were enrolled in the study after 7 days of exposure to DCAD diets in two commercial dairy herds. Urine pH was determined daily from mid-stream urine samples from enrollment to calving. Fed DCAD was determined from feed bunk samples obtained during 29 (Herd 1) and 23 (Herd 2) consecutive days. Plasma Ca concentration was determined within 12 h after calving. Descriptive statistics were generated at the herd- and cow-level. Multiple linear regression was used to evaluate the associations between urine pH and fed DCAD for each herd, and preceding urine pH and plasma Ca concentration at calving for both herds. At herd-level, the average urine pH and CV during the study period were 6.1 and 12.0% (Herd 1) and 5.9 and 10.9% (Herd 2), respectively. At the cow-level, the average urine pH and CV during the study period were 6.1 and 10.3% (Herd 1) and 6.1 and 12.3% (Herd 2), respectively. During the study period, fed DCAD averages were -121.3 and -165.7 mEq/kg of DM and CV 22.8 and 60.6% for Herd 1 and Herd 2, respectively. No evidence of association between cows' urine pH and fed DCAD was observed in Herd 1, whereas a quadratic association was observed in Herd 2. When both herds were combined, a quadratic association was observed between the urine pH intercept (at calving) and plasma Ca concentration. Although average urine pH and fed DCAD were within recommended ranges, the high variability observed indicates that acidification and fed DCAD are not constant, and often outside the recommended ranges in commercial settings. Monitoring of DCAD programs is warranted to ensure their effectiveness under commercial settings.

Production and reproduction responses for dairy cattle supplemented with oral calcium bolus after calving: Systematic review and meta-analysis.

Among the commonly implemented strategies developed to support calcium (Ca) metabolism postpartum, oral Ca supplementation is within the most studied. However, research shows varying responses to treatment in regard to production and reproduction. Our objectives were (1) to identify and synthesize the literature evaluating the associations between postpartum oral Ca supplementation as bolus and milk yield and risk of pregnancy to first service using a systematic review, and (2) to quantify these associations using meta-analytical methods. Nine relevant studies published between January 2010 and September 2021 were identified after systematic search of 4 databases (Biosis, CAB Abstracts, Medline, Scopus). The studies were conducted in commercial confined and grazing farms. Eight of the 9 studies reported feeding low to negative dietary cation-anion difference diets prepartum. Oral Ca bolus supplementation strategies varied among studies but were predominantly centered on the first 24 h postpartum. Milk yield and pregnancy to first service were evaluated in 9 and 6 of the studies, respectively. Other productive (energy-corrected milk yield, peak milk yield, or fat and protein concentrations) and reproductive (estrus cyclicity, days from calving to first service, or pregnancy by 150 or 210 days in milk) outcomes were evaluated in 4 of the studies. The meta-analyses revealed a lack of evidence for associations between prophylactic blanket postpartum oral Ca bolus supplementation and milk yield (including 8 studies) or risk of pregnancy to first service (including 6 studies). Some of the evaluated studies reported statistically significant associations after data stratification. However, not enough studies reported estimates for the evaluated conditional factors to perform a meta-analysis among the identified subgroups. In conclusion, future research should study and report the production, reproduction, and health estimates of cow-level conditional factors of interest for the evaluated response, and investigate alternative regimes of oral Ca bolus supplementation.

Dynamics of serum immunoglobulin G and total protein concentrations in dairy calves during the first 2 weeks of life.

The aim of the present study was to describe the dynamics of serum IgG (determined with radial immunodiffusion) and total protein (TP; determined with refractometry) concentrations during the first 16 d of life. Secondary objectives were to evaluate the transfer of passive immunity (TPI) classification at d 1 of life as a conditional factor for the aforementioned dynamics, and to describe over time changes on calves' TPI classification. At a commercial raising operation, 36 calves (19 Holstein, 17 Jersey) were sampled immediately after arrival (d 1) and at d 4, 8, 12 and 16 of life, for serum IgG and TP concentration, and hematocrit determination (HCT). Transfer of passive immunity was categorized based on serum IgG (IgG-Poor: IgG <18 g/L; IgG-Good: IgG 18 to <25 g/L; IgG-Excellent: IgG ≥25 g/L) and TP concentrations (TP-Poor: <5.8 g/dL; TP-Good: 5.8 to <6.2 g/dL; TP-Excellent: ≥6.2 g/dL). Multiple linear regression was used to evaluate serum IgG and TP changes over time, considering the effects of time after birth, breed, HCT, and TPI classification at d 1 of life. At d 1, median serum IgG and TP concentrations were 29.9 g/L and 6.3 g/dL, respectively (interquartile ranges: 21.3-42.3 g/L and 5.6-6.7 g/dL, respectively). Dynamics of serum IgG and TP concentrations were conditional to TPI at d 1 of life. Serum IgG concentration declined over time for IgG-Excellent and IgG-Good calves (18.1 and 4.6 g/L, respectively), but remained constant for IgG-Poor calves. Serum TP concentration declined over time in the 3 TPI groups but it was more marked for TP-Excellent (27%) and TP-Good (19%) than for TP-Poor (14%) calves. At d 1, 83.3% of the calves were classified as IgG-Excellent or IgG-Good, whereas 77.8, 55.6, 41.7, and 58.3% of calves were classified within these categories at d 4, 8, 12, and 16 of life, respectively. Similarly, at d 1, 66.7% of calves were classified as TP-Excellent or TP-Good, whereas 47.2, 36.1, 25.0, and 2.8% were classified within these categories at d 4, 8, 12, and 16 of life, respectively. In summary, our results indicate that serum IgG and TP concentrations decline over 16 d of life, and the decline is associated with TPI classification at d 1 of life. Further studies are needed to determine the biological implications of serum IgG and TP decline after d 1 of life, and to elucidate the factors determining the different dynamics. Our results suggest that current thresholds for TPI classification should be interpreted carefully when the age of calves is unknown or outside the age range used to define those thresholds (>24 h to 7 d).

Effects of rumen-native microbial feed supplementation on milk yield, composition, and feed efficiency in lactating dairy cows.

The objective of this study was to evaluate the effects of two rumen-native microbial feed supplements (MFS) on milk production, milk composition, and feed efficiency. A total of 90 multiparous cows between 40 and 60 d in milk were enrolled in a randomized block design study. Within each block (baseline milk yield), cows were randomly assigned to: control (no microbial feed supplementation), MFS1 (0.33 g/kg total mixed ration [TMR] of an MFS containing a minimum of Clostridium beijerinckii at 2 × 106 CFU/g and Pichia kudriavzevii at 2 × 107 CFU/g), or MFS2 (0.33 g/kg TMR of a MFS containing a minimum of C. beijerinckii at 2 × 106 CFU/g, P. kudriavzevii at 2 × 107 CFU/g, Ruminococcus bovis at 2 × 107 CFU/g, and Butyrivibrio fibrisolvens at 2 × 107 CFU/g). Cows were housed in a single group and fed the study diets ad libitum for 270 d. Individual milk yield was recorded using electronic milk meters, and milk fat and protein were measured using optical in-line analyzers at each of two daily milkings. Treatment and treatment by time effects were assessed through multiple linear regression analyses. Treatment effects were observed for milk and energy-corrected milk (ECM) yields, milk fat and protein yields and concentrations, dry matter intake (DMI), and feed efficiency; those effects were conditional to time for milk yield, DMI, and feed efficiency. Overall, milk, ECM, fat, and protein yields were higher for MFS2 compared with control cows (+3.0, 3.7, 0.12, and 0.12 kg/d, respectively). Compared with MFS1, milk yield was higher and protein yield tended to be higher for MFS2 cows (+2.9 and 0.09 kg/d, respectively). In contrast, MFS1 cows produced 0.17 and 0.08 units of percentage per day more fat and protein than MFS2 cows, and 0.07 units of percentage per day more protein than control cows. Dry matter intake and feed efficiency were higher for MFS2 cows compared with MFS1 cows (+1.3 kg/d and 0.06, respectively), and feed efficiency was higher for MFS2 cows compared with control cows (+0.04). Where observed, treatment by time effects suggest that the effects of MFS2 were more evident as time progressed after supplementation was initiated. No effects of microbial supplementation were observed on body weight, body condition score, somatic cell count, or clinical mastitis case incidence. In conclusion, the supplementation of MFS2 effectively improved economically important outcomes such as milk yield, solids, and feed efficiency.

This study evaluates the effects of two rumen-native microbial feed supplements (MFS) on milk yield, composition, and feed efficiency in lactating dairy cows. Ninety multiparous Holstein cows between 40 and 60 d in milk were assigned to control (no microbial feed supplementation), MFS1 (Clostridium beijerinckii and Pichia kudriavzevii), or MFS2 (C. beijerinckii, P. kudriavzevii, Ruminococcus bovis, and Butyrivibrio fibrisolvens) total mixed ration supplementation. Overall, MFS2 cows had higher milk and milk component yields than control and MFS1, while MFS1 cows had higher milk component concentrations than control and MFS2. Feed efficiency was higher for MFS2 compared with control and MFS1 cows. Microbial feed supplementation improved economically important outcomes such as milk yield, solids, and feed efficiency.

Association of low serum calcium concentration after calving with productive and reproductive performance in multiparous Jersey cows.

Consequences of postpartum low blood calcium (Ca) concentration are still under study and literature describing this condition in Jersey cows is scarce. A prospective cohort study was conducted to evaluate the association of low serum Ca concentration shortly after calving with milk and energy-corrected milk yields, somatic cell count linear score, and pregnancy to first service and within 150 d in milk in multiparous Jersey cows from 2 commercial herds. Blood samples for serum Ca determination were collected on average at 3 h 10 min postpartum from 352 multiparous Jersey cows. Productive data up to the 10th monthly test were obtained from the Dairy Herd Improvement Association and reproductive data were obtained from herd records. Multiple linear, log-binomial, and Cox's proportional hazards regressions were used to evaluate the association of low serum Ca concentration with productive and reproductive outcomes. Serum Ca concentration ≤2.18 mmol/L was associated with 1.43 and 1.85 kg/d more milk and energy-corrected milk. However, lower serum Ca concentrations were associated with a 0.28-unit-higher somatic cell count linear score per monthly test (Ca ≤2.00 mmol/L), and decreased pregnancy risk at first service (risk ratio = 0.64; Ca ≤1.94 mmol/L) and hazard of pregnancy within 150 d in milk (hazard ratio = 0.40; Ca ≤1.90 mmol/L). The present study is based on a convenience sample of multiparous Jersey cows from 2 commercial herds; further research including more herds and additional blood Ca determinations is needed to describe postpartum blood Ca dynamics and its association with productive and reproductive outcomes for the Jersey breed.

Effects of postpartum oral calcium supplementation on milk yield, milk composition, and reproduction in multiparous Jersey and Jersey × Holstein crossbreed cows.

The objective of the present study was to evaluate the effects of postpartum oral calcium supplementation on milk yield, energy-corrected milk yield, milk fat concentration, milk protein concentration, and somatic cell count linear score across the first 3 monthly tests postpartum, peak milk yield, risk of pregnancy at first service, and hazard of pregnancy by 150 d in milk on 1,129 multiparous Jersey and Jersey × Holstein crossbreed cows from 2 commercial dairies. After calving, cows were systematically assigned to control (no oral calcium supplementation; n = 567) or oral calcium supplementation at 0 and 1 d in milk (oral Ca; 50 to 60 g of calcium as boluses; n = 562). Monthly test milk yield, composition, and somatic cell count information was obtained from the Dairy Herd Improvement Association. Herd records were used for reproductive data. Statistical analysis was conducted using generalized multiple linear, Poisson, and Cox's hazard regressions. Treatment effects were evaluated considering cow-level information available at parturition (parity, breed, previous lactation milk yield, previous lactation length, dry period length, gestation length, body condition, and locomotion score at calving, calving ease, and calf sex). In addition, for a subset of cows serum calcium concentration before treatment administration was evaluated (n = 756). Overall, oral calcium supplementation did not affect the evaluated productive and reproductive variables. However, effects conditional to previous lactation length and calving locomotion score were observed. Milk yield and energy-corrected milk yield across the first 3 monthly tests were 1.8 kg/d higher for supplemented cows with a previous lactation length within the fourth quartile, compared with control cows on the same quartile. Energy-corrected milk yield tended to be 1.1 kg/d lower for supplemented cows with a previous lactation length within the first quartile, compared with control counterparts. Peak milk yield tended to be 1.6 kg higher for supplemented cows with a calving locomotion score ≥2, compared with control cows with the same locomotion score. Treatment effects were not conditional to serum calcium concentration before treatment administration. Our results suggest that postpartum oral calcium supplementation effects are conditional to cow-level factors such as previous lactation length and calving locomotion score in multiparous Jersey and Jersey × Holstein crossbreed cows.