Journal of Dairy Science最新文献

Heat stress compromises the growth, health, and welfare of dairy heifers from an early age. With the rising frequency of summer heat-stress days, innovative and effective mitigation strategies are increasingly needed. This study evaluated the effects of continuous active ventilation on thermo-physiological responses and hutch microclimate in outdoor-housed dairy heifers during a continental summer (June to August, average temperature-humidity index = 71 ± 7.6). Holstein heifers (n = 32) were enrolled at birth and sequentially assigned to passive (PASS; rear window opened ∼20 degrees, and vents opened 50%) or active (ACT; solar-powered fan redirecting airflow via a custom opening in the hutch rear window, and rear vents open at 50%) ventilation. Fans operated continuously from 3 to 28 d of age, then were turned off. Heifers were monitored until 56 d, corresponding to 1-wk postweaning. During the ventilation treatment period, all heifers were restricted using fencing to 1 h outside (unshaded) and 1 h inside their respective hutches between 1100 and 1300 h 3 times per week. After each restriction, rectal temperature (RT), sweating rate (SR; measured at the neck and rump), skin temperature (ST; measured at the neck and rump), and the difference between "outdoor" and "indoor" values were analyzed. Hutch air speed (AS), particulate matter, formaldehyde, and ammonia levels were monitored inside the hutch. Calf BW and stature were recorded at 7, 14, 21, and 28 d (during ventilation treatment period) and at d 42 and 56 (postventilation period). Airborne bacterial counts inside hutches were assessed before occupancy and on d 28. Health scores and lung ultrasounds were conducted at age-dependent frequencies throughout the study. The ACT hutches had higher internal AS than PASS (1.11 vs. 0.07 ± 0.02 m/s). Both groups showed reductions in SR, ST, and RT after re-entering the hutch, but ACT hutches led to greater reductions in heifers' thermal indices. Ventilation type had no effect on health. Growth parameters, grain intake, and feed efficiency were similar between groups during the ventilation period, but ACT heifers were 4 and 5.5 kg lighter at d 42 and 56, respectively. Although the time spent inside the hutches during the day (regardless of age) was similar between ventilation groups, ACT heifers spent more time lying down when outside the hutch. By d 28, ACT hutches tended to have lower ammonia, formaldehyde, and decreased airborne bacteria (3,466 vs. 29,800 cfu/m³). Providing active ventilation improved the internal microclimate of the hutch and heifer thermoregulation. Additional research is warranted to determine the value of extended ventilation beyond 28 d during persistent hot weather.

In September 2023, bluetongue virus serotype 3 (BTV-3) emerged in the Netherlands for the first time. To be prepared for a potential resurgence in 2024, a study was performed during early spring 2024, considered as a low-risk period, to estimate the prevalence of BTV-3 and identify associated risk factors in Dutch dairy cattle. Between December 2023 and April 2024, bulk tank milk (BTM) samples from 12,756 dairy herds were tested to estimate the herd-level and within-herd antibody prevalence. Additionally, an online survey was distributed to participating farmers to collect farm management information from 2023. Animal movement data were obtained from the national identification and registration database. Multivariable logistic regression was performed to quantify associations between potential risk factors and the probability of BTV-3 infection. Herd-level prevalence was 64% (95% CI: 63%-65%). Assuming that BTM test results provide a reliable indication of within-herd prevalence, the expected within-herd prevalence was 36% (95% CI: 35%-37%) in antibody-positive herds. Using BTM as a proxy for within-herd prevalence, the nationwide cow-level prevalence was estimated at 19% (95% CI: 19%-20%). For 5,253 dairy herds, both prevalence data and survey data were available. Factors associated with a lower odds of the presence of BTV-3 antibodies in bulk milk included the presence of large ventilation openings and use of mechanical ventilation while cattle were housed indoors. Factors associated with higher odds included grazing (both limited and longer periods), introduction of cattle from BTV-3 high-risk areas, presence of sheep on the farm, and the month of first BTV notification in the herd's postal code area. No association was found between the use of insecticides and the presence of antibodies. This study shows that although the herd level prevalence after the first BTV-3 epidemic season was substantial, cow-level prevalence at the national level was still relatively low, leaving a large population of cattle susceptible for BTV-3 in 2024. In addition, several management factors were identified, which inform preventive strategies to reduce the risk and the impact of future BTV-3 infections in dairy herds.

Consumer preference for Cheddar cheese is influenced by its aroma characteristics, with aroma serving as a key sensory attribute determining consumer acceptance. This study innovatively integrates qualitative descriptive analysis (QDA) with electronic nose (e-nose) technology to systematically characterize the flavor profiles of 27 common Cheddar cheeses available in the Chinese market. We evaluated 6 odor attributes of cheese using QDA and rapid capture of volatile flavor compounds by e-nose. Using the obtained QDA and e-nose datasets, 4 machine learning algorithms, namely, logistic regression, Gaussian support vector machine, k-nearest neighbors, and decision tree, were used to classify and predict the preference of Chinese consumers for Cheddar cheese. The study recruited 152 consumers, who categorized their preferences into "like," "neutral," and "dislike" based on preference intensity. Principal component analysis revealed that the first 2 principal components of the QDA and e-nose data cumulatively explained 58.5% and 84.3% of the total variance, respectively. When using the full feature set, the classification accuracies of the 4 machine learning models were 87.5%, 87.5%, 75.0%, and 81.2%, respectively. After feature optimization (excluding QDA indicators), model performance significantly improved, achieving accuracies of 87.5%, 92.9%, 87.5%, and 92.9%, respectively. This study confirms the effectiveness and application potential of combining sensory omics with machine learning methods in predicting cheese consumption preferences. It provides key technical support for the precise development of cheese products tailored to Chinese consumers' flavor preferences and holds significant practical implications for implementing flavor-directed regulation in the dairy industry.

The objective of this meta-analysis was to evaluate the association of estrus detection within the voluntary waiting period (VWP) using automated activity monitoring (AAM) systems with reproductive performance in lactating Holstein cows. A comprehensive literature search was conducted in PubMed, ScienceDirect and Google Scholar using specific search terms. Inclusion criteria focused on studies that assessed estrus detection within the VWP using AAM systems. Six manuscripts involving 8,621 cows were included. Reproductive outcomes of interest were: (1) the proportion of cows inseminated at first service upon estrus detection detected by an AAM system; (2) pregnancy per artificial insemination (AI) at first service; (3) the proportion of cows pregnant within 150 DIM. Cows were classified based on the number of automated estrus alerts (AEA) within the VWP into 2 groups: (1) no estrus alert (EstrusNo); (2) at least one estrus alert (EstrusYes). Statistical analyses were conducted using MedCalc, incorporating 7 experimental groups from the selected manuscripts. The overall proportion of cows without estrus detection within the VWP was 36.6% (95% CI: 24.4%-49.8%). Cows (n = 5,093) in the EstrusYes group had greater odds for receiving AI upon estrous detection at first service (odds ratio [OR] = 3.36; 95% CI 2.32-4.88) compared with cows (n = 2,631) in the EstrusNo group. Cows (n = 5,577) with estrus detection within the VWP had greater odds for conceiving at first service (OR = 1.59; 95% CI 1.27-1.98) compared with cows (n = 2,793) without estrus detection within the VWP. Cows (n = 5,637) with estrus detection within the VWP had greater odds for pregnancy within 150 DIM (OR = 1.75; 95% CI 1.54-1.99) compared with cows (n = 2,815) without estrus detection within the VWP. There was substantial heterogeneity among the experimental groups, except for the effect of estrus detection within the VWP on pregnancy within 150 DIM. In summary, cows with no AEA within the VWP cows had inferior reproductive performance compared with cows with AEA. Therefore, estrus detected by AAM systems within the VWP is an important predictor of reproductive performance.

The interpretation of milk pregnancy-associated glycoproteins (PAG) ELISA tests can potentially be improved by understanding the variations in PAG levels throughout gestation. We hypothesized that milk yield (MY) on test day has a meaningful effect on these variations, but that other factors may influence this relationship. The objective of our study was to investigate and quantify the interactions between test-day MY and parity and breed, considering the known fluctuations in PAG levels as a function of the number of days in pregnancy (DIP). Milk samples (n = 272,042) submitted to the Lactanet (Canadian Network for Dairy Excellence, Canadian DHIA program) laboratory from 2013 to 2021 for pregnancy testing using a commercial PAG ELISA test, conducted between 25 and 210 DIP, were compared with records of insemination and calving dates to identify pregnant cows at testing. Only cows with a confirmed calving were included and a multivariable model was built with PAG ELISA value as the outcome variable and DIP, MY at testing, parity, breed, and their interactions included as fixed-effect independent variables. To account for variability at the herd and cow levels, the herd and cow identification variables were incorporated as random effects. Pregnancy-associated glycoprotein fluctuations relative to DIP were consistently observed at all levels of these variables. High-yielding, multiparous, and Holstein cows exhibited lower milk PAG levels. Even at the same threshold of MY, multiparous cows had lower PAG levels compared with primiparous cows, and Holstein cows had lower PAG levels compared with Jersey and Ayrshire cows, particularly in early gestation, thus confirming the age and breed effects beyond their associations with MY. Lesser milk PAG levels in multiparous and Holstein cows can be partially, but not entirely, attributed to their higher MY. Beyond MY, parity and breed help further explain PAG variations through gestation. Although these variables effects are unlikely to misclassify pregnancy under most conditions, accounting for them may improve the interpretation of pregnancy diagnosis with this test.

Livestock methane emissions contribute to 18% of global greenhouse gas emissions. Integrating methane production into breeding goals has the potential to mitigate methane emissions and contribute to more sustainable livestock systems. To achieve this through genetic selection, large datasets of phenotypic records are required, making the use of direct measurement of methane emissions limited on a broad scale. Consequently, alternative approaches, such as using predicted methane emissions derived from more easily measured traits, have been proposed. The objective of this study was to estimate the genetic parameters of weekly average milk mid-infrared-predicted methane production (PCH₄) and its genetic correlation with milk yield (MY), fat yield (FY), and protein yield (PY) in Canadian Holstein dairy cows. We analyzed a total of 37,202 PCH₄ records and corresponding test-day records for MY, FY, and PY collected between 119 and 179 DIM from 18,505 first-lactation Canadian Holstein cows distributed over 100 herds. Several statistical models were evaluated to estimate the genetic parameters of PCH₄. These included a single-trait model and 3 separate 2-trait random regression models that employed fifth-degree Legendre polynomials on weeks of lactation. The estimated heritability of PCH₄ ranged from 0.37 (SE = 0.06) to 0.45 (SE = 0.02), indicating a moderate genetic influence on predicted methane production. The genetic correlations between PCH₄ and test-day MY, FY, and PY ranged from -0.23 (SE = 0.06) to -0.13 (SE = 0.06), 0.3 (SE = 0.06) to 0.48 (SE = 0.08), -0.17 (SE = 0.07) to -0.09 (SE = 0.06), respectively, suggesting low to moderate associations between PCH₄ and the production traits. These results suggest that PCH₄ is moderately heritable and can be used for genetic selection to mitigate methane emissions in dairy cows. However, the positive unfavorable genetic correlation with FY should be considered when selecting animals for lower PCH₄ to avoid potential negative impacts on fat yield. These findings contribute to the ongoing efforts to improve the environmental sustainability of the livestock industry while maintaining productivity.

Reproductive efficiency is critical to the profitability and productivity of dairy farms. However, reproductive traits have often been overlooked in favor of enhancing milk production, resulting in unintended genetic antagonism. This study focused on estimating genetic parameters and genetic trends for economically important reproductive traits which include conception rate (CR), days open (DO), age at first calving (AFC), number of services per conception (NS), and calving interval (CInt), using 33,203 records of Holstein cattle that were under intensive management in Shandong Province, China. We employed univariate (heritability estimate) and multivariate (correlation) analyses that integrated phenotypes with the pedigree data spanning 5 generations. The results demonstrated low heritability estimates for reproductive traits, ranging from 0.043 to 0.159, highlighting a limited additive genetic influence but suggesting the possibility of genetic improvement through genomic selection. Among the traits evaluated, AFC demonstrated the highest heritability (0.159) in cows, whereas the lowest values (0.043 and 0.044) were observed for NS and CR, respectively. Strong genetic correlations were observed among the reproductive traits. Conception rate showed a strong and antagonistic genetic correlation with NS (-0.79). Phenotypic correlations reflected the same pattern, with CR and NS exhibiting strong negative correlations (-0.91). The analysis of EBV over time revealed gradual genetic advancements in CInt, DO, and CR, although the progress was inconsistent. These gradual and inconsistent gains suggest that the longstanding emphasis on milk traits may have compromised efforts to improve reproductive performance. Therefore, more focused and sustained genetic selection efforts targeting reproductive characteristics are essential to achieve substantial genetic gains. Future breeding programs that integrate these parameters could enhance fertility traits in Holstein cows in China.

Reliability (REL) is a metric used to assess how accurately breeding values are predicted. Calculating theoretical REL requires the prediction error variance from the inverse of the coefficient matrix of the mixed model equations, which is computationally intensive for large populations or complex models. In such cases, REL are approximated. In routine genetic evaluations it is not feasible to evaluate animals received between evaluation cycles. As an interim solution, these individuals would rely on indirect predictions (IP) based on SNP effects, and their associated reliability approximated based on the variance of estimated SNP effects. This study aimed to approximate IP reliabilities when SNP effects are estimated from multi- and single-breed single-step genomic evaluations. Two reliability approximations were compared: 1) REL_IP, based on an approximated prediction error covariance (PEC) of estimated SNP effects, and 2) REL_GEBV, a benchmark REL calculated in routine genetic evaluations. In the multibreed analysis, the regression slope of REL_GEBV on REL_IP was ~1, and the intercept was equal to zero for Holstein (HO). For Jersey (JE), slopes were 0.60 (males) and 0.78 (females), and intercepts were 0.32 (males) and 0.15 (females). For Brown Swiss (BS), slopes were 0.88 (males) and 0.82 (females), and intercepts were 0.03 (males) and 0.08 (females). Correlations between both reliabilities were higher than 0.96 for HO and BS, 0.79 (males) and 0.69 (females) for JE. In the single-breed analysis, JE showed no dispersion issues, with slopes of 1 and intercepts of zero, and correlations equal to 0.99 for both sexes. For BS, reliabilities were slightly under-dispersed, with slopes of 1.14 (males) and 1.08 (females). Additionally, single-breed evaluations yielded more consistent reliability averages within each breed. In contrast, multibreed evaluation showed that dominant breeds disproportionately influenced reliability estimates of smaller breeds, highlighting the importance of approximating the PEC within-breed to avoid biased reliability estimates.

The maternal environment during gestation influences fetal development, with long-lasting effects on postnatal health and productivity. This study evaluated the effect of prenatal heat stress (PNHS) on blood DNA methylation of dairy calves immediately after birth and whether such modifications persist into early life. Holstein calves were born to dams exposed to either PNHS (n = 36, temperature-humidity index >68, access to shade of a freestall barn) or prenatal cooling (PNTN; n = 37, access to shade and evaporative cooling) during the last 54 ± 5 d of gestation. Whole-genome enzymatic DNA methyl sequencing was performed on blood samples collected at birth (d 0; n = 3 PNHS, n = 5 PNTN) and 1 wk post-weaning (d 63 of age; n = 8 PNHS, n = 8 PNTN). From birth onward, all calves were actively cooled and managed under the same conditions. At birth, 682,898 differentially methylated cytosines (DMC) were identified genome-wide. Principal component analysis using 55,304 DMC located in genes expressed in blood cells revealed a clear clustering by prenatal treatment. However, at weaning, clear clustering by treatment was no longer observed using 23,977 treatment-associated DMC in blood-expressed genes, despite 97,289 DMC persisting genome-wide from birth to weaning. Immune cell deconvolution showed only minor differences in granulocytes (d 0) and CD4/CD8⁺ T cell proportions (d 63), suggesting methylation changes were not driven by cell-type composition. Gene ontology analysis identified more than 30 enriched pathways at each time point, mainly related to immunity, inflammation, and metabolism. Several differentially methylated genes (e.g., NMI, DUSP6, CD38, VPS37B) were common to both time points, suggesting persistent programming. Despite attenuation of global differences at weaning, a subset of 500 highly discriminant DMC remained informative for treatment separation. Blood-based methylation signatures could serve as early biomarkers of prenatal heat stress exposure and guide management and selection strategies to improve calf resilience.