Journal of Dairy Science最新文献

{"title":"A synthetic analog of the bovine-appeasing pheromone facilitates adaptive responses during disease in dairy calves.","authors":"J Garcia-Alvarez, E Descout, A Cozzi, S M Rutter, A Beaver","doi":"10.3168/jds.2025-26759","DOIUrl":"https://doi.org/10.3168/jds.2025-26759","url":null,"abstract":"<p><p>Gastrointestinal and respiratory infections are the main cause of morbidity and mortality in the first months of life in young dairy calves, with an important negative effect on animal welfare and production. Appeasing pheromones act through olfactory pathways to influence stress-related physiological and behavioral responses in mammals and have shown promising results in a variety of domestic animals. A synthetic analog of the bovine-appeasing pheromone (BAP) has been observed to reduce veterinary costs in dairy calves and modulate the clinical expression of respiratory illness, potentially influencing the timing of symptom presentation and immune response in beef calves and young bulls. The objectives of this study were to observe the influence of BAP on disease incidence and recovery in dairy calves, and on physiological and behavioral stress responses during naturally occurring disease episodes. In the present randomized controlled trial, 72 female Holstein Friesian dairy calves were randomly allocated to receive BAP or a placebo once every 2 wk from birth to 4 wk after milk weaning. Clinical disease affected 33 calves, across a total of 44 recorded illness episodes (24 in the BAP group and 20 in the placebo group; no significant difference between groups). Conditions included gastrointestinal infections, respiratory infections, navel infections, and other clinical symptoms such as fever and lameness. It was hypothesized that diseased dairy calves in the BAP treatment would display fewer signs of stress compared with calves receiving the placebo and their recovery would be faster. Calves were equipped with triaxial accelerometers on the hind leg postnatally, and their activity levels were observed throughout the trial. Data on live weight gain was also obtained, and calves were fitted with heart rate monitors every week for at least 24 h to assess heart rate variability (HRV). During periods of disease, BAP was associated with a reduction in the activation of the neuroendocrine system as evidenced by higher HRV parameters, including increased standard deviation of beat to beat of normal sinus beats (SDNN) and root mean squares of successive differences (RMSSD). Calves in the BAP group also displayed a faster recovery of their activity levels and HRV parameters compared with the placebo group. These results suggest a potential welfare benefit of the use of BAP during bouts of sickness.</p>","PeriodicalId":354,"journal":{"name":"Journal of Dairy Science","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145273240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Investigation of seasonal microbiome changes in raw milk between conventional and organic farming practices.","authors":"Daria Van De Grift, Eiseul Kim, Seung-Min Yang, Alyssa Thibodeau, Jenifer Cruickshank, Lisbeth Goddik, Si Hong Park","doi":"10.3168/jds.2025-26743","DOIUrl":"https://doi.org/10.3168/jds.2025-26743","url":null,"abstract":"<p><p>Raw milk microbiota is influenced by farming practices, environmental exposure, and seasonal changes. This study investigated how organic and conventional dairy farming practices influence the microbial composition of raw milk over a 1-yr period. Milk and environmental samples were collected quarterly from 7 dairy farms (4 organic and 3 conventional) in Oregon and analyzed using microbiome sequencing. Across all seasons, the microbial community of raw milk was largely similar between organic and conventional farms, with Escherichia-Shigella being the most abundant genus. Aerobic plate counts were significantly higher in conventional raw milk during winter and summer. Organic milk showed greater seasonal variation in α diversity (Shannon index 1.81 ± 0.40 in winter to 1.01 ± 0.34 in fall), whereas conventional milk remained more stable. No significant β diversity differences were observed between farming types. Shared microbial taxa between raw milk and environmental sources varied by season and farming type, reflecting the influence of confinement and grazing. For example, Romboutsia was more abundant during grazing seasons in organic farms, whereas Clostridium sensu stricto 1 appeared uniquely in conventional milk in winter. These seasonal and housing-related trends highlight how farm management shapes milk microbiota.</p>","PeriodicalId":354,"journal":{"name":"Journal of Dairy Science","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145273288","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"INVITED REVIEW: Animal welfare in pasture-based dairy systems-A systematic scoping review to identify progress, priorities, and future directions.","authors":"M Verdon, L Field, K Schütz, R Bryant","doi":"10.3168/jds.2025-26981","DOIUrl":"https://doi.org/10.3168/jds.2025-26981","url":null,"abstract":"<p><p>This systematic review examines the past and present focus of welfare research in pastoral dairy production systems and uses these insights to suggest future research priorities. We included original research articles published between 2000 and 2024 that studied dairy cows, weaned youngstock or preweaning calves in pastoral dairy systems and reporting on animal welfare outcomes. Review articles were excluded. Three thousand peer-reviewed manuscripts written in English were screened for inclusion. The 678 eligible articles extracted were categorized by welfare domain using the Five Domains framework (i.e., nutrition, health, environment, behavior, and mental state) and inductively assigned up to 5 descriptive key words to reflect the main welfare issue(s) addressed. Welfare research output increased from 19 to 60 publications per year over the past (2000-2019) to present periods (2020-2024), respectively. Most studies (74.0%) focused on cows, with fewer publications on the calf and weaned youngstock. Across all cattle classes and years, health was the most represented welfare domain, addressed by 69% of calf, 54% of youngstock, and 53% of cow studies, whereas the mental state domain was addressed in less than 1% of research. The article key words were used to assess changes in welfare focus topics over time. From 2000 to 2019, 34 calf welfare topics were identified, with research primarily focusing on colostrum management and passive immunity (21%). Presently (2020-2024), of the 42 topics published on the calf, extended suckling systems (19%) dominate (i.e., systems providing extended cow-calf contact). For weaned youngstock, 33 topics were published between 2000 and 2019, and parasitism was a key welfare theme. The present youngstock research continues to focus on parasite control (19% of studies covering 31 topics). Past research on cow welfare (94 topics) concentrated on pasture access and lameness. In recent years, 106 different topics have been covered by the cow literature. Of these, emerging technologies, such as virtual fencing and automated health monitoring, represent the most studied topics (14%), closely followed by pasture access (13%). Future research should increase focus on calves and youngstock, particularly in relation to environment, nutrition, behavior, and their effects on mental state. Extended suckling systems warrant continued attention. Longitudinal studies exploring how early-life environments shape heifer resilience and adaptability are encouraged. Addressing climate-related challenges while preserving the welfare benefits of pasture access is critical. Progress will require ongoing collaboration between science and industry, balancing immediate needs with investment in longer-term, transformative welfare solutions.</p>","PeriodicalId":354,"journal":{"name":"Journal of Dairy Science","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145273386","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Genetic insights into bovine spastic syndrome (Crampy) in Holstein dairy cattle.","authors":"Gabriella Condello, Flavio S Schenkel, Isis C Hermisdorff, Colin Lynch, Christina M Rochus, Brian J Van Doormaal, Filippo Miglior, Christine F Baes","doi":"10.3168/jds.2025-27026","DOIUrl":"https://doi.org/10.3168/jds.2025-27026","url":null,"abstract":"<p><p>Bovine spastic syndrome, known as Crampy, is a neuromuscular disorder in cattle. Affected cattle, 2 yr or older, suffer from involuntary muscle spasms in their hind limbs, leading to discomfort and reduced mobility. This often results in early culling from the herd, causing substantial financial loss for producers. Given the welfare implications and economic burden associated with Crampy, it is crucial to identify effective strategies to mitigate its occurrence. In this study, we assessed the feasibility of genetic selection to reduce Crampy by estimating variance components, evaluating the effect of incorporating genomic information, investigating Crampy's relationship with other economically important traits, and identifying genomic regions associated with Crampy in Canadian Holstein dairy cattle. A dataset comprising 54,826 animals, including 1,952 cases of Crampy, from 678 Canadian dairy herds, was provided by Lactanet Canada (Guelph, ON, Canada). Of these animals, 22,408 (including 408 with Crampy) were genotyped. Both threshold and linear models were used to estimate variance components, with observed scale h² estimates ranging from 0.057 to 0.085. The inclusion of genomic data significantly increased the reliability of breeding values by 5% to 17%. Through a GWAS using GCTA software, a total of 41 significant SNPs were found to be significantly associated with Crampy. Functional analysis revealed 44 genes, among which we have highlighted the genes WNK2 (BTA8), DTNBP1 (BTA23), and ADK (BTA28), which have been associated with ion transport, muscle function, and neuron signaling, respectively. Enriched colocated QTL annotations linked to ketosis, muscle calcium content, and muscle zinc content were also identified, highlighting the role of metabolic processes and mineral homeostasis in muscle function. Breeding value correlations between Crampy and production, health, longevity, and type traits, and the selection indices were moderately low but favorable, indicating that current breeding strategies may indirectly select against Crampy. These findings highlight genomic selection as a viable strategy to mitigate Crampy in Canadian dairy herds, emphasizing the need for continued phenotyping for this disorder and optimization of breeding practices to improve animal welfare and sustainability.</p>","PeriodicalId":354,"journal":{"name":"Journal of Dairy Science","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145273220","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Exterior traits of milk-deprived and milk-fed calves as indicators for body condition or nutritional status.","authors":"Jan Kurek, Theresa M Liegsalz, Anton M Vorndran, Anna Kurek, Veronika Huber, Georg Hammerl, Hubert Spiekers, Julia Steinhoff-Wagner","doi":"10.3168/jds.2025-27130","DOIUrl":"https://doi.org/10.3168/jds.2025-27130","url":null,"abstract":"<p><p>The intake of sufficient milk in the postnatal age is crucial for the physical development of the calf. Farmers struggle to assess whether the calves have consumed sufficient colostrum or milk on farms with unobserved birth, in cow-bonded calf-rearing systems or early group housing with unobserved bucket feeding. The study aimed to find exterior traits that can be used to classify the body condition and nutritional status of suckling calves during wk 1 to 4 after birth. In a second dataset, threshold values for the percentage change in flank circumference in relation to the milk intake (% BW) were determined in calves aged 8 to 10 d after birth. Therefore, at first, calves (n = 85) were measured and scored on 2 farms before feeding and 1 h after voluntary milk intake in the morning. For the second dataset, 10 calves had a voluntary uptake of different milk volumes (range % BW) from d 8 to 10. Significant differences in body parameters between the age groups and sex were analyzed using a Kruskall-Wallis nonparametric ANOVA. A nonparametric receiver operating characteristic analysis (ROC) was used to derive the threshold values for the distinction between milk-deprived and milk-fed status in calves and threshold values for changes in flank circumference in relation to milk intake % BW. The intake-associated gain of the calves could be visualized by measuring and scoring the external body parameters. Sex influenced only flank circumference (milk-fed) in wk 2. Using the ROC, the flank width showed a better model quality (0.54-0.68 vs. 0.39-0.64) and true-positive rate (64%-79% vs. 47%-87%) than the flank circumference. The left or right hunger pit showed the best model quality (0.61-1.00) and excellent true-positive rates (76%-100%). The false-positive rate was in the lower range (8%-23%). Following milk intake, changes in flank circumference were more distinctly detectable at lower intake levels (below 5% of BW) than at higher levels. Within this lower range, the ROC analysis yielded excellent area under the curve values and high accuracy in distinguishing between the amount of milk consumed % BW. In contrast, as milk intake increased to 6% to 10% of BW, the diagnostic performance declined noticeably. Suitable indicators were identified to sufficiently assess the body condition and nutritional status of newborn suckling calves, which could be implemented on farms to recognize and prevent critical situations in the absence of milk intake.</p>","PeriodicalId":354,"journal":{"name":"Journal of Dairy Science","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145273243","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mesoscale fractal whey protein particles derived from microscale linear-shaped protein assemblies (Part 2): Foaming properties and heat stability.","authors":"Hanyu Shi, Haotian Zheng","doi":"10.3168/jds.2025-27190","DOIUrl":"https://doi.org/10.3168/jds.2025-27190","url":null,"abstract":"<p><p>This study investigates the functionality of mesoscale whey protein particles (WPP) derived from fiber- and ribbon-shaped whey protein assemblies produced via a liquid antisolvent precipitation-based method. The air-water (A-W) interfacial characteristics, foaming properties, and heat stability of WPP were evaluated and compared with the original whey protein source, whey protein isolate (WPI). Adsorption dynamics and dilatational rheology at the A-W interface were characterized using pendant drop and oscillating drop methods, respectively. Foamability and foam stability were assessed using a dynamic foam analyzer, and heat stability was evaluated by examining changes in particle size distribution (PSD) profiles and turbidity before and after heat treatment at 95°C for 5 min. Whey protein particles achieved a quasi-equilibrium surface pressure comparable to WPI after 3 h of adsorption but showed lower dilatational elastic moduli during dilatational deformation. Although WPI exhibited faster surface adsorption, no significant difference was observed in the rate constant of penetration (k_p) between WPP and WPI. Compared with WPI, reconstituted freeze-dried WPP dispersions did not improve foamability, likely due to slower A-W interface adsorption associated with their larger particle sizes; however, they demonstrated enhanced foam stability, evidenced by a longer 75%-volume lifetime. This improvement is likely attributed to the entrapment of WPP within the lamellae and Plateau borders of foam structure, which may increase local viscosity and block the liquid drainage channels, thereby retarding foam collapse. Moreover, WPP exhibited minimal changes in their PSD and turbidity after heat treatment, suggesting enhanced heat stability relative to WPI.</p>","PeriodicalId":354,"journal":{"name":"Journal of Dairy Science","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145273460","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The effect of bovine leukemia virus infection on health and growth of nonreplacement dairy calves.","authors":"K Broadfoot, F van der Meer, R Couto Serrenho, F Pharo, A Keunen, D L Renaud","doi":"10.3168/jds.2025-27122","DOIUrl":"https://doi.org/10.3168/jds.2025-27122","url":null,"abstract":"<p><p>The objective of this cohort study was to determine if bovine leukemia virus (BLV) positivity, identified using quantitative PCR (qPCR), was associated with health and growth outcomes in nonreplacement dairy calves. A commercial calf-raising facility located in Southwestern Ontario was used, where a total of 768 male dairy calves (726 Holstein, 42 crossbred), estimated to be 3 to 10 d of age, had 3 blood samples taken at 1 d, 30, and 84 after arrival to the facility. Whole blood EDTA samples were taken and sent to the University of Calgary Faculty of Veterinary Medicine for qPCR analysis to determine positivity for BLV. Calves were determined to be positive using a baseline threshold of >200 relative fluorescence unit by <40 cycles. All calves were health scored 2 times daily for fecal consistency and respiratory disease, using the UC Davis respiratory scoring chart. Additionally, calves were weighed at time of arrival and weekly thereafter until they left the facility at 84 d. Mixed linear regression models were built to assess ADG (kg/d) over 84 d and feed efficiency (ME/kg of gain), whereas a Poisson model was built to assess the number of observations with a respiratory score of ≥5. Further, a negative binomial model was built to assess the number of observations with diarrhea (score of ≥2), and a zero-truncated Poisson model was built to assess the number of observations with no clinical signs of respiratory disease (e.g., respiratory score of 0). Treatment for respiratory disease and diarrhea was also analyzed using a Cox proportional hazard model. Two calves had incomplete blood sampling and were therefore removed from the analysis, leaving a total of 766 calves. A total of 43 (5.9%) calves tested positive for BLV via qPCR testing over the 84-d period. Calves that were BLV-positive were associated with a greater number of observations with a respiratory score of ≥5 (incidence rate ratio [IRR] = 1.91, 95% CI: 1.69 to 2.17) and a lower number of observations with a score of 0 (IRR = 0.98, 95% CI: 0.95 to 1.00). There was no difference identified between BLV positivity and ADG (kg/d), feed efficiency (ME/kg of gain), or diarrhea. Overall, this study identifies an association between BLV status and respiratory disease occurrence in preweaning calves. Although the underlying mechanisms and long-term effects remain unclear, these findings highlight the need for further research to determine whether BLV plays a causal role in respiratory disease in calves.</p>","PeriodicalId":354,"journal":{"name":"Journal of Dairy Science","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145273443","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"β-Hydroxybutyrate inhibits the spontaneous apoptosis of neutrophils through a degranulation-macrophage-1 antigen axis in cows with subclinical ketosis.","authors":"Kexin Wang, Guowen Liu, Ke Zhang, Zhiyong Li, Yan Ren, Shang Jiang, Xiliang Du, Lin Lei, Wenwen Gao, Zhe Wang, Xinwei Li, Yuxiang Song","doi":"10.3168/jds.2025-26516","DOIUrl":"10.3168/jds.2025-26516","url":null,"abstract":"<p><p>Subclinical ketosis (SCK), a common metabolic disorder in dairy cows during the peripartum period, is accompanied by systemic inflammation and elevated circulating BHB. β-Hydroxybutyrate contributes to the development of systemic inflammation by inhibiting the spontaneous apoptosis of neutrophils in SCK cows. However, the underlying molecular mechanism is still unclear. This study investigated the role of the degranulation-macrophage-1 antigen (Mac-1) axis in this process. The results demonstrated that BHB promoted the degranulation process and activated membrane Mac-1 (CD11b/CD18) on neutrophils both ex vivo and in vitro. Neutrophils were isolated from healthy cows and treated with 2 mM BHB, a specific degranulation inhibitor, or a Mac-1 blocking antibody in vitro. We found that the released granule contents during degranulation activated the intracellular Mac-1 signaling pathway, which was involved in BHB-mediated inhibition of bovine neutrophil apoptosis. Overall, our findings reveal that the degranulation-Mac-1 axis plays a critical role in regulating BHB-induced inhibition of spontaneous neutrophil apoptosis in dairy cows with SCK.</p>","PeriodicalId":354,"journal":{"name":"Journal of Dairy Science","volume":" ","pages":"11403-11417"},"PeriodicalIF":4.4,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144768198","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Genetic background of calving ease in beef-on-dairy.","authors":"Arielly O Garcia, Ashley A Mikush, John B Cole, Shogo Tsuruta, Ignacy Misztal, Simone E F Guimarães, Daniela Lourenco","doi":"10.3168/jds.2025-26503","DOIUrl":"https://doi.org/10.3168/jds.2025-26503","url":null,"abstract":"<p><p>A common practice in dairy herds is to breed females not selected as replacement heifers to beef bulls. This increases the market value of the surplus calves sold for beef purposes. Some beef breed associations have built selection indices focusing mainly on carcass traits; however, calving ease (CE) is also an important trait, given that crossbreeding with beef bulls can change gestation patterns (e.g., gestation length) or calf conformation (e.g., weight and size), generating a negative effect on the health, and consequently on the production, of the cows. We used linear and threshold animal models to estimate genetic parameters and breeding values for direct and maternal additive effects for CE in beef-on-dairy crosses, considering only the first or the first 3 lactations. We analyzed 231K CE records in the first lactation and 1.2 million in the first 3 lactations from Holstein and Jersey cows inseminated with Angus, Charolais, or Simmental semen. Although CE was scored in 5 categories, we reduced this to a binary trait (1 = easy and 2, 3, 4, 5 = difficult). The average incidence of difficult calving (scores ≥2) was ∼15%. Direct and maternal heritabilities for the linear (threshold) model were 0.01 ± 0.002 (0.01 ± 0.001) and 0.02 ± 0.002 (0.04 ± 0.004), respectively, using the first lactation, and equal to 0.01 ± 0.002 (0.01 ± 0.009) and 0.19 ± 0.002 (0.26 ± 0.006), respectively, considering the first 3 lactations. Maternal heritabilities were always greater than the direct ones. Maternal heritabilities were inflated when we considered more than one lactation, most likely because of a confounding with the maternal permanent environmental effect that could not be estimated. Linear and threshold models provided similar direct EBV rankings, with a correlation of at least 0.86 when considering all different breeds; for maternal effect, it was high for dairy breeds (>0.9) and close to zero in beef breeds. Validation metrics were better for the linear model with only first lactation records. Although with the small direct heritabilities, the results showed that direct genetic variability exists, and that it would be possible to select beef bulls based on their direct EBV for CE in beef-on-dairy systems. One of the challenges in beef-on-dairy analyses is the lack of pedigree depth on the sire side. When this is the case, we suggest using linear models considering only the first lactation to evaluate CE, given that EBV are highly correlated with those obtained by the threshold model but are less biased and converge almost 10 times faster, proving to be more efficient for routine genetic evaluations.</p>","PeriodicalId":354,"journal":{"name":"Journal of Dairy Science","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145224611","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characterization of a novel heat tolerance trait and subsequent haplotype block-based analysis to identify associated regions in Dutch Holstein cattle.","authors":"T Pook, M L van Pelt, J Vandenplas, I Adriaens, L Zetouni, C Orrett, Y de Haas, C Kamphuis, B Gredler-Grandl","doi":"10.3168/jds.2025-26870","DOIUrl":"https://doi.org/10.3168/jds.2025-26870","url":null,"abstract":"<p><p>Heat stress is a major environmental challenge affecting dairy cattle, leading to behavioral changes, production losses, and welfare concerns. As heat stress events intensify and become more frequent due to climate change, identifying animals that are able to maintain high production levels during heat stress events, commonly referred to as heat tolerance, is crucial for sustainable dairy production. In this study, we develop a pipeline to quantify the population-wise impact of heat stress on a dairy cattle population and subsequently define individual-based heat tolerance traits. Data from 677,318 Dutch Holstein cows were analyzed, including 15.6 million mid-infrared spectra and 762 million records from automated milking systems. An iterative approach using kernel regression was employed to estimate the population-wise effects of heat stress. Results indicate that fat and protein percentages decrease approximately linearly with increasing temperature-humidity index (THI), with an absolute reduction of 0.3% as THI increases from 30 to 70. In contrast, milk yield remains stable until a THI of 60, after which production losses increase quadratically, reaching a loss of 5.0% at a THI of 75. We subsequently define the heat tolerance phenotype of an animal as the slope from a linear regression model of the residuals of the population-wise models against THI for milk yield, concentration of fat, protein, lactose, and specific fatty acids. Compared with reaction-norm models, individual records per cow are combined into one joint record before model fitting, thus reducing computing times and allowing more flexibility in the design of the model. Heritabilities for heat tolerance traits ranged from 0.05 to 0.12, and genetic variances indicate substantial potential for breeding as an improvement of the population by 1 genetic standard deviation would already offset 69% of the losses in fat percentage, 65% in protein percentage, and 11% in milk yield. Heat tolerance based on milk yield showed favorable correlations with most commercial traits, whereas heat tolerance based on fat and protein percentage showed negative correlations with health and resilience. A GWAS using both SNPs and haplotype blocks from the software HaploBlocker identified potential QTL across the genome, with particularly strong signals on BTA5, 14, and 20. These findings support the long-term potential of genetic improvement through breeding for heat tolerance but highlight the need for complementary management strategies to mitigate heat stress impacts in the short term.</p>","PeriodicalId":354,"journal":{"name":"Journal of Dairy Science","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145224639","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}