Journal of Dairy Science

Continuous video offers a dynamic view of dairy-cow behaviour, but its value for precision nutrition depends on alignment with physiological context. We developed a dairy digital-twin framework that fuses identity-associated behavioural records from an established video-analytics layer with body weight, milk production, milk fat, parity and days in milk. The 16-cow analytical cohort was monitored for up to 11 days in one tie-stall barn, yielding 153 cow-days after quality exclusions applied before model fitting. NRC (2001) expected dry matter intake provided a transparent physiological reference compatible with the daily records. In matched leave-one-cow-out analysis, adding video-derived feeding duration to body weight, fat-corrected milk and days in milk reduced RMSE from 2.015 to 1.763 kg DM/day, MAE from 1.267 to 1.159 kg DM/day and MAPE from 4.5% to 4.2%, while R{superscript 2} increased from 0.500 to 0.617. A secondary reduced index achieved RMSE 2.362 kg DM/day and MAPE 5.8% across held-out cows. Cow-level analysis delineated the operating domain: median per-cow MAPE was 4.15%, whereas the sole cow at 15 days in milk had MAPE 28.8%. Two independently recorded veterinary events were temporally concordant with unusual feeding trajectories, providing descriptive biological context. Because the endpoint was NRC-derived, these metrics quantify reference reconstruction rather than accuracy against observed intake. By converting continuous behavioural events into auditable cow-day states, the framework links physical animals to physiologically contextualized digital counterparts and establishes a scalable foundation for operator-focused dairy digital-twin decision support.

This study evaluated the potential of milk mid-infrared (MIR) spectroscopy, combined with routinely available on-farm variables, for predicting serum metabolic, immune, and inflammatory biomarkers in early-lactation cows. Data included 5,936 blood samples from 4,442 cows across 23 Australian dairy herds, with paired milk MIR spectra and serum measurements for up to 14 biomarkers. Prediction models were developed using partial least squares regression and evaluated using nested 10-fold random cross-validation and leave-one-herd-out validation. The results show that while basic herd-test data, including milk fat, protein, and lactose concentration, as well as on-farm variables, including DIM, calving age, breed, and herd could predict serum biomarkers, combining MIR spectra with these on-farm variables produced the best overall performance. In random cross-validation, blood urea nitrogen (BUN) was predicted most accurately (R2 = 0.78), while {beta}-hydroxybutyrate (BHB) and nonesterified fatty acids (NEFA) showed moderate accuracy (R2 = 0.56 and 0.44, respectively). BUN also showed the strongest external validation performance, with leave-one-herd-out R2 = 0.58 and comparable accuracy for predicting records collected after 70 days in milk (R2 = 0.65). BHB and NEFA had moderate leave-one-herd-out accuracy but did not transfer beyond early lactation. Most other biomarkers showed low or inconsistent external validation performance. Overall, MIR spectroscopy combined with on-farm variables shows promise for routine prediction of BUN, BHB and NEFA, which can be used for monitoring and genetic evaluation of, for example, ketosis and energy deficit. Initial random cross-validation results for glucose, bilirubin and cholesterol were promising, but more data is needed to improve the prediction accuracy and robustness of the predictions. HighlightsO_LIMilk MIR can predict several serum biomarkers in early-lactation dairy cows. C_LIO_LIMIR-predicted blood urea nitrogen shows the greatest accuracy and robustness. C_LIO_LIMIR-predicted {beta}-hydroxybutyrate and nonesterified fatty acids show moderate accuracy. C_LIO_LIMost mineral, hepatic, and inflammatory biomarkers had limited accuracy. C_LIO_LIRoutine MIR phenotyping is most promising for BUN, BHB, and NEFA. C_LI SummaryMilk mid-infrared (MIR) spectroscopy and on-farm variables are evaluated as a high-throughput tool to predict health-related serum biomarkers in early-lactation dairy cows. The data include 5,936 paired blood and milk samples from 4,442 cows across 23 Australian dairy herds and up to 14 serum biomarkers. Prediction models are developed using partial least squares regression with nested random cross-validation and leave-one-herd-out validation. Blood urea nitrogen (BUN) shows the greatest and most transferable prediction accuracy across herds and lactation stages. {beta}-hydroxybutyrate (BHB) and nonesterified fatty acids (NEFA) are predicted with moderate accuracy, but only during early lactation. Random cross-validation results for glucose and bilirubin are promising, but larger datasets are needed for robust external validation. Most other mineral, hepatic, and inflammatory biomarkers show limited external prediction accuracy. These results indicate that MIR-based routine health phenotyping is most promising for BUN, BHB, and NEFA.

Accurate real-time monitoring of milk quality during milking is essential for sustainable dairy farming, yet factors such as cow parity may affect the performance of near-infrared (NIR) spectroscopic sensing systems. This study investigated how cow parity (the number of calvings) impacts the reliability and accuracy of NIR spectroscopy in assessing key milk quality indicators: fat content, lactose, and somatic cell count (SCC). Experiments were conducted at Hokkaido University with two cows in their second parity. Milk spectra were recorded across 700-1050 nm using the NIR system, while fat and lactose were measured with a MilkoScan device and SCC with a Fossomatic device. Calibration models were developed using first parity, second parity, and combined datasets through partial least squares regression. Model performance was evaluated via coefficients of determination and standard errors of prediction. Results showed comparable accuracy for milk fat and SCC across parities, whereas lactose measurements were more affected. Cross-validation between first and second parity datasets further confirmed parity-dependent variations, particularly for lactose. These findings suggest that cow parity should be considered when implementing NIR-based milk quality monitoring, supporting more precise, resource-efficient, and sustainable dairy management practices.

Dozens of missed recessive loci affecting homozygous carriers life expectancy were recently reported. This article details the clinical, biological and pathological manifestations of a new bovine genetic disorder caused by an ITGB7 p.G375S point mutation in the French Holstein cattle breed. Our thorough study involved database analysis of genotyped cattle and a series of case-control investigations of forty homozygous mutants for the causative variant. These mutants had a significantly shorter lifespan (fewer than 64% surviving past three years vs. 87% in controls), along with reduced body weight, daily weight gain, and dairy performance. The mutation did not affect most biochemical parameters, but a marked lymphocytic leucocytosis, moderate eosinophilia and differences in faecal microbiota were observed. Although non-pathognomonic symptoms may be confused with those of common environmental diseases, the blood profile effectively identified suspected carriers who developed ill-thrift and poor growth as heifers. Our research demonstrates that the bovine ITGB7 p.G375S substitution leads to reduced longevity, poor condition and production, in most homozygous carriers. Furthermore, this spontaneous model may help to refine the functions of the {beta}7 integrin in immune homeostasis and defence.

Bovine mastitis are mainly caused by bacterial infection. They are responsible for economic losses and have an impact on the health and welfare of animals. The increase in the somatic cell count in milk during mastitis is mainly due to the influx of neutrophils which have a crucial role in the elimination of pathogens. For a long time, these first line defenders has been view as microbes killers with limited role in the orchestration of the immune response. However, their role is more complex and we recently characterized a MHC-II expressing neutrophil subset with regulatory capacities in cattle. In this study, we questioned the implication of different neutrophils subsets in the mammary gland immunity during clinical and subclinical mastitis. Here, we described for the first time that, in blood as in milk, neutrophils are a heterogeneous population and encompass at least two subsets distinguishable with their expression of MHC-II. We observed higher bactericidal capacities of milk MHC-IIpos neutrophils as compared to their classical counterparts, due to a higher production of ROS and phagocytosis ability. MHC-IIpos neutrophils are enriched in milk during a subclinical mastitis as compared to blood. Moreover, we observed a positive and highly significant correlation between MHC-IIpos neutrophils and T lymphocytes present in milk during subclinical mastitis. To conclude, our study could open the way to the discovery of new biomarkers of mastitis inflammation.

This study develops an Artificial Intelligence-driven benchmarking tool to reduce methane emissions in Canadian dairy farms, responding to the urgent need to mitigate environmental impacts from agriculture. Utilizing a comprehensive dataset from over 1000 dairy farms and processors across Canada, combined with satellite-driven methane emission data, we apply advanced machine learning technologies and data analytics, including geospatial analysis and time series forecasting. This approach identifies critical emission hotspots and temporal trends. We tested several predictive models--ARIMA, LSTM, GBR, and PROPHET--with the LSTM model showing the greatest accuracy in forecasting emissions, demonstrated by the lowest Root Mean Squared Error (RMSE) of 15.40. Our results highlight the transformative potential of AI tools in agricultural environmental management by providing dairy farmers and policymakers with precise, real-time emission insights. This facilitates informed decision-making and the implementation of effective emission reduction strategies. This study not only advances understanding of emission dynamics in dairy farming but also underscores the role of technology in sustainable agricultural practices and achieving environmental targets consistent with global agreements.

The effect of methane-mitigating feed additives on dairy cows has been widely explored; however, confusing conclusions have been reached due to factors such as the inclusion of different doses and experimental conditions in which the additives are tested, or even a small sample size. We present the first extensive study assessing the effects of methane-mitigating feed additives on milk production across several commercial dairy farms. This study used a previously developed predictive AI-driven model based on microbiome samples; the model predicts farms where a significant reduction of methane emissions is expected due to the applied feed additives. Thus, in this study, each feed additive was supplied to a large number of farms, widely distributed across different climatic areas in Israel. The data analysis followed two simulated scenarios: (1) a naive approach, where feed additives are supplied indiscriminately, and (2) an optimized approach, where feed additives are supplied only to farms with a high likelihood of being positively impacted in terms of reduced enteric methane emissions (50% of the farms). The results show that each feed additive significantly increased milk production compared to the control groups. This increase in milk production was significantly higher in the optimized scenario. Other related parameters such as somatic cells were also improved. Our results suggest that the feed additives positively affect milk production, reaching a maximum expression when the AI-driven model is applied.

BackgroundImproving feed efficiency has become a common target for dairy farmers to meet the requirement of producing more milk with fewer resources. To improve feed efficiency, a prerequisite is to ensure that the cows identified as most or least efficient will remain as such, independently of diet composition. Therefore, the current research analysed the ability of lactating dairy cows to maintain their feed efficiency while changing the energy density of the diet by changing its concentration in starch and fibre. A total of 60 lactating Holstein cows, including 33 primiparous cows, were first fed a high starch diet-low fibre (diet S+F-), then switched over to a low starch diet-high fibre (diet S-F+). To know if diet affect feed efficiency, we compared the ability of feed efficiency to be maintained within a diet over subsequent lactation stages, known as repeatability of feed efficiency, with its ability to be maintained across diets, known as reproducibility of feed efficiency. To do so we used two indicators: the estimation of the error of repeatability/reproducibility, which is commonly used in metrology, and the coefficient of correlation of concordance (CCC), which is used in biology. The effect of diet change could also lead to a change in cows sorting behaviour which could potentially affect feed efficiency if for example the most efficient cows select more concentrate than the least efficient. We therefore analysed the relationship between the differences in individual feed refusals composition and the differences in feed efficiency. To do so, the composition of each feed refusal was described with its near infra-red (NIR) spectroscopy and was performed on each individual feed ingredient, diet and refusals and used as composition variable. The variability of the NIR spectra of the refusals was described with its principal components thanks to a principal component analysis (PCA). The Pearson correlation was estimated to check the relationship between feed efficiency and refusals composition, i.e. sorting behaviour. ResultsThe error of reproducibility of feed efficiency across diets was 2.95 MJ/d. This error was significantly larger than the errors of repeatability estimated within diet, which were 2.01 MJ/d within diet S-F+ and 2.40 MJ/d within diet S+F-. The CCC was 0.64 between feed efficiency estimated within diet S+F- and feed efficiency estimated within diet S-F+. This CCC was smaller than the one observed for feed efficiency estimated within diet between two subsequent lactation stages (CCC = 0.72 within diet S+F- and 0.85 within diet S-F+). Feed efficiency was poorly correlated to the first two principal components, which explained 90% of the total variability of the NIR spectra of the individual refusals. This suggests that feed sorting behaviour did not explain differences in feed efficiency. ConclusionsFeed efficiency was significantly less reproducible across diets than repeatable within the same diet over subsequent lactation stages, but cows ranking for feed efficiency was not significantly affected by diet change. This loss in repeatability across diets could be due to a more pronounced feed sorting subsequent to the change in diet composition. However, the differences in sorting behaviour between cows were not associated to feed efficiency differences in this trial neither with the S+F- diet nor with the S-F+ diet. Those results have to be confirmed on diets having different forage to concentrate ratios to ensure that the least and most efficient cows will not change.

The aim of the study was to describe the metabolic responses on energy metabolism to a period of negative nutrient balance induced by feed restriction (FR). Seven multiparous Holstein cows (93 ± 15 days in milk) were randomly assigned to 7 treatments in a 7 × 4 Youden square design. Daily intake was restricted to provide 60% of energy requirements during 5 d except for one treatment with ad libitum (AL) feeding. While 5 out of 7 experimental treatments involved abomasal supplementation of amino acids or glucose, in this article we evaluated only the effects of a negative nutrient balance by comparing both control treatments (AL and FR). Data of 2 cows within the AL group were removed due to sickness and therefore it had n = 2. Milk and energy corrected milk yield were reduced by FR. Yields of milk protein and lactose were lower during FR than during AL but the yield of milk fat only had a tendency (P > 0.06) to be lower with FR. Milk protein concentration was lower with FR than with AL but concentration of milk lactose and fat were not different between diets. The FR induced a decrease in plasma insulin and glucose concentrations, with quadratic decreasing trends both reaching nadirs on d 3. Simultaneously, non-esterified fatty acids (NEFA) concentration was greater and increased quadratically, peaking at d 3 during FR. There were no differences in daily β-hydroxybutyrate concentration, but it increased linearly until d 4 with FR. Comparison of the variation in concentration after feeding of insulin, NEFA and glucose could indicate a likely increased insulin sensitivity for peripheral NEFA uptake and a resistance for glucose uptake. This mechanism would contribute to decrease NEFA in circulation and sparing of glucose for lactose synthesis, respectively. Metabolic adaptations to a short-term reduction in dry matter intake include lipid mobilization, as well as modulation of peripheral tissue endocrine sensitivity in order to maintain yield of milk components production but prioritizing milk fat and lactose over milk protein.Implications The short-term feed restriction model described in this article can serve as an alternative to study metabolic adaptations during the transition period. The response of energy metabolism observed sets the baseline to measure the effect of nutrients supplementation and identify those candidates that will improve milk production and overall health after calving.Competing Interest StatementThe authors have declared no competing interest.View Full Text

Providing a semi-refined chelate of magnesium with mixed organic acids gave controlled magnesium supplementation of equivalent effectiveness to conventional uncontrolled administration of MgO in regard to prevention of milk fever in dairy cows. The supplement was palatable and supplementation produced no adverse health effects as adjudged by veterinary supervision. Monitoring productivity of cows provided with the supplement compared with controls indicated that the use of the supplement provided a paranutritional improvement in feed utilisation, resulting in a significant increase in milk solids yield of up to 23% through the period of supplementation, together with an improvement in body reserves sufficient to sustain a continuing milk solids yield advantage of up to 5% for two months after cessation of feeding. Since this increase in productivity was achieved without an increase in feed intake, use of the experimental supplement is considered to have resulted in a prebiotic effect in ruminant fermentation and consequently a commensurate reduction in methane intensity of production. Important Note on history of projectThe investigations reported in this paper were conducted under strict, independent veterinary supervision. This was because the responsible animal ethics committee first stated that the proposed study of the efficacy of a novel means of meeting magnesium supplemental requirements was of no academic interest, and refused to assess an application for ethics approval on those grounds. When the first experiment reported suggested the possibility of a prebiotic effect, the committee said that because there was no prior publication of such an effect in ruminants, the experimental hypothesis could not be sustained. This was despite the fact that prebiotic effects were well-known in humans and monogastric animals. As a consequence, the Committee refused to assess the research. Subsequent investigations (e.g https://peerj.com/articles/18103) clearly indicate that the material under investigation could exert the prebiotic effect seen in monogastrics. In light of the present interest in inhibition of methanogenesis, the results reported below are of particular interest, requiring that they be placed in the public domain. Note that across both experiments, no adverse events related to administration of the prebiotic were observed by the veterinarian. Conduct of the investigations reported has been compared with the ARRIVE guidelines, and found to be compliant.

To investigate how the disturbances associated with a relocation to a bedded-pack barn, such as a housing system change, a milking system change and a social regrouping, impacts the behavior of lactating dairy cows, 38 cows from a total of 9 tie-stall or free-stall commercial farms were moved to a newly built bedded-pack barn on an enrollment basis, with a social regrouping occurring after 2 weeks. Scan sampling of video data was done to assess behavior expression in the pen, and live data was collected to assess milking reactivity and animal handling procedures. Results indicate that the cows adapted quickly to the relocation to the new housing system as there were no changes in the locations in the pen, the body positions or the behaviors of cows in time between arrival and regrouping. The social regrouping had a bigger impact with a decrease in 16% of the observed time spent lying and an increase of 9.7% of the observed time spent feeding. Cows also adapted quickly to the milking procedures with a rapid decrease in the occurrence of negative social interactions between cows at the parlor, and in needing less human-animal manipulations and less time to be brought to the parlor. The housing system of origin had a slight effect on behaviors with cows from tie-stalls spending 1.7 times more of the observed time lying than free-stall cows, and free-stall cows spending 1.6 times more of the observed time feeding than tie-stall cows. This study provides a better understanding of how dairy cows respond to disturbances and is encouraging for producers that need to make changes to their current housing system as cows were shown to be quickly adaptable to the challenges presented to them. SummaryDairy cows from cubicle systems were shown to adapt quickly after a relocation to a bedded pack barn, the first use of a milking parlor, and a social regrouping. This was supported by limited changes observed in their behaviors after the disturbances, and observed deviations were temporary and short-lived. Animal handling procedures also observed a quick improvement in time with the trips to the milking parlor needing 2x less time and 3.5x fewer physical contacts from handlers after 5 days. These results are encouraging to producers needing to make changes to their barns.

The aim of the study was to describe the metabolic responses of protein metabolism to a period of negative nutrient balance induced by feed restriction (FR). Seven multiparous Holstein cows (93 ± 15 days in milk) were randomly assigned to 7 treatments in a 7 × 4 Youden square design. Daily intake was restricted to provide 60% of energy requirements during 5 d except for one treatment with ad libitum (AL) feeding. While 5 out of 7 experimental treatments involved abomasal supplementation of AA or glucose, in this article we evaluated only the effects of FR by comparing both control treatments (AL and FR). Data of 2 cows within the AL group were removed due to sickness and therefore it had n = 2. A rapid decrease of most amino acids in plasma was paired with an increase in blood urea N with its peak on d 2 and decreasing afterwards. On the other hand, Lys, Arg, Gly, Gln, and Cys were greater during FR. Comparing the fluctuation of all the essayed N components in circulation across the 5-d period, protein tissue mobilization may have supplied amino acids for catabolism to provide needs for N and energy precursors.Implications The short-term feed restriction model described in this article can serve as an alternative to study metabolic adaptations during the transition period. The response observed of the protein metabolism sets the baseline to measure the effect of nutrients supplementation and identify those candidates that will improve milk production and overall health after calving.Competing Interest StatementThe authors have declared no competing interest.View Full Text

T-lymphocytes are key mediators of adaptive cellular immunity and knowledge about distinct subsets of these cells in healthy and infected mammary gland secretions remains limited. In this study, we used a multiplex cytometry panel to show that staphylococcal mastitis causes the activation of CD4+, CD8+ and {gamma}{delta} T-cells found in bovine milk. We also highlight remarkable differences in the proportions of naive and memory T-cells subsets found in blood and milk. These observations will contribute to a better understanding of cell-mediated immune mechanisms in the udder and to the development of new therapeutic and preventive strategies targeting mastitis.

To identify factors affecting rumination time (RT), factorial analyses in a dairy farm were performed. In univariate analyses, differences in distribution were observed between low (< 45 kg/d) and high ([&ge;] 45 kg/d) milk yield (MY) before the heat season, early and peak lactation periods and mid and late at the start of the heat season, and 1-2 and [&ge;] 3 parity at the start of the heat season. Multiple regression analysis confirmed that RT was affected by low MY, early to peak and 1-2 parity cows, low MY, mid to late and 1-2 parity cows, and low MY, early to peak and [&ge;] 3 parity cows (coefficients = -37.039, -25.353, -44.805 respectively, P < 0.05). When the cows were classified by MY before the heat season, the RT and MY of the high-MY group remained higher than the low-MY group until before the severe heat (THI [&ge;] 84 continued). However, when cows were classified by RT before the heat season, there was no difference in MY between the low-RT (< 485 min/d) and the high-RT group (> 485 min/d). In conclusions, MY is a factor affecting RT up to moderate heat but RT is not a sufficient condition affecting MY.

The relationship between luteal size and plasma progesterone concentration in purebred cows has been investigated previously. However, there is limited information on this topic in Indian crossbred cows. This study aimed to evaluate the relationship between luteal size parameters (diameter and area) and plasma progesterone concentration in healthy pregnant and non-pregnant Indian crossbred cows. Fifty healthy lactating crossbred cows were artificially inseminated after estrus detection and retrospectively classified into pregnant (n=29) and non-pregnant (n=21) based on the results of ultrasonographic pregnancy diagnosis. Data on luteal diameter, luteal area, and plasma progesterone concentration collected on Days 7, 14, and 20 in non-pregnant cows and on Days 7, 14, 20, 25, 30, 35, 40, and 60 in pregnant cows were analyzed. Spearmans correlation test was used to evaluate the association between the corpus luteum size parameters and the plasma progesterone concentration. Luteal area was positively correlated with plasma progesterone concentration in both pregnant ({rho}=0.48, P<0.001) and non-pregnant ({rho}=0.43, P=0.001) cows. Luteal diameter had a relatively weaker correlation with plasma progesterone concentration in both pregnant ({rho}=0.45, P<0.001) and non-pregnant ({rho}=0.24, P=0.058) cows. These results suggest that luteal area is a better indicator of CL function than luteal diameter in healthy Indian crossbred cows.

Field methods to diagnose bovine respiratory disease (BRD) do not accurately identify airway inflammation and lack clinical sensitivity. New diagnostic modalities, such as thoracic ultrasound (TU), computer-assisted lung auscultation (CALA), and transtracheal wash (TTW), have recently emerged which may deliver accurate diagnosis and prediction of BRD in clinical settings. Therefore, we sought to compare TU, CALA, and TTW fluid cytologic assessment in stocker cattle at risk for BRD in a pilot study. We enrolled 17 high-risk mixed-breed beef steers, sampled 10 and 21 days after arrival and conventional management, in a pilot cross-sectional observational study. Cattle were examined daily for 82 days for clinical BRD. On day 10, 16 cattle received CALA, and 10 and 8 of these received TU and TTW, respectively. On day 21, 12 cattle received CALA and TTW, and 10 received TU. CALA was scored as 1-5. Lung consolidation and/or comet tails were evaluated by TU. TTW was evaluated by 200-cell differential count, with inflammation defined as >20% neutrophils. Relationships between each diagnostic test, and between diagnostic tests and clinical BRD, were evaluated by logistic regression (P<0.10). Fourteen cattle were treated for BRD. CALA scores ranged 1-3; three cattle had lung consolidation. On day 10, 5 of 6 cattle previously treated for BRD and 0 of 3 not treated had >20% TTW neutrophils. On day 21, 5 of 9 treated cattle and 1 of 3 not treated had >20% TTW neutrophils. No significant relationship between CALA, TU, and TTW inflammation existed. TTW inflammation was associated with BRD diagnosis (P=0.0586). CALA and TU results were unrelated to TTW inflammation. Cytologic assessment of TTW may improve antemortem diagnosis of BRD.

The discovery that a naturally occurring, biologically active {beta}-carotene-oxygen copolymer compound is the main product formed in spontaneously oxidized {beta}-carotene has stimulated interest in its potential health benefits. The copolymer, formed in nature or synthetically by the air-oxidation of {beta}-carotene, possesses beneficial immune modulating activities that previously had been attributed to {beta}-carotene itself. Support for these benefits is provided by previous studies showing that supplementation in feed with low parts-per-million levels of copolymer-rich, fully oxidized {beta}-carotene (OxBC) helped reduce the negative impact of subclinical necrotic enteritis in broilers and improved growth in weaned piglets. To further assess these potential benefits, two trials were conducted in swine raised under commercial conditions in Vietnam. Trial 1, a 140-day full-grow, post-wean study with 500 28-day-old pigs, compared 2, 4 or 8 ppm OxBC against both an unsupplemented and an antibiotic control group. OxBC and antibiotics each improved growth rate, feed efficiency, and body weight compared to the control (P<0.001). Animals receiving 4 and 8 ppm OxBC performed better than did animals on antibiotics (P<0.001). In starter pigs, OxBC reduced the occurrence of diarrhea dose-dependently (4 and 8 ppm) and to a greater extent than did antibiotics (P<0.001). Trial 2, a 49-day study with 420 piglets, was conducted in two-stages. In Stage 1 (pre-wean), OxBC in the transition (creep) feed produced a dose-dependent trend toward increased body weight over 21 days, reaching significance at the highest inclusion level (16 ppm) (P<0.001). In Stage 2 (post-wean), body weight gain showed a dose-dependent trend and was significant for both 8 ppm OxBC and the antibiotics at 28 days post-wean (P<0.001). Feed conversion was better at 8 ppm OxBC and for the antibiotic group (P<0.001). These findings support the concept that {beta}-carotene-oxygen copolymers help optimize immune function, and provide validation for the effectiveness of this strategy in enhancing animal performance in the absence of in-feed antibiotics.

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 heat tolerant animals is crucial for sustainable dairy production. This study develops a pipeline to quantify the population-wise impact of heat stress on a dairy cattle population and subsequently defines individual-based heat tolerance traits. Data from 677,318 Dutch Holstein cows, including 15.6 million mid-infrared spectra and 762 million records from automated milking systems, were analyzed. 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% from THI = 30 to THI = 70. In contrast, milk yield remains stable until a THI of 60, after which production losses increase quadratically reaching 5.0% at a THI of 75. The phenotype of an animal is subsequently defined as the slope in a linear regression model of the residuals of the population-wise models against THI for milk yield and concentration of fat, protein, lactose, and specific fatty acids. Compared to reaction-norm models, individual records per cow are combined before model fitting, thereby reducing computation 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 one 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 to health and resilience. A genome-wide association study using both SNPs and haplotype blocks from the software HaploBlocker identified potential QTLs across the genome, with particularly strong signals on BTA5, 14, and 20. These findings support the potential of breeding for heat tolerance but highlight the need for complementary management strategies to mitigate heat stress impacts. Interpretive summaryThis study introduced a novel, computationally efficient method to quantify the impact of heat stress in dairy cattle and define novel heat tolerance traits based on milk production data from automated milking systems. Our results indicate quadratically increasing losses in milk yield with increasing heat load. The identified heat tolerance traits show substantial genetic variance, moderate heritabilities, and favorable correlation to key production traits. These findings highlight the potential for incorporating heat tolerance into dairy breeding goals to mitigate climate change impacts, improve animal welfare, and enhance sustainable milk production.

Studies using fistulated ruminants have shed light on digestion and fermentation in the rumen and yielded tools to determine the feed efficiency of diets, limit effluents or anticipate variability in the quality of animal products. However, the ethical acceptability of such studies has been called into question. Our objective was to determine whether oral-stomach sampling (OSS) is an acceptable alternative to sampling through a ruminal cannula in characterizing the variability of rumen fluid composition induced by an acidogenic dietary challenge in dairy cows. During three four-week periods (P1, P2, P3), six rumen-fistulated cows were fed a standard diet based on supplemented corn silage (periods 1 and 3) alternating with a diet enriched with starch (period 2). Rumen juice was collected through cannulas at three locations in the rumen (reticulum, ventral sac or a mix of both) and by OSS, once per week at 0830 h, i.e. before morning feeding, and once every third week of each period at 1330 h, i.e. 4.5 hours after morning feeding. Whatever the sampling method or location, ruminal pH was lower in period 2 compared to periods 1 and 3 at 1330 h (6.21 vs. 5.57 vs. 6.12 in periods 1, 2 and 3). Ruminal pH was higher when obtained by OSS rather than cannulation, whatever the sampling location (on average, +0.44 points at 0830 h and +0.56 points at 1330 h). Mineral composition indicated a presumed dilution by saliva of OSS samples. This was also consistent with lower concentrations of volatile fatty acids. The next steps will be to analyze the associated variations in in vitro rumen fermentation parameters and microbiota composition. ImplicationsThe use of fistulated ruminants to elucidate ruminal physiology is currently controversial in society. In order to minimise, reduce or replace these experimental models, alternatives to ruminal fistula sampling are being evaluated. Here we focus on oral stomach sampling (OSS). We show that OSS can be a satisfactory alternative to cannula sampling in the evaluation of rumen fermentation parameters, especially for the molar proportion of volatile fatty acids, rumen pH, and rumen volatile fatty acid and ammonia concentrations. We also show that OSS must be standardized to avoid salivary contamination affecting the quality of the results.

Most common housing systems for dairy cows restrict their movement, which can influence welfare, gait, and hoof health of dairy cows. Outdoor access has been proposed as a management practice to offset these restrictions, but reported effects on cows locomotion vary and may not always be captured by traditional clinical assessments. In this study, we investigated gait and hoof through clinical (i.e., visual locomotion scoring and hoof lesion assessment) and subclinical (3D motion analysis, kinetic assessment, hoof infrared thermography and measuring claw conformation) methods to assess how limited provision of outdoor access affects non-lame cows housed in movement restricted environment. Thirty-six Holstein tie-stall cows were either given 1day/week (EX1) or 3days/week (EX3) of outdoor access (1h/day) during 5 consecutive weeks. Clinical and subclinical assessments of gait and hoof were performed before (Pre-trial), after 5 weeks of outing (Post-trial) and 8 weeks after outing (Follow-up). The results of this study revealed no clinical effect of outdoor access on cows locomotion score and hoof lesion prevalence. However, for subclinical assessment, both groups showed an increase in stride and stance time at Post-trial, with an increase in pressure applied by cows while standing in EX3 group and a reduction in coronary band temperature in both groups at Post-trial and Follow-up. Contact area and claw conformation changed after provision of outdoor access in both groups. This study illustrates that with the use of subclinical methods; we can reveal effects of outdoor access on gait and hoof health that might not be visible using the traditional methods.