Journal of Dairy Science最新文献

Milk fatty acid (FA) composition is an indicator of both farm management and the nutritional quality of dairy products. Few studies have linked diverse, multicountry observational farm data to milk FA variation through a validated machine learning workflow. We surveyed 75 European farms representing a broad gradient of production intensity, analyzed seasonally pooled bulk milk samples for 12 FA traits, and examined 29 management practices. A 2-stage workflow combined optimized random forests (RF) to predict FA and rank practices, with conditional inference trees to visualize management synergies and trade-offs. RF models achieved high predictive accuracy (R² ≥ 0.50) for 8 traits: α-linolenic acid, eicosapentaenoic acid, docosapentaenoic acid, CLA, n-6:n-3 PUFA ratio, linoleic acid, vaccenic acid (VA), and branched-chain fatty acids (BCFA). Conditional inference trees models had comparable accuracy (R² ≥ 0.50) for all these traits except VA and BCFA. Across models, fresh grass intake, maize silage and concentrate use, stocking rates, herd size, milk yield, and mineral fertilizer were dominant drivers, together explaining most variance in the models. Farms adopting low-input, pasture-based strategies were consistently associated with lower n-6:n-3 PUFA ratios and higher n-3 PUFA, CLA, and BCFA in milk, highlighting synergies alongside trade-offs between production intensity and nutritional quality. Although this profile is associated with favorable health outcomes and contributes to meeting dietary recommendations, further targeted validation is needed to confirm generalizability and adaptability across dairy production contexts.

In humid continental climates, dairy cattle are exposed to episodic periods of high temperature and humidity for several months each year. This environment is characterized by large fluctuations in temperature between season and even within the same day creating unique challenges for maintaining thermal balance and animal performance. However, the impact of prenatal heat stress during the close-up period on calf birth weight in this type of climate has not been well established. The objective of this observational study was to determine whether close-up cows exposed to summer conditions of a humid continental climate show physiological signs of heat stress, and whether their heifer calves born to cows gestating under humid summer conditions have lower birth weights. Close-up Holstein dairy cows (82 nulliparous, 51 parous) were enrolled at 2 commercial dairy farms in Ontario, Canada during the close-up period (-21 d to calving) between May and August of 2024. Cow gestation length averaged 276 ± 5 d (mean ± SD). The farms were visited 3x/wk for the study period, with cow respiration rate, rectal temperature, and skin temperature recorded at each visit for a subset of 102 cows that were bred with sexed semen (71 nulliparous, 31 parous). Heifer calves (n = 133) were weighed after birth, with calves averaging 1.1 ± 0.9 d of age at weighing; calves were weighed on the day of calving (d 0; n = 39), on d 1 (n = 57), on d 2-4 (n = 37). Data loggers, placed within pen just above cow level, recorded ambient temperature and relative humidity at 10-min intervals. Temperature-humidity indices (THI) were calculated for each cow's close-up period, including average daily THI, maximum THI, and average h/d for which THI exceeded the thresholds of 62, 65, 68, and 72. Daily THI averaged 67.0 ± 3.25 (range = 59.5-73.1). The daily maximum THI averaged 72.7 ± 3.07 (range = 65.1-78.7). The average time per day (and range) above the THI thresholds of 62, 65, 68, and 72, were 19.0 ± 4.19 h/d (7.2-24.0 h/d), 15.3 ± 5.05 h/d (2.7-23.8 h/d), 11.5 ± 5.36 h/d (0.43-23.0 h/d), and 5.3 ± 3.60 h/d (0.0-13.8 h/d), respectively. Cow respiration rate and both average and maximum skin temperatures were positively associated with all THI metrics. Calf birth weight averaged 41.0 ± 4.5 kg (range = 31.3-53.5 kg). For each 1-unit increase in daily average THI and maximum THI, calf birth weight (±SE) was reduced by 0.45 ± 0.18 kg and 0.44 ± 0.17 kg, respectively. Each 1 h increase in time (h/d) THI exceeded 62, 65, 68, and 72, birth weight decreased by 0.24 ± 0.12 kg, 0.30 ± 0.12 kg, 0.29 ± 0.11 kg, and 0.47 ± 0.17 kg, respectively. Overall, the results indicate that close-up cows in moderate, yet humid continental climate summer conditions experience negative consequences, specifically physiological signs of heat stress and reduced calf birth weight; this highlights the need to implement cooling strategies for close-up cows even in temperate regions.

A meta-analysis and a meta-regression were conducted to compare DMI, production performance, feed efficiency (FE), and milk N efficiency (milk N yield/N intake) of Holstein and Jersey cows. Only experiments in which purebred Holsteins and Jerseys enrolled in the same study, under similar experimental conditions, were used to build the data sets (n = 30 peer-reviewed articles). The weighted raw mean difference (WMD) between breeds was computed for each comparison, and weights were assigned based on the inverse of the variance. A meta-regression was run to explore the impact of continuous (year of publication, DIM, dietary concentrations of NDF, CP, and forage) and categorical (forage type: corn silage, alfalfa/grass-clover mix, and other forage sources ["Others"]) covariates on the WMD of observed and estimated variables. Jerseys had lower DMI (-4.15 kg/d), milk yield (-10.8 kg/d), yields of milk fat (-61.6 g/d) and milk true protein (-211 g/d), and ECM yield (-5.11 kg/d) than Holsteins. Contrarily, concentrations of milk fat (+16.1 g/kg) and milk true protein (+6.98 g/kg), DMI (% of BW [+0.44%) and % of metabolic BW (MBW = BW^0.75; +0.64%), and ECM yield (% of BW [+0.64%] and % of MBW [+1.63%]) were greater in Jersey versus Holstein cows. Whereas FE (milk yield/DMI) was lower (-0.26 kg/kg) in Jerseys than Holstein cows, breed did not affect FE (ECM yield/DMI) and milk N efficiency. Year of publication widened the WMD of milk fat and milk true protein concentrations and ECM yield (% of MBW), and it narrowed that of DMI (kg/d), milk true protein yield, and N intake, favoring Jerseys over Holsteins. In addition, DIM narrowed the gap between breeds for the variables yields of milk, ECM yield (kg/d), milk fat, and milk N yield, and widened the gap for DMI (% BW and % of MBW) and ECM yield (% of BW and % of MBW), all in favor of Jerseys. Dietary concentrations of NDF, CP, and forage collectively impacted the WMD of BW, yields of milk and milk lactose, milk true protein and milk lactose contents, ECM yield (% of BW and % of MBW), FE (milk yield/DMI), and N intake, but did not consistently benefit Holsteins or Jerseys. Corn silage affected all WMD, except milk fat yield, ECM yield (% of BW and % of MBW), FE (milk yield/ECM), and MNE. In comparison with corn silage, alfalfa-grass/clover mix diets affected the WMD of DMI (kg/d and % of MBW), milk yield, milk fat and milk true protein yields, ECM yield (kg/d), N intake, and milk N yield, favoring Holsteins over Jerseys. Compared with corn silage, the forage type Others affected the WMD of milk fat and milk true protein concentrations, DMI (% of BW), and ECM yield (% of BW and % of MBW), benefiting Jersey versus Holstein cows. In conclusion, the WMD of FE (ECM yield/DMI) and MNE were similar across breeds and the continuous (year of publication and DIM) categorical (forage type) covariates largely influenced the WMD of several observed and estimated variables.

This qualitative study was conducted to explore the perceptions of Canadian dairy veterinarians of continuing education (CE) programs and the factors that influence their participation. Five focus groups were conducted with a total of 20 dairy veterinarians in Canada to discuss their experiences, motivations, and barriers related to participation in CE. Three main themes were identified through applied thematic analysis: 1) motivation for CE, 2) CE format considerations and preferences, and 3) improvements to CE to enhance its effectiveness. Participants shared that their motivation for CE participation ultimately focused on producer success. The wide range of available CE opportunities allowed participants to shape and focus their careers on areas of personal and professional interest. However, it was also emphasized that the design and delivery of many CE programs must be improved to encourage veterinary participation. While face-to-face CE was considered stimulating and interactive, time constraints often limited in-person attendance. The accessibility of virtual and asynchronous CE, specifically webinars and online courses, facilitated knowledge transfer in a manner that participants felt equally instructive as a face-to-face atmosphere. Participants agreed that virtual CE eliminated resource barriers such as time and geographic location, which supported its uptake, although in-person CE was often favored due to the added benefit of interacting and socializing with peers. Regardless of the format, many CE programs were criticized for being overly technical, lacking practical recommendations, or in the case of commercially funded CE, being perceived as biased. While the results of this study may be transferable within a similar context, they cannot be generalized to all Canadian veterinarians. The findings from this research highlight opportunities to improve veterinary CE by promoting veterinarian-producer collaboration, integrating practical applications with technical content, and adopting engaging delivery methods. Implementing these strategies will enhance program effectiveness and encourage sustained participation.

Caffeine is known to improve the vigor and survivability of premature babies, however, there is little information on its effects on neonatal dairy calves. Green tea extract has high natural caffeine content, with potential for additional polyphenol-related health benefits. The objective of this study was to determine how different doses of green tea extract, administered at birth, affects the vigor, behavior, health, and growth of dairy calves during their first 28 d of life, particularly those born from cows experiencing dystocia. Heifer calves were assigned to 1 of 3 treatments: 1) single (SNG; n = 42) 15-mL dose of green tea extract (Calf Perk, TechMix, LLC; containing 327.6 mg of naturally occurring caffeine, a minimum of 40% corn syrup as energy, 25% water, 1% vegetable oil to suspend the solution, and preservatives including cassia oil, xanthan gum, and citric acid), 2) 30-mL double dose (DBL; n = 39; 2 × 15-mL tubes of Calf Perk; 655.2 mg caffeine), and 3) control (CON; n = 39; 15-mL placebo of water, corn syrup, xanthan gum, and vegetable oil). Calves were given the treatment orally within 2 h of life, before colostrum feeding. Blood was sampled and vigor scores occurred between 0 and 72 h of life, while health scoring (including symptoms of respiratory illness and diarrhea) occurred at 24 h of life and then twice weekly until 28 d of age. BW was recorded at birth and weekly for 28 d. The DBL calves (23.7 ± 0.22 of a possible 30-point vigor score) had moderately improved overall average vigor scores throughout the duration of the study compared with CON calves (23.1 ± 0.20), while SNG calves (23.1 ± 0.23) did not differ from CON calves. No differences were detected between treatment groups for instances of respiratory illness (2.7 ± 0.08) or diarrhea (1.2 ± 0.06). No differences in ADG were detected in wk 1 (0.54 ± 0.03 kg/d) and 3 (0.49 ± 0.03 kg/d); however, in wk 2 SNG calves tended to gain more than CON calves (0.46 vs 0.33 ± 0.05 kg/d). SNG calves also tended to gain more than CON calves (0.98 vs 0.87 ± 0.05 kg/d) in wk 4. As result, SNG calves were heavier than CON (58.9 vs 57.3 ± 0.50 kg) calves at 28 d of age, while DBL calves did not differ (57.3 kg). Although the effects of dystocia were considered for all outcomes measured, the effects of green tea supplementation on calves born from a dystocia calving compared with those from a eutocia calving remains unclear. Overall, a double dose of green tea extract supplementation was associated with improved vigor, while a single dose resulted in greater weight gain in calves.

A long-standing objective in ruminant nutrition is to ensure an adequate supply of the key trace metals Zn, Cu, and Mn, while accounting for bioavailability, nutritional interactions, and not exceeding tolerance. In practice, however, dietary supplementation often by far exceeds reference nutritional guidelines, largely as a precaution against the multiple uncertainties of trace mineral supply. Current reference recommendations are determined using fixed and highly conservative uptake coefficients, an approach that overlooks both the opportunities and limitations of absorptive regulation, the primary homeostatic mechanism controlling trace metal balance. While generous supplementation should mitigate deficiency risks, it also introduces the less recognized risk of exceeding tolerable availability. Recent complete balance studies demonstrate that homeostatic downregulation of trace metals can be overwhelmed at dietary levels commonly observed in practice, underscoring the need for a new framework to define supplementation. We therefore developed an approach that integrates 3 elements: (1) stochastic analysis of basal dietary supply; (2) stochastic analysis of net nutrient requirements; and (3) probabilistic assessment of the likelihood that dietary supply falls outside the lower or upper boundaries of homeostatic regulation for these metals in cattle. This last element addresses the main limitation of current dietary guidelines by considering the dynamic range of absorptive regulation: maximum uptake rates achievable during upregulation and minimum uptake rates attainable during downregulation, instead of assuming fixed absorption coefficients. As a result, this framework defines ranges of adequate dietary supply rather than a single minimum requirement. The probability distribution of nutrient supply was derived from variation in dry matter intake, diet composition, and trace mineral occurrence in feedstuffs, whereas the distribution of net trace metal requirements was defined by the variability of the components of a classic factorial requirement approach applied to different animal conditions. These distributions were then compared against earlier defined boundaries of homeostatic regulation. This risk-based approach supports preventive supplementation of Cu, Zn, and Mn for dairy cattle across most physiological and productive states. At the same time, it highlights the risk to exceed tolerance thresholds under current supplementation practices, even at levels commonly considered safe. Overall, this analysis introduces novel reference guidelines to trace metal nutrition, demonstrating the opportunity to improve adequacy and reduce risk by reevaluating conventional supplementation strategies.

Wine lees (WLs), a by-product of the wine industry, represent a promising source of bioactive compounds, including diketopiperazines (DKPs). This study aimed to extract, characterize, and evaluate the effects of DKP-enriched WL fractions on immune cell responses under in vitro thermal stress conditions using an ovine model. Wine lees from white, rosé, and red vinifications were subjected to microwave-assisted extraction using water as a green solvent. Extracts were fractionated by flash liquid chromatography and chemically characterized by GC-MS/MS to identify DKP-rich fractions. Two DKP-enriched fractions (F1 and F2) from each vinification were tested at 0.4 and 0.8 mg/mL on sheep peripheral blood mononuclear cells (PBMCs) exposed to normothermic and hyperthermic conditions (37°C, 39°C, and 43°C). PBMC proliferation, viability, and cytokine secretion (IL-6, IL-1β, IL-10, and IFN-γ) were evaluated following mitogenic stimulation. DKP-enriched fractions reduced PBMC proliferation at 37°C and 39°C, whereas hyperthermia at 43°C resulted in a general impairment of immune cell responsiveness. Cytokine profiling indicated a pro-inflammatory response under thermal stress, with DKP treatment reducing IL-10 secretion at 39°C. Overall, these findings provide mechanistic insight into immune cell responses to DKPs under heat stress conditions in sheep and should be considered hypothesis-generating, providing a scientific rationale for future in vivo investigations in dairy animals.

This study was conducted to explore the effects of branched-chain fatty acids derived from lanolin (BCFAs-DFL) on growth performance, digestibility, blood metabolites, intestinal development, and fecal bacterial structure of calves aged 0 ~28 d. Twenty-four newborn Holstein dairy calves [birth weight = 41.88 ± 4.56 kg, mean ± SD] were divided into the control group (Control) receiving whole milk without BCFAs-DFL and the treatment group (BCFA) receiving whole milk with BCFAs-DFL (4g/d) supplementation according to the randomized block design based on their birth weight and birth date. Calves fed BCFAs-DFL had higher ADG, feed efficiency, heart girth, and total-tract apparent digestibility of nutrients, while the treatments did not affect total DMI. Plasma cholesterol and haptoglobin were lower in calves fed BCFAs-DFL than in the control group. BCFAs-DFL reduced the frequency of diarrhea, the duration of diarrhea, and the number of medication doses required for treating diarrhea. In contrast to the control group, feeding BCFAs-DFL increased the gene relative expression of tight junction protein 1, claudin 2, β-defensin-1, β-defensin 4, regenerating islet-derived protein (REG) 3α, REG 3γ, and IL-10 in the small intestine of calves, while decreasing the gene relative expression of IL-1β and TNF-α. Supplementation with BCFAs significantly elevated the total content of short-chain fatty acids (SCFAs) in calf feces, as well as the proportions of isobutyric acid and butyric acid relative to total SCFAs. In addition, the relative abundance of Subdoligranulum and Faecalibacterium was significantly increased in the feces of calves fed BCFAs-DFL at 14 d of age, and Prevotella_9 was the first to appear in the BCFA group at 14 d of age. Overall, this study explored the impact of BCFAs-DFL on the health status of calves in the early stage of their lives, laying a foundation for the research on BCFAs-DFL in terms of the intestinal health of young ruminants.

Staphylococcus aureus (S. aureus), a major foodborne pathogen contaminating dairy products, threatens food safety and public health via food poisoning and severe infections like bacteremia. Conventional culture-based methods are time-consuming, while advanced techniques need expensive equipment, limiting on-site use. To address this, we developed a novel Magnetic Mesoporous MnOx Nanozyme Probe (MMMNPs) by integrating Mesoporous MnO_x Nanozyme with oxidase-mimetic activity, Fe₃O₄ magnetic nanoparticles, and S. aureus-specific aptamers. The synthesis involved the preparation of hydrothermal Fe₃O₄, the synthesis of MnO_x, and the construction of a composite with bond positions and electrostatic interactions. For detection, MMMNPs mixed with samples underwent magnetic separation, followed by TMB-triggered color reaction. S. aureus (0 - 10⁶ cfu·mL^-1) inhibited probe activity, fading solution from deep blue to colorless. There was a good linear correlation (R² = 0.980) between the shift of the absorbance peak at 652 nm and the logarithm of S. aureus concentration, with a LOD of 3.33 cfu·mL^-1 for UV-Vis detection and 1x10² cfu·mL^-1 for naked-eye visual detection.The probe exhibited high specificity, with no response to interfering bacteria, and demonstrated good applicability in spiked milk (recovery: 86.84% - 113.81%, RSD <5%). Unexpectedly, lower detection limits and better linearity were also achieved in the milk samples. Preliminary tests confirmed Mag-MnOx's significant bacteriostatic activity against S. aureus. This low-cost, easy-to-operate strategy enables S. aureus detection and elimination, promising on-site use in food safety and clinical diagnosis.

This study aims to determine the effects of feeding, management, and reproductive strategies used to reduce age at first calving (AFC) on production and reproductive performance through meta-analytic methods. A literature search using 3 search engines was conducted to identify prospective studies that evaluated AFC for data extraction. Inclusion criteria included specific dairy breeds, a treatment group with an AFC below 26 mo of age, and prospective enrolment of heifers. There were few prospective studies suitable for meta-analysis, with 16 studies containing 35 appropriate experiments. There was substantial heterogeneity likely due to differences in study design and interventions used to induce an AFC difference. Outcomes were assessed using classical multilevel random effects meta-analytic models with standard mean difference, effect sizes, or risk ratios being evaluated where appropriate. Meta-regression was performed using the difference in age at first calving. There was a loss of production for first lactation milk (-2.06 L/d of earlier calving), fat (-0.12 kg/d of earlier calving), and protein (-0.08 of kg/d earlier calving) yield for heifers calving at a younger age than their peers. There were no differences in second and third lactation milk yield, calving difficulty, heifer reproductive performance, survival to calving, and survival to the end of first lactation. While the production in first lactation is decreased, this may be offset by fewer days to first calving without compromising the heifers' ability to calve, become pregnant for the first time, or survive to the end of first lactation. Given the lack of prospective studies, more randomized controlled experiments over multiple lactations, including health, production, and reproductive data, are needed to evaluate this topic further.