Journal of Dairy Science最新文献

Feed efficiency is a critical trait in dairy cattle production, with profound implications on both economic profitability and environmental sustainability. The objective of this study was to assess genetic relationships between feed intake and feed efficiency traits of calves and first-lactation Holstein cows. Data from 795 calves and 720 primiparous cows were analyzed, with feed intake measured as metabolizable energy intake (MEI) in calves and DMI in cows. Calf MEI was summarized as weekly averages across 2 key developmental phases: wk 1 to 3 (MEI1) and wk 7 to 9 (MEI2). Dry matter intake was recorded weekly from lactation wk 9 to 44. Feed efficiency was defined as residual feed intake (RFI) in primiparous cows and residual metabolizable energy intake (RMEI) in calves, estimated for the same 2 developmental periods as MEI (RMEI1 and RMEI2). In both cases, efficiency was expressed as the deviation of observed intake from expected intake based on energy sinks. Using a multitrait repeatability model, genetic correlations were estimated among the 6 traits (MEI1, MEI2, RMEI1, RMEI2, DMI, and RFI). Notably, genetic correlations were moderate and positive between MEI2 and DMI at 0.49 ± 0.15 and RFI at 0.44 ± 0.21. In contrast, the genetic correlations of MEI1 with DMI was 0.15 ± 0.15 and RFI was 0.12 ± 0.21, which were close to zero and not significant. The genetic correlation between RFI and RMEI1 was estimated at -0.35 ± 0.26, indicating a possible negative relationship, although not significant. A moderately high positive genetic correlation was estimated between RFI and RMEI2 at 0.71 ± 0.36. These findings suggest that RMEI2 seems to be favorably genetically correlated with RFI, whereas RMEI1 shows no or perhaps a relatively weak unfavorable association with RFI. The results likely reflect physiological differences in calf rumen development, but support the potential for early selection based on RMEI2 to enhance cow feed efficiency.

Genomic selection (GS) has revolutionized animal breeding and accelerated genetic gains in breeding programs. Although GS has become common in cosmopolitan dairy cattle breeds, its implementation in local breeds has begun only more recently, or is still in progress. However, the introduction of GS in some cosmopolitan breeds has also been associated with increased inbreeding rates, raising concerns about the potential effects of GS on genetic diversity in smaller or local breeds. Our aim was to investigate the impact of GS on genetic diversity in 5 (small) local cattle breeds from 3 European countries: Meuse Rhine Yssel (MRY; from the Netherlands); Norwegian Red (NRC; from Norway); and Abondance (ABO), Tarentaise (TAR), and Vosgienne (VOS; from France). We investigated changes in population demographic structure, as well as trends and rates of kinship and inbreeding, using both pedigree- and genomic-based measures. The population size varied depending on the breed, with Vosgienne being the smallest and NRC being the largest. Single nucleotide polymorphism genotypes were available for 4,645 MRY, 193,489 NRC, 16,387 ABO, 8,578 TAR, and 4,472 VOS animals. Animals were genotyped with more than 40,000 SNPs. Overall, following the implementation of GS in these breeds, we observed a reduction of up to 4 years in generation intervals for sires, fewer calves that later became sires, and, for the French breeds, a broader sire usage. Such changes were likely due to GS enabling the preselection and screening of more young bulls. Additionally, the contributions of the top 10 sires were more evenly distributed after the introduction of GS. Although changes in inbreeding and kinship rates occurred after the introduction of GS, we found no consistent pattern across breeds: pedigree (and genomic runs of homozygosity [ROH]-based) inbreeding rates per generation increased in MRY from -0.67 before GS to 0.51 after GS (from -1.12 to 0.93) and TAR from 0.35 to 0.93 (from 0.68 to 0.86), but decreased in NRC from 0.26 to 0.05 (from 0.10 to 0.06), Abondance from 1.19 to 0.99 (from 2.39 to 0.58), and Vosgienne from 0.53 to 0.23 (from 0.88 to 0.19). Moreover, analysis of genomic ROH-based inbreeding by length class showed that after the implementation of GS, the largest changes in inbreeding level and inbreeding rates per generation occurred for shorter ROH segments. Our study suggests that changes and increases in inbreeding rates may occur after the introduction of GS, although they may not be directly due to the introduction of GS per se, but rather due to population management strategies, such as optimal contribution selection. Our findings emphasize the importance of monitoring changes in both genetic diversity and population demographic structure after implementing GS in local breeds, as well as adjusting breeding strategies when needed to ensure long-term sustainability.

Timed artificial insemination (TAI) protocols have revolutionized reproductive management in dairy cattle, but their interaction with genetic factors affecting fertility traits remains poorly understood. This study was performed to investigate whether TAI protocols influence the genetic architecture of fertility traits compared with traditional heat detection (HD) systems. The dataset included 3,842 reproductive management protocol descriptions, classified as either TAI (2,002 records) or HD (1,840 records), with a final dataset with records from 90,298 first lactation cows. Genotypic data included 6,985 cows with records for first service to conception (FSTC) and days open (DO), and 7,220 cows with records for calving to first service (CTFS). After quality control, 44,819 SNP markers were retained for analysis. Variance components were estimated using a Bayesian single-step GBLUP multiple-trait animal model including milk yield. Heritabilities were consistently low across all fertility traits and reproductive management scenarios, ranging from 0.01 (95% highest posterior density [HPD]: 0.006 to 0.011; CTFS under TAI) to 0.04 (95% HPD: 0.035 to 0.044; DO under TAI). Importantly, genetic correlations between the same trait under HD and TAI were moderate to high but significantly less than unity: 0.74 ± 0.04 for FSTC, 0.89 ± 0.03 for CTFS, and 0.91 ± 0.01 for DO. Genome-wide association studies identified different associations depending on reproductive management systems. Functional annotation revealed 53 protein-coding genes within ±100 kb of significant SNPs, with distinct candidate genes identified for TAI and HD. In addition, QTL enrichment analysis demonstrated that traits under HD candidate regions were associated with broader functional categories, including milk production, reproduction, and exterior traits, whereas traits under TAI showed enrichment primarily for health-related traits. This study provides an empirical comparison of genetic parameters for fertility traits in dairy cattle under both TAI and traditional HD systems using large-scale real-world data. Our findings suggest that TAI influences the expression of genetic variation underlying reproductive traits, emphasizing the importance of accounting for reproductive management in genetic evaluations. This could be achieved by treating fertility under different systems as genetically distinct but correlated traits in multiple-trait models.

This study investigated the effects of 25-hydroxycholecalciferol (HyD) supplementation on I) plasma acute phase reactants, cytokines, and Ig concentrations in colostrum in multiparous Holstein cows from three weeks prepartum to 21 DIM and II) plasma concentrations of fat-soluble vitamins, Ig concentrations, mineral, and metabolites of newborn calves. Forty-two cows were assigned to receive either cholecalciferol (D₃) or HyD. From 21 days before the expected calving until parturition, the D₃ group received 0.475 mg/d (0.035 mg/kg of DM) of D₃, and the HyD group received 1.45 mg/d (0.108 mg/kg of DM) of HyD. From parturition until 21 DIM, the D₃ group received 0.625 mg/d (0.024 mg/kg of DM) of D₃, and the HyD group received 0.625 mg/d (0.024 mg/kg of DM) of D₃ plus 1.0 mg/d of HyD (0.056 mg/kg of DM equal to 0.080 mg/kg of DM in total). Tail blood samples were collected from cows on days -7 (6 ± 2 days), -3 (2 ± 1 days), 0 (13 ± 8 hours post-calving), 1 (36 ± 11 hours post-calving), 10 (9 ± 2 days), and 20 (16 ± 2 days) relative to calving for plasma analysis of fat-soluble vitamins (A and E), acute phase proteins (haptoglobin [Hap] and serum amyloid A [SAA]), and cytokines (tumor necrosis- α [TNF-α], interferon-γ [IFN-γ], IL-10). Additionally, a blood sample was taken from a jugular vein of the calves 48 ± 3 (mean ± SD) hours after birth. For plasma TNF-α concentration in cows, there was an interaction between treatment and time with lower prepartum concentrations in HyD compared with D₃; however, the difference was reduced at calving and reached the same level as D₃ group at 20 DIM. No treatment effect was observed for plasma Hap, SAA, IFN-γ, or IL-10. Plasma 25-OH-D₃ concentration of newborn calves in HyD group was higher than in calves from D₃ group (13.9 and 8.9 pg/mL, respectively), while plasma 25-OH-D₂, vitamin A, and vitamin E concentrations were unaffected by the treatment. There was a linear relationship between plasma 25-OH-D₃ in calves and in their dams. Colostrum IgA, IgM, and IgG concentrations were not affected by treatment. In line with the colostrum results, plasma IgA, IgM, and IgG of calves were not different between D₃ and HyD groups. There was no significant difference in plasma Ca and inorganic P concentrations between D₃ and HyD groups in newborn calves. In conclusion, HyD supplementation had limited impact on acute phase reactants, and cytokine in transition dairy cows. Dietary supplementation of HyD during the close-up period increased plasma 25-OH-D₃ concentrations in the newborn calves without affecting plasma Ca and inorganic P. Additionally, the increased plasma 25-OH-D₃ concentrations did not affect Ig concentrations in either colostrum or calf plasma.

The interest in rearing dairy calves within cow-calf contact (CCC) systems, allowing full (all calves) and partial (some calves) contact, is increasing, driven by growing societal criticism of the early separation of cow and calf after birth. This empirical study aimed to examine the differences between existing early-separation systems (ESS), dairy cow-calf contact systems for some calves (CCS), and dairy cow-calf contact systems for all calves (CCA). An online survey of farmers in Germany was conducted to describe the status quo, identify future challenges, and highlight research gaps. First, a comprehensive questionnaire with 22 open and 26 closed questions was developed. All participants answered partly the same questions (12 open and 15 closed), but specific questions varied according to the rearing system. Only fully completed questionnaires were included in the statistical analysis. After the descriptive analysis, a generalized linear model was applied to examine differences among the 3 rearing systems (ESS vs. CCS vs. CCA). Additionally, Spearman rank correlations were calculated within CCS and CCA. Feeding practices differed between the rearing systems. On 78.6% of farms with CCA and 62.5% of farms with CCS, calves received colostrum directly from the udder, whereas this was the case on only 3.12% of farms with ESS. In CCS and CCA, monitoring the reported intake of colostrum or whole milk by calves was identified as a major transition challenge. Farmers (CCA and CCS) ensured that suckling calves had sufficient milk primarily by regulating the amount of milk retained in the udder. In ESS, participants observed that object-sucking of calves occurred more frequently than in CCA (11.7% ± 1.59% vs. 0.95% ± 0.53% of calves). The participating farms stated greater occurrence rates of health and management issues in CCA compared with ESS, including problems with milk ejection (11.8% ± 3.99% vs. 3.25% ± 0.64% of cows). Farmers (CCA) also observed that cows exhibited increased vocalizations and more frequent movement after separation from the calves. Similarly, participants reported that calves also showed more vocalizations and decreased performance following separation after a longer contact period between cow and calf. Perceptions of transition challenges varied depending on prior assumptions (ESS) or hands-on experience in CCC systems (CCS and CCA). These responses highlight the need for further research to develop practical solutions for the main reported challenges, to ensure a smooth transition without negative effects on cow and calf health and welfare.

Excessive nonesterified fatty acids (NEFA) during the transition period impose metabolic stress on the bovine mammary gland. High NEFA levels induce oxidative stress and trigger apoptosis in bovine mammary epithelial cells. Prohibitin 2 (PHB2) is a mitochondrial inner-membrane scaffolding protein known for its role in maintaining mitochondrial cristae integrity and regulating apoptosis. However, the specific effect of PHB2 on apoptosis in response to NEFA-induced stress in bovine mammary epithelial cells remains unclear. Therefore, this study aimed to investigate the regulatory role of PHB2 in high-NEFA-induced bovine mammary epithelial cells apoptosis, as well as the underlying mechanisms involved. First, mammary gland tissue from healthy (n = 15, BHB < 0.6 mM) and ketotic cows (n = 15, BHB > 3.0 mM) were collected. Compared with healthy cows, ketotic cows exhibited higher protein abundances of cleaved caspase-3 and cleaved PARP, lower protein abundances of PHB2 and long-form OPA1 (L-OPA1) in mammary glands, increased terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) labeling in mammary tissues, and elevated lactate dehydrogenase activity in milk. Second, MAC-T cells were treated with NEFA (0, 0.3, 0.6, or 1.2 mM). MAC-T treated with 1.2 mM NEFA displayed increased protein abundance of cleaved caspase-3, cleaved PARP and cytoplasmic cytochrome c (Cyt C), and decreased protein abundance of PHB2, L-OPA1, and mitochondrial Cyt C. Additionally, MAC-T treated with 1.2 mM NEFA had increased apoptosis rate and TUNEL labeling. Third, MAC-T cells were transfected with small interfering RNA to silence PHB2 or plasmid for overexpression of PHB2, followed by treatment with or without NEFA. PHB2 silencing aggravated NEFA-induced apoptosis in MAC-T cells, and PHB2 overexpression alleviated this effect. Fourth, MAC-T cells were transfected with noncleavable OPA1 mutant overexpression adenovirus. Overexpression of noncleavable OPA1 mutant ameliorates NEFA-induced mitochondrial dysfunction and apoptosis. In conclusion, PHB2 alleviates NEFA-induced mitochondrial dysfunction and apoptosis by preventing OPA1 cleavage.

Automatic milking systems (AMS) are increasingly used in dairy farming for their benefits to farmers (e.g., increased milk production, saving labor, positive lifestyle changes) and cows (e.g., voluntary milking). Providing cows choice over when to be milked allows for a form of behavioral freedom (i.e., agency) within an environment where control may otherwise be limited. Our narrative review critically explores how cows interact with AMS, including the timing and frequency of accessing the milking unit. We describe how external system-based factors can affect access to the AMS. For example, we note that "voluntary" milking still requires cows to be milked at regular intervals, typically incentivized through rewards such as feed. Within this constraint, free-flow systems (in contrast to forced-flow systems) provide animals with greater control over the milking process and other activities. However, feed reward predictability tends to be lower in free-flow systems compared with forced-flow systems, as too-frequent AMS entries are unrewarded. We also describe how characteristics of the individual cow affect access to the AMS, including the positive effects of prior experience with milking robots (e.g., multiparous cows, AMS training), higher social status, personality, and motivation to obtain AMS-associated rewards. Animals lacking these characteristics, such as primiparous or lower-ranking individuals, may be more susceptible to barriers restricting access to the AMS. We conclude that AMS can increase agency over the milking process, but design characteristics aimed at enhancing labor efficiency and milk production constrain agency. Moreover, the degree of control over the milking process is limited by characteristics of the cow. New research is required to understand how AMS can be managed to better accommodate individual differences and enhance animal agency.

Supplementation with Saccharomyces cerevisiae fermentation-derived postbiotics (SCFP) in calves can improve calf growth and health. This study evaluated the effects of SCFP supplementation in the calf diet on growth, health, rumen fermentation, and rumen microbiota during the first 70 d of life in 2 independent calf experiments conducted under different maternal dietary contexts. The dams of the calves consisted of 400 pregnant Holstein dry cows that received either a basal far-off and close-up TMR without SCFP (n = 200) or the same diets supplemented with SCFP (n = 200) beginning at dry-off. From these dams, 144 female calves were enrolled and allocated within maternal dietary background, blocked by birth date, and randomly assigned to receive SCFP or not in the calf diet, resulting in 2 independent experiments (n = 36 calves per group, 4 groups in total): experiment 1, CC (dam: -SCFP, calf: -SCFP) and CT (dam: -SCFP, calf: +SCFP); and experiment 2, TC (dam: +SCFP, calf: -SCFP) and TT (dam: +SCFP, calf: +SCFP). Growth performance, serum metabolites and antioxidant and anti-inflammatory indicators, diarrhea incidence, and rumen fermentation and microbial composition were measured. In experiment 1, CT calves showed greater weaning weight and preweaning ADG, reduced diarrhea incidence, and altered rumen microbial community structure at 70 d of age, with enrichment of Erysipelotrichaceae_UCG-002 and Sharpea. In experiment 2, TT calves tended to have greater preweaning ADG, whereas weaning weight was unaffected. In both experiments, calves supplemented with SCFP consistently reduced preweaning diarrhea risk. At 70 d of age, rumen microbial diversity was not affected, although calves in the TT group exhibited greater total volatile fatty acid and ammonia-nitrogen concentrations. In conclusion, direct SCFP supplementation to calves during the preweaning period improved growth performance and health and modified rumen fermentation and microbial composition. Differences in calf responses between experiments highlight the need for future studies with replicated maternal treatments to clarify the role of maternal supplementation.

In grazing dairy systems, the CP content of perennial ryegrass-white clover pastures often exceeds cows' nutritional requirements. Excess dietary nitrogen (N) is excreted in urine, increasing the risk of N leaching into soil and waterways or being released as nitrous oxide, a greenhouse gas. The relationship between milk urea concentration and excess dietary N may provide an indicator to support managing the risk of higher urinary N losses. The first objective of this observational study was to compare milk urea concentration within and between lactation seasons, in bulk milk collected from dairy herds using pasture-based systems in New Zealand. The second objective was to identify farm management factors that affect bulk milk urea (BMU) concentration by comparing farms with divergent BMU. Milk urea was measured in tank milk (n = approximately 2.2 million collections per lactation season; approximately 230 collections per farm across approximately 9,600 farms, with milk collected daily or every 2 d) over the 2016-2017, 2017-2018, 2018-2019, and 2019-2020 lactation seasons. Divergent BMU farms (n = 50/group), with annual mean BMU consistently low (L50) or high (H50) across New Zealand over 4 seasons, were selected and their farm management metrics (farm-reported, annual) and milk production were compared. Additionally, divergent BMU groups within 7 different New Zealand regions were compared (n = 50/group per region). Bulk milk urea concentration from all farms across all 4 lactation seasons followed a normal distribution (range 0 to 69.5 mg/dL), increased through lactation (25.5, 27.5, and 31.6 mg/dL for spring, summer, and autumn, typically corresponding to early, mid, and late lactation, respectively), and varied between lactation seasons. Monthly BMU ranged from 13 to 26 mg/dL for L50 and from 33.2 to 45.8 mg/dL for H50. Distributions of milking frequency, breed, and geographical region were different for L50 and H50. Farm area, herd size, and milk solids production per cow were similar between the 2 groups, whereas milk production per hectare and stocking rate (cows/ha) were greater for H50. Estimated total DM eaten per hectare, pasture and crops eaten per cow and pasture and crops eaten per hectare were all greater for H50. The H50 group applied substantially more annual N fertilizer. Observations for L50 and H50 groups were mirrored by regional divergent BMU groups, with some exceptions that likely reflect differences in farm management systems between regions. Understanding drivers of BMU concentration may provide tools for farmers to improve N use efficiency and reduce risk of excess urinary N loss from dairy herds.

The purpose of this study was to evaluate the quality and functional characteristics of set-type yogurt manufactured using different concentrations of Echium amoenum extract (EE, 0.25% and 0.50%, wt/wt), Urtica dioica extract (UE, 0.25% and 0.50%, wt/wt) and mixture of them (0.25% of EE + 0.25% of UE, wt/wt). Physicochemical, rheological, antioxidant, microstructure, color, and sensory properties of manufactured yogurts were analyzed during refrigerated storage at 4°C for 21 d. According to the results, utilization of different concentrations of EE, UE, or their mixture in the formulation of set-type yogurt showed significant increase in titratable acidity, viability of lactic acid bacteria, antioxidant activity, and total phenolic content, and significant decrease in pH value. In addition to having more compact structure, the yogurt fortified with 0.25% of EE had the lowest value of syneresis and the highest values of water holding capacity along with storage and loss modulus among the experimental samples. In terms of sensory properties, whereas the yogurt containing 0.25% of EE showed similar overall acceptability to the control sample, the yogurts fortified with 0.50% of EE and 0.25% of EE + 0.25% of UE had more overall acceptance points compared with yogurts manufactured using different concentrations of UE. The results revealed the possibility for manufacture of functional set-type yogurt with potential health-promoting properties by monitoring the type and ratio of selected herbal extracts containing functional properties.