Journal of Dairy Science最新文献

The aim of this cross-sectional observational study was to assess whether nulliparous Holstein heifer fertility is associated with (1) energy reserve-related traits, such as body condition score (BCS) and body weight (BW); (2) ovarian reserve-related traits, such as Anti-Müllerian hormone (AMH) and antral follicle count (AFC); and (3) development-related traits, such as anogenital distance (AGD) and vulval length (VUL). From August 2022 through July 2023, we used a prospective approach in which the phenotypic traits (BCS, AMH, AFC, AGD, BW, and VUL) of 698 Holstein heifers were measured once at approximately 12 mo of age (at the beginning of the breeding program). All heifers were submitted to the herd reproductive management from 367 ± 3 d of age and 297 kg of BW until 570 d of age, or 5 breedings. Fertility outcomes (age at first service, pregnancy per AI (P/AI) at first service, age at conception, and number of services per conception) were retrieved from software records. Pearson correlations were performed among phenotypic traits collected. The strongest correlations (r >0.5) observed were for AGD with VUL and AMH with AFC. Associations of phenotypic traits with fertility outcomes were determined using generalized linear models. Body condition score was the phenotypic trait most associated with fertility outcomes. Associations of AMH, AFC, AGD, BW, and VUL with fertility were not observed or very weak. Further, we divided the data into BCS tertiles and performed association analyses by category. The top BCS tertile was associated with greater BW (365.7 ± 1.8 vs 356.0 ± 1.5 kg), greater P/AI at first service (65.0 ± 4.0 vs 52.0 ± 4.0%), and fewer number of services per conception (1.5 ± 0.10 vs 1.8 ± 0.09) compared with the bottom tertile. Moreover, AGD was greater in the top and bottom tertiles compared with the middle tertile. Finally, BCS was associated with time to conception based on the Cox proportional hazards survival analysis, indicating that heifers with greater BCS became pregnant earlier. Based on the results observed in the current study, we would expect benefits for fertility by improving management practices that result in heifers with greater BCS at first service, but ovarian reserve-related traits (AMH, AFC) and developmental traits (AGD, VUL) were not associated with fertility outcomes in our study.

Undigested P and N are excreted and contribute to the environmental impacts of dairy farming. Degradation of phytate in the rumen has been shown to be high but variable, leading to incomplete phytate-P utilization and resultant antinutritional impacts of phytate along the gastrointestinal tract. We investigated the effect of a novel bacterial 6-phytase (PhyG) on the apparent total-tract digestibility (ATTD) and excretion of DM, phytate-P (PP), P, CP and NDF in lactating dairy cows. Forty-eight lactating Holstein-Friesian cows were assigned to 3 treatments with 16 cows per treatment in a randomized block design. Cows averaged 44.1 kg milk/d, and 124 DIM at the experiment start. Diets were fed ad libitum as a TMR that was formulated to meet nutritional requirements except for P which was fed at 92% of the recommendation. Treatments comprised a control diet (CON) and the control diet supplemented with 2,000 or 5,000 phytase units/kg DM of PhyG. The experiment lasted for 19 d including a 14 d diet adaptation period and a 5 d fecal collection period. Dry matter intake did not differ across treatments. The ATTD of PP in CON was 88.5%, indicating incomplete phytate degradation. The ATTD of ash, P and CP increased linearly, whereas the ATTD of PP and NDF increased both linearly and quadratically with increasing PhyG dose level; with PhyG at 5,000 FTU/kg, the ATTD of PP, P, CP and NDF increased by 9.2, 13.7, 4.1 and 7.5% points above CON, respectively. Fecal excretion of ash, PP, P and NDF were reduced linearly. Supplementation of PhyG also reduced excretion of PP quadratically and CP excretion tended to be reduced linearly. Body weight and milk yield did not differ across treatments, but milk protein yield tended to increase linearly with increasing PhyG dose. The addition of PhyG to the diet of lactating dairy cows improved nutrient utilization and decreased nutrient excretion. It could therefore contribute to reducing the environmental impacts of dairy production.

High nonesterified fatty acid (NEFA) concentrations in cows with clinical ketosis lead to metabolic dysfunction in mammary cells, resulting in oxidative stress. Studies have shown that autophagy is impaired in the mammary glands of ketotic cows, while enhancing autophagy mitigate oxidative stress in these animals. Cullin3 (CUL3), an E3 ubiquitin ligase, is integral for maintaining cellular homeostasis, particularly regulation of oxidative stress and autophagy. Whether CUL3 is involved in mitigating NEFA-induced oxidative stress is unknown. This study aimed to investigate the protective effects and underlying mechanisms whereby CUL3 mitigates NEFA-induced oxidative stress in mammary epithelial cells. First, mammary gland tissue and blood samples were collected from healthy cows [n = 12, β-hydroxybutyrate (BHB) < 0.6 mM] and cows with clinical ketosis (n = 12, BHB > 3.0 mM). Compared with healthy cows, cows with clinical ketosis had reduced productive performance, decreased CUL3 expression, impaired autophagic activity, and increased oxidative stress status in mammary tissue. In vitro, incubating MAC-T with 1.2 mM NEFA downregulated CUL3 expression, impaired autophagy, and increased oxidative stress. Adenovirus-mediated overexpression of CUL3 attenuated NEFA-induced accumulation of peroxides and reactive oxygen species (ROS), while silencing of CUL3 via siRNA exacerbated these effects. Even when nuclear factor erythroid 2 related factor 2 (NFE2L2) expression was reduced by overexpression of CUL3, there was no worsening of NEFA-induced reductions in mRNA levels of NFE2L2 downstream target genes [NADPH quinone oxidoreductase 1 (NQO1), Heme oxygenase-1 (HMOX1), Glutamate-cysteine ligase catalytic (GCLC) and Glutamate cysteine ligase modifier subunit (GCLM)]. The reduction in NEFA-induced oxidative stress by CUL3 was diminished upon autophagy related 5 (ATG5) silencing suggesting that CUL3 alleviates NEFA-induced oxidative stress via autophagy. Additionally, CUL3 overexpression aggravated the NEFA-induced decrease in BCL2 apoptosis regulator (BCL2) expression while alleviating the NEFA-induced decrease in beclin1(BECN1) expression. Under NEFA treatment, overexpression of BCL2 partly mitigated the CUL3-induced elevation in BECN1. Overall, oxidative stress and impaired autophagy characterize mammary tissue of cows with clinical ketosis. CUL3 activation, likely through the BCL2-BECN1 pathway, enhances autophagy and mitigates NEFA-induced oxidative stress in MAC-T cells. Thus, targeting CUL3-mediated autophagy could be a promising therapeutic strategy to reduce oxidative stress-induced damage in bovine mammary epithelial cells.

The negative energy balance (NEB) state in dairy cows is a critical factor affecting health, reproduction, and production, particularly during early lactation. Multiple blood and milk biomarkers change when dairy cows are in the NEB state. Direct measurement of NEB is impractical for large-scale use due to costs, necessitating reliance on indirect predictors such as milk mid-infrared (MIR) spectrometry-based predicted biomarkers. However, the genetic relationships between NEB and its potential biomarkers remain unclear. This study aimed to (1) compare measured reference NEB with MIR-predicted NEB (PNEB), a novel energy deficit score (EDS), 15 biomarkers, and 3 production traits; (2) estimate genetic parameters among these traits using a 20-trait repeatability model, quantifying the ability of the 19 other studied traits (logit-transformed EDS (LEDS), 15 biomarkers, and 3 production traits) to genetically predict logit-transformed PNEB (LPNEB); and (3) evaluate the causal effects of LPNEB on the 19 traits through a recursive model. Two datasets were used: dataset I (127 cows, 965 records) provided reference data for objective (1), and dataset II (25,287 first-parity cows, 30,634 records) enabled genetic analysis used for objectives (2) and (3). Traits were analyzed using Pearson correlations, multiple-diagonalization EM-REML-based genetic parameter estimation, and recursive modeling. The studied traits had moderate to moderate-high h² ranging from 0.16 to 0.38. The genetic correlations between LPNEB and the studied traits ranged from -0.60 to 0.85 for LEDS and 0.87 for MIR-predicted blood nonesterified fatty acids (+). Analysis of genetic predictability of LPNEB revealed that the 19 other traits together explained 89% of the genetic variance of LPNEB, with all 15 biomarkers alone contributing the largest fraction with 82%, LEDS alone 65%, nonesterified fatty acids (NEFA) alone 62%, and all traits except LEDS 85%, indicating that LEDS contains useful additional information. Recursive modeling further identified 8 traits, including NEFA and LEDS, as highly dependent on LPNEB, highlighting their potential as robust biomarkers. This study demonstrates the utility of MIR-predicted traits for understanding the genetic mechanisms of NEB and its potential for integration into breeding programs, while emphasizing cautious interpretation of these results due to limitations of MIR-predictions of studied traits to represent directly measured traits.

A healthy uterine environment is essential for establishing and maintaining pregnancy and normal embryo development after insemination. In this context, the primary objectives of this study were to assess the genetic background of vaginal discharge score (VDS) traits during the voluntary waiting period in Holstein cows and to identify genomic regions and candidate genes influencing postpartum uterine health based on the integration of phenotypic, genomic, and transcriptomic data sets. Genetic parameters of 5 VDS traits defined according to lactation stage (VDS1, VDS2, VDS3, VDS4, and VDS5) were estimated based on VDS records from 64,241 Holstein cows that calved between 2019 and 2023 and genomic information from 2,489 cows. Genome-wide association studies (GWAS) were performed aiming to identify genomic regions associated with VDS traits. Differentially expressed genes and modular genes were obtained through RNA-seq data of uterine secretion from 6 healthy and 6 diseased cows. The VDS traits had low heritability estimates ranging from 0.006 ± 0.002 to 0.081 ± 0.011. Among the VDS traits, there were relatively strong genetic correlations between VDS1 (0-14 DIM) and metritis (0.678-0.763) as well as VDS3 (29-55 DIM) and endometritis (0.579-0.628). A total of 190 genes harboring 32 significant SNPs were identified as candidate genes regulating VDS in primiparous cows. The candidate genes identified were significantly enriched for pathways involved in cytokine-cytokine receptor interaction, MAPK signaling, and oxytocin signaling. Based on RNA-seq data of uterine secretions, 2,803 differentially expressed genes and 3,570 modular genes were identified. Furthermore, 7 genes were identified based on GWAS, differential gene expression, and weighted gene co-expression network analysis. The genes VSTM1, IL10RA, FXYD5, C2CD5, CETN4, ALS2CL, and PBX1 were considered to be the most promising candidate genes influencing postpartum uterine health in Holstein cows. This study provides novel insights on the genetic background of postpartum uterine health in Holstein cows. The results obtained can contribute to further refinements of selection indexes for improving uterine health and fertility in dairy cattle.

Raw milk is known to harbor a complex microbial community, including microorganisms of technological and human health interest. However, it can also be a source of pathogenic and spoilage bacteria, such as spore-forming bacteria and Pseudomonas spp. Despite cleaning and disinfection procedures, biofilms in milking machines are difficult to remove and represent a major source of milk contamination. This work aims to describe biofilms in milking machines at both the laboratory and farm scales. Encouraging studies on the microbiota of milking machine biofilms, the parameters influencing changes in biofilm composition, and the methods used to characterize them are essential for managing the formation and composition of these biofilms. Enhancing such knowledge will help improve the understanding of milking machine biofilms and their impact on the quality of milk and dairy products.

The objective of this study was to investigate the association of postcalving IMI with milk production and SCC during the first 3 test days after calving, as well as the risk of clinical mastitis occurrence and culling within the first 100 DIM in first-lactation Holstein dairy cows. This retrospective cohort study was conducted at one commercial dairy farm in New York. Postcalving IMI was assessed by means of bacteriological testing of composite milk sample aseptically obtained from all quarters at the day of calving or between 7 and 13 DIM. Data on monthly test-day milk yield and SCC, as well as on the occurrence of clinical mastitis and culling within the first 100 DIM were retrieved from the farm management software. We used generalized linear mixed models to study the associations of postcalving IMI with milk yield and SCC. We found that cows with an IMI with Pasteurella multocida had lower milk yields compared with those without a postcalving IMI, whereas cows with an IMI with Staphylococcus chromogenes had higher milk yields. Similarly, cows infected with Staphylococcus aureus, Staphylococcus chromogenes, Staphylococcus simulans, Streptococcus dysgalactiae, Streptococcus uberis, or Pasteurella multocida had higher SCC compared with their culture-negative herdmates. Logistic regression analyses revealed associations between postcalving IMI and the occurrence of clinical mastitis and culling within the first 100 DIM. Compared with cows without a postcalving IMI, the odds ratio and 95% CI of clinical mastitis were 4.00 (2.76-5.79) for cows with a Streptococcus dysgalactiae IMI, 4.45 (3.16-6.26) for cows with a Streptococcus uberis IMI, and 9.87 (4.88-19.96) for cows with a Pasteurella multocida IMI. Cows identified with an IMI with Staphylococcus aureus, Streptococcus dysgalactiae, Streptococcus uberis, or Pasteurella multocida had higher odds of culling within the first 100 DIM compared with their culture-negative herdmates. The odds ratios (95% CI) were Staphylococcus aureus, 6.36 (4.44-9.13); Streptococcus dysgalactiae, 2.02 (1.42-3.40); Streptococcus uberis, 2.12 (1.40-3.20), and Pasteurella multocida, 2.23 (1.01-4.93). Due to the lack of molecular strain typing of postcalving cultures and those obtained from clinical mastitis cases, we cannot infer a cause-effect relationship. Future research to study the significance and identify possible risk factors of postcalving IMI in first-lactation animals is warranted.