Journal of Dairy Science最新文献

Elevated concentrations of free fatty acids (FFA; ≥1.20 mmol/100 g of fat) reduce milk quality by changing milk sensory and functional properties. Bulk tank FFA levels vary between milk pickups, and there is limited research to identify factors associated with these short-term fluctuations in FFA. A time-temperature recorder (TTR) may be used on dairy farms to identify milk quality concerns through producer alarms related to milk cooling, storage, and contact surface sanitization. The objective of this study was to investigate whether specific TTR alarms could be associated with short-term increases in bulk tank milk FFA. An observational cross-sectional study was conducted, and data from TTR units on 177 farms in Ontario, Canada, were collected and analyzed. A subset of 751 alarms from 120 farms was used. For each alarm, the baseline FFA concentration (average FFA across 7 pickups before the alarm, if no alarm present) was compared with the alarm-associated FFA. The average FFA for all bulk tank milk samples associated with any single TTR alarm (0.90 ± 0.50 mmol/100 g of fat) was greater than the baseline average FFA (0.88 ± 0.41 mmol/100 g of fat). More than 15% (n = 113) of TTR alarm-associated samples were elevated (≥1.20 mmol/100 g of fat). Observations from a bulk tank sample with a "milk too cold" alarm had the highest average FFA (1.31 mmol/100 g of fat) and were the only ones with a significant increase in FFA compared with the baseline. Using a mixed linear regression model, the associated increase in FFA was 0.36 mmol/100 g of fat when a "milk too cold" TTR alarm occurred. The absence of additional cooling was also a risk factor for increased FFA and a "milk too cold" alarm. These results suggest that a "milk too cold" TTR alarm could help explain short-term increases in FFA on dairy farms with bulk tank milk temperature recording.

The increasing incidence of vitamin D deficiency in Europe has generated interest in naturally enhancing vitamin D levels in commonly consumed foods, such as milk, by biofortification (defined here as increasing the concentration of a specific nutrient in a food by changing the diet or management of an animal). Endogenous, solar-driven biosynthesis of vitamin D is a potentially modifiable option for boosting vitamin D concentrations in milk. The objective of this study was to quantify milk and plasma vitamin D responses in housed cows exposed to artificial UV-B light over 12 wk. Two 2 × 2 factorial experiments (experiment 1 and 2) were conducted, each using 32 late-lactation Holstein dairy cows (separate cows in each experiment). Factors examined were level of supplementary UV-B lighting (no UV-B vs. UV-B) and the inclusion of a dietary additive, L-cysteine (Control vs. Additive). Cows were exposed to supplemental UV-B light for 30 and 60 min/d (experiment 1 and 2, respectively). Exposing cows to UV-B increased mean milk concentrations of vitamin D₃ by 44.2% (experiment 1) and by 112% (experiment 2), compared with no-UVB. Milk concentrations of 25-(OH)-D₃ also increased by 24.2% (experiment 1) and 20.9% (experiment 2). Mean milk vitamin D₂ concentration was increased by 33% by UV-B treatment in experiment 2. Milk 25-(OH)-D₂ levels were unaffected by UVB exposure. Milk concentrations of vitamin D₃ changed with time, as did milk concentrations of vitamin D₂. Milk concentrations of 25-(OH)-D₂ changed with time in experiment 1, there was a treatment × time interaction for milk vitamin D₃ concentrations in experiment 1, and a trend for an interaction in experiment 2. Mean plasma 25-(OH)-D₃ concentration increased with UV-B treatment in experiment 1 only. Mean plasma 25-(OH)-D₃ concentration decreased over time in experiment 1 but was unaffected in experiment 2. Dietary additive had no effect on any aspect of cow performance, and there were no interactions between UV-B and additive. The UV-B treatment did not affect milk yield or milk fat, protein, or lactose concentrations. Milk yield and milk fat, protein, and lactose concentrations changed with time, and there was a treatment × time interaction for milk yield (experiment 2 only). This study demonstrates the potential for increasing the vitamin D₃ content of milk produced by housed cows by short exposure (30-60 min/d) to supplementary UV-B light as a successful biofortification strategy.

Enteric methane emissions (EME) are the main source of anthropogenic GHG in the dairy industry. Certified food products, such as Parmigiano Reggiano cheese, are particularly interested in monitoring their environmental impact. To achieve this, a rapid, cost-effective method, applicable at the population level, is to estimate EME from predicted milk fatty acids obtained by milk mid-infrared spectroscopy. The aim of this study was to evaluate the variation in EME-derived traits according to dairy system and farm-level animal welfare indicators in farms belonging to the Parmigiano Reggiano Consortium. The final dataset used for the analysis integrated milk test-day records, mid-infrared spectra, and farm animal welfare assessment data, resulting in 1,256,135 records from 174,180 cows on 940 multibreed dairy farms. Dairy systems were identified by clustering farms according to their common characteristics and practices. These included 2 traditional systems (one from the Apennine region and the other prevalent in the Po Plain) and 2 modern systems (both prevalent in the Po Plain, one with and the other without the use of TMR). This study analyzed different EME phenotypes, including methane emissions per day, emissions relative to kilograms of DMI, and emissions per unit of production (corrected milk, fresh cheese, and cheese solids). The effect of animal welfare and dairy systems on individual methane emissions was evaluated using mixed models. Three groups of farm-level welfare indicators were considered: management practices, housing structure and equipment, and animal-based measures. These indicators are part of the national animal welfare evaluation conducted by the Italian National Reference Center for Animal Welfare (CReNBA, Brescia, Italy). The results showed that the dairy system and the interaction between dairy system and breed affected all traits. The general trend was that modern dairy systems produced more grams of methane per day than traditional systems, but their emissions per unit of production were lower. Breed-related EME variations across dairy systems were especially notable in Reggiana cattle. The overall effect of the animal welfare on EME traits was minor compared with the dairy system or breed effects. Across the 5 EME traits analyzed, only 2 showed significant associations with management (methane expressed in g/d and relative to kg of DMI) and one with animal-based measures (methane production in g/d), whereas no effects were observed for structure and equipment. In light of these findings, producers of high-quality foodstuffs, such as Parmigiano Reggiano cheese, may take into account the impact of different sources of variation in EME in the process of selecting a suitable production system. The results of this study could be helpful in improving farm-level management, as well as in the development and implementation of breeding programs aimed at reducing the environmental impact of dairy farming.

In this study, a thermostable β-glucosidase derived from a hot spring metagenome was successfully immobilized on linen fabric to create an eco-friendly and reusable biocatalyst for lactose hydrolysis. The enzyme is derived from a metagenome of the high-temperature Pisciarelli hot springs, an extreme environment known to yield robust biocatalysts with industrial relevance. Two immobilization strategies were employed: direct covalent binding (Lf-β-glucosidase) and binding via a spacer arm (LfEG-β-glucosidase). The latter exhibited superior enzymatic performance, retaining 76.6% of its initial activity and demonstrating enhanced thermal and operational stability. Both free and immobilized forms of enzyme showed similar pH and temperature optima, with the immobilized form exhibiting significantly improved long-term thermostability and storage stability-retaining full activity after 1 yr at 4°C. The LfEG-β-glucosidase biocatalyst was effectively applied in the enzymatic treatment of cheese whey, retaining 90% activity after 15 reuse cycles, yielding more than 6.4 g of glucose. These findings highlight the promising use of biodegradable, low-cost linen fabric as a carrier for thermostable enzymes in food biotechnology. The high efficiency and reusability of the developed biocatalyst offer a compelling solution for lactose hydrolysis and valorization of dairy industry by-products, particularly whey, within a circular and environmentally conscious production model.

The periparturient period in dairy cows is marked by major metabolic and physiological changes that increase disease susceptibility and challenge immune function. However, the function of T helper (CD4⁺) cells across the periparturient period remains poorly understood. This study evaluated the in vitro metabolic function, proliferation capacity and phenotype of T helper cells across the periparturient period. Multiparous Holstein cows (n = 22) having mean ± SD lactation of 4.16 ± 1.34 were sampled at -28, +3, and +28 d relative to calving. Peripheral blood mononuclear cells were isolated and T helper cells were obtained using magnetic sorting. A Seahorse XF HS Mini analyzer was used to assess the metabolic function through a T cell metabolic persistence assay, measuring glycolysis and oxidative phosphorylation via extracellular acidification and oxygen consumption rates respectively. Cells were treated either with assay medium (nonactivated) or phorbol 12-myristate 13-acetate and ionomycin (activated) for metabolic measurements, as this combination induces rapid, receptor-independent activation. For proliferation capacity, isolated T helper cells were incubated with concanavalin A, as it provides sustained stimulation to assess clonal expansion, for 72h and tracked using cell trace in a flow cytometer. Cytokine production was measured in the cell culture supernatant using a MILLIPLEX Bovine Cytokine/Chemokine kit. RNA was extracted from isolated cells, and gene expression of immune-related and metabolic markers were evaluated by quantitative PCR. Data were analyzed using a linear mixed effect model in R 4.4.3 using day relative to calving, activation status and block as fixed effect and cow as a random effect. When properly, time of the assay and its interaction with day relative to calving was included as a fixed effect. Activated T helper cells showed greater glycolytic and oxidative metabolism at +3 and +28 d compared with -28. Expansion index was highest at +3 (2.65), followed by +28 (2.38) and -28 (1.91). Proinflammatory cytokine production, like IL-1 α, IL-1 β and IL-6 also increased during +3 and +28 compared with -28. However, no significant differences in gene expression were detected across time points. These findings suggest that T helper cell metabolism and proliferation capacity are upregulated after calving and that these cells express a more proinflammatory phenotype, indicating that after parturition, immune function on this subset of cells does not appear to be suppressed.

Our objective was to evaluate the effect of abomasal infusions of increasing doses of docosahexaenoic acid (DHA; 22:6 n-3) on plasma and milk fatty acids (FA) and milk production of mid-lactation dairy cows. Eight multiparous ruminally cannulated Holstein cows (97 ± 37 DIM, 49.2 ± 3.3 kg/d milk) were assigned to a 4 × 4 Latin square design. Treatments consisted of abomasal infusions of 0, 2, 4, and 6 g/d of DHA with 11-d treatment periods and 10-d washout periods. The DHA was provided via an enriched algal oil (65% DHA) and suspended in ethanol (∼200 g/d). Samples were collected during the final 4 d of each period. Pre-planned orthogonal contrasts included the linear, quadratic, and cubic effects of increasing DHA. Results are presented in the following order: 0, 2, 4, and 6 g/d of DHA. Increasing DHA dose did not affect yields of milk, FCM, ECM, milk fat, or milk protein. Increasing DHA dose linearly increased DHA in plasma phospholipids (0.30, 0.50, 0.64, 0.82 g/100 g FA), triacylglycerols (0.09, 0.25, 0.40, 0.51 g/100 g FA), and cholesterol esters (0.04, 0.04, 0.05, 0.06 g/100 g FA). Similarly, increasing the dose of DHA linearly increased milk fat content of DHA (0.01, 0.04, 0.06, 0.08 g/100 g FA), total n-3 fatty acids (0.56, 0.57, 0.63, 0.63 g/100 g FA), and the yield of DHA in milk (0.19, 0.58, 0.91, 1.18 g/d). Absorbed DHA was positively correlated with the DHA in total plasma lipids (0.42), plasma phospholipids (0.70), plasma triacylglycerols (0.92), and milk fat (0.93). In conclusion, these findings indicate that although short-term DHA supplementation did not alter milk production, it increased DHA incorporation into key plasma lipids and milk fat and reduced SCC. Plasma or milk fat DHA content may serve as indicators of DHA absorption in practical feeding scenarios.

The objective of this study was to compare the economic performances of 3 pasture-based systems: a perennial ryegrass (Lolium perenne L.; PRG) receiving 250 kg N/ha (PRG-250N); a PRG-white clover (Trifolium repens L.; WC) receiving 125 kg N/ha (PRGWC-125N); and a multispecies (MSS) sward composed of grasses, legumes, and herbs receiving 125 kg N/ha (MSS-125N). Sward and animal performances were measured over 3 years in a system-scale study involving 3 farmlets at Teagasc Moorepark, Ireland. Subsequently, based on the physical data collected, an economic performance of each sward system was evaluated using current output prices and input costs in the Moorepark Dairy Systems Model. The economic results show similar net farm profitability for both PRG-250N and PRGWC-125N. The PRGWC-125N system had lower costs linked to fertilizer; however, more grass silage was purchased due to reduced grass production. The MSS-125N system outperformed both PRG-250N and PRGWC-125N in net farm profitability (+€167/ha and +€148/ha, respectively) due to increased milk output coupled with reduced N fertilizer use. Sensitivity analyses indicated that MSS-125N was the most profitable system under varying milk and fertilizer prices. Given the variability of clover and herb establishment between paddocks for PRGWC-125N and MSS-125N, an increase in the reseeding frequency and oversowing frequency was simulated and resulted in reductions in farm profitability for both systems (€-14.25/ha per year and €-28.25/ha per year, respectively). This study underscores the potential of increasing sward species diversity using clovers and herbs to sustain economic performances of pasture-based systems while reducing fertilizer N reliance and enhancing animal performance. Further long-term research is required to investigate persistence and economic viability of both PRGWC and MSS under varying climatic and management conditions to validate the longer-term results of the first 3 years of the study.

Our objectives were to describe subclinical mastitis and identify its risk factors among grazing dairy ewes in New Zealand. Gland-level milk samples were collected from ∼15 randomly selected ewes on each of 20 dairy sheep farms at early, mid, and late lactation in a repeated cross-sectional study. California Mastitis Tests (CMT; measured on a scale of 0, trace, 1, 2, or 3) and aerobic bacterial culture were performed at the gland level, and SCC at the ewe level using composite milk samples. Subclinical mastitis was defined at the ewe level as having 1 or 2 bacteriologically positive glands and SCC >500 × 10³ cells/mL or a CMT score ≥1 (or both). Milk samples were collected from 893 ewes, and complete subclinical mastitis data were available for 856 ewes. Median (range) SCC was 128,000 (2,000-34,953,000) cells/mL. A CMT score ≥1 in one or both glands was found in 21.2% of ewes. Bacteria were isolated from 5.5% of glands, with the most common species being non-aureus staphylococci (4.0% of glands) and Staphylococcus aureus (0.6% of glands). The prevalence of subclinical mastitis was 6.4% (95% CI = 4.6%-8.7%) and was not strongly clustered within farms (intraclass correlation coefficient = 0.04). Ewes with moderate or severe teat end hyperkeratosis had 6.4 times higher odds of subclinical mastitis than ewes with no or mild hyperkeratosis, and ewes with asymmetric udders had 2.3 times higher odds. The odds declined across the 3 visits. The prevalence was low compared with studies of more intensively farmed ewes in the northern hemisphere, but the bacterial causes were consistent. Subclinical mastitis management should be focused at the ewe level before the farm level, given the weak clustering within farms. When addressing or preventing a subclinical mastitis challenge, producers should consider teat end hyperkeratosis and udder asymmetry as simple visual screening tools but not rely on them alone to identify ewes at risk of subclinical mastitis. We present new information for New Zealand grazing dairy ewes, examine udder asymmetry as a diagnostic tool for subclinical mastitis, and show that, although prevalence was lower in New Zealand, the dominant pathogens are consistent, supporting the broader relevance of these findings to international mastitis control, albeit with adaptations for pasture-based systems.

Our objective was to determine the separate effects of lactose, soluble mineral concentration, and added dipotassium phosphate (DKP) on the heat stability of milk protein beverages made from rehydrated milk protein concentrate (MPC) with 85% crude protein on a DM basis (MPC85). Seven batches of rehydrated (7.5% protein) liquid MPC were made from each of 2 lots of MPC85 powder. Treatment 1 was 7.5% MPC85 in deionized (DI) water. Treatment 2 was 7.5% MPC85 that was rehydrated with 4°C Jenness-Koops (JK) buffer, a mix of salts that simulate milk salts. Treatment 3 was 7.5% MPC85 with JK buffer with 4.8% (wt/wt) anhydrous lactose added. Treatment 4 was 7.5% MPC85 with a dilution of JK buffer to ∼14% of its original concentration. Treatment 5 was 7.5% MPC85 with diluted JK buffer with lactose added to 0.6% (wt/wt). Treatment 6 was 7.5% MPC85 in DI water with 0.15% (wt/wt) DKP. Treatment 7 was 7.5% MPC85 rehydrated with 4°C UF permeate. Heat stability testing was conducted using an oil bath with a 30-s hold time at 6 temperatures: 135°C, 140°C, 145°C, 150°C, 155°C, and 160°C. The composition of the solute phase of rehydrated and smoothed dried MPC85 had a large impact on the heat stability and aggregation of milk proteins caused by UHT thermal processing temperatures. When MPC85 was rehydrated in deionized water, it had the highest heat stability and the least protein aggregation, and the heat stability was not increased by the addition of DKP. The heat stability of MPC85 was decreased by rehydration in a typical concentration of milk salts (i.e., JK buffer) and was further decreased by the addition of 4.8% anhydrous lactose to the JK buffer. When the MPC85 was rehydrated in UF milk permeate (i.e., milks salts + lactose), the heat stability was comparable to the JK buffer with added lactose. Using diluted JK buffer (∼14% of the level of milk salts and lactose) in MPC85 resulted in increased heat stability that was similar to rehydration in deionized water.

Automated milk feeders (AMF) generate large-scale longitudinal milk feeding data in calves, providing a great opportunity for deriving the novel traits that may be included in cattle breeding programs. For group-housed dairy calves, genetic selection for social dominance could have important implications on improving animal welfare and health, optimizing management practices, and possibly improving cow performance through indirect genetic selection. In this study, we derived and estimated genetic parameters for 6 calf social dominance indicators using a dataset consisting of 4,164,960 AMF visit records from 8,632 American Holstein female calves, including 5,910 calves with genomic data for 64,767 autosomal SNPs. We also assessed the genetic relationship of the derived social dominance traits with 7 calf traits related to feeding, growth, and health. Variance components were estimated using the average-information REML method and the single-step genomic BLUP approach. We observed that the varied weightings of time intervals between 2 consecutive visits to AMF did not have a clear effect on the calculated social dominance phenotypes. Among the social dominance traits, David's score (DS), adjusted DS by chance (adjDS), Kondo-Hurnik Index (KHI), and adjusted KHI by dominance probability (probKHI) were found to be moderately heritable with h² estimates (±SE) ranging from 0.180 ± 0.017 (DS) to 0.210 ± 0.018 (probKHI), whereas Elo-rating scoring and success index were lowly heritable or less robust to the varied weights of visit time interval. Furthermore, the heritable indicators (DS, adjDS, KHI, and probKHI) had moderate and positive genetic correlations with average milk consumption per visit and average number of daily unrewarded visits, and weak positive correlations with birth weight. All dominance traits evaluated were lowly or not genetically correlated with the number of treatment records for bovine respiratory disease before 60 d of age. Our findings contribute to understanding the genetic basis of social behaviors in dairy calves. Several dairy calf social dominance traits in American Holsteins were found to be heritable with substantial additive genetic variance. However, further studies need to be performed to identify potential genetic relationships with economically and socially relevant traits in breeding programs, such as health, welfare, and performance traits.