Journal of Dairy Science最新文献

Cronobacter sakazakii is a significant foodborne pathogen commonly found in dairy processing environments. Under chlorine stress, C. sakazakii may survive by adopting stress-resistant phenotypes such as biofilm and viable but nonculturable (VBNC) state. The formation of these phenotypes is regulated by the stringent response. However, the mechanisms by which the stringent response directs phenotypic fate differentiation under different chlorine concentrations remain unclear. In this study, we exposed C. sakazakii to chlorine concentrations (0.1-100 μg/mL) for 24 h and quantified viable cells, 100S ribosome levels, extracellular polymeric substances, and stringent response signals. The results showed that C. sakazakii exhibited pronounced differentiation into biofilm and VBNC phenotypes under chlorine stress ranging from 0.1 to 100 μg/mL. At low chlorine concentration (0.1 μg/mL), biofilm viable cell counts reached 5.10 × 10⁵ cfu/mL, accompanied by significant increases in extracellular polysaccharides and proteins, promoting biofilm formation. In contrast, at high chlorine concentration (100 μg/mL), VBNC cell counts rose to 5.99 × 10⁵ cfu/mL, extracellular components declined, and 100S ribosome levels were significantly elevated, indicating deeper metabolic dormancy. Time-course analysis further revealed that the first 0.5 h after chlorine treatment represents a critical window for phenotypic differentiation. During this period, the stringent response alarmone guanosine tetraphosphate (ppGpp) levels increased by 1.55- to 5.16-fold compared with the control and regulated the formation of biofilm and VBNC phenotypes. Gene expression analysis revealed that in the relA-overexpressing strain, ppGpp ribosome dimerization genes rmf and hpf were upregulated by 5.51- and 2.82-fold, VBNC-related genes ppk and lon upregulated by 3.44- and 3.24-fold, whereas biofilm-related genes dgcQ and bcsA were downregulated by 2.86- and 3.98-fold. These changes guided the selection of phenotypic fate differentiation: Low ppGpp levels interacted with cyclic diguanylate monophosphate (c-di-GMP) to promote biofilm formation, whereas high ppGpp levels induced VBNC phenotype by activating the PPK/Lon cascade. This study not only deepens our understanding of the mechanisms governing bacterial fate determination under environmental stress but also provides a theoretical basis and potential strategies for optimizing dairy disinfection processes and reducing pathogen survival.

Within the past decade, the use of beef semen in the dairy industry has risen, leading to a growing number of dairy × beef crossbred calves being born. However, limited studies compare the health and growth performance of purebred dairy and crossbred calves during the preweaning phase. This study aimed to evaluate the association of breed with morbidity, mortality, and growth performance during an 84-d rearing period. A total of 640 male calves were enrolled upon arrival to a calf-rearing facility and were classified as either Holstein (n = 446) or crossbred (n = 194), which were identified by hide color. Breed, source (local farm versus auction), and BW were recorded upon arrival. Calves were fed milk replacer (MR) twice daily until weaning, which occurred between d 42 and 63, and solid feed and water were offered ad libitum throughout the study. Health exams were performed twice daily, evaluating fecal consistency from arrival to d 21 and respiratory health from arrival to d 84. Mortalities and treatments administered, including electrolytes, nonsteroidal anti-inflammatory drugs, and antibiotics, were recorded throughout the study. Solid feed intake and BW were measured weekly following enrollment, and MR refusals were recorded daily. Statistical models, including Cox proportional hazards, Weibull, negative binomial, and linear regression, were built in Stata 18 (StataCorp LP) to assess the association of breed with calf health and growth. Holstein calves had a greater incidence of diarrhea compared with crossbred calves (incidence rate ratio = 1.23; 95% CI: 1.01-1.51) and a higher hazard of receiving a second (hazard ratio [HR] = 1.62; 95% CI: 1.04 to 2.51) or third (HR = 2.47; 95% CI: 1.24 to 4.91) treatment for respiratory disease. With respect to growth performance, crossbred calves had increased BW by d 28 and weighed 7.13 ± 1.31 kg (95% CI: 4.56 to 9.70) more than Holsteins by d 84. Similarly, ADG was greater for crossbreds starting between d 28 and 35. Feed-to-gain conversion ratios (FCR) were lower for crossbred calves during both the preweaning and weaning phases; however, Holstein calves had improved FCR between d 70 and 77 compared with crossbred calves. These results suggest that crossbred calves may be able to overcome illness quicker and with fewer therapeutic interventions than Holsteins in the rearing period while achieving superior growth performance.

Genetic improvement of fertility in dairy cattle remains a significant challenge due to the complex interplay between reproductive and environmental factors resulting in low heritability traits. Recent advancements in sensor technologies have allowed for the assessment of estrus-related traits as indicators of fertility. Three sensor-derived estrus traits previously associated with fertility outcomes include estrus duration (ED), maximum estrus intensity (MEI), and the interval from calving to first estrus (CTFE). The objectives of this study were to estimate the genetic parameters of ED, MEI, and CTFE in Holsteins, to assess the reliability of EBVs, to evaluate the inclusion of genomic information, and to estimate breeding value correlations with economically important traits. Phenotypes were derived from activity-monitoring collars (CowScout, GEA) between 2020 and 2023 from a single farm in Slovakia. After editing, 8,363, 8,092, and 2,909 records on 2,390, 2,360, and 2,147 cows were available for analysis of ED, MEI, and CTFE, respectively. Heritability estimates for the traits were low to moderate, with values of 0.18 ± 0.02 for MEI, 0.16 ± 0.02 for ED, and 0.07 ± 0.03 for CTFE. Repeatability across lactations was 0.34 ± 0.03 for CTFE, but no significant permanent environmental effect was found across lactation for MEI and ED. Repeatability within lactation was low for MEI (0.25 ± 0.02) and ED (0.19 ± 0.01). The average reliability of EBVs was moderate for phenotyped cows, with values of 0.32 ± 0.05 for CTFE and 0.48 ± 0.09 for MEI and ED. For sires with at least 10 daughters, EBV reliability ranged from 0.56 ± 0.11 for CTFE to 0.79 ± 0.13 for MEI and ED. Inclusion of genomic information did not greatly affect genetic parameters and resulted in marginal improvements to reliability of breeding values. Genetic correlations among estrus traits were moderate and favorable, indicating that better performance of 1 trait will correspond to improved performance in the other 2 traits. Breeding value correlations between estrus traits and economically important traits were generally favorable. These results suggest that sensor-derived estrus traits are heritable, with potential for more rapid progress in reproduction than currently evaluated traits. Future research should estimate proper genetic correlations between estrus traits and other economically important traits and expand data sets to enhance the genetic evaluations of these sensor-derived estrus traits.

Prebiotics promote the proliferation and colonization of probiotics in the intestine; therefore, synergistic application of probiotics and functional oligosaccharides can confer significant health benefits to the host. This study optimized a complex prebiotic combination that enhanced the growth of Lactobacillus paracasei ProSci-92 by measuring the optical density at 600 nm, pH, and viable cell counts. Through response surface optimization, the optimal ratio was determined to be 1.959% trehalose, 1.029% inulin, and 1.582% fructooligosaccharides. Under these conditions, cell density reached 1.629 ± 0.012, and the viable cell count was (6.5 ± 0.28) × 10⁹ cfu/mL, representing increases of 12.3% and 1.67-fold, respectively, compared with the de Man, Rogosa, and Sharpe agar medium control group. The optimized compound was subsequently applied to fermented milk; its rheological properties, texture characteristics, and viable bacterial counts were analyzed using sucrose as the control. The results show that the compound group coagulated 1 h earlier than did the sucrose control, and exhibited higher elasticity and viscosity coefficients. During the 28-d storage period, the pH decreased gradually (final value: 4.16), titratable acidity remained low (final value: 102°T [degrees of titratable acidity]), viable bacterial count remained above 10⁸ cfu/mL, and water-holding capacity averaged 65.86%. Moreover, both textural attributes and sensory evaluation scores improved significantly. Metabolomic analysis identified 87 differential metabolites between the PC92-Oli (experimental) group and the PC92-Suc (control) group, which were primarily associated with the ABC transport system, AA biosynthesis, and carbon metabolism pathways. The compound oligosaccharide mixture activated specific metabolic pathways in the strain, promoted the synthesis of functional metabolites, inhibited fatty acid production, and accelerated extracellular polysaccharide synthesis. These findings provide a strong scientific basis for enhancing the product development and functional properties of probiotic fermented milk, and offer innovative perspectives and strategies for improving its production and storage characteristics.

Lymphocyte count (LC) is an important hematological parameter in dairy cows. Historical studies establishing LC reference intervals often included cows that were not tested for bovine leukosis virus (BLV). As a result, BLV-infected cows showing subclinical lymphocytosis were possibly included in those studies, leading to higher LC reference intervals. Because BLV (among other pathogens or processes) can cause persistent lymphocytosis, including BLV-infected cows when establishing LC reference intervals could lead to their overestimation. Our objectives were to propose updated LC reference intervals for Holstein cows and to estimate the most discriminant LC threshold for differentiating cows belonging to the low- versus high-LC distributions. We conducted a cross-sectional observational study to collected blood samples from 631 Holstein cows, irrespective of their BLV status, across 8 herds in Québec, Canada. Blood samples were analyzed on the day of collection to determine LC in 10⁹ cells/L. Using Gaussian finite mixture models, we identified the 2 most probable Gaussian LC distributions representing healthy versus abnormal cows within the complete dataset (i.e., all sampled lactating cows analyzed together, regardless of age), and within 2 age groups: young (2-4 yr-old lactating cows) and older cows (>4-year-old lactating cows). We used the identified distributions to propose LC reference intervals for Holstein cows. Then, we determined the most discriminant LC thresholds to distinguish cows belonging to the low- versus high-LC distributions (the latter being presumed to be affected by either a short-term or chronic immunological alteration). To assess persistent lymphocytosis, we collected a second set of blood samples 4 mo later from cows with an initial LC ≥5.5 × 10⁹ cells/L. The LC reference intervals were 1.5 to 5.5 × 10⁹ cells/L in the complete dataset, and 1.9 to 6.0 and 1.6 to 4.5 × 10⁹ cells/L, in young and older cows, respectively. The most discriminant LC thresholds were ≥5.5 × 10⁹ cells/L in the complete dataset, ≥5.5 × 10⁹ cells/L for young cows, and ≥4.5 ×  10⁹ cells/L for older cows. The probability of belonging to the Gaussian LC distribution representing presumably abnormal values from cows affected by either a short-term or chronic immunological alteration increased markedly with increasing LC but was also high for cows with a very low LC (<1.5 × 10⁹ cells/L). Persistent lymphocytosis was observed in 77% (49/64) of cows in the young group and 98% (55/56) of cows in the older group. The reference LC intervals proposed are lower than those reported in previous studies and reflect an expected age-related variation. The proposed LC thresholds provide a practical marker of chronic lymphocytosis.

Food allergies are a major challenge in current healthcare. Probiotics and human milk oligosaccharides (HMO) are increasingly being used to address food allergies. However, the role of nonfucosylated neutral oligosaccharides in food allergies remains unclear. Moreover, HMO interact positively with probiotics, but the synergistic effects and underlying mechanisms of their combined action in alleviating food allergies remain poorly understood. Consequently, Bifidobacterium longum ssp. infantis (B. infantis), which exhibits the greatest capacity to use HMO, was chosen for this study. The effects of lacto-N-neotetraose (LNnT), B. infantis, and their combination on allergy was assessed using an ovalbumin (OVA)-induced allergic mouse model. The mechanisms underlying the alleviation of food allergies by LNnT + B. infantis were also investigated through genomics and metabolomics. The results demonstrated that LNnT and B. infantis exerted partial modulatory effects on allergic symptoms, BW, mast cell degranulation, cytokine levels, and immune cell populations in mice. Notably, the simultaneous administration of LNnT and B. infantis significantly outperformed the administration of either LNnT or B. infantis alone, indicating a synergistic effect. Furthermore, LNnT + B. infantis was found to alleviate intestinal injury. Gut microbiota analysis revealed that LNnT + B. infantis reduced the abundance of the allergy-associated bacterium Desulfovibrio and significantly increased the levels of beneficial bacteria, including Lactobacillus, Limosilactobacillus, and Blautia. The LNnT + B. infantis treatment also enhanced steroid hormone biosynthesis, ascorbate and aldarate metabolism, and nucleotide metabolism. Some substances in these pathways are produced by the gut microbiota and are linked to allergy amelioration. In conclusion, LNnT + B. infantis alleviates food allergies by modulating the gut microbiota and its associated metabolic functions in OVA mice.

Lactoferrin (LF) is a naturally occurring heat-sensitive globular glycoprotein that undergoes denaturation and aggregation during thermal treatment, thereby affecting its binding with other components. In this study we examined the impact of thermal treatment (50°C-90°C) of LF on the physicochemical, structural, and functional properties of self-assembled ternary complexes comprising LF, chlorogenic acid (CA), and low methoxyl pectin (LMP). At all heating temperatures, thermally treated LF exhibited enhanced particle size, turbidity, and zeta-potential compared with native LF​. Structural characterization revealed a pronounced reduction in α-helix content with thermal intensity, whereas SDS-PAGE patterns confirmed the onset of protein aggregation phenomena above 70°C. Thermally modified LF was assembled with CA and LMP under neutral pH to yield ternary complexes, which exhibited enhanced zeta-potential, greater turbidity, and increased fluorescence intensity with a characteristic redshift compared with those incorporating unheated LF. The emulsifying and foaming properties of ternary complexes were improved, whereas emulsifying and foaming stability decreased with increasing thermal treatment temperature. Although the antioxidant activity of ternary samples decreased when LF was heated, it still maintained a relatively high level (>70% for 2,2-diphenyl-1-picrylhydrazyl and >80% for 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt). Antibacterial activity of LF and ternary complexes decreased due to thermal treatment, yet they still retained the ability to inhibit Escherichia coli and Staphylococcus aureus. Collectively, these findings elucidate that thermal treatment of LF tailors the structural and functional properties of its ternary complexes with polyphenols and polysaccharides, enabling their rational design for specific food applications.

The objective of this study was to compare growth and future milk production of Holstein calves fed either an intensified liquid feeding program (INT; n = 32) or a conventional early weaning program (CON; n = 33). At 3 d of age, female Holstein calves in individual hutches were assigned to CON (milk replacer [22% CP, 20% fat] plus starter [18% CP, as fed]) or INT (milk replacer [28% CP, 20% fat] plus starter [22% CP, as fed]). In yr 1, 12 calves on CON and 11 calves on INT were used, whereas in yr 2, there were 21 calves on each treatment. For CON, calves were fed a constant amount of milk replacer (1.25% of birth weight as powder) through wk 4, were fed one-half of that amount during wk 5, and were weaned at the end of wk 5. For INT, calves were fed milk replacer at 2% of BW during wk 1 and 2.5% of BW during wk 2 to 5 (adjusted weekly in yr 1, held constant in yr 2). During wk 6, calves were fed half the amount offered during wk 5 and were weaned at the end of wk 6. After wk 8, calves were housed together by treatment in superhutches through wk 12. Total milk replacer consumed was greater for INT compared with CON, but CON consumed greater amounts of calf starter over the 8 wk trial. Body weight, withers height, body length, and heart girth were increased during the milk-fed period and through wk 8. Average daily gain was greater for INT at wk 4, at weaning, and at wk 8. Gain to feed ratio was greater for INT than CON. By wk 12, there was no difference in BW between groups. Calving BW and age at first calving were not different between groups. Primiparous cows that were fed INT as calves produced 1,048 kg more milk than CON herdmates. Production of milk protein also was greater for INT, but milk fat did not differ between groups. In conclusion, feeding more milk replacer to calves resulted in greater early growth, but that was not maintained through 12 wk. Regardless, primiparous cows fed INT as calves produced more milk and milk protein than those fed CON.