Journal of Dairy Science最新文献

Listeria monocytogenes is a highly adaptable foodborne pathogen that causes multiple foodborne illness outbreaks annually despite stringent food safety measures. The ubiquitous presence of L. monocytogenes in agricultural production environments provides easy routes of contamination to the human food production chain. The remarkable resilience of L. monocytogenes in harsh food processing and preservation conditions presents further challenges to controlling this pathogen in food and food processing plants. Furthermore, there is an increasing consumer demand for natural antimicrobials in food. Aspergillus oryzae is a food fermentation fungus with a GRAS (generally recognized as safe) status and is a workhorse in biotechnology applications. In this study, we examined the antimicrobial activity of Aspergillus oryzae fermentates and extracts toward L. monocytogenes, both in laboratory cultures and contaminated milk. A. oryzae-derived antimicrobials can be obtained in 2 culture conditions, which we term NP1 and NP2. Laboratory cultures of L. monocytogenes were effectively and rapidly killed by both NP1 and NP2 extracts. In contaminated milk, the NP1 extract was bactericidal, whereas the NP2 extract was bacteriostatic. Nevertheless, the NP2 extract was heat stable, retaining antimicrobial activity even after boiling. Profiling L. monocytogenes transcriptional response to a sub-inhibitory level of NP2 fermentate, we observed significant shifts in amino acid metabolism and iron uptake, suggesting that these pathways can be tackled to increase the efficacy of NP2. Taken together, A. oryzae fermentates and extracts are promising candidates for natural antimicrobial treatments in food and food processing environments.

Understanding the nutritional protein requirements of yak calves is the basis of precise feed formulation. Regulating feed protein can reduce environmental impacts, which is particularly crucial for the rearing and management of yak calves. In this study, we used a combination of comparative slaughter, feeding, and digestibility trials to determine the net protein requirements of suckling yak calves. Thirty-five yak male calves with similar weights at 60 d of age were divided into 5 groups: early slaughter (ES), mid-term slaughter (MS), late slaughter (AL), 70% feeding (R70), and 40% feeding (R40). The ES, MS, and AL groups were used for comparative slaughter trials, while the AL, R70, and R40 groups were used for ad libitum feeding experiments. The results indicated that at different feeding levels, low feeding levels were not conducive to calf growth. For yak calves with body weights of approximately 40-90 kg, the nitrogen digestibility ranged from 49.36% to 59.32%, and the nitrogen retention rate ranged from 36.59% to 48.97%. The net protein requirement for yak calf maintenance is 2.90 g/kgW^0.75·d^-1. The equation for the net protein requirement for yak calf growth is NPg(kg) = 0.0543 × EBW^0.0833(kg). Muscle metabolomics results indicated that the protein content in the muscle tissue did not increase with feeding level or body weight. With an increase in the feeding level, the nutritional protein level provided by the diet increases, which regulates changes in steroid hormone biosynthesis, ovarian steroidogenesis, cortisol synthesis and secretion, and carbon metabolism, promoting an increase in hormone-like metabolites in the muscle tissue. These data we obtained provide guidance for the efficient rearing of yak calves and provide basic data for further research on the nutritional requirements.

Artificial Insemination (AI) is a common method used internationally for breeding cattle but may have the potential to introduce pathogenic bacteria to naïve populations during the process. Certain bacterial pathogens, such as Mycoplasmopsis bovis, have been a priority for disease transmission control and prevention via bovid semen for certain countries. One such method to prevent the transmission of infectious agents during the AI process has been prophylactically adding antimicrobials to both the neat and extended semen to kill or inhibit bacterial growth. A study published in 1988, detailed a method using a combination of Gentamicin, Tylosin, Lincomycin, and Spectinomycin (GTLS) as a means of controlling certain pathogenic bacteria in extended bovine semen. This was widely adopted and is still in use today, with Certified Semen Services (CSS) making it required for their members. Publications since 1988 have provided evidence against the efficacy of the GTLS cocktail, arguing that M. bovis specifically is not being adequately controlled. Along with globally increasing antimicrobial resistance, a verification of the efficacy of the GTLS cocktail was warranted. Here the authors spiked various strains of bacteria into bovine GTLS-extended semen and quantified the bactericidal and bacteriostatic effect using bacterial culture. Our results demonstrate that multiple strains of C. fetus subspecies venerealis and H. somni as well as one strain each of Ureaplasma diversum and Leptospira interrogans were effectively killed by the GTLS cocktail. However, the GTLS cocktail had only a bacteriostatic effect on several strains of M. bovis.

The increase in healthy eating habits has driven demand for functional foods, characterized by their beneficial effects when consumed regularly. Probiotics, typically Lactic Acid Bacteria (LAB), are among the most used bioactive components in their formulation. However, various conditions can reduce their viability (Log cfu g^-1). Spray drying, a protective method used to address this issue, employs prebiotics such as inulin and maltodextrin as wall materials, due to their selective fermentation by LAB and intestinal microbiota. In ice cream, the inclusion of encapsulated probiotics is recommended due to its compatibility as a dairy-based carrier. Additionally, sweet whey has been proposed as an ingredient in ice cream formulation to mitigate the environmental impact of this byproduct. The primary objective of this study was to determine the Spray-drying parameters for probiotics to incorporate them into ice cream formulated with sweet whey. Spray-drying parameters, including encapsulation efficiency, moisture content, and water activity, were evaluated based on probiotic strains (Lactobacillus reuteri and Lactobacillus plantarum), inlet temperature (110°C, 120°C, and 130°C), and maltodextrin concentrations (5%, 10%, 15%, and 20%) using a multilevel factorial experimental design. For the ice cream, parameters such as microencapsulated probiotic viability (Log cfu g^-1), pH, acidity, overrun (O%), freezing point (°C), time to the first drip (D min), and melting percentage (M%) were assessed. The optimal encapsulation conditions were achieved with L. plantarum at 130°C and 10% maltodextrin. Finally, the microencapsulated powder was incorporated into ice cream, and the product's viability exceeded the recommended minimum concentration (10 Log cfu g^-1).

The SLICK1 allele of the prolactin receptor gene (SLICK1) is associated with a short hair coat and thermotolerance in cattle. SLICK1 includes a single base pair deletion that creates a premature stop codon and prevents transcription of 120 amino acids involved in JAK/STAT signaling. It is unknown if SLICK1 modifies JAK/STAT signaling or the transcriptional response to prolactin. To investigate PRLR-associated signaling pathways in heterozygous SLICK1+/- Holsteins (slick), we performed immunohistochemistry on skin explants obtained from slick (n = 5) and non-slick (n = 6) heifers to evaluate phosphorylated (p)STAT1, pSTAT3, and pSTAT5 immunoreactivity (pSTAT1+, pSTAT3+, pSTAT5+) in hair follicles (HF) and sweat glands (SG). In slick skin, more HF lacked pSTAT3 immunoreactivity compared with non-slick skin. No difference was found for the proportion of pSTAT1+ or pSTAT5+ HF, nor the proportion of pSTAT1+ and pSTAT3+ SG between genotypes. Within immunoreactive HF and SG, there were no differences between genotypes in the proportion of pSTAT1+, pSTAT3+, or pSTAT5+ cells in HF, or pSTAT1+ and pSTAT3+ cells in SG. Next, we investigated pSTAT3 immunoreactivity and the transcriptome of slick and non-slick skin explants after exposure to a controlled level of prolactin in vitro. Skin explants from slick (n = 6) and non-slick (n = 6) heifers were cultured for 36 h in the presence of 50 ng/mL recombinant ovine prolactin, bisected, and each half underwent immunohistochemistry for pSTAT3 or RNA sequencing. No difference was found between genotypes in the proportion of pSTAT3+ HF or SG, nor the proportion of pSTAT3+ cells within HF or SG. RNA was poly-A enriched and sequenced using Novaseq6000 (Illumina) and 221,342,181 reads were mapped to the bovine genome (bosTau 9). The DESeq package was used to determine the differentially expressed genes (DEG) with P < 0.01 and fold-change > 1.5. There were 87 upregulated and 79 downregulated DEG in slick compared with non-slick skin. Ingenuity Pathway Analysis identified IL-17, leukocyte extravasation, and wound healing as upregulated signaling pathways, as well as activation of TNF, IL-1β, OSM, IFNγ, IL-17α, and IL-1R and inhibition of SHH and BMP4 upstream of the DEG. Analysis of genomic regions within ± 2 kb of all DEG's respective transcription start sites revealed enrichment of 3 binding sites for the OCT1 transcription factor in slick skin. In conclusion, our results suggest differences in local immune regulation, hair growth inhibition, and tissue remodeling in slick skin.

Fatty liver is a major metabolic disorder in perinatal dairy cows, characterized by elevated plasma concentrations of nonesterified fatty acids (NEFA) and hepatic inflammation. Glutathione S-transferase mu 2 (GSTM2), a phase II detoxification enzyme, regulates cellular antioxidant and detoxification processes in nonruminants. However, its involvement in NEFA-induced hepatic inflammation in dairy cows with fatty liver remains unclear. This study aimed to elucidate the role of GSTM2 in mediating hepatic inflammation caused by elevated NEFA levels in dairy cows with severe fatty liver. An in vivo study was conducted using 10 healthy cows (hepatic triglyceride [TG] content <1%) and 10 cows with severe fatty liver (hepatic TG content >10%), matched for the number of lactations (median = 3, range = 2-4) and DIM (median = 9 d, range = 3-15 d). Liver tissue and blood samples were collected before feeding. Compared with healthy cows, cows with severe fatty liver had higher plasma concentrations of NEFA, BHB, haptoglobin (HP), plasma amyloid A (SAA), and lower plasma concentration of glucose. These cows also showed significantly lower abundance of hepatic GSTM2 and overactivated hepatic inflammatory pathways, as indicated by increased abundance of phosphorylated inhibitor of κB (IκB)α and nuclear factor κB (NF-κB) p65, NLR family pyrin domain containing 3 (NLRP3), apoptosis-associated speck-like protein containing CARD (ASC), and caspase-1 (CASP1), as well as mRNA levels of tumor necrosis factor α (TNFA), IL6, and IL1B. In vitro, hepatocytes isolated from 5 healthy calves (1 d old, fasted female, 30-40 kg of BW) were used to determine the effects of GSTM2 on hepatic inflammation. First, hepatocytes were treated with NEFA (1.2 mM) for varying durations (0.5, 1, 3, 6, 9, 12, 15, or 18 h). The NEFA treatment significantly increased the phosphorylation of IκBα and NF-κB p65, protein abundance of NLRP3, ASC and CASP1, and mRNA levels of TNFA, IL6 and IL1B, peaking at 9 and 12 h. Second, hepatocytes were treated with different concentrations of NEFA (0, 0.6, 1.2, or 2.4 mM) for 9 h, which decreased GSTM2 protein and mRNA abundance. Meanwhile, GSTM2 was silenced using small interfering RNA or overexpressed using adenovirus for 48 h in hepatocytes, followed by NEFA treatment. Silencing GSTM2 augmented the NEFA-induced increase in phosphorylation of IκBα and NF-κB p65, as well as protein abundance of NLRP3, ASC and CASP1, and mRNA levels of TNFA, IL6 and IL1B. Conversely, overexpression of GSTM2 mitigated these inflammatory signals upon NEFA treatment. In summary, these findings indicate that GSTM2 plays a crucial role in modulating NEFA-induced hepatic inflammation. Targeting GSTM2 may offer new strategies to treat or prevent fatty liver disease in dairy cows.

High pressure processing (HPP) and low temperature storage (0°C) were explored as alternatives to freezing for extending the performance shelf life of low-moisture part-skim (LMPS) Mozzarella intended for export. Batches (n = 5) of reduced Na LMPS Mozzarella were manufactured using camel chymosin as a lower proteolytic type of rennet. Cheeses were stored for 2 wk at 4°C, divided into control (non-HPP) and HPP (600 MPa for 3 min) groups, and stored at 3 different temperatures (4, 0, and -18°C) for 365 d. Analyses were performed at 0, 90, 150, 210, 270, and 365 d of storage. Frozen and 0°C samples (∼2.3 kg) were thawed/tempered at 4°C for 1 wk before analysis. Urea-PAGE and quantification of the pH 4.6 soluble N over time were used to monitor primary proteolysis. Body and rheological properties were monitored using texture profile analysis (TPA) and dynamic low-amplitude oscillatory rheology. Changes in flavor, body, shred properties, and pizza performance were evaluated using quantitative descriptive analysis with 12 trained panelists using a 15-point scale. HPP treatment caused ∼5 log cfu/ml reduction in starter counts, partial solubilization of the insoluble Ca, and a small pH increase (from ∼5.2 to 5.3). The rate of primary proteolysis was reduced by HPP and low temperature storage. HPP treatment reduced initial cheese hardness, but no further significant decrease was observed over storage time, while the hardness of non-HPP samples decreased over the 365 d of storage, apart from the frozen samples. In pizza applications, blister quantity development and loss of strand thickness were limited by storage at -18°C. Freezing LMPS Mozzarella to -18°C gave the least changes in proteolysis and pizza performance over the 365 d of study, storage of cheese at 0°C slowed the loss of hardness and the deterioration of pizza performance attributes. The combination of HPP and 0°C storage of cheese resulted in little change in blistering quantity of pizza during the 365 d of study, whereas cheese stored at 0°C had blisters covering much of the pizza after this extended storage time. Combining HPP with low temperature storage is a promising alternative approach to freezing for the extension of the functionality shelf life of LMPS Mozzarella.

The antibacterial efficacy of clove extracts (Syzygium aromaticum) prepared using 80% ethanol and water against pathogenic bacteria was evaluated, along with the development of a novel antimicrobial milk beverage incorporating these extracts. Seven flavored milk beverage (FMB) treatments were prepared: a control and 6 with clove extracts at 0.5%, 0.7%, and 1% for each solvent. The effects on physicochemical, phytochemical, antioxidant, microbiological, color, and sensory properties were assessed over 15 d of storage at 4 ± 1°C. The ethanolic clove extract exhibited significantly higher antimicrobial activity against Staphylococcus aureus, Listeria monocytogenes, E. coli O157, Salmonella typhi, and Klebsiella pneumoniae, with inhibition zone diameters of 20 mm, 21 mm, 20 mm, 19 mm, and 20 mm, respectively, compared with the aqueous extract. On d 0, the sample of 1% ethanolic clove extract (FMB3) showed the highest proximate analysis values, including TS (22.41%), protein (4.61%), fat (4.58%), ash (0.97%), and gross energy (108.65 Kcal). It also showed the highest pH (6.7), flavor score (19.20), texture score (9), and overall acceptability score (39.50) and the lowest carbohydrate content (12.27%), lightness value (69.60), and yellowness value (97.47). Over the 15-d storage period, the total phenolic content (TPC), total flavonoid content (TFC), and total antioxidant capacity (TAC) increased, with the FMB3 sample exhibiting the highest TPC (58.70 mg/100 g), TFC (46.15 mg/100 g), and TAC (487.10 mg/100 g). All beverages remained free from yeasts and molds, and FMB3 exhibited the lowest bacterial count (5.13 log cfu/mL). The results indicate that ethanolic clove extract effectively inhibits spoilage and pathogenic organisms and enhances the sensory and functional properties of FMB. This finding offers a promising approach for improving the quality and safety of dairy products.

Abiotic stressors reduce farm animal productivity, and one of the most globally studied is heat stress (HS) because it compromises almost every profitability metric. Surprisingly, the biological consequences of seemingly very different stressors are highly conserved. Thus, although this review focuses on the broad impact of stress, describing the biology and etiology of how HS alters farm animal productivity provides the conceptual foundation for how all stressors can become pathological. Suboptimal production during HS was traditionally thought to result from hypophagia. However, independent of feed intake, HS affects a plethora of endocrine, physiological, metabolic, circulatory, and immunological variables. It is becoming increasingly clear that these changes are chronologically causal and that the etiological epicenter is a compromised gastrointestinal tract (GIT) barrier. A hyperpermeable GIT allows luminal contents to infiltrate, and these antigens stimulate an immune response with local and systemic inflammatory implications. Once activated, most leukocytes switch from oxidative phosphorylation to aerobic glycolysis and increase their glucose utilization. The glucose requirement of an intensely triggered immune system can exceed 2 kg/d in a lactating dairy cow. Whole-body metabolic adjustments are coordinated to ensure glucose is prioritized for the immune system and this is primarily characterized by increased basal and stimulated circulating insulin, hypercortisolemia, and hyperprolactinemia. This hormonal profile is accompanied by decreased adipose tissue mobilization and skeletal muscle insulin resistance. Interestingly, the aforementioned physiology is almost identical to distinctly different abiotic and biotic stressors. For example, feed restriction, weaning, cold stress, and noise stress all have a similar metabolic and inflammatory footprint, and this physiology can be closely recapitulated by experimentally-induced immune activation. Ultimately, these stressors are "psychological" and emanate their pathology from a compromised GIT barrier. Stress negatively affects GIT epithelia via at least 2 mechanisms: (1) mast cell degranulation and (2) immune cell creation of an apical pro-oxidant environment that paradoxically favors pathogen colonization. The metabolic, physiological, and immunological consequences of stress are highly conserved, and these analogous responses are symmetrical because the GIT is seemingly ground zero for all of them.