Journal of Dairy Research最新文献

Lactotransferrin (LTF), a critical multifunctional glycoprotein, plays an essential role in the immune defence, growth and development, and milk quality of dairy cows. The regulatory mechanisms governing gene expression are intricate, with sequence variations in the promoter region potentially exerting a substantial impact on gene expression. In this study, sequencing analysis of the bovine lactotransferrin promoter region was conducted, leading to the identification of two linked single nucleotide polymorphism (SNP) sites. A significant association between these SNPs and lactotransferrin content was observed in a cohort of 301 Holstein cows. Subsequently, further investigation into the transcriptional activity of various lactotransferrin genotypes was performed by constructing promoter fragments encompassing different lactotransferrin genotypes. The findings reveal that the two SNPs significantly influence the activity of the lactotransferrin promoter, thereby affecting lactotransferrin expression. These results hold substantial implications for advancing our understanding of the regulatory mechanisms underlying lactotransferrin expression and for the genetic enhancement of dairy cows.

This research paper addresses the hypothesis that the in vivo criterion of bovine somatic cell count (SCC) < 200,000 cells/ml milk as a diagnostic marker for healthy mammary tissue is not suitable to be adopted to milk samples taken post slaughter. To study immune mechanisms associated with intramammary infections, we developed a mammary explant model. As SCC is routinely applied to differentiate between healthy and inflamed mammary tissue, donor cows were selected based on their milk SCC obtained in vivo. Furthermore, milk cell differentiation for early mastitis detection via flow cytometry allows identification of leucocyte subpopulations and complements SCC. To replace in vivo examination and allow for post mortem selection of donor cows, this explorative study aimed to investigate how slaughter influences the reliability of SCC and differential milk cell count (DMCC) and to assess their validity as diagnostic markers for udder health in bovine milk samples obtained post slaughter. Therefore, quarter milk samples from cows were obtained in vivo and post mortem and analysed to determine SCC and DMCC and identify major mastitis pathogens. The logarithmized numbers of SCC, non-viable cells, viable cells, lymphoid cells, polymorphonuclear (PMN) and large cells per ml milk were compared using linear mixed-effects models in milk samples obtained from cows in vivo and post mortem. The number of lymphoid cells, PMN and large cells was significantly higher in milk samples obtained post mortem than in vivo, with PMN being the most prominent cell population. Higher milk SCC values measured post mortem might be explained by migration of leucocytes into the periphery during slaughter. This should be considered when modelling intramammary infection in vitro using udder tissue. Reflecting these findings, it is not feasible to endorse SCC as a reliable marker for post mortem selection of donor cows with healthy mammary tissue for in vitro models.

This study tested the effects of the methylenetetrahydrofolate reductase (MTHFR) rs110692574 polymorphism and rumen-protected choline and methionine supplementation on biochemical parameters, milk yield, reproductive performance and health status during the transition period in Holstein cows raised in Türkiye. Genotypes of 356 cows were determined using the tetra-primer amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) method. Following genotyping, 80 cows were selected and assigned to four groups based on nucleotide genotype at two loci (homozygous CC and heterozygous CT) and dietary supplement (choline or choline + methionine). Blood samples were collected on day 21 prepartum, on the day of parturition (day 0), and on day 21 postpartum to measure homocysteine, folic acid, vitamin B12, and non-esterified fatty acid concentrations. beta-hydroxybutyric acid (BHBA) values and production data were obtained from the farms' routine monitoring records. Statistical analyses were performed using repeated-measures analysis of variance (ANOVA) to assess time-dependent effects, and a general linear model was used for between-group comparisons at the same time points. The frequency of the CT genotype was 12.64%. The polymorphism significantly affected folic acid and vitamin B12 concentrations across different stages of the transition period. Feed supplementation had a significant effect on folic acid concentrations on calving day and on day 21 postpartum, as well as on milk yield on days 100, 200 and 305. Moreover, the polymorphism was significantly associated with folic acid and vitamin B12 concentrations on day 21 prepartum and with BHBA values on day 7 postpartum. This variation was linked to specific health issues that could lead to decreased productivity. In conclusion, genotype-based nutritional strategies were found to play a key role in maintaining metabolic balance and enhancing productivity during the transition period.

The confirmatory factor analysis technique was used to quantify a latent variable for test-day lactation performance (TDLP) in the first parity of Chinese Holstein dairy cows by applying five measurable traits, including test-day milk yield (TDMY), test-day milk fat percentage (TDFP), test-day milk protein percentage (TDPP), test-day somatic cell score (TDSCS) and test-day milk urea nitrogen (TDMUN). The standardised factor loadings of TDMY, TDFP, TDPP, TDSCS, and TDMUN for describing TDLP were 0.46, -0.52, -0.70, -0.14 and -0.19, respectively. Genetic analysis was conducted using a multivariate repeatability model within a Bayesian framework. The posterior means for the heritability and repeatability estimates of TDLP were 0.26 ± 0.02 and 0.34 ± 0.02, respectively. In general, posterior means for heritability and repeatability estimates of the measurable traits were low to medium. The heritability estimates ranged from 0.05 for TDSCS to 0.28 for TDPP, and repeatability estimates ranged from 0.15 for TDMUN to 0.38 for TDMY. The latent variable of TDLP exhibited positive genetic (0.62) and phenotypic (0.40) correlations with TDMY, whereas its genetic and phenotypic correlations with other measurable traits were negative, ranging from -0.96 (TDLP-TDPP) to -0.11 (TDLP-TDSCS). The corresponding phenotypic correlations ranged from -0.85 (TDLP-TDPP) to -0.07 (TDLP-TDSCS). It may be concluded that breeding for higher TDLP might increase TDMY but could reduce milk composition traits. In general, the negative genetic and phenotypic correlations suggest a trade-off between milk quantity (yield) and quality (composition).

This Research Communication reports the physicochemical properties, aflatoxin levels and antibiotic residues in buffalo milk. The milk and feed samples were collected from nine farms in Peninsular Malaysia, with the lactation stage studied in one farm. Buffalo milk composition varied across farms; Petaling Jaya showed high fat and total solids but low protein and solids non-fat (SNF), while Jitra 1 and Seberang Perai 2 exhibited higher protein, casein and SNF. Langkawi and Hulu Langat had higher moisture, ash and lactose levels. Early and late lactation were linked to higher protein and casein. Aflatoxin B₁ in feed was undetectable; however, aflatoxin M₁, amoxicillin and oxytetracycline were present in milk but below the regulatory limits. These findings indicate that current on-farm management practices are effective in ensuring the safety and quality of buffalo milk, while continuous monitoring remains crucial.

Plasminogen is an inactive protease in milk, which can be activated to plasmin. Whole milk contains fat and in response to lipase activity, free fatty acids are released. Free fatty acids are not known to act as an activator for plasminogen. The aim of this study was to determine whether commercial bovine plasminogen could be activated to plasmin by commercial free fatty acids present in milk, and also to determine if plasminogen activators to plasmin are present in abnormal milk using milk agar plates and the Merck protease assay. Fatty acids and activators present in abnormal milk had the ability to activate plasminogen to plasmin, which could, after weeks, harm milk protein stability during extended storage time (ultra-high temperature milk). The milk agar plate technique containing plasminogen could detect plasmin activators present in abnormal milk. This can act as an indicator of high-risk milk being used within the ultra-high temperature milk industry.

This research paper investigated the hypothesis that the high production of 3-methylbutanal by lactic acid bacteria is achieved not only through a direct metabolic pathway but also via an indirect pathway. 3-methylbutanal is a flavour compound that contributes to the sensory profile of various cheeses, often described as nutty, malty, or chocolate-like depending on its concentration and the cheese matrix. Although it is desired in certain cheese varieties, its acceptability varies among different cheese types. Among the various compounds responsible for this nutty scent, 3-methylbutanal plays a pivotal role. Certain strains of lactic acid bacteria are known to produce 3-methylbutanal from leucine, via both direct and indirect pathways. While it has commonly been assumed that the direct pathway is the primary mechanism, this study reports the discovery of Lactococcus cremoris AJ01, which produces 3-methylbutanal predominantly through an indirect pathway. We first investigated the effects of milk fermentation conditions on 3-methylbutanal and acid production by strain AJ01. The effect of leucine supplementation on 3-methylbutanal production was then examined. Finally, we explored the metabolic pathway responsible for 3-methylbutanal synthesis in this strain, determined the nucleotide sequence of the pyruvate dehydrogenase gene involved in the indirect pathway, and evaluated its enzyme activity to assess its contribution to production. When cultured in milk at 20 °C, strain AJ01 produced titratable acidity at >0.6% and 3-methylbutanal at >6 mg/kg within 18 h. Adding leucine to the milk enhanced 3-methylbutanal production, while excessive leucine supplementation inhibited it. Strain AJ01 exhibited activity of pyruvate dehydrogenase, while no activity of α-keto acid decarboxylase, the direct-pathway enzyme, was detected, suggesting that it produces 3-methylbutanal via the indirect pathway. These findings may contribute to the effective management and enhancement of flavour profiles in fermented dairy products, particularly cheeses.

High-temperature short-time (HTST, 72°C, 15 s) pasteurization can be successfully used for human milk (HM) preservation. The purpose of this study was to compare the effects of different HTST heating methods: microwave (MHTST) and standard convective (CHTST) on macronutrients, fatty acids (FAs), lactoferrin (LF), vitamin C, lysozyme (LZ), α-amylase (α-A) activity, lipid oxidation and antioxidant properties of HM. Regardless of the heating methods, the macronutrients and FA content, LZ activity and antioxidant properties of HM proved to be insensitive to HTST treatment, while the concentration of vitamin C decreased by 42.6% and 50.2%, and the activity of α-A by 6.0 and 7.2% when using MHTST and CHTST, respectively. LF content changed significantly only when CHTST was used (42.3% reduction). There were no negative effects of microwave heating under controlled conditions on the HM components. Satisfactory results regarding the impact of MHTST on HM composition and potential economic benefits suggest that this technology can be applied in HM banks to ensure adequate safety and quality.

The aim of this study was to investigate whether hair can be used as a non-invasive sample material that is less influenced by homeostasis than blood. Blood analysis is an invasive method of assessing trace element status, concentrations can be influenced by homeostasis, and they might not accurately reflect the true status of the animal. Thus, hair samples could play an important non-invasive role in diagnosing chronic deficiencies. The study group included 100 veal calves of a variety of different breeds and crossbreeds aged between 2 and 5 months, consisting of both sexes. Samples were taken to compare different locations and colours of hair. The concentration of trace elements Mn, Fe, Se, Co, Cu, Zn and Mo of different coloured ear and shoulder hair (black, brown and white) were measured, and concentrations were compared with those in the liver, kidney, muscle and blood plasma. All samples were measured with triple-quadrupole collision/reaction cell ICP-MS. This study showed that both hair colour and hair location have an influence on trace element concentration. In this animal series, no strong correlations could be found between trace element concentrations in hair and other tissues, suggesting that such an approach is only feasible when a heterogeneous animal series is used. Whether hair is a feasible sample material for trace element analysis cannot be conclusively answered; a larger sample size and further studies on other influencing factors would have been required. In addition, the procedure would need to be highly standardized, as both sampling localization and hair colour appear to have an influence.