Journal of Dairy Research最新文献

The study was undertaken to estimate the genetic parameters of lactation curve parameters of Wood's function in Jersey crossbred cattle using the Bayesian approach. Data on 33,906 fortnightly test day milk yields of 1,718 lactation records of Jersey crossbred cows, maintained at the ICAR-National Dairy Research Institute in West Bengal, were collected over a period of 40 years. The lactation curve parameters including 'a' (initial milk yield after calving), 'b' (ascending slope up to peak yield) and 'c' (descending slope after peak yield) and lactation curve traits, peak yield (y_max), time of peak yield (t_max) and persistency of milk yield (P) of individual cow for each lactation were estimated using the incomplete gamma function (Wood's model) by fitting the Gauss-Newton algorithm as an iteration method using PROC NLIN procedure of SAS 9.3. Variance components and genetic parameters of lactation curve parameters/traits were estimated by a repeatability animal model using the Bayesian approach. Estimates of heritabilities were found to be 0.18 ± 0.05, 0.09 ± 0.03 and 0.11 ± 0.04 for parameters 'a', 'b' and 'c', respectively and 0.24 ± 0.05, 0.12 ± 0.04, and 0.15 ± 0.05 for y_max, t_max and P, respectively. Repeatability estimates were 0.31 ± 0.03, 0.21 ± 0.04 and 0.30 ± 0.04 for parameters 'a', 'b' and 'c' respectively and 0.39 ± 0.03, 0.24 ± 0.03 and 0.37 ± 0.03 for y_max, t_max and p, respectively. Genetic correlations among lactation curve parameters/traits ranged from -0.75 to 0.95. Existence of genetic correlations among lactation curve parameters/traits indicated substantial genetic and physiological relationships among lactation curve parameters/traits of Jersey crossbred cattle.

The milk fat globule membrane (MFGM) is formed by complex cell biological processes in the lactating mammary epithelial cell which result in the release of the milk fat globule (MFG) into the secretory alveolus. The MFG is bounded by a continuous unit membrane (UM), separated from the MFG lipid by a thin layer of cytoplasm. This unique apocrine secretion process has been shown in all of the mammary species so far investigated. Once the MFG is released into the alveolus there is a considerable transformation of the UM with its attached cytoplasm. This is the MFGM. The transformation is stable and expressed milk shows the same transformed MFGM structure. Again, this transformation of structure is common to all mammalian species so far investigated. However, the explanation of the transformation very much depends on the method of investigation. Transmission electron microscope (TEM) studies suggest a literal breakdown to a discontinuous UM plus cytoplasm in patches and strands, whereas more recent confocal laser scanning light microscopy (CLSM) studies indicate a separation, in a continuous UM, of two phases, one liquid ordered and the other liquid disordered. This review is designed to show that the TEM and CLSM results show different views of the same structures once certain deficiencies in techniques are factored in.

This research communication describes the reproductive and productive parameters and somatic cell count (SCC) of primiparous and multiparous cows from specialized dairy Holstein herds in South region of Brazil, and correlates these parameters using test-day records. A total of 24 011 records of animals from 75 producers obtained between 2017 and 2018 were used. The variables analyzed included milk production, SCC, milk fat, protein and urea nitrogen contents and reproductive characteristics (number of services per conception, service period and percentage of pregnant cows). Data were analyzed using multivariate logistic regression and the statistical differentiation between the classes of SCC and milk production. Milk production, SCC, number of services per conception and service period were all higher in multiparous cows. The percentage of pregnant cows was higher when the SCC was less than 200 000 cells/ml and was higher in primiparous cows. There was no adverse effect of milk production on reproductive parameters in high producing cows (>40 kg milk/d), however, the percentage of pregnant cows with this production level was significantly higher in multiparous cows. In conclusion, the milk production level need not affect the reproduction of specialized dairy cows if the animals are kept under adequate environmental conditions.

This study investigated the age at first calving in Holstein heifers and its impact on various production parameters. A sample of 737 Holstein heifers born between 2015 and 2018 and finishing their first lactations between 2018 and 2020 was included. Cluster analysis revealed three groups based on age at first calving: high precocity, medium precocity and low precocity. Medium-precocity group exhibited the highest 305-day milk yield and peak milk production. Additionally, the same group demonstrated superior mean production per lactation, 305-day milk protein content, and 305-day milk yield. The lowest somatic cell count was found in the low-precocity group. In conclusion, medium-precocity cows showed better results such as higher 305-day milk yield and peak milk production.

This study aimed to evaluate the effect of shortening the dry period in high-yielding cows of different body condition scores (BCS). We report colostrum and milk quality, some serum metabolites, BCS changes, and some reproductive parameters with measurements being made over the first two months of lactation. Cows were grouped based on the length of the dry period (normal: about 50 d and short: about 28 d) and BCS (moderate: 2.75 to 3.5 and high ≥ 3.5). Short dry period decreased colostrum volume and, in combination with high BCS only, caused a decrease in milk production. Short dry period moderate BCS cows had the highest serum insulin concentration on day 14 after calving and highest glucose concentration on day 28, but neither differed significantly when measured over the whole period. By contrast, short dry period cows had significantly lower concentrations of non-esterified fatty acids and beta-hydroxybutyrate measured over the whole period. Post-partum loss of BCS was less in short and especially so in the short, moderate BCS group. Following a synchronization protocol at 35 d postpartum. The cows with a short dry period and moderate BCS had lower open days, days to first postpartum estrus and services per conception. It was concluded that short dry periods and moderate BCS had a positive influence on serum metabolites, BCS changes and reproductive parameters.

This research communication paper addresses the hypothesis that the use of therapeutic alternatives for mastitis, such as intramammary ozone, can cure the disease with lower costs and without harmful residues for human consumption and without formation of microbial resistance like the ones caused by indiscriminate use of antibiotics in dairy farms. The study was performed in 36 mammary quarters from 12 dairy cows with subclinical mastitis grade three. The experimental units were randomly assigned into four groups and each group received a treatment. Treatments comprised (a) 20 μg/ml ozone gas; (b) 40 μg/ml ozone gas; (c) negative control treatment of 12.5 μg/ml ozonated saline and (d) positive control treatment of 100 mg of cephalexin + 100 mg of neomycin + 10 mg of prednisolone, all by intramammary injection. In all quarters, milk was collected before and after the application of treatments for California mastitis test and evaluation of milk composition, somatic cell count, and bacterial cultures. The results indicated that the use of intramammary ozone did have a therapeutic effect, and whilst this was less than that of antibiotics, ozone does confer some advantages. Treated milk had a good composition, the treatment cost was low, milk withdrawal may not be necessary and there is no risk of antibiotic resistance.

We studied the genetic polymorphism of beta-lactoglobulin (β-Lg) whey protein in Gangatiri zebu cows for this Research Communication. The polymorphic nature of milk protein fractions and their association with milk production traits, composition and quality has attracted several efforts in evaluating the allelic distribution of protein locus as a potential dairy trait marker. Genetic variants of β-Lg have highly significant effects on casein number (B > A) and protein recovery (B > A) and also determine the yield of cheese dry matter (B > A). Molecular techniques of polyacrylamide gel electrophoresis and high-resolution accurate mass-spectroscopy were applied to characterize the β-Lg protein obtained from the Gangatiri breed milk. Sequence analysis of β-Lg showed the presence of variant B having UniProt database accession number P02754, coded on the PAEP gene. Our study can provide reference and guidance for the selection of superior milk (having β-Lg^B) from this indigenous breed that could potentially give a good yield of β-Lg for industrial applications.

The aim of this research paper was to evaluate the effect of a slow-release milk replacer on health and behaviour of neonatal dairy calves. This was done with the potential benefits to welfare during transport in mind. A total of 15 calves were randomly divided into three groups of 5, namely, a control group fed twice in 24 h with 3 l of a conventional milk replacer, a slow-release group fed once in 24 h with 2 l of conventional milk replacer and 1 litre of a specialised micro-encapsulated feed and an enriched-replacer group fed once in 24 h with 3 l of milk replacer enriched with micellar casein. Blood samples were taken before feeding and 6, 12, 18 and 24 h after and analysed for acid-base parameters, electrolytes, glucose, haemoglobin, cortisol, insulin, cholecystokinin and adiponectin. Calf behaviour was recorded between 6 and 14 h after feeding. There was a significant increase in blood pH 6 h after feeding in all groups, but the glucose, HCO₃ ^- and base excess increased significantly in the slow-release group only, whereas sodium increased significantly in the enriched group only. Glucose levels remained significantly higher in the slow-release group, relative to the control, at 6, 12, and 18 h after feeding. Insulin levels changed significantly over time in the enriched and control group but remained constant in the slow-release group. Insulin levels were significantly higher in the control group when compared to the slow-release group after feeding. Adiponectin changed significantly over time after feeding in the control group only, but no significant changes were observed between the feeding groups. Behavioural patterns were similar in control and slow release groups but less favourable (less lying time, more vocalisations) in the enriched group. In conclusion, once-daily feeding of slow-release milk replacer demonstrated favourable patterns of blood variables related to satiety and hunger as well as behavioural patterns that did not differ from conventional twice-daily feeding.