The Effect of Rumination Time on Milk Performance and Methane Emission of Dairy Cows Fed Partial Mixed Ration Based on Maize Silage

The objective of this study was to determine the effect of the rumination time on milk yield and composition as well as methane emission during lactation in high-yielding dairy cows fed a partial mixed ration based on maize silage without pasture access. A total of 365 high-yielding Polish Holstein-Friesian multiparous dairy cows were included in the study covering 24 to 304 days of lactation. Methane emission, rumination time, and milk production traits were observed for the period of 12 months. Next, the data from the cows were assigned to three groups based on daily rumination time: low rumination up to 412 min/day (up to 25th rumination percentile), medium rumination from 412 to 527 min/day (between the 25th and 75th percentile), and high rumination above 527 min/day (from the 75th percentile). Rumination time had no effect on milk yield, energy-corrected milk yield, or fat and protein-corrected milk yield. High rumination time had an effect on lower fat concentration in milk compared with the medium and low rumination groups. The highest daily CH4 production was noted in low rumination cows, which emitted 1.8% more CH4 than medium rumination cows and 4.2% more than high rumination cows. Rumination time affected daily methane production per kg of milk. Cows from the high rumination group produced 2.9% less CH4 per milk unit compared to medium rumination cows and 4.6% in comparison to low rumination cows. Similar observations were noted for daily CH4 production per ECM unit. In conclusion, a longer rumination time is connected with lower methane emission as well as lower methane production per milk unit in high-yielding dairy cows fed a maize silage-based partial mixed ration without pasture access.

Association of Feed Efficiency, Feeding Rate, and Behaviour with the Milk Performance of Dairy Cows

Identification of the associations of cow feed efficiency with feeding behaviour and milk production is important for supporting recommendations of strategies that optimise milk yield. The objective of this study was to identify associations between measures of feed efficiency, feed intake, feeding rate, rumination time, feeding time, and milk production using data collected from 26 dairy cows during a 3 month period in 2018. Cows averaged (mean ± standard deviation) 2.2 ± 1.7 lactations, 128 ± 40 days in milk, 27.5 ± 5.5 kg/day milk, 1.95 ± 0.69 kg feed/1 kg milk—the measure used to express feed conversion ratio (FCR), 575 ± 72 min/day rumination time, and 264 ± 67 min/day feeding time during the observation period. The coefficient of variation for rumination time (min/d) was 12.5%. A mixed linear model was selected for analyses. The most feed inefficient cows with the highest FCR (≥2.6 kg feed/1 kg milk) showed the lowest milk yield (24.8 kg/day), highest feed intake (78.8 kg), highest feeding rate (0.26 kg/min) and BCS (3.35 point). However, the relative milk yield (milk yield per 100 kg of body weight) was the highest (4.01 kg/day) in the most efficient group with the lowest FCR (≤1.4 kg feed/1 kg milk). Our study showed that the most efficient cows with the lowest FCR (≤1.4 kg feed/1 kg milk) had the highest rumination time (597 min/day; p < 0.05), feeding time (298 min/day; p < 0.05), rumination/activity ratio (4.39; p < 0.05) and rumination/feeding ratio (2.04; p < 0.05). Less active cows (activity time 164 min/day; p < 0.05) were the most efficient cows with the lowest FCR (≤1.4 kg feed/1 kg milk). The behavioural differences observed in this study provide new insight into the association of feed behaviour and feed efficiency with milk performance. Incorporating feeding behaviour into the dry matter intake model can improve its accuracy in the future and benefit breeding programmes.

Association of genetic variants in STAT5B gene with milk performance and mastitis related traits in dairy cattle

Udder performance and health are important traits in dairy cattle worldwide. The present study aimed to explore the association of single nucleotide polymorphisms (SNPs) in the STAT5B gene in dairy cattle with milk performance and mastitis related traits. The study included 201 cows of three pure breeds (i.e. Holstein Friesian, Jersey and Achai) and two crossbred cattle at four established dairy farms in Khyber Pakhtunkhwa, Pakistan. The milk samples were analysed for somatic cell count (SCC) and milk composition (i.e. fat , protein and lactose percentages). The generalized linear model was deployed for association analysis using SAS. The pool DNA sequencing showed four (three synonymous and a 3/ UTR) SNPs in STAT5B. These SNPs were further validated in all DNA samples using SNaPshot assay. The breed-wise analysis showed that most of the SNPs were consistent with Hardy-Weinberg equilibrium (P>0.05). The association analysis revealed a significantly higher protein percentage in TT genotype and lower SCC in CC genotypes of SNP 1 (exon 2, C>T), whereas in SNP 2 (exon 16, T>C) the TT genotypes revealed significantly lower SCC and SCS compared with other genotypes (P<0.05). SNP 4 (3/ UTR, C>T) showed significantly lower SCC and frequency of clinical mastitis in the heterozygous (CT) genotype compared to the homozygous genotypes. The in silico predictions revealed changes in the RNA secondary structure for SNP 2 and SNP 3. The study suggests that STAT5B should be considered as a candidate gene, and the variants identified as useful genetic markers for improved milk composition and udder health.

Effects of Calcium Propionate on Milk Performance and Serum Metabolome of Dairy Cows in Early Lactation

Background: Most of the dairy cows in early lactation suffer from a period of negative energy balance (NEB) and hypocalcemia metabolic disorders. Calcium propionate is a source of energy and calcium for alleviating NEB and hypocalcemia. The objective of the study was to investigate the changes of milk compositions and blood metabolites of postpartum dairy cows fed with calcium propionate for 5 weeks.Methods:Thirty-two multiparous Holstein cows after calving were randomly allocated to control (CON), low calcium propionate (LCaP), medium calcium propionate (MCaP) and high calcium propionate (HCaP) groups with 8 cows per group balanced with parity, milk yield and body weight. The dairy cows in the four groups were oral drenching with 0, 200, 350, 500 g/d calcium propionate per cow from calving to d 35 in early lactation, respectively.Results:The results showed that the milk yield in MCaP group was significantly higher than those in the other groups. At d 35, the somatic cell count (SCC) in MCaP group tended to be lower than those in other groups. Compared with the CON group, serum non-esterified fatty acid (NEFA) in MCaP and HCaP groups tended to decrease. The serum alanine aminotransferase (ALT) concentration in MCaP group was lowest among the four groups. The concentration of aspartate aminotransferase (AST) in HCaP group was significantly higher than the other groups. Feeding calcium propionate had no significant effect on serum calcium, phosphorus and magnesium concentrations. The serum parathyroid hormone (PTH) in HCaP group tended to decrease. The calcium propionate treatments significantly decreased the serum alkaline phosphatase (ALP) level. The MCaP treatment significantly decreased serum total antioxidant capacity (T-AOC), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and catalase (CAT) activity, while increased the concentration of malondialdehyde (MDA) when compared with the other groups. The metabolomic results showed that calcium propionate significantly affected the bile acid compositions. Conclusions: It was concluded that the 350 g/d calcium propionate feeding level could significantly improve milk performance, alleviate body fat mobilization and bone calcium utilization, however decrease antioxidant capacity of dairy cows as well. The effect of calcium propionate on milk performance and serum metabolites in early lactation cows may be regulated through the serum bile acids metabolism.

Evolutionary Analysis of OAT Gene Family in River and Swamp Buffalo: Potential Role of SLCO3A1 Gene in Milk Performance

The organic anion transporter (OAT) family is the subfamily of the solute carrier (SLC) superfamily, which plays a vital role in regulating essential nutrients in milk. However, little is known about the members’ identification, evolutionary basis, and function characteristics of OAT genes associated with milk performance in buffalo. Comparative genomic analyses were performed to identify the potential role of buffalo OAT genes in milk performance in this study. The results showed that a total of 10 and 7 OAT genes were identified in river buffalo and swamp buffalo, respectively. These sequences clustered into three groups based on their phylogenetic relationship and had similar motif patterns and gene structures in the same groups. Moreover, the river-specific expansions and homologous loss of OAT genes occurred in the two buffalo subspecies during the evolutionary process. Notably, the duplicated SLCO3A1 gene specific to river buffalo showed higher expression level in mammary gland tissue than that of swamp buffalo. These findings highlight some promising candidate genes that could be potentially utilized to accelerate the genetic progress in buffalo breeding programs. However, the identified candidate genes require further validation in a larger cohort for use in the genomic selection of buffalo for milk production.