Milk Yield Traits Research Articles

Some Yield and Growth Traits of Anatolian Buffaloes and the Effects of First Calving Age and Calving Interval on These Traits

Numerous in-depth studies have described the fertility traits, growth performance and milk yield traits of dairy animals, which are considered indicators of welfare, but there are limited studies examining these traits within the framework of cause-effect relationships, especially in buffaloes. The aim of this study was to determine the changes in some milk, growth and fertility traits of Anatolian buffaloes over the years in some dairy farms where the Buffalo Breeding Project in Public Conditions was implemented in Samsun province and, to investigate the effects of first calving age (FCA) and calving interval (CI) on milk and growth traits. The study was conducted in 27 buffalo farms (3295 buffalo cows and 3317 buffalo calves) located in Bafra district, the region with the highest buffalo population in Samsun province, Türkiye. The data was taken from records previously kept within the scope of the relevant project. The data such as growth characteristics [birth weight (BW), 6th and 12th-mo live weight (LW) values of calves born between 2013-2020] and lactation traits of cows [lactation milk yield (LMY) and lactation duration (LD)] and FCA and CI values were analyzed by analysis of variance. The effect of years on LMY of buffalo cows was found to be significant, and significant positive changes were determined from year to year. In addition, the BW, 6th-mo, and 12th-mo LW values of calves also varied from year to year. As the FCA value of buffaloes increased, the BW, 6th-mo, and 12th-mo LW values of calves and LMY of cows increased. Similarly, CI values affected the BW values of calves (P<0.01), and LMY and LD values increased in parallel with the increase in CI values. Consequently, determining the lactation and growth traits of buffaloes could benefit developing herd management practices that would optimize these performance indicators.

Strong associations between the FGF-2 gene and productivity traits of Holstein-Friesian dairy cattle

Sustainability in dairy cattle farms depends on the efficiency of milk yield and reproductive traits. Thus, this study aimed to investigate the effect of the FGF-2/Csp6I gene and major environmental factors on these traits in Holstein-Friesian cattle. A total of 212 whole blood samples were collected from the Vena coccygea of cattle and the data obtained from these samples were used in all statistical analyses. Then, the restriction fragment length polymorphism (RFLP) method (determination of genotypes) was conducted and programs including PopGene (allele and genotype frequencies), Minitab (association analyses) and MTDFREML (variance components and genetic parameters) were used. Alleles A (0.4269) and G (0.5731) as well as genotypes AA (0.174), AG (0.505) and GG (0.321) were found, indicating that the population is polymorphic and in Hardy-Weinberg equilibrium (P > 0.05). The effect of the Csp6I polymorphism of FGF-2 gene on peak milk yield (PMY) (P < 0.01); lactation milk yield (LMY), milking time (MT), 305-day and 200-day lactation milk yield (LMY305 and LMY200), average daily milk yield (ADMY) (P < 0.05); 100-day lactation milk yield (LMY100), age of using in first breeding (AUFB) and number of inseminations per conception (NIPC) (P < 0.10) were significant. The heritability of milk yield traits and the correlation between direct and maternal heritability for reproductive traits were high. Furthermore, the breeding value of PMY was higher for the AA genotype (0.745 ± 0.292) than for the AG genotype (−0.268 ± 0.171) (P < 0.05). As a result, the A allele and AA genotype for the FGF-2/Csp6I gene had an increasing effect on milk yield without compromising reproductive performance in Holstein-Friesian dairy cattle.

Evaluation of performance and estimation of genetic parameters for milk yield and reproductive traits in Awassi and Asaf sheep breeds and crosses in the Palestinian territory.

This study aimed to estimate genetic parameters, including heritability and repeatability, for milk yield and prolificacy in sheep. It included 3682 records from 1837 ewes across various breeds: Awassi, Assaf, and Awassi x Assaf crosses, two Awassi lines: Improved Awassi, AFEC Awassi. The study measured total milk yield (TMY), yield up to 120 days (TMY120), and yield up to 150 days (TMY150), alongside reproductive traits: litter size (LS), number of lambs born alive (NLBA), and lambing interval (LI). The analysis utilized a mixed model and the REML procedure to estimate genetic parameters. Results indicated that litter size (LS) had no significant impact on milk traits, whereas breed, location, ewe parity, and lambing season showed significant effects. Lactation length also significantly influenced TMY. For reproductive traits, treatment was significant for NLBA, with location associated with breed, parity, and season affecting all traits. Heritability estimates for TMY ranged from 0.00 in Awassi x Assaf crosses to 0.11 in Awassi, and for TMY120 and TMY150, from 0.00 in Awassi x Assaf crosses to 0.16 in Awassi. Estimates for LS and NLBA varied similarly. The heritability for LI was 0.03 in Awassi and zero in other breeds and crosses. The findings suggest that in the northern West Bank regions of Nablus and Jenin, Assaf or Awassi x Assaf breeds are preferable. The study underscores the importance of comprehensive performance and pedigree recording for effective sheep farm management.

Identification of Genetic Associations of IDH2, LDHA, and LDHB Genes with Milk Yield and Compositions in Dairy Cows.

Previous study revealed that isocitrate dehydrogenase (NADP (+)) 2, mitochondrial (IDH2), lactate dehydrogenase A (LDHA), and lactate dehydrogenase B (LDHB) genes were significantly differentially expressed in liver tissues of Holstein cows among different lactation periods and associated with lipid and protein metabolism; hence, they were considered as candidates for milk production traits. Herein, the genetic effects of the three genes on milk yield, fat, and protein traits were studied by association analysis using 926 Chinese Holstein cows from 45 sire families. As a result, five single nucleotide polymorphisms (SNPs) in IDH2, one in LDHA, and three in LDHB were identified by re-sequencing, and subsequently, they were genotyped in 926 Chinese Holstein cows by genotyping by target sequencing (GBTS). With the animal model, single-locus association analysis revealed that four SNPs in IDH2 and one SNP in LDHA were significantly associated with milk, fat, and protein yields (p ≤ 0.0491), and three SNPs in LDHB were associated with milk yield, milk fat yield, and fat percentage (p ≤ 0.0285). Further, four IDH2 SNPs were found to form a haplotype block significantly associated with milk yield, fat yield, protein yield, and protein percentage (p ≤ 0.0249). In addition, functional predictions indicated that one SNP in LDHA, g.26304153G>A, may affect transcription factor binding and two SNPs, g.88544541A>G and g.88556310T>C could alter LDHB mRNA secondary structure. In summary, this study profiled the significant genetic effects of IDH2, LDHA, and LDHB on milk yield and composition traits and provided referable genetic markers for genomic selection programs in dairy cattle.

Estimation of Genetic Parameters for Milk Production Rate and Its Stability in Holstein Population.

Milk production rate (MPR) refers to the rate of milk secretion per hour (kg/h), calculated from the harvested milk yield and milking interval, and it is considered an appropriate measure to evaluate the production potential of cows. The objective of this study was to estimate the phenotypic and genetic parameters of milk production rate traits. In this study, the milking records of 4760 Holstein cows were collected, and four milk yield traits and six milk production rate traits were defined. The MIXED procedure was used to detect the impacts of non-genetic effects on milk yield and milk production rate traits, including parity, measured season and lactation stage. Variance and covariance components for milk yield and milk production rate traits were estimated using a univariate linear repeatability model. Parity, measurement season and lactation stage had significant effects (p < 0.01) on milk yield, milk production rate and its stability. Milk yield and milk production traits had high heritability, and ranged from 0.25 to 0.39. The stability of milk production rate had low heritability (0.04~0.05). Milk production rate is beneficial for the devolving novel trait in dairy breeding and provides new insights for herd management and genetic selection of production performance of dairy cattle.

Improvement of dairy characters in farms and breeding value of the breeding bulls when assessing the quality of offspring

The article presents studies on comparison of the levels of precocity and milk productivity indicators of the daughters of Holstein bulls, who are evaluated for the quality of offspring simultaneously in two breeding plants of the Moscow region. According to the official ratings of breeding values, the bulls were divided into groups of "improving" and "worsening". The ratio of the daughters of the "best" and "worst" breeding bulls was 511:568 and 160:127 heads over the farms. It was determined which values of the differences in the "daughter – mother" indicators were increased in groups of officially evaluated bulls that received ratings of "improvers" and "deteriorators" according to the characteristics in these two breeding plants. The bulls being tested were fixed individually, and according to the number of pairs as the main ones. At the first insemination, the daughters of the "improving" group of bulls had 6.5–8.5 kg increased live weight of, but were relatively older by 0.36–0.6 months. According to the milk yield trait, the total yield of milk fat and protein, highly rated fathers in breeding plants were significantly inferior to competitors with low breeding value in milk yield by 688–1136 kg, according to the difference "mother – daughter" in the total yield of milk fat and protein per lactation – by 43.1–97.3 kg. In one of the farms, the "daughter – mother" differences in milk yield in all bull clusters increased by 599–1275 kg of milk; according to mass fat fraction (MFF) — by 0.02–0.20% and for mass protein fraction (MPF) — by 0.19–0.31%; in another farm, the increase in milk yield was by 43.8–1551 kg of milk and 0.05–0.13% according to the MPF. The daughters of the "worst" fathers in terms of MFF and MPF significantly outperformed the group of daughters of the "best" fathers in terms of "daughter–mother" differences by 35.6 and 61.7 kg of total milk protein and fat output over 305 days of lactation. At the same time, there were no significant differences between daughters and peers. The relativity of the official definition of the values of the breeding value of breeding bulls has been proved. It is proposed, regardless of the "commercial" and previously conducted estimates of breeding bulls, to take into account the indices of pedigrees and types of selection when breeding them. Conclusions are drawn about the significant influence of the factor and selection methods on the values of milk production traits; in order to save growing costs, it is proposed to optimize the live weight and age of insemination of heifers in farms.

Genome-wide copy number variation regions in indigenous (Bos indicus) cattle breeds of Tamil Nadu, India.

Identification of large scale structural polymorphisms (Copy number variations) of more than 50 bp between the individuals of a species would help in knowing genetic diversity, phenotypic variability, adaptability to tropical environment and disease resistance. Read depth-based method implemented in CNVnator was used for calling copy number variant regions on sequenced data obtained from WGS from 15 pooled samples belonging to five draught cattle breeds of Tamil Nadu. A total of 11,605 CNV regions (CNVRs) were observed covering a genome size of 18.63 percent. Among these, 11,459 were restricted to autosomes, consisting of 11,013 deletions, 353 duplications and 93 complex events. These CNVRs were annotated to 4,989 candidate genes. A total of 8,291 numbers of CNVRs were shared among the five cattle breeds as also supported by PCA and STRUCTURE analyses and 1,172 CNVRs were breed-specific. Four out of five selected breed-specific CNVRs were validated using real-time PCR. Genes with CNVRs are related to milk production (BTN1A1, ABCA1 and LAP3), disease resistance (TLR4 and DNAH8), adaptability (SOD1, CAST and SMARCAL1), growth (EGFR, NKAIN3), reproduction (BRWD1 and PDE6D), meat and carcass traits (MAP3K5 and NCAM1) and exterior (ATRN and MITF) traits. Gene enrichment analysis based on the gene list retrieved from the CNVRs disclosed over-represented terms (p<0.01) associated with milk fat production. NETWORK analysis had identified 13 putative candidate genes involved in milk fat percentage, milk fat yield, lactation persistency, milk yield, heat tolerance, calving ease, growth and conformation traits. The genome-wide CNVRs identified in the present study produced genome-wide partial CNV map in indigenous cattle breeds of Tamil Nadu.

DEPENDENCE OF MILK PRODUCTIVITY AND SIGNS OF LONGEVITY OF COWS OF THE HOLSTEIN AND UKRAINIAN BLACK-SPOTTED DAIRY BREED ON THE LENGTH OF THE SERVICE PERIOD

Impact research of the duration of service period on the longevity traits of Holstein and Ukrainian Black-and-White dairy cows was conducted in the herd of private enterprise "Burynske" in Sumy district. It has been established that the milk yield of cows for 305 days and full lactation according to the assessment data of the first, third and best lactations and, in general, for the entire life, grew under the condition of increasing the duration of service period to the level of 140 days, regardless of breed. A further increase in the duration of service period for 141 days led to a decline in the above-mentioned traits. The highest lifetime milk yield was obtained from a group of cows with a service period length of 121–140 days, which amounted to 31955 ± 606.7 kg in Holsteins, and 30188 ± 624.4 kg for Ukrainian Black-and-White dairy breed. Against the background of increase in the duration of service period, rising rates of lifetime, productive use and the number of used lactations was observed in cows of experimental breeds. However, the yield per day of life and productive use decreased in groups of Holstein breed with a service period of ˃ 80–161 &lt; days, from 14.6 to 10.3 kg and from 24.7 to 14.6 kg, respectively. In the groups of cows of the Ukrainian Black-and-White dairy breed with the duration of service period ˃ 80–161 &lt; days, corresponding reduction in milk yield per day of life and productive use amounted to 13.1–9.5 and 21.9–13.2 kg. A direct, medium-level, reliable relationship between the service period length and the traits of lifetime, productive use, milk yield and milk fat during life was revealed, which was within the range of r = 0.193–0.311 in Holstein cows and Ukrainian Black-and-White dairy r = 0.145–0.251. An inverse and highly reliable relationship was found between the duration of service period and the milk yield per day of life and productive use in Holstein cows (r = -0.268 and -0.383) and Ukrainian Black-and-White dairy breed (r = -0.255 and -0.325). The strength of influence the duration of service period of cows on their lifespan, productive use and number of used lactations was 22.4–27.5% for Holstein breed, and 21.4–24.3% for Ukrainian Black-and-White dairy breed. Traits of lifetime milk productivity of Holstein cows depended on the duration of service period by 12.2–31.3% and of Ukrainian Black-and-White dairy cows by 13.4–28.9%.

Genetic parameters, genome-wide association study, and selection perspective on gestation length in 16 French cattle breeds

Lifetime productivity is a trait of great importance to dairy cattle populations as it combines information from production and longevity variables. Therefore, we investigated the genetic background of lifetime productivity in high-producing dairy cattle by integrating genomics and transcriptomics data sets. A total of 3,365,612 test-day milk yield records from 134,029 Chinese Holstein cows were used to define 6 lifetime productivity traits, including lifetime milk yield covering full lifespan and 5 cumulative milk yield traits covering partial lifespan. Genetic parameters were estimated based on univariate and bivariate linear animal models and the Restricted Maximum Likelihood (REML) method. Genome-wide association studies (GWAS) and weighted gene co-expression network analyses (WGCNA) were performed to identify candidate genes associated with lifetime productivity based on genomic data from 3,424 cows and peripheral blood RNA-seq data from 23 cows, respectively. Lifetime milk yield averaged 24,800.8 ± 14,396.6 kg (mean ± SD) across an average of 2.4 parities in Chinese Holstein population. The heritability estimates for lifetime productivity traits ranged from 0.05 (±0.01 for SE) to 0.10 (±0.02 for SE). The estimate of genetic correlation between lifetime milk yield and productive life is 0.88 (±0.3 for SE) while the genetic correlation with 305d milk yield in the first lactation was 0.49 (±0.08 for SE). Absolute values for most genetic correlation estimates between lifetime productivity and type traits were lower than 0.30. Moderate genetic correlations were found between udder related traits and lifetime productivity, such as with udder depth (0.33), rear udder attachment height (0.33), and udder system (0.34). Some single nucleotide polymorphisms and gene co-expression modules significantly associated with lifetime milk yield were identified based on GWAS and WGCNA analyses, respectively. Functional enrichment analyses of the candidate genes identified revealed important pathways related to immune system, longevity, energy utilization and metabolism, and FoxO signaling. The genes NTMT1, FNBP1, and S1PR1 were considered to be the most important candidate genes influencing lifetime productivity in Holstein cows. Overall, our findings indicate that lifetime productivity is heritable in Chinese Holstein cattle and important candidate genes were identified by integrating genomic and transcriptomic data sets.

Genome-wide association study for milk yield, frame, and udder conformation traits of Gir dairy cattle

Genome-wide association studies (GWAS) are employed to identify genomic regions and candidate genes associated with several traits. The aim of this study was to perform a GWAS to identify causative variants and genes associated with milk yield, frame, and udder conformation traits in Gir dairy cattle. Body conformation traits were classified as "frame," and "udder" traits for this study. After genotyping imputation and quality control 42,105 polymorphisms were available for analyses and 24,489 cows with pedigree information had phenotypes. First, P-value was calculated based on the variance of the prediction error of the SNP-effects on the first iteration. After that, 2 more iterations were performed to carry out the weighted single-step genome-wide association methodology, performed using genomic moving windows defined based on linkage disequilibrium. The significant SNPs and top 10 windows explaining the highest percentage of additive genetic variance were selected and used for QTL and gene annotation. The variants identified in our work overlapped with QTLs from the animal QTL database on chromosomes 1 to 23, except for chromosome 4. The Gir breed is less studied than the Holstein breed and as such the animal QTL database is biased to Holstein results. Hence it is noteworthy that our GWAS had similarities with previously described QTLs. These previously known QTLs were related to milk yield, body height, rump angle, udder width, and udder depth. In total, 5 genes were annotated. Of these genes, FAM13A and CMSS1 had been previously related to bone and carcass weight in cattle.

Detection of Polymorphisms in FASN, DGAT1, and PPARGC1A Genes and Their Association with Milk Yield and Composition Traits in River Buffalo of Bangladesh.

This study aimed to identify SNPs in the intron, exon, and UTR regions of the FASN, DGAT1, and PPARGC1A genes and to investigate their possible association with milk yield and composition traits in the riverine buffalo of Bangladesh. A total of 150 DNA samples from riverine buffalo were used for PCR amplification with five pairs of primers, followed by association studies using a generalized linear model in R. SNP genotyping was performed by direct sequencing of the respective amplicon. Traits analyzed included DMY, fat%, protein%, and SNF%. This study identified 8 SNPs in FASN (g.7163G>A and g.7271C>T), DGAT1 (g.7809C>T and g.8525C>T) and PPARGC1A (g.387642C>T, g.387758A>G, g.409354A>G, and g.409452G>A). Genotypic and allelic frequencies differed significantly for each SNP genotype and did not follow the Hardy-Weinberg principle (p < 0.01 or p < 0.001) in most cases. The g.7163G>A and g.7271C>T SNP genotypes of the FASN gene were significantly associated with milk fat%, with the latter also significantly associated with SNF%. The g.8525C>T polymorphism of the DGAT1 gene significantly affected protein% (p < 0.01). Additionally, PPARGC1A gene polymorphisms showed significant associations: g.387642C>T with fat% (p < 0.05); g.387758A>G and g.409354A>G with protein% (p < 0.001) and SNF% (p < 0.01); and g.409452G>A with DMY (p < 0.001), fat% (p < 0.05), and protein% (p < 0.01). Reconstructed haplotypes of the PPARGC1A gene were significantly associated (p < 0.01) with all traits except SNF%. These findings suggest that polymorphisms in these three candidate genes have the potential as molecular markers for improving milk yield and composition traits in the riverine buffalo of Bangladesh.

Prediction of First Lactation Milk Yield on The Basis of Test Day Yield Using Multiple Linear Regression in Gir Cows

The test-day model is a method of choice for the study of milk yield traits, and this method is very important in countries like India, where herd size is generally smaller and lacks a well-established milk recording system. The present investigation was carried out on 365 records of Gir cows maintained at a cattle breeding farm from 1986 to 2014 with the objective of predicting the first lactation milk yield using monthly test day milk records. MLR was used with the backward elimination method. The optimum equation had total five variables (test days) viz. TD1, TD2, TD3, TD4 and TD5. This equation gave an accuracy of prediction of 77.71%. Therefore, it is concluded that first lactation 305 day milk yield could be predicted as early as 5th month of lactation with higher degree of accuracy.

Heat Stress Effects on Physiological and Milk Yield Traits of Lactating Holstein Friesian Crossbreds Reared in Tanga Region, Tanzania.

Global warming caused by climate change is a challenge for dairy farming, especially in sub-Saharan countries. Under high temperatures and relative humidity, lactating dairy cows suffer from heat stress. The objective of this study was to investigate the effects and relationship of heat stress (HS) measured by the temperature-humidity index (THI) regarding the physiological parameters and milk yield and composition of lactating Holstein Friesian crossbred dairy cows reared in the humid coastal region of Tanzania. A total of 29 lactating Holstein Friesian x Zebu crossbred dairy cows with 50% (HF50) and 75% (HF75) Holstein Friesian gene levels in the second and third months of lactation were used. The breed composition of Holstein Friesians was determined based on the animal recording system used at the Tanzania Livestock Research Institute (TALIRI), Tanga. The data collected included the daily temperature, relative humidity, daily milk yield, and physiological parameters (core body temperature, rectal temperature, respiratory rate, and panting score). THI was calculated using the equation of the National Research Council. The THI values were categorized into three classes, i.e., low THI (76-78), moderate THI (79-81), and high THI (82-84). The effects of THI on the physiological parameters and milk yield and composition were assessed. The effects of the genotype, the parity, the lactation month, and the interaction of these parameters with THI on the milk yield, milk composition, and physiological parameters were also investigated. The results show that THI and its interaction with genotypes, parity, and the lactation month had a highly significant effect on all parameters. THI influenced (p ˂ 0.05) the average daily milk yield and milk fat %, protein %, lactose %, and solids-not-fat %. As the THI increased from moderate to high levels, the average daily milk yield declined from 3.49 ± 0.04 to 3.43 ± 0.05 L/day, while the fat % increased from 2.66 ± 0.05% to 3.04 ± 0.06% and the protein decreased from 3.15 ± 0.02% to 3.13 ± 0.03%. No decline in lactose % was observed, while the solid-not-fat % declined from 8.56 ± 0.08% to 8.55 ± 0.10% as the THI values increased from moderate to high. Also, the THI influenced physiological parameters (p ˂ 0.05). The core body temperature (CBT), rectal temperature (RT), respiratory rate (RR) and panting score (PS) increased from 35.60 ± 0.01 to 36.00 ± 0.01 °C, 38.03 ± 0.02 to 38.30 ± 0.02 °C, 62.53 ± 0.29 to 72.35 ± 0.28 breaths/min, and 1.35 ± 0.01 to 1.47 ± 0.09, respectively, as the THI increased from low to high. The THI showed a weak positive correlation with the average daily milk yield and fat percentage, whereas the protein, lactose, and solids-not-fat percentages showed negative relationships with THI (p ≤ 0.05). CBT, RT, RR, and PS showed positive relationships (p ≤ 0.05) with THI. These negative relationships indicate that there is an antagonistic correlation between sensitivity to HS and the level of production. It is concluded that the THI, the genotype, the parity, and the lactation month, along with their interactions with THI, significantly influenced the milk yield, milk composition, and physiological parameters of lactating Holstein Friesian dairy crosses at THI thresholds ranging from 77 to 84.

Exploring the Interplay between the Hologenome and Complex Traits in Bovine and Porcine Animals Using Genome-Wide Association Analysis.

Genome-wide association studies (GWAS) significantly enhance our ability to identify trait-associated genomic variants by considering the host genome. Moreover, the hologenome refers to the host organism's collective genetic material and its associated microbiome. In this study, we utilized the hologenome framework, called Hologenome-wide association studies (HWAS), to dissect the architecture of complex traits, including milk yield, methane emissions, rumen physiology in cattle, and gut microbial composition in pigs. We employed four statistical models: (1) GWAS, (2) Microbial GWAS (M-GWAS), (3) HWAS-CG (hologenome interaction estimated using COvariance between Random Effects Genome-based restricted maximum likelihood (CORE-GREML)), and (4) HWAS-H (hologenome interaction estimated using the Hadamard product method). We applied Bonferroni correction to interpret the significant associations in the complex traits. The GWAS and M-GWAS detected one and sixteen significant SNPs for milk yield traits, respectively, whereas the HWAS-CG and HWAS-H each identified eight SNPs. Moreover, HWAS-CG revealed four, and the remaining models identified three SNPs each for methane emissions traits. The GWAS and HWAS-CG detected one and three SNPs for rumen physiology traits, respectively. For the pigs' gut microbial composition traits, the GWAS, M-GWAS, HWAS-CG, and HWAS-H identified 14, 16, 13, and 12 SNPs, respectively. We further explored these associations through SNP annotation and by analyzing biological processes and functional pathways. Additionally, we integrated our GWA results with expression quantitative trait locus (eQTL) data using transcriptome-wide association studies (TWAS) and summary-based Mendelian randomization (SMR) methods for a more comprehensive understanding of SNP-trait associations. Our study revealed hologenomic variability in agriculturally important traits, enhancing our understanding of host-microbiome interactions.

Effect of parity and lactation stage on milk yield, udder and teat morphometric traits of Friesian-Bunaji crossed cows

Abstract. Data for this study were collected from 40 multiparous (F1) Friesian x Bunaji cows at the dairy herd of the National Animal Production Research Institute (NAPRI) Shika, Nigeria, to assess the effect of parity and lactation stage on milk yield, udder and teat morphometric traits of Friesian-Bunaji crossed cows as well the relationships between the parameters measured. The data collected include udder circumference (UC), udder depth (UD), udder width (UW), fore teat length (FTL), and hind teat length (HTL) and were subjected to Analysis of Variance (ANOVA). The means with significant difference were separated using Duncan Multiple Range Test modelled in SAS (2004) statistical package and the correlation analysis was performed using correlation procedure in SAS to identify relationships between morphometric traits and milk yield. The results obtained showed that parity had significant (p&lt;0.05) effect on udder circumference, hind teat length and milk yield. The highest udder circumference (23.60±2.50 cm) and hind teat length (2.80±0.34 cm), respectively, were found in parity 5 and the least ones were obtained in parity 1. Parity 2 had significantly (p&lt;0.05) higher milk yield (8.60±0.72 litres) followed by parity 4 (7.13±1.14 litres) but similar to parity 3 (6.67±0.58 litres) and the least (6.20±1.24 litre) was obtained in parity 5 (6.20±1.24 litres) but similar with parity 1 (6.25±0.75 litres). The results for lactation stage revealed no significant (p&gt;0.05) difference in all the parameters except milk yield. The early lactation stage had significantly (p&lt;0.05) higher milk yield (8.15±0.35 litre) followed by mid lactation stage (5.80±0.58 litre) but similar with the milk yield (4.38±0.86 litre) at late lactation stage. The results obtained for correlation indicated that the udder and teat morphometric traits and the milk yield measured showed varying degrees of relationships. The phenotypic correlations were positive and negative, low to high ranging from 0.00 to 0.69. The highest correlation coefficient (r=0.69; p&lt;0.01) was obtained between udder circumference and udder depth. All the udder and teat morphometric traits measured were negatively correlated with the milk yield except udder width (UW) and had no significant (p&gt;0.05) difference. Based on the results in this study, it can be concluded that parity has effect on udder circumference, hind teat length and milk yield with second parity having the highest milk yield 8.60±0.72 litre/day), while lactation stage had no effect in all the morphometric traits except on milk yield with the early stage having the highest milk yield (8.15±0.35 litre/day). The second parity and early lactation stage are recommended for high milk yield in Friesian x Bunaji cows in the studied area.

Genetic parameters for milk yield and reproductive traits in Honduran Holstein cattle.

The aim of this study was to estimate the (co)variance components and genetic parameters for milk yield adjusted to 305d (MY305), calving-to-conception interval (CCI), number of services per conception (NSC) and calving interval (CI) of Honduran Holstein cows, by fitting a bivariate animal model using Maximum Restricted Likelihood procedures. Model included the fixed effects of calving number, the contemporary calving group (farm-season-year of calving and the cow age as covariate). The estimated means and standard deviations for MY, CCI, NSC and CI were, 5098.60 ± 1564.32kg, 168.27 ± 104.71 days, 2.46 ± 1.69 services, and 448.73 ± 109.16 days, respectively; and their estimated heritabilities were 0.21 ± 0.05, 0.03 ± 0.028, 0.02 ± 0.024 and 0.06 ± 0.04, respectively. The genetic correlations between MY305 and CCI, NSC and CI were positive and antagonist, with values of 0.64 ± 0.52, 0.99 ± 0.56, and 0.32 ± 0.24 respectively. Even though moderate to low heritability was estimated for MY305, systematic selection for milk yield, with a reduction in reproductive efficiency, if considered as the only selection criterion is important to be considered. By including reproductive traits and considering permanent environment effects into the breeding program, might yield a slow, but constant and permanent improvement over time.

5 Rumen microbiome and metabolome in dairy cattle performance

Abstract Cattle rumen microbiome converts fibrous feed to nutrients that directly influence cattle’s growth and performance. Recent research has revealed the composition and function of rumen microbiome can affect many economically important traits in cattle such as feed efficiency, milk/meat yield and quality, methane emission, metabolic health and so on. In this presentation, the research on the assessment of to what extent the rumen microbiome and its metabolites, as well as host metabolites contribute to milk production and quality traits will be focused and discussed. It has been evident that some dairy cows can produce large amounts of milk under the same nutritional and management conditions. Recent research has revealed that in addition to host genetics and diet, parity and days in milk of dairy cows can affect the rumen microbiota, and both core and pan rumen bacteriome can potentially contribute to variations of milk production traits. Additionally, the analysis of rumen metagenomics and metabolomics of dairy cows with varied milk production yield showed that some key bacterial taxa (for example, Prevotella species), and their functions (such as branched-chain amino acids biosynthesis, methanogenesis), some rumen microbial metabolites (mainly amino acids, carboxylic acids, and fatty acids) significantly differed between high and low production cows. Further integrated analysis with serum metabolomics of the cos revealed the varied contributions of rumen microbial composition, functions, metabolites, and the serum metabolites to the milk protein yield of a dairy cow, a potential new trait that can be used for high-quality milk production, respectively. The fundamental understanding of the role of rumen microbiome and its metabolome contributing to milk yield and protein yield traits can provide novel insights into future manipulation of rumen microbiome to enhance milk production and quality.

Prolactin gene (C576A) polymorphism is associated with milk production performance in crossbred Anglo-Nubian dairy goats

Crossbred Anglo-Nubian goats (Anglo-Nubian × native goat breeds), are valued for exceptional milk production and adaptability. In-depth research on these goats is imperative to propel advancements in dairy goat breeds and enhance milk production efficiency within the region. The present study aims to assess polymorphism in prolactin (C576A) gene and determine the influence of different prolactin (PRL) genotypes to milk yield performance in crossbred Anglo-Nubian dairy goats raised from Awang, Opol, Misamis Oriental and Talay, Dumaguete City, Negros Oriental. Genomic DNA was extracted from hair follicles using commercial DNA extraction kit and PCR-RFLP was performed for the genotyping of the C576A polymorphism located in exon 5 of goats’ prolactin gene using Eco241 restriction enzyme. Genotypic frequencies of 0.56 for AA, 0.44 for AB, while allelic frequencies of 0.78 for A, and 0.22 for B were recorded. All populations followed the Hardy–Weinberg principle, except for dairy goats from Farm A located in Opol, Misamis Oriental. A two-way factorial (2 × 4) in a Randomized Complete Block Design was used to evaluate the relationship between genotypes and milk yield performance. AB genotype goats produced significantly higher milk yield traits (average daily milk yield and total milk production) than AA genotype, an indication that the polymorphism in the caprine PRL (C576A) gene influenced milk yield performance in the population of studied crossbred Anglo-Nubian goats. These results have to be validated in other dairy goat breeds.

Milk yield and quality at udder quarter level are influenced by quarter position, pathogen, and somatic cell score

There is a paucity of information about milk composition and quality at the quarter level from complete milking of the udder, mainly because of the difficulties of sampling procedures which imply the adoption of a vacuum system connected to four independent buckets. The objective of this study was to evaluate the effect of quarter position, intramammary infection status, and somatic cells on milk yield and composition at the mammary quarter level of Simmental cows. Milk samples were collected during three consecutive days, after milking individual mammary quarters of 10 lactating cows separately, for a total of 120 quarter milk samples. Samples were analysed for composition, somatic cell count (SCC), differential SCC, and bacterial culture. Somatic cell count was log-transformed to somatic cell score (SCS) to achieve normality of distribution. Sources of variation of milk yield and quality traits were investigated using a linear mixed model which included the fixed effects of quarter position (1 to 4), pathogen presence (positive or negative), and SCS class (low, medium-low, medium-high, and high). The interaction between cow and quarter position was included as random effect. Quarter position significantly affected milk yield, with rear udder quarters yielding more milk compared to their front counterparts, but with negligible effects on milk composition. Classes of SCS influenced milk composition, in a way that quarters with high SCS had lower lactose content and higher differential SCC. This study is a contribution towards the possibility to better understand physiological processes at cow udder quarter level.

Genetic evaluation for milk and semen variables on Egyptian buffaloes

2584 lactation records of Egyptian buffaloes calving between1992 to 2010 kept at Natafe El Gadded farm were studied. Several variables Animal model (SVAM) was used. Milk variables are milk production (MP), days in milk (DM), and calving interval (CI) and semen quality are ejaculate volume (EV) life of sperm (LS) and total Motility (TM). The overall means of MP, LL, CI, EV, LS, and TM were 2025 kg, 203 d, 447 d, 3.25 ml, 65.91% and 58.40%, respectively. Heritabilities were 0.23, 0.13, 0.02, 0.08, 0.27 and 0.24, for milk production, lactation length, current calving interval, ejaculate volume, live of sperm and total motility, respectively. Genetic association among MP and each of DM and CI were positive and were 0.80, 0.04, respectively, while among DM and CI was negative (-0.54). Genetic association among EV and each of LS and TM were .04 and -0.03, respectively, while among LS and TM was (1.0). In conclusion, our findings provide useful information on the heritability of milk production, life of sperm and mass motility traits in Egyptian buffaloes and relationships among them and should assist in selection for improvement of milk yield and semen traits in Egyptian buffaloes and bulls.