• Asian-Australasian Journal of Animal Sciences
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• 제32권1호
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• pp.14-22
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• 2019

Objective: The aim of the study was to find a possible association between the ${\beta}-$ and ${\kappa}-casein$ and ${\beta}-lactoglobulin$ genotypes and important milk physiochemical and technological characteristics such as acidity, alcohol stability, the contents of some minerals and the parameters of acid fermentation ability (FEA) in Czech Fleckvieh Cattle. Methods: Milk and blood samples were collected from 338 primiparous Czech Fleckvieh cows at the same stage of lactation. The genotypes of individual cows for ${\kappa}-casein$ (alleles A, B, and E) and ${\beta}-lactoglobulin$ (alleles A and B) were ascertained by polymerase chain reaction-restriction fragment length polymorphism, while their ${\beta}-casein$ (alleles $A^1$, $A^2$, $A^3$, and B) genotype was determined using melting curve genotyping analysis. The data collected were i) milk traits including active acidity (pH), titratable acidity (TA), alcohol stability (AS); calcium (Ca), phosphorus (P), sodium (Na), magnesium (Mg), and potassium (K) contents; and ii) yoghurt traits including active acidity (Y-pH), titratable acidity (Y-TA), and the counts of both Lactobacilli and Streptococci in 1 mL of yoghurt. A linear model was assumed with fixed effects of herd, year, and season of calving, an effect of the age of the cow at first calving and effects of the casein and lactoglobulin genotypes of ${\beta}-CN$ (${\beta}-casein$, CSN2), ${\kappa}-CN$ (${\kappa}-casein$, CSN3), and ${\beta}-LG$ (${\beta}-lactoglobulin$, LGB), or the three-way interaction between those genes. Results: The genetic polymorphisms were related to the milk TA, AS, content of P and Ca, Y-pH and Lactobacilli number in the fresh yoghurt. The CSN3 genotype was significantly associated with milk AS (p<0.05). The effect of the composite CSN2-CSN3-LGB genotype on the investigated traits mostly reflected the effects of the individual genes. It significantly influenced TA (p<0.01), Y-pH (p<0.05) and the log of the Lactobacilli count (p<0.05). Conclusion: Our findings indicate that the yoghurt fermentation test together with milk proteins genotyping could contribute to milk quality control and highlight new perspectives in dairy cattle selection.

• Asian-Australasian Journal of Animal Sciences
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• 제20권1호
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• pp.12-18
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• 2007

The objective of the study was to compare ranking of Sahiwal bulls selected on the basis of highest lactation milk yield of their dams with their estimated breeding values (EBVs) using an animal model. Data on 23,761 lactation milk yield records of 5,936 cows from five main Livestock Experiment Stations in Punjab province of Pakistan (1964-2004) were used for the study. At present the young A.I bulls are required to be from A-category bull-dams. Dams were categorized as A, B, C and D if they had highest lactation milk yield of ${\geq}$2,700, 2,250-2,699, 1,800-2,249 and <1,800 litres, respectively. The EBVs for lactation milk yield were estimated for all the animals using an individual animal model having fixed effect of herd-year and season of calving and random effect of animal. Fixed effect of parity and random effect of permanent environment were incorporated when multiple lactation were used. There were 396 young bulls used for semen collection and A.I during 1973-2004. However, progeny with lactation yields recorded, were available only for 91 bulls and dams could be traced for only 63 bulls. Overall lactation milk yield averaged 1,440.8 kg. Milk yield was 10% heritable with repeatability of 39%. Ranking bulls on highest lactation milk yield of their dams, the in-vogue criteria of selecting bulls, had a rank correlation of 0.167 (p<0.190) with ranking based on EBVs from animal model analysis. Bulls' EBVs for all lactations had rank correlation of 0.716 (p<0.001) with EBVs based on first lactation milk yield and 0.766 (p<0.001) with average EBVs of dam and sire (pedigree index). Ranking of bulls on highest lactation yield of their dams has no association with their ranking based on animal model evaluation. Young Sahiwal bulls should be selected on the basis of pedigree index instead of highest lactation yield of dams. This can help improve the genetic potential of the breed accruing to conservation and development efforts.

• Asian-Australasian Journal of Animal Sciences
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• 제25권9호
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• pp.1216-1222
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• 2012

Somatic cells count (SCC), milk yield (MY) and pedigree information of 2,791 first lactation cows that calved between 1990 and 2010 on 259 Thai farms were used to estimate genetic parameters and trends for SCC and its genetic association with MY. The SCC were log-transformed (lnSCC) to make them normally distributed. An average information-restricted maximum likelihood procedure was used to estimate variance components. A bivariate animal model that considered herd-yr-season, calving age, and regression additive genetic group as fixed effects, and animal and residual as random effects was used for genetic evaluation. Heritability estimates were 0.12 (SE = 0.19) for lnSCC, and 0.31 (SE = 0.06) for MY. The genetic correlation estimate between lnSCC and MY was 0.26 (SE = 0.59). Mean yearly estimated breeding values during the last 20 years increased for SCC (49.02 cells/ml/yr, SE = 26.81 cells/ml/yr; p = 0.08), but not for MY (0.37 kg/yr, SE = 0.87 kg/yr; p = 0.68). Sire average breeding values for SCC and MY were higher than those of cows and dams (p<0.01). Heritability estimates for lnSCC and MY and their low but positive genetic correlation suggested that selection for low SCC may be feasible in this population as it is in other populations of dairy cows. Thus, selection for high MY and low SCC should be encouraged in Thai dairy improvement programs to increase profitability by improving both cow health and milk yield.

• Asian-Australasian Journal of Animal Sciences
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• 제19권5호
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• pp.627-631
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• 2006

The objective of this study was to evaluate the association of genetic differences in the bovine leptin gene and milk yield, reproduction, body condition score (BCS), and plasma glucose level in Iranian Holstein cows. In total, two hundred and thirty eight cows were used and genotyped for a restricted fragment length polymorphism at the leptin gene locus. Two genotypes, AA and AB, have been distinguished which have the frequencies of 0.89 and 0.11, respectively. The genotypes were distributed according to the Hardy - Weinberg equilibrium ($x^2$ = 0.733). During the first 12 wk of lactation, milk yield and composition, live weight, BCS and plasma glucose were measured in 50 cows. Data were analyzed based on a repeated measures ANOVA. During this period, milk yield and composition, live weight, BCS and plasma glucose level were similar among the genotypes. The first cumulative 60-d milk yield, 305-d milk yield, days to first breeding, days open and days from first breeding to conception using previous lactation records were also analyzed using Standard Least Square within mixed models. Fixed effects were year, season, parity and age at calving, and sire. For the reproductive traits the cumulative first 60-d milk yield was also added to the model. Animal was fitted as a random effect. A significant association was detected between the RFLP-AB genotype and 305-d milk yield (p<0.05). The first 60-d cumulative milk yield was similar for the two genotypes (p = 0.21) and tended to be higher in the heterozygous cows. The heterozygous genotypes at the above mentioned locus had a trend to better reproductive performance than the homozygous. The results demonstrate that the RFLP B-allele can yield a higher 305-d milk production with a trend to better reproductive performance.

• 한국임상수의학회지
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• 제33권4호
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• pp.200-204
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• 2016

This study investigated whether presynchronization with GnRH 6 days before initiation of the Ovsynch program improved reproductive outcomes in dairy cows. Additionally, postponement of initiation of the Ovsynch program for cows during the metestrus phase by 5 days was investigated to determine if it improved reproductive outcomes. To accomplish this, 941 Holstein dairy cows with unknown estrous cycle were randomly allocated into an Ovsynch group (n = 768; $100{\mu}g$ gonadorelin [a GnRH analogue], $500{\mu}g$ of cloprostenol [$PGF_{2{\alpha}}$ analogue] seven days later, $100{\mu}g$ gonadorelin 56 h later and timed artificial insemination [AI] 16 h after) and a G6-Ovsynch (n = 173) that received $100{\mu}g$ GnRH followed by the Ovsynch program 6 days later. Additionally, 272 dairy cows with known estrous cycle (metestrus stage) received the Ovsynch 5 days later (Day 5-Ovsynch group, n = 272). The odds ratio (OR) for pregnancy was analyzed by logistic regression using the LOGISTIC procedure in SAS. The treatment group (p < 0.001) and AI season (p < 0.05) significantly affected the probability of pregnancy, whereas farm, cow parity, calving to AI interval, and body condition score had no affect (p > 0.05). The Day 5-Ovsynch group had a higher probability of pregnancy (OR: 1.71) than the Ovsynch group, while that of the G6-Ovsynch group was intermediate (p > 0.05). Cows inseminated during winter had a higher OR (1.39) than those inseminated during spring. Overall, additional GnRH treatment 6 days before the Ovsynch did not improve reproductive outcomes, whereas postponement of the initiation of Ovsynch by 5 days for cows during metestrus improved reproductive outcomes.

• Asian-Australasian Journal of Animal Sciences
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• 제13권3호
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• pp.277-286
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• 2000

A total of 21,441 milking records of biweekly test-days were collected from six dairy farms of Almarai company, Saudi Arabia to determine the effect of days open on lactation curve and milk production during the period of 1991 to 1996. These records included cows calved in two seasons: winter, for cows calved from October to March and summer, for cows calved from April to September. Season of calving did not have a significant effect on the last biweekly points of the curve, and this is due to the effect of the evaporative cooling system. Days open had a marked effect on milk production. The difference in milk yield between cows with days open <60 days and days open >150 days was 1,021 liter. Moreover, the difference in milk yield at early lactation decreased from 1,021 to 829 liter as the days open increased from 75 to 125, due to the decrease in the effect of conception on milk production with advancing lactation. These data also showed that the middle part of the curve (105-255) was the least affected part by the variation in days open because the pregnancy effect become more obvious after five months of conception. These data showed that the dairy cattle produce more than 70% of the milk yield during the first 250 days of the lactation curve.

• Asian-Australasian Journal of Animal Sciences
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• 제24권8호
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• pp.1031-1040
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• 2011

The objective of this study was to characterize factors influencing genetic improvement of dairy cattle for milk production at farm level. Data were accumulated from 305-day milk yields and pedigree information from 1,921 first-lactation dairy cows that calved from 1990 to 2007 on 161 farms in Central Thailand. Variance components were estimated using average information restricted maximum likelihood procedures. Animal breeding values were predicted by an animal model that contained herd-year-season, calving age, and regression additive genetic group as fixed effects, and cow and residual as random effects. Estimated breeding values from cows that calved in a particular month were used to estimate genetic trends for each individual farm. Within-farm genetic trends (b, regression coefficient of farm milk production per month) were used to classify farms into 3 groups: i) farms with negative genetic trend (b<-0.5 kg/mo), ii) farms with no genetic trend (-0.5 kg/$mo{\leq}b{\leq}0.5$ kg/mo), and iii) farms with positive genetic trend (b>0.5 kg/mo). Questionnaires were used to gather information from individual farmers on educational background, herd characteristics, farm management, decision making practices, and opinion on dairy farming. Farmer's responses to the questionnaire were used to test the association between these factors and farm groups using Fisher's exact test. Estimated genetic trend for the complete population was $0.29{\pm}1.02$ kg/year for cows. At farm level, most farms (40%) had positive genetic trend ($0.63{\pm}4.67$ to $230.79{\pm}166.63$ kg/mo) followed by farms with negative genetic trend (35%; $-173.68{\pm}39.63$ to $-0.62{\pm}2.57$ kg/mo) and those with no genetic trend (25%; $-0.52{\pm}3.52$ to $0.55{\pm}2.68$ kg/mo). Except for educational background (p<0.05), all other factors were not significantly associated with farm group.

• 한국임상수의학회지
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• 제24권2호
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• pp.119-124
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• 2007

Milk components analysis was carried out milk yield(MY), milk fat(MF), milk protein(MP), milk urea nitrogen(MUN), milk solid(MS), day of non-pregnant condition(DNPC), and days of primipara(DPRI) involved. Dairy farms were divided high, middle and low groups according to the standard records for milk components. Examination records were divided by farm, parity, year, season and month, the number of samples were 28,957. MUN concentration was below 12 mg and when the MPP was below 3.0%, the days of non-pregnant condition were $94{\pm}10.77$ days but concentration of MUN was under 12 mg and when MPP was above 3.2%, longer period of non-pregnant condtion of $181.3{\pm}9.25$ was noted. The days of gestation of the first calving cow was $495.9{\pm}9.04$ days when the concentration of MUN was below 12mg/dl and MPP was under 3.0%. If the concentration of MUN was 12 mg/dl and when the MPP was over 3.2%, the days of gestation were $511.0{\pm}8.36$ days. It was believed that the concentrations of MPP and MUN have significant effects on the days of non-pregnant condition and the days of gestation. Determination of MY, MF, MS, and MUN was Milkoscan $4,000{\sim}5,000$ Serier(FOSS Electric Co., Copenhagen, Denmark). MUN standard concentration was 12-18(mg/dl) similar to blood urea nitrogen(BUN). Mutual relationship of milk components(MF, SCC, MY, DNPC, MS) and MUN concentration was low in regression analysis.

• Asian-Australasian Journal of Animal Sciences
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• 제32권3호
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• pp.334-340
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• 2019

Objective: The objective of this study was to investigate the genetic components of daily milk yield and to re-rank bulls in South Korea by estimated breeding value (EBV) under heat stress using the temperature-humidity index (THI). Methods: This study was conducted using 125,312 monthly test-day records, collected from January 2000 to February 2017 for 19,889 Holstein cows from 647 farms in South Korea. Milk production data were collected from two agencies, the Dairy Cattle Genetic Improvement Center and the Korea Animal Improvement Association, and meteorological data were obtained from 41 regional weather stations using the Automated Surface Observing System (ASOS) installed throughout South Korea. A random regression model using the THI was applied to estimate genetic parameters of heat tolerance based on the test-day records. The model included herd-year-season, calving age, and days-in-milk as fixed effects, as well as heat tolerance as an additive genetic effect, permanent environmental effect, and direct additive and permanent environmental effect. Results: Below the THI threshold (${\leq}72$; no heat stress), the variance in heat tolerance was zero. However, the heat tolerance variance began to increase as THI exceeded the threshold. The covariance between the genetic additive effect and the heat tolerance effect was -0.33. Heritability estimates of milk yield ranged from 0.111 to 0.176 (average: 0.128). Heritability decreased slightly as THI increased, and began to increase at a THI of 79. The predicted bull EBV ranking varied with THI. Conclusion: We conclude that genetic evaluation using the THI function could be useful for selecting bulls for heat tolerance in South Korea.

• Animal Bioscience
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• 제37권4호
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• pp.576-590
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• 2024

Objective: The objective of this study was to identify genes associated with 305-day milk yield (MY) and fat yield (FY) that also influence the adaptability of the Thai multibreed dairy cattle population to tropical conditions. Methods: A total of 75,776 imputed and actual single nucleotide polymorphisms (SNPs) from 2,661 animals were used to identify genomic regions associated with MY and FY using the single-step genomic best linear unbiased predictions. Fixed effects included herd-year-season, breed regression, heterosis regression and calving age regression effects. Random effects were animal additive genetic and residual. Individual SNPs with a p-value smaller than 0.05 were selected for gene mapping, function analysis, and quantitative trait loci (QTL) annotation analysis. Results: A substantial number of QTLs associated with MY (9,334) and FY (8,977) were identified by integrating SNP genotypes and QTL annotations. Notably, we discovered 17 annotated QTLs within the health and exterior QTL classes, corresponding to nine unique genes. Among these genes, Rho GTPase activating protein 15 (ARHGAP15) and catenin alpha 2 (CTNNA2) have previously been linked to physiological traits associated with tropical adaptation in various cattle breeds. Interestingly, these two genes also showed signs of positive selection, indicating their potential role in conferring tolerance to trypanosomiasis, a prevalent tropical disease. Conclusion: Our findings provide valuable insights into the genetic basis of MY and FY in the Thai multibreed dairy cattle population, shedding light on the underlying mechanisms of tropical adaptation. The identified genes represent promising targets for future breeding strategies aimed at improving milk and fat production while ensuring resilience to tropical challenges. This study significantly contributes to our understanding of the genetic factors influencing milk production and adaptability in dairy cattle, facilitating the development of sustainable genetic selection strategies and breeding programs in tropical environments.