Models for Estimating Genetic Parameters of Milk Production Traits Using Random Regression Models in Korean Holstein Cattle

Abstract

The objectives of the study were to estimate genetic parameters for milk production traits of Holstein cattle using random regression models (RRMs), and to compare the goodness of fit of various RRMs with homogeneous and heterogeneous residual variances. A total of 126,980 test-day milk production records of the first parity Holstein cows between 2007 and 2014 from the Dairy Cattle Improvement Center of National Agricultural Cooperative Federation in South Korea were used. These records included milk yield (MILK), fat yield (FAT), protein yield (PROT), and solids-not-fat yield (SNF). The statistical models included random effects of genetic and permanent environments using Legendre polynomials (LP) of the third to fifth order (L3–L5), fixed effects of herd-test day, year-season at calving, and a fixed regression for the test-day record (third to fifth order). The residual variances in the models were either homogeneous (HOM) or heterogeneous (15 classes, HET15; 60 classes, HET60). A total of nine models (3 orders of polynomials×3 types of residual variance) including L3-HOM, L3-HET15, L3-HET60, L4-HOM, L4-HET15, L4-HET60, L5-HOM, L5-HET15, and L5-HET60 were compared using Akaike information criteria (AIC) and/or Schwarz Bayesian information criteria (BIC) statistics to identify the model(s) of best fit for their respective traits. The lowest BIC value was observed for the models L5-HET15 (MILK; PROT; SNF) and L4-HET15 (FAT), which fit the best. In general, the BIC values of HET15 models for a particular polynomial order was lower than that of the HET60 model in most cases. This implies that the orders of LP and types of residual variances affect the goodness of models. Also, the heterogeneity of residual variances should be considered for the test-day analysis. The heritability estimates of from the best fitted models ranged from 0.08 to 0.15 for MILK, 0.06 to 0.14 for FAT, 0.08 to 0.12 for PROT, and 0.07 to 0.13 for SNF according to days in milk of first lactation. Genetic variances for studied traits tended to decrease during the earlier stages of lactation, which were followed by increases in the middle and decreases further at the end of lactation. With regards to the fitness of the models and the differential genetic parameters across the lactation stages, we could estimate genetic parameters more accurately from RRMs than from lactation models. Therefore, we suggest using RRMs in place of lactation models to make national dairy cattle genetic evaluations for milk production traits in Korea.

Genetic analysis of reproductive characteristics in Iran-Black sheep

“…Decreasing reproductive performance after approximately 5 parities can be explained by an increase in twinning rate and conception rate with age (Fourie & Heydenrych, 1983). The results from this study were in agreement with those reported by Baneh, Hafezian, Rashidi, Gholizadeh, and Rahimi (2009). As reported by Ekiz et al (2005), effect of ewe age on reproductive traits of different sheep breeds is common.…”

Effect of parity on lactation traits in crossbred Holstein Friesian in Ethiopia

“…The mean daily milk yield during the early lactation for the 2 nd party is higher by 2.32 litters (13.4%) than the daily mean milk yield for the 1 st parity. This agreed with Cho et al (2016) who reported a difference between first and second parity as for stage of lactation. The pattern of mean daily milk production throughout the lactation period (Fig 1) and during the early lactation stage (Fig 2) indicated that first lactation cows have the lowest peak yields but the highest days in milk (DIM) at peak and more persistent than the second lactation cows.…”

“…The higher total and daily milk yield in the second parity cows during the early lactation is since mature cows can gain body weight and condition quickly after calving whereas the first calvers face lactation stress and partition nutrients for continuous body growth and milk production which is in agreement to Kashoma et al (2015). Also, this shows the same result that persistency of lactation in the first parity is higher than in the second parity but there was a lower peak milk yield in the first parity (Cho et al 2016). However, higher daily milk yield in the first parity cows obtained during the late lactation (fig 3)might be related to the ability to gain body weight and condition in the first calvers at a late stage after full recovery from lactation stress and full mature age.…”

Estimation the Genetic Parameters for Milk Yield in Romanian Spotted, Simmental Type Cattle Breed

“…Kaps and Spehar (2004) obtained higher heritability for fat yield for 305 days 0.31 and lower heritability 0.27 for protein yield for Simmental cattle than in our study. Cho et al (2016) reported low test-day heritability estimates ranged from 0.08 to 0.15 for milk, 0.06 to 0.14 for fat, 0.08 to 0.12 for protein according to days in milk in Holstein breed cows. Kheirabadi and Razmkabir (2016) observed low heritability estimates for milk 0.204, fat 0.096 and protein 0.047 to Holstein cattle.…”