Estimation of Genetic Parameters for Weights at Different Ages in Anatolian Buffalo Calves

Estimating the genetic parameters of traits in livestock populations is a key requirement for genetic improvement programmes. These parameters include the heritabilities of all traits of interest as well as the genetic and phenotypic correlations among them. The genetic parameters such as heritability should be estimated with reliability to determine the accurate breeding values of buffaloes for different growth yields. The heritability is estimated from recorded livestock performance data and the pedigree relationships in the population. Genetic parameters are estimated by classic methods like paternal half-sib correlation. But modern methods such as REML procedure is accepted more confident in last decades. Due to using animal models which take advantage of all relationships between an animal and the other recorded individuals in the population. This method provides an unbiased estimation of genetic parameters in the selection (Thevamanoharan et al., 2001). Using this type of methods would accelerate the speed of contemporary breeding programs. Community based Anatolian Buffalo Breeding Project is one of the genetic improvement purpose programs in the world. It is conducted with approximately 28809 buffalo cows maintained at 2767 farms in 18 provinces throughout Turkey. The pure breeding and selection method was preferred in this national project started in 2011 by the Turkish Ministry of Agriculture and Forestry (MAF) for 5 year of periods continued until now (Kaplan et al., 2019). This study was planned to estimate the heritabilities, genetic and phenotypic correlations of body weights in Anatolian Buffaloes occupied a significant place in terms of animal genetic resources in Turkey (Kaplan et al., 2015).

The study was carried out in the community-based Anatolian Buffalo Breeding Project of Ýstanbul between the years 2012-2021. The project is governed by the General Directorate of Agricultural Research and Policies centered in Ankara. Buffaloes were maintained at 80 different farms under extensive conditions. A total of 7649 birth weight (BW), 4623 sixth-month weight (SMW) and 3133 yearling weight (YW) records were obtained from the software named “manda yildizi” (Tekerli, 2015-2019). Firstly, least squares analysis was performed to calculate fixed effects on traits under investigation by using Minitab general linear options (Minitab, 2017). Environmental factors observed to be significant sources of variation for body weights were fitted as fixed effects in the subsequent analysis. Genetic parameters were estimated with animal models by using the REML procedure of Wombat software (Meyer, 2006).
The statistical mixed model is as follows: Where:
Y = Vector of observations for each trait.
b = Vector for the fixed effects.
u = Vector of the effects for individual animals.
e = Vector of residuals.
X and Z = Incidence matrices for b and u.

The result of analysis of variance and heritabilities for various body weights obtained from the animal model analysis have been presented in Table 1 and 2. The estimate of heritability for birth weight (0.14±0.03) was in agreement with the findings of some researchers (Malhado et al., 2007; Thiruvenkadan et al., 2009; and Pandya et al., 2015; Joshi et al., 2022) who reported the heritability estimates ranging from 0.09 to 0.19 in different breeds of buffaloes. However, several other researchers (Thevamanoharan et al., 2001; 2006; Shahin et al., 2010; Akhtar et al., 2012; Falleiro et al., 2013; Gupta et al., 2015; El-Naser, 2019; Kaplan, 2021; Medrado et al., 2021) have reported higher estimates (0.23-0.66) of heritability for this trait. A wide variation of heritability for a trait may be due to some factors like breed, herd, growing side and even periods of time. A low heritability estimate for birth weight in this population indicated that larger proportion of the phenotypic variation was due to the environmental effects and a smaller fraction was due to effects of the genes.
 

 

       
The heritability estimate for sixth-month weight of the buffaloes was 0.22±0.05. A few moderate estimates of heritability for the trait have also been reported by several researchers (Thiruvenkadan et al., 2009; Pandya et al., 2015) in Murrah and Surti buffaloes. In a study conducted by Shahin et al., (2010) heritability estimates for sixth-month weight were reported to be high as compared with the present study, but Gupta et al., (2015) and Joshi et al., (2022) reported lower heritabilities. The results of the present study suggested that sixth-month weight of the buffaloes was moderately heritable and could be used in selection.
 
The heritability estimate for yearling weight was 0.39±0.07 in this study. This is in agreement with the findings of Malhado et al., (2007) and Medrado et al., (2021) in different buffalo breeds. The estimate of heritability for yearling weights obtained in the present study was higher than the values (0.10-0.20) reported by some researchers (Thiruvenkadan et al., 2009; Akhtar et al., 2012; Falleiro et al., 2013; Pandya et al., 2015; Joshi et al., 2022). But different studies (Shahin et al., 2010; Falleiro et al., 2013; Gupta et al., 2015; Kaplan, 2021) reported higher estimates of heritability for certain buffalo breeds. Nearly high and greater than twice the standard error estimate of heritability for body weight at one year of age suggested that most of the observed variation in this trait may be due to the additive effects of the genes.
 
The result of genetic and phenotypic correlation coefficients among body weights at different ages have been presented in Table 3. The estimates of genetic correlation between birth weight and weight at different ages were medium to high and positive and it is higher than the previous reports (Gupta et al., 2015; Kaplan, 2021; Medrado et al., 2021; Joshi et al., 2022) on buffaloes. This situation may be due to the structure of the data and using a different method.
 
 

Genetic correlations were generally positive and higher while phenotypic correlations were relatively lower. The higher genetic correlations between sixth-month and yearling weights in this study indicate that selection to one of them would also result in rapid development in growth traits in subsequent generations.

Genetic variations in growth traits of Anatolian buffalo calves were found to be promising for improvement. The present study reveals that the yearling weight can be used as a selection tool for genetic improvement of growth traits considering its high heritability and positive genetic correlations at different ages.

We would like to thank the Ministry of Agriculture and Forestry, General Directorate of Agricultural Research and Policies, Türkiye, for allowing access to these invaluable data.