GENETIC AND NON-GENETIC FACTORS AFFECTING SURVIVABILITY, GROWTH AND REPRODUCTIVE PERFORMANCE OF BOER AND CENTRAL HIGHLAND GOATS AND THEIR CROSSES REARED AT ATAYE FARM, NORTH SHOA, ETHIOPIA

Abstract

This study was conducted at Ataye site of Debre-Birhan Agricultural Research Center. Data pertained to512 kids/ yearlings of Boer (B), Central Highland Goats (CHG), and F1 (B X CHG), F2 (a) (F1 X F1), F2 (b) (B X F1), were collected from 381 kiddings, recorded between 2012 and 2017. The study was aimed to access the effects of genetic and non-genetic factors on growth, reproductive and survivability performances of the above genotypes. The data was analyzed using GLM of SAS (9.0) to investigate the effect of genetic and non-genetic factors (dam parity, sex, year, season and type of birth) affecting body weight and daily weight gain from birth to 1 year of age, litter size and weight at birth and at weaning. Non-parametric tests were used to investigate the genetic and non-genetic factors influencing the conception, kidding and abortion rates. Survival analysis study was carried out using Weibull proportional hazards models using Survival Kit version 6.0 and chi square sub-dividing analysis using SAS (9.0) was used to access the genetic and non-genetic factors influencing the survival of the kids from birth to yearling age. Similarly Animal model were used for the estimation of genetic parameters and sire ranking based on their breeding value estimates using WOMBAT®. The overall least-squares means for body weight (kg) at birth, at weaning, at six months and at yearling and body weight gain to weaning, weaning to six-months and six months to yearling (grams) were 2.68±0.04, 9.11±0.19, 11.69±0.26, 16.41±0.38, 69.73±1.89, 30.48±1.54 and 24.33±1.21 respectively. Genotype and all the studied non genetic factors affected the body weight and weight gain from birth to yearling age. However, parity of the doe only influenced body weight gain six month to yearling. Weaning weights were not affected by sex of the kids. Yearling weights were not affected by breed and season of birth. Similarly season of birth did not affect six-month weight. The overall conception, kidding and abortion (%) of the does were recorded to be 48.75, 77.05 and 20.49 respectively. Genetic and non-genetic factors influence the studied traits but kidding and abortion percentages were not affected significantly by mating season similarly conception (%) were not affected by mating weight. The overall least-squares means for litter size at birth was (1.40±0.03), at weaning was (0.67±0.03), litter weight (kg) at birth was (3.63±0.07) and at weaning was (10.68±0.28) respectively. The traits were not affected by parity. Similarly litter size at birth and at weaning were not affected by breed of the doe and season of kidding. Litter size at birth was not affected by year of kidding while litter weight at weaning was not affected by type of birth. The overall least squares means for body weight at mating and at kidding (kg) of the does were 26.52±0.40 and 28.04±0.39 respectively. These traits were affected by breed of the does and year of mating year but not by season of mating. The heritability estimates ranged were slightly over estimated due to small sample size. The h2 among the (B and F1) for body weight at birth, at weaning, at six-months and at yearling ages were (0.43±0.28 and 0.73±0.17), (0.78±0.50 and 0.67±0.27), (0.75±0.52 and 0.65±0.27) and (0.23±0.70 and 0.65±0.27). Similarly genetic and phenotypic correlations were also over estimated. Sires were also ranked based on their estimated breeding values for body weight from birth to yearling age among the B and F1. The overall survival (%) of the kids at day 4, 90, 180 and 365 were 73.99, 53.57, 47.98 and 40.27 respectively. The above survivability traits were not influenced by sex and parity. Similarly survival at day 90 and 180 were not affected by genotype. Season of birth also influenced the survivability of the kids at the 4th day (after birth). So from this study we can conclude that the overall growth, reproductive and survivability performances of all the studied genotypes were quit low which indicating their sub-optimal adaptability to the study area. Thus, evaluating the genotypes based on a large sample size reared across different locations under different management is desired to come to a definite conclusion. Similarly as the yearling weight were highly correlated with the weaning and six month weight then we can therefore consider them as indicator traits for yearling weight of the goats. The findings also showed variation across bucks (based on their EBV) for the growth traits.