Environmental and genetic effects on birth weight in graded-up goat kids

Abstract

A linear model analysis was carried out to study the effect of sex, litter size, age of dam, year, birth period and genetic group on birth weight in goats. Genetic groups consisted of graded-up goats from backcrosses of local goats with Alpine, Granadina, Nubian, Saanen and Toggenburg sires, classified as low grade (from 1/2 to 3/4 of exotic genes) and high grade (over 3/4 of exotic genes). Heritabilities were also obtained for low- and high-grade kids. The data concern 4623 records from a farm under a stall feeding system in the north of Mexico. All of the main fixed effects but only the genetic group × birth period interaction were significant (P < 0.05). Males were heavier than females and singles were heavier than double and multiple-born kids. Birth weight means increased as dam age increased. Birth weight means for high and low grade kids were, respectively, 3.3 and 3.2 kg in Alpine kids, 3.1 and 3.2 in Nubian, 2.7 and 2.9 in Granadina, 3.3 and 3.3 in Saanen and 3.3 and 3.1 in Toggenburg. Heritability estimates were 0.40 ± 0.14 and 0.44 ± 0.18 in high and low grade kids, respectively. Key words: Goat kids, birth weight, Alpine, Granadina, Nubian, Saanen, Toggenburg, crossbreds, heritability, non-genetic factors