Multiple and stepwise regression of reproduction efficiency on linear type traits in Sahiwal cows

Abstract

Shakeel Nouman and Yasir Abrar

Data on some production performance traits of 1000 milch Sahiwal cows from 3451 cows maintained at the Livestock Experiment Station, Bahadurnagar, Okara, Pakistan during the period from 2000 to 2009 were selected to study the relationship between 12 linear type traits and reproductive performance of the Sahiwal cows. The reproductive efficiency (RE) was measured in terms of calving interval from the first five lactations. The type scores were standardized for stage of lactation, age at first calving and scoring. The mean scores of linear type traits (rump width, stature, chest and body, suspensory ligament) varied from 72.6±0.78 to 81.1±0.83 points. The estimates of heritability (h 2 ) for most of these type traits were medium 0.31±0.22 to high 0.82±0.31 and indicated the existence of large additive genetic variability for these traits in this breed. The phenotypic correlations of linear type traits with RE ranged between -0.1.6 ± 0.08 and 0.10 ± 0.09. All the 12 linear type traits accounted for 92.96% of the variability in RE of Sahiwal cows. Step-wise regression analysis revealed that 75% of the variation accounted by all linear type traits in RE could be predicted by a sub-set of four type traits (TT) which included stature, chest and body, pelvic angle and udder depth. It was concluded that in the case of absence of records, the reproductive performance of Sahiwal cows can be predicted at an early age using some linear type traits.