Effect of maternal haemoglobin variants and lamb genotype on pre-weaning growth rate of sheep of Northern Nigerian and their crosses

Abstract

Pre-weaning growth trait of sheep of Northern Nigerian (Balami, Uda and Yankasa) subjected to diallel crossing were estimated using 127 lambs. The study was conducted at National Animal Production Research Institute (NAPRI), Zaria, Nigeria. Blood (5ml) samples were collected from ewes and rams that produce the lambs to evaluate the effect of parental haemoglobin (Hb) variant on the pre-weaning growth rate of lambs. Weight and average daily gain (ADG) of lambs were obtained at 2 weeks interval to 12th week. The data obtained were subjected to analysis of variance using General Linear Model Procedure of SAS. Pair-wise difference was used to separate the mean. Frequency of ewes’ Hb genotype in relation to lambs was sorted and tested with Chi Square Procedure of SAS. The result showed that HbAB was the predominant (P<0.01) variant in the studied population, observed in 60% of the ewes and 100% of the sires. Allele A had the highest frequency (62%) in the dam population. The genotypic distribution of Hb variants in the population significantly deviated from Hardy Weinberg equilibrium (χ² = 50.8, P<0.01). HbAB and HbBB dams gave birth to lambs that were heavier (P<0.01) than lambs from HbAA from birth to 12 weeks of age. Crossbred lambs from Balami rams and Uda ewes (BL x UD) recorded the highest weight (4.47±0.20 kg) at birth while the least weight (1.73±0.20 kg) at birth was obtained from crossbred lambs given birth to by Yankasa rams and Balami ewes (YK X BL). Pure Balami lambs (BL X BL) was outstandingly superior (P<0.05) to lambs from other genotypes starting from the second week of age up to weaning (12^th week). BL X BL also recorded the highest (238.09±12.42 g) average daily gain from birth to 2 weeks of age (ADG2). The ADG decreased linearly as the lambs advanced in age from birth to weaning. Balami sheep are capable of expressing their genetic potentials (better growth than others) in the Northern Guinea Savannah zone of Nigeria. Genetic improvement of growth traits of Nigerian sheep using indigenous stock should focus on the exploitation of genetic potentials in terms of faster growth rate of Balami sheep.

Keywords: Maternal haemoglobin variants, lamb genotype, growth rate and sheep