Two microsatellite markers OarHH35 and BMS2508, closely associated with high levels of reproduction in sheep, were analysed for polymorphisms in Xiangdong black goat, Nanjiang brown goat, Guizhou black goat and Boer goat. The number of alleles for OarHH35 was 11, 8, 7 and 10, respectively, in the four goat breeds. That for BMS2508 was 9, 5, 6 and 7. The polymorphic information content (PIC) values for OarHH35/BMS2508 in the above-mentioned goats were respectively 0.8294/0.8047, 0.8399/0.6894, 0.7985/0.6910 and 0.8582/0.7688. By analysing the dominant effect of the two microsatellite markers on litter size of Xiangdong black goat, it was shown that microsatellite markers BMS2508 and OarHH35 significantly influenced (P<0.05) litter size of goats. At the OarHH35 locus, the least squares means (LSM) of genotype 135/135 bp was the highest (3.67 number born/litter). Moreover, LSM of genotypes 123/135 bp and 125/125 bp also reached 3.00 kids born/litter, indicating that alleles 135 bp and 125 bp exerted a significant positive effect on the litter size in Xiangdong black goat. At the BMS2508 locus, LSM of genotypes 132/145 bp and 93/132 bp for litter size was 4.00 and 3.25 kids born/litter respectively, but that of genotype 122/122 bp for litter size was only 1.00 kid/litter, so alleles 145 bp and 93 bp had significant positive effects on the litter size of Xiangdong black goat, and the allele 122 bp had a significantly negative effect.

Genetic and non-genetic factors affecting survival during the post-weaning period from 3 to 12 months of age were assessed in 823 kids (217 Black Bengal, 410 Jamunapari × Black Bengal and 196 Beetal × Black Bengal) born during 1981-86. The overall survival rates during 3 to 6 and 6 to 12 months of age were 79·22 (s.e. 4·06) and 82·02 (s.e. 5·49)% respectively. Variation in survival rate during 3 to 6 months of age was significant due to season of their birth (P < 0·01) and birth weight (P < 0·05). Survival rate during 6 to 12 months of age varied due to genetic group (P < 0·01), sex (P < 0·05) and birth weight (P < 0·05). Type of birth (litter size), dam's weight at kidding and filial generation had no significant effect on survival rate during the post-weaning period. Birth weight of kids had a positive linear relationship with their survivability during post-weaning period. Summer-born kids had significantly lower survival rates from 3 to 6 months of age compared with those born in the winter and monsoon periods. Heritability estimates for survival rates during the post-weaning period were not significantly different from zero.

The present study was carried out on 1243 kids (379 Black Bengal; 568 Jamunapari × Black Bengal and 296 Beetal × Black Bengal) born between 1981 and 1986. Data were analysed to study the influence of genetic group, sex, season of birth, type of birth, birth weight, dam's weight at kidding, filial generation and parity of dam (as covariate) on survivability of kids during the pre-weaning period (0 to 90 days of age). The overall survival rates during 0 to 15, 16 to 30, 31 to 60, 61 to 90 and 0 to 90 days of age were 81·68 (s.e. 2·89), 95·55 (s.e. 2·00), 90·77 (s.e. 2·33), 93·31 (s.e. 2·59) and 69·94 (s.e. 3·65) % respectively. Variation in survival rates from 0 to 15 days of age was significant due to genetic group (P < 0·01), birth weight (P < 0·01), dam's weight at kidding and parity of dams as a covariate (P < 0·05). Season of birth (P < 0·05), weight of kids (P < 0·01) and dam's weight at kidding (P < 0·01) had significant effects on survival rate during 0 to 90 days of age. Sex and type of birth had no significant effect on survival rates. The interaction effects of genetic groups with season of birth and sex on pre-weaning survival rates were not significant in all ages except the effect between genetic group and sex during 31 to 60 days of age. An improvement in survival rates during the period of study was noticed with the increase in filial generation number from Fj to F3, although the difference was not significant except from 61 to 90 days of age (P < 0·05). Birth weight of kids had a positive linear relationship with survivability during the pre-weaning period. Summer-born kids had a significantly lower survival rate than those born in the winter and monsoon periods from 16 to 30, 61 to 90 and from 0 to 90 days of age. A negative linear relationship was observed between dam's weight at kidding and survival rates of kids from 0 to 90 days of age except the 25 to 30 kg dams deviate. Heritability estimates of survival rates during pre-weaning periods were not significantly different from zero, indicating that improvement by simple selection is probably limited.