GENOTYPES AT THE HAL LOCUS AND REPRODUCTIVE TRAITS IN PIGS OF THE BREEDING POPULATION OF THE LANDRACE BREED

The results presented were obtained in a breeding population of the Landrace breed. Genotypes at the HAL locus were determined by haplotyping after Hojny et al. [1987] using four polymorphic loci GPI, H, A1BG and PGD of the linkage group of 6th chromosomes. All piglets were subjected to the halothane test. In a group of 106 sows, the overall numbers of litters in HAL genotypes N/N, N/n and n/n were 5.68, 5.81 and 4.96, resp. The evaluation of the causes of sow disposal showed that the number of stress-susceptible n/n sows, culled due to reproductive disorders, was twice that of N/N sows. Within groups of individual genotypes, great variability was found to exist. This is a basis for successful breeding programmes with well-defined genotypes. The investigations into the reproductive performance revealed inferior parameters in stress-susceptible sows. With respect to HAL genotypes, the difference between sows, dominant N/N [11.8] and recessive n/n homozygotes [10.3], in the total number of births was 1.46 piglets and in the number of piglets weaned 0.73. Preweaning mortality of piglets in N/N, N/n, and n/n sows was 11.2, 8.6 and 9.7 %, resp. The analysis of reproduction in boars of HAL genotypes showed that the number of total births was best in n/n genotypes [11.3 piglets]. As for the number of piglets weaned, best were N/N boars [9.2 piglets]. The percentage of pre-weaning mortality of piglets from N/N, N/n and n/n boars was 8.3, 10.5 and 11.5, resp. The other part of the study gives results concerning reproduction in different combinations of parents af HAL genotypes. As for the total number of births, the best combination was N/n boars X N/N sows [11.8 piglets] and the worst N/N X n/n [10.4], the difference being 1.42 piglets per litter. The number of liveborn piglets was highest in n/n X N/N [11.1] and lowest in n/n X N/n [9.8], the difference being 1.17 piglets. As for the number of piglets weaned, N/n X N/N [9.8] was the best combination and N/n X X n/n [8.6] the worst one. The evaluation of the piglets weaned with respect only to the genotype of the sire or the dam showed that N/N genotypes were the best. However, their mutual combination took up the 7th position out of the 9 combinations studied. From the viewpoint of four reproductive indices (number of total births, live births, piglets weaned and litter weight at 21 days) studied in a breeding herd of Landrace pigs for 3 years, the combination of n/n boars with N/N sows gave the best results. Compared with other combinations of genotypes at the HAL locus, this combination was the second best in the number of total births, the best in the number of liveborn piglets, the second best in the number of piglets weaned and the best in litter weight. The results suggested that it became necessary to know HAL genotypes of breeding animals showing susceptibility to stress so that genotypes chosen might be suitable for the breeding goal.