V. Hruban

SLB, A NEW ALLOANTIGENIC SYSTEM OF THE PIG

An alloantigen segregating in the double back‐cross families, distinct from serologically determinable transplantation antigens controlled by the major histocompatibility complex (SLA), was detected in pigs by the complementdependent lymphocytotoxic technique. The system was designated SLB and its product (antigen SLB‐Al) was demonstrated in all lymphocytes from the lymph nodes, thymus and peripheral blood, but not in the erythrocytes. Back‐cross matings supplied evidence of the dominant heredity of SLB‐Al. Detection of further SLB antigens was unsuccessful, so that only two alleles (SLB‐Al and SLB‐A‐) could be determined in families. Double back‐cross families revealed a close linkage between the SLB locus and the L blood group locus. Maximum lod score values were calculated in recombination fraction θ= 0.10.

Development of a semi-inbred line of Landrace pigs. I. Breeding performance and immunogenetic characteristics.

During 15 years of inbreeding of pigs (Canadian Landrace) a semi-inbred line has been developed. The inbreeding coefficient (Fx) is 0·84, which theoretically corresponds to between 8-9 generations of brother/sister matings. At the highest inbreeding level (0·84) the mean number of newborn piglets in the litter was 7·2 (5 litters, n = 36) including 5 stillborn (13·8%). The mean birth weight of the litter was 8·56 kg (5 litters, n = 31) the mean piglet birth weight was 1·23 kg and at the age of 21 days the mean weight of a litter was 33·24 kg with a mean piglet weight of 5·44 kg. During inbreeding, immunogenetic alloantigenic systems were investigated. Of 15 known erythrocyte systems, alleles of loci J, K, and of the most polymorphic system E, segregated. As to other immunogenetic systems (histocompatibility, leucocyte and allotypes) 2 SLA haplotypes (major histocompatibility complex) and 2 alleles of the SLC leucocyte system segregated. Allotransplants of the skin in SLA compatible siblings survived for a mean of 50·7 days (n = 77) compared with 10·8 days (n = 29) in non-inbred siblings. Tests of blastic transformation activated by T and B lymphocyte mitogens revealed a normal cell-mediated immune response. After immunization with some cell membrane alloantigens a normal humoral response was also recorded. All tested animals were halothaneresistant and tolerated a 10-min exposure to 5% without developing malignant hyperthermia. Depression due to inbreeding was manifested by a reduced reproductive ability (smaller number of piglets, frequent incidence of gonadal hypoplasia, diminution or loss of libido).

Changes in the phenotype for halothane sensitivity in pigs

Abstract One hundred-and-one hybrids of the Canadian Landrace, Large White, Belgian Landrace and Duroc breeds were repeatedly tested for sensitivity to halothane at the age of 8–15 weeks. Changes in the number of reactors were recorded in the experiment. The number of reactors was 40 in the first test, 33 in the second and 30 in the third. Two individuals changed from non-reactors to reactors; 12 reactors assessed by the standard halothane test ceased to differ during repeated tests from non-reactors. However, these individuals with secondary non-reactivity transmitted halothane-sensitivity to the progeny.