Haemoglobin type and reproductive performance in Australian Merino sheep

Haemoglobin type and reproductive performance of sheep grazing oestrogenic pastures

The effect of haemoglobin types A and B on reproductive performance of ewes grazing oestrogenic pastures was studied in four commercial flocks in 1973 and in an additional five in 1974 (a total of nine flocks). The number of ewes lambing per ewe mated differed significantly (P< 0·05) between mating types (male AA × female AA, male AA × female AB, male BB × female AB and male BB × female BB). Differences between mating types in the number of lambs born per ewe exposed to the ram and in the number of lambs weaned per ewe exposed to the ram bordered on significance (0·05<P<0·1). Matings involving BB sires were superior to matings involving AA sires. This finding differs from previously published evidence on this topic. There were no significant differences in lamb mortality or in the number of lambs born per parturition. Reproductive performance did not differ amongst ewe genotypes. Age of dam, farm and year had significant effects on most of the reproductive characteristics studied. Three significant interactions (P<0·05) involving mating type were found: mating type × age on number of ewes lambing per ewe exposed to the ram, mating type × farm on number of lambs born per parturition and mating type × year on lamb mortality. Due to the relatively small differences observed in reproductive performance between mating types it is concluded that selection for haemoglobin type is unlikely to overcome the problem of low reproductive performance in sheep grazing oestrogenic pastures.

A note on the association of haemoglobin types with ewe and ram fertility and lamb mortality in Indian sheep

Haemoglobin types of two Indian breeds of sheep were related to ram and ewe fertility and lamb mortality. Rams with Hb B type had a significantly higher number of lambs born to ewes mated to them. Ewe fertility and lamb mortality were better, but not significantly so, in animals with Hb B type.

A comparison of the beta A-and beta B-globin gene clusters of sheep

Domestic sheep have two common alleles at the adult beta-globin locus, beta A and beta B. Here we report the structure of the beta-globin locus of A-haplotype sheep. The locus consists of 12 genes, organized as a triplicated 4-gene set: 5' epsilon 1-epsilon II-psi beta I-beta C-epsilon III-epsilon IV-psi beta II-beta A-epsilon V-epsilon VI-psi beta III-beta F 3'. This arrangement is identical to that of the closely related goat locus. Sheep with the B haplotype have a locus arrangement consisting of a duplicated four-gene set, lacking the beta C gene as well as three other genes present in A sheep and goats. In order to understand the evolutionary history of the B sheep locus, we have sequenced the beta B gene from these sheep, and the beta C gene from A-haplotype sheep, and compared the sequences to those of the sheep beta A, goat beta C, and beta A, and cow adult beta genes. Our results indicate that the beta B gene has diverged recently from the beta A gene, and therefore the beta B locus structure may have resulted from a recent deletion from a triplicated locus.

Hemoglobins in sheep: multiple differences in amino acid sequences of three beta-chains and possible origins

Among the three adult sheep hemoglobins (A, B, and C), two (A and B) are reportedly products of alleles. The beta-chains of A and B differ by at least seven scattered amino acid residues whereas the beta-sequence of C differs from A by at least 16 residues and from B by at least 21 residues. These changes suggest that the origin of C-beta antedated the divergence of A and B. Five shared differences between A-beta and C-beta with respect to B-beta can be interpreted as the result of selective advantage in favor of B. A complex of additional mechanisms has possibly been involved in maintaining the A-B- C porymorphism.