Haemoglobin genotype, reproductive performance and response to PMSG in sheep J. P. Hanrahan, J. F. Quirke, N. P. Wilkins and E. M. Gosling An Foras Taluntais, Beldare, Tuam, Co. Galway and *Zoology Department, University College, Galway, Ireland There have been several reports of an association between haemoglobin genotype and reproductive performance in sheep (e.g. Evans & Turner, 1965; Obst, Seamark & McGowan, 1971; Purser & Hall, 1974). Recently Pant & Pandey (1975) presented evidence that Hb type influenced the response of ewes to superovulatory doses of PMSG. A subsequent report of a similar study of Welsh mountain ewes found no association between Hb type and response to PMSG (Trounson, Willadsen, Moor & Tucker, 1976). Egg-transfer experiments with Finnish Landrace (Finn) and Galway donors provided an op¬ portunity to extend the findings of Pant & Pandey (1975) and Trounson et al (1976). In addition to typing all donor ewes, 5 pedigree Galway rams and all male and female individuals of the Texel and Lleyn breeds in our flocks were typed. The Galway, Texel and Lleyn breeds are similar in type and probably have common ancestry. The Finn ewes were representative of our stock and most of the Galway ewes had been selected as donors because of an outstanding fecundity record (best 5 % of the population). Lleyn sheep were also highly selected on the basis of a prolificacy index. The Texel animals were unselected on previous performance. The Finn and Galway ewes were induced to superovulate by an intramuscular injection of 1500 i.u. or 2000 i.u. PMSG (Folligon: Intervet) on Day 12 or 13, respectively, of the oestrous cycle. These doses are equivalent per unit metabolic body size. The response to PMSG (the number of CL and large follicles > 6 mm diam.) was observed at laparotomy for egg recovery and data were available for the egg-recovery and fertilization rates. The natural ovulation rate had been recorded at two cycles for all of the Finn ewes. Haemoglobin types were determined by starch-gel electrophoresis in tris-EDTA-borate buffer at pH 8-9 (Gahne, Rendei & Venge, 1960). Our identification ofthe Hb types was kindly confirmed by Dr J. G. Hall (A.B.R.O.) with reference to standard material. Gene frequency differences were analysed by using the G-test procedure (Sokal & Rohlf, 1969). Results and discussion Table 1 presents the results for all sheep studied. Breed differences are significant and the high frequency of the Hb-A alíele in the Finn ewes is consistent with the result of Evans et al (1958a). The frequency of the Hb-A alíele is extremely low in the Galway breed and all pedigree-registered animals (58) were homozygous. Leicester-type sheep are considered to have played a large part in the forma¬ tion of the Galway breed (Martin, 1971) and the present results are consistent with the frequency of less than 005 for Hb-A in the Leicester and Border Leicester breeds (Evans et al, 1958b). The value for the Texel sheep is considerably below the values summarized by Agar et al. (1972). The fact that only three Galway ewes carried the Hb-A alíele made it impossible to examine the effects of Hb type on response to PMSG in both breeds. Accordingly only data for Finn ewes are presented (Table 2). There was no significant difference among the Hb types with respect to natural ovulation rate, although the small number of BB ewes were almost one egg below the other two types. The Hb types are clearly different with regard to ovarian response to PMSG. AA ewes produced approximately twice as many CL as the other Hb types. This was also true of total ovarian response Downloaded from Bioscientifica.com at 09/28/2021 04:52:30PM via free access Table 1. Distribution of sheep among Hb type classes by breed Hb type No. of Frequency Breed ewes tested AA AB BB of A Finnish Landrace 69 53 13 3 0-862 Galway 89 0 3 86 0017 Texel 37 0 7 30 0095 Lleyn 17 1 5 11 0-206 Gene frequency differences Among all breeds: d.f. = 3 G = 31011 < 0001 Finnish Landrace versus d.f. = 1 G = 292-52 < 0001 long-tail breeds : Among long-tail breeds : d.f. = 2 G= 17-59 <0 01 Table 2. Performance characteristics of Finnish Landrace ewes by Hb type Hb type Difference Trait AA AB BB AA versus AB Body weight (kg) 45 ± 0-98 48 ± 1-87 40 ± 3-90 N.S. Ovulation rate 3-51 ±0-19 3-50 ±0-38 2-67 ± 0-80 N.S. Response to PMSG Corpora lutea (CL) 13-23 ± 1-20 7-58 ± 2-39 600 ± 4-79 < 001 CL + large follicles ( ) 14-90 ±1-20 8-83 ± 2-39 800 ± 4-79 < 001 Log (CL+1) 1-068 + 0-0406 0-880 ±00812 0-742 ± 0-1625 < 005 Log(T+l) 1-136 ±00121 0-943 ± 00694 0-916 ±0-1389 < 005 Values are mean ± S.E.M. (no. of CL + no. of large follicles). Because the assumption ofnormality does not hold for response to PMSG and the standard deviation is approximately proportional to the mean (unpublished analyses), the data were transformed to logarithms. Analysis of the results on the transformed scale confirmed the significance of the observed differences and showed that the effect of Hb alíele on response was linear with respect to the number of Hb-A alíeles ( < 0-05). There was no evidence for significant dominance effects. The effect associated with Hb type in the Finn ewes is opposite in sign to that noted by Pant & Pandey (1975) who found that ewes with the AA phenotype gave the poorest response to PMSG. These results, taken together with those of Trounson et al (1976), suggest the existence of an interaction between the effects of genes responsible for Hb type and ewe breed. The alternative expla¬ nation, that a locus affecting response is closely linked with the Hb locus, would require the assump¬ tion of linkage disequilibrium which seems unlikely for the Finnish Landrace breed. It is possible that the extreme selection practised in choosing the Galway sheep ensured the very high frequency of the Hb-B alíele. However, similar selection in the Lleyn population did not yield a similarly high frequency. Further studies will be necessary to establish whether there is an association between Hb type and fecundity in these populations. The fact that AA and AB Finn ewes differ markedly in ovarian response to PMSG and yet have identical ovulation rates suggests that the factors responsible for differences in response to PMSG have no role in determining natural ovulation rate. This conclusion is supported by the results of selection experiments in mice for response to exogenous gonadotrophin (Bradford, 1968; Land & Falconer, 1969). The response of AB and BB Finn ewes to PMSG is very similar to that found in Galway sheep and somewhat lower than for Texel ewes (unpublished data), which suggests that breed differences may be explained by differences in the frequency of Hb alíeles. However, the results ofTrounson et al (1976) argue against this conclusion and further study of the effects associated with seems warranted. Hb type Downloaded from Bioscientifica.com at 09/28/2021 04:52:30PM via free access References Agar, N.S., Evans, I.V. & Roberts, J. (1972) Red blood Land, R.B. & Falconer, D.S. (1969) Genetic studies of cell potassium and haemoglobin polymorphism in ovulation rate in the mouse. Genet. Res. 13, 25-46. sheep : a review. Anim. Breed. Abstr. 40,407-436. Martin, I. (1971) The genetic history and breed structure Bradford, GE. (1968) Genetic control of ovulation of the pedigree Galway sheep breed. M. Agr. Sci., rate and embryo survival in mice. Response to thesis, National Univ. Ireland. selection. Genetics, Princeton 61, 905-921. Obst, J.M., Seamark, R.F. & McGowan, G.J. (1971) Evans, J.V. & Turner, H.N. (1965) Haemoglobin type Haemoglobin type and fertility of Merino ewes and reproductive performance in Australian Merino grazing oestrogenic (Yarloop clover) pastures. sheep. Nature, Lond. 207, 1396-1397. Nature, Lond. 232, 497-498. Evans, J.V., Harris, H. & Warren, F.L. (1958a) Pant, H.C. & Pandey, M.D. (1975) Influence of haemo¬ Haemoglobin and potassium blood types in some globin type on the induced ovulation rate in sheep. non-British breeds of sheep and in certain rare Nature, Lond. 258, 738-739. British breeds. Nature, Lond. 182, 320-321. Purser, A.F. & Hall, G.J. (1974) Fertility and survival Evans, J.V., Harris, H. & Warren, F.L. (1958b) The in hill sheep in relation to their haemoglobin type. distribution of haemoglobin and blood potassium Proc Br. Soc. Anim. Prod. (New Series) 3, 95. types in British breeds of sheep. Proc. R. Soc 149, Sokal, R.R. & Rohlf, FJ. (1969) Biometry. W. H. 249-262. Freeman & Co., San Francisco. Gahne, B., Rendel, J. & Venge, O. (1960) Inheritance Trounson, A.O., Willadsen, S.M., Moor, R.M. & of ß-globulins in serum and milk from cattle. Nature, Tucker, E.M. (1976) Haemoglobin type and super- Lond. 186, 907-908. ovulation in ewes. Nature, Lond. 262, 329. Received 18 April 1977 Downloaded from Bioscientifica.com at 09/28/2021 04:52:30PM via free access.