PSV-22 - Productivity at weaning of F1 Dorper x Pelibuey ewes carrying the FecGE allele of the ovine GDF9 gene

Abstract: The FecG^E allele of the ovine GDF9 gene has been reported segregating in the Pelibuey hair type breed in México. Homozygous E/E ewes reproduce normally, in contrast to the sterility of homozygous ewes reported for other GDF9 variants. Thus, potential exists to cross homozygous and carrier Pelibuey ewes with meat type rams of low-prolificacy but well-adapted breeds to obtain F1 commercial flock ewes. The aim was to evaluate ewe productivity, as total lamb weight weaned (TWW), of FecG^E carrier vs non-carrier F1 Dorper x Pelibuey ewes. Sixty one first lambings ewes (34 carrier and 27 non-carrier) equally served with two Texel rams were used. Management was under feedlot conditions. Genotyping was done by real time PCR (StepOnePlus) using the FAMACTTCAAACAGTTTCTTTTTMGBNFQ and VICTCAAACAGTGTCTTTTTMGBNFQ probes (Applied Biosystems). Type of birth (TB; twins vs single) and weaning (TW) were analyzed with PROC CATMOD of SAS. Fixed effects of ewe genotype (carrier vs non-carrier), contemporary group and ram of service were included in a logistic generalized linear model. Lamb weaning weights were adjusted to a common age of 75 d and by sex. Equivalent to male average birth lamb weight (ABW), average weaning lamb weight (AWW) and TWW per ewe were analyzed with PROC GLM of SAS. Carrier ewes had more twins (P < 0.01) for TB (75 vs 19.4 %) and TW (58.8 vs 21.7 %) than non-carrier ewes. Equivalent to male ABW on carrier ewes was lower (P < 0.05; 3.17 ± 0.21 vs 3.97 ± 0.20 kg) than for non-carrier ewes but not difference (P >0.05) was observed for AWW (21.96 ± 0.85 vs 22.93 ± 0.90 kg). Ewe productivity, as indicated by TWW, was higher (P < 0.05; 33.16 ± 1.78 vs 27.23 ± 1.88 kg) for FecG^E carrier ewes than for the non-carrier ones. More research on this topic deserves further attention, especially under range conditions, with multiple parity ewes, different years and reproductive activity seasons, using a larger simple.