INFLUENCE OF ESTRUS PRE-SYNCHRONIZATION ON REPRODUCTIVE VARIABLES IN KATAHDIN EWES CARRIERS OF THE GDF9 GENE

Background: Genetic improvement in the sheep species focuses on increasing the number of offspring per sheep. Heritable characteristics such as ovulation rate, fertility, and prolificacy are desirable. Objective: To evaluate the influence of estrus pre-synchronization with PGF2α on the manifestation of estrus, onset and return to estrus (1st and 2nd), pregnancy, lambing, prolificacy, and fertility in Katahdin ewes carrying exon 2 of the gene Factor Growth and Differentiation 9 (GDF9). Methodology: Seventy-two ewes were randomized into four treatments (T): T1 (n = 18), ewes without GDF9 gene and without estrus pre-synchronization; T2 (n = 17), ewes without GDF9 gene and with estrus pre-synchronization; T3 (n = 19) ewes with the GDF9 gene and without estrus pre-synchronization, and T4 (n = 18), ewes with the GDF9 gene and with estrus pre-synchronization. Results: The presence of estrus, the onset of estrus, and returns to estrus, pregnancy, and lambing percentages were not different between treatments (p>0.05). The average pregnancy and lambing in both cases were 86.2% and the average general prolificacy was 1.4 lambs per ewe for all four treatments. There were also no significant differences for the prolificacy or fertility rate (p>0.05). Implications: The present study contributes to the understanding of the use of presynchronization with PGF2α and the effect of the presence of exon 2 of the GDF9 gene on reproductive variables. Conclusions: The presynchronization of estrus with PGF2α and the presence of exon 2 of the GDF9 gene in ewes of the Katahdin breed did not have a significant effect on the reproductive variables evaluated.