Cordero Arbelo, Génesis

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    Prevalencia e inserción del gen de fecundidad FecB (Booroola) para el mejoramiento de la productividad de ovinos criollos en Puerto Rico
    (2023-05-11) Cordero Arbelo, Génesis; Fernández Van Cleve, John; College of Agricultural Sciences; Rodríguez Carías, Abner A.; Jiménez Cabán, Esbal; Department of Animal Science; Maldonado Ramírez, Sandra L.
    In sheep, prolificacy is determined by lambs per lambing, which is directly related to the ovulation rate. In Puerto Rico, criollo ewes commonly produce single parturitions which is a valid reason to introduce fecundity genes such as the FecB (Booroola) to improve the sustainability of the ovine industry. The objectives of this experiment were to determine the presence of the Booroola gene in the local flocks and to introduce the gene in the criollo flocks. Blood samples (279 criollos, 123 Katahdin, 58 Dorper, 24 Royal White, 2 Pelibuey and 1 Barbados Blackbelly) were collected from ewes in 15 local flocks (6 agricultural regions and 10 municipalities) to determine the presence of the gene. Samples were shipped to a commercial laboratory in the US (Gene Check, Colorado, USA) to identify the following genotypes: homozygote (BB), heterozygote (B+) or wild type (++), by PCR-RFLP. Flocks sampled around the island were all wild type. Two known FecB (B+) carrier rams (Dorset x Ile de France) were acquired from a commercial farm (Tamarack Lamb & Wool, Minnesota, USA) for the second phase of the experiment. Two breeding seasons were designed, the first with a group of 20 non-carrier criollo ewes (criollo x Dorper) with one of the FecB carrier rams (0051C), in a 54-day season. Attached to the chest of the ram was a harness with a crayon to mark when they served the ewes. The number of ewes served, and pregnancy rates were 80% (N = 16) and 44% (N = 7), respectively, and 71% of the lambing’s were twins (N = 5). Blood samples showed that 70% of the lambs (N = 7) were heterozygous carriers of the FecB gene (B+) and 30% were non-carriers (N = 3). Thirty (30) criollo ewes were used for the second breeding trial, in a 34-day breeding season, with the two carrier rams (0020M & 0051C), for a total of 15 ewes per ram. The rams mated 100% of the ewes, and the pregnancy rates were 87% (N = 13) for the 0020M and 93% (N = 14) for the 0051C. There were two cases of abortion, one for each group. After the lambing season, blood samples showed that the offspring of 0020M (N = 12) were 50% heterozygous carriers (N = 6) and the ones from 0051C (N = 19) 42.1% were heterozygous carriers (N = 8). This breeding trial (0051C) produced 6 twin lambing’s (46.1%). The results of this experiment demonstrate a positive effect of introducing the FecB gene as shown by the incidence of twins in the local criollo non-carrier ewes and the high incidence of the gene in the progeny. The high heritability of the gene in these trials is a potential tool for the improvement of reproductive performance on the local flocks and motivates continued research with the FecB gene. Also, the resulting offspring (F1) can be further studied to observe additive effects on the ovulation rate and litter size with breeding seasons where both parentals are known carriers of the gene.