Resumen

ZAVALA ELIZARRARAZ, Rafael et al. Effect of genotype on puberty in hair sheep ewe lamb on tropical areas. Zootecnia Trop. [online]. 2008, vol.26, n.4, pp.465-473. ISSN 0798-7269.

The objective was to evaluate the effect of hair sheep ewe lamb genotype on age and body weight to first corpus luteum and first observed estrous in dry tropic conditions. The study was performed with 94 ewe lambs Pelibuey (25), Blackbelly (12), Dorper (12), Katahdin (23), and Saint Croix (22). Ewe lambs were maintained in rotational grazing for 7 h/d on Cynodon nlemfuensis and were supplemented with 500 g/d of concentrate (16% CP). Endoscopies and lamb weight were recorded every 28 d from 150 d of age. A 6.5 mm diameter endoscope was used to determine the ovarian activity, follicular growth, luteal structures or scars present from the previous cycle. Presence of corpus luteum and first estrous behavior were used as puberty indicators. The data were analyzed with a linear model that included as independent variables breed, lambing season, and lambing type, and as dependent variables, age and weight at puberty, number of follicles, and corpus luteum. The age and weight to first corpus luteum observed were higher (P<0.05) in Dorper ewe lambs (292.3 d; 43.2 kg) and Katahdin (272.6 d; 36.5 kg) than Blackbelly (250.1 d; 24.7 kg), Pelibuey (231.8 d; 27.6 kg), and Saint Croix (252.3 d; 28.5 kg). The onset of puberty in evaluated breeds was 252.5 d of age. The season of birth affected the age (P<0.05), but not the weight of first corpus luteum observed. Ewe lambs born in July-August had 284.7 d of age, but on the other hand, those born in September-October were 266.7 d of age. Single ewe lambs were oldest and heavier (P<0.05) (266.6 d; 34.1 kg) than multiple birth ewes (242.5 d; 28.8 kg). The mean of variables studies were higher, but similar tendencies (P>0.05) were obtained with first estrous behavior, except the effect of birth seasons on live weight. These results demonstrate higher precocity in Pelibuey, Blackbelly, and Saint Croix breeds than Dorper and Katahdin.

Palabras clave : puberty; corpus luteum; estrous behavior; hairsheep ewe lambs; genotype.

        · resumen en Español     · texto en Español     · Español ( pdf )