Resumen

RODRIGUEZ, Yhoangel; MARTINEZ G, Gonzalo  y  GALINDEZ G, Rafael. Non-genetic factors affecting birth weight in registered Brahman cattle. Zootecnia Trop. [online]. 2009, vol.27, n.2, pp.163-173. ISSN 0798-7269.

To determine the influence of some non-genetic factors on birth weight of Brahman registered cattle, 4078 observations were analyzed. All the animals were grazing and under sanitary management according to the conditions of every herd. The statistical model included herd (H: 1 to 4), year of birth (AN: 1996 to 2005), season of birth (EN: dry and rainy), age of mother at calving (EM: 3, …, 10 ó more years), and sex (S: males and females) and the interactions H x AN, H x EN, H x S, AN x EN, and AN x EM. The average PN was 34.68 ± 0.29 kg. The PN was affected by all the environmental factors studied, except EN; however, some differences existed between EN within H and AN due to the interactions H x EN and AN x EN. The effects S and H had the largest effect on the variation of PN. The interactions with H indicate that the direction and magnitude of the effects are not constant inside every herd. Important differences existed among herds, being 5.49 kg for the extreme ones. The difference between the best years (2002 and 2005) and the worst year (1996) was 3.25 kg. Cows of 3, 4, and 10 ó more years gave birth smaller calves (in average 1.11 kg), than cows from 5 to 9 years. Male calves weighed 2.25 kg more than female.

Palabras clave : beef cattle; Brahman registered cattle; environmental factors; prenatal growth.

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