Effect of ruminally protected Methionine on the productive and reproductive performance of grazing <Emphasis Type="Italic">Bos indicus</Emphasis> heifers raised in the humid tropics of Costa Rica |
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| Authors: | L Alonso M Maquivar C S Galina G D Mendoza A Guzmán S Estrada M Villareal R Molina |
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| Institution: | Departamento de Reproducción, Facultad de Medicina Veterinaria y Zootecnia de la Universidad Nacional Autónoma de México, Mexico, Mexico. |
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| Abstract: | With the objective of evaluating the effect of methionine supplementation prior to a breeding program, thirty one heifers
(Bos taurus x Bos indicus) were used averaging 386 ± 29 days of age and a mean body weight of 402.6 ± 28 kg. Fifteen of the animals received a
supplement (SG) during 45 days with molasses-urea mixture (2 kg molasses + 407 g urea/head/day), plus 10 g of ruminally protected
methionine. The other sixteen heifers did not receive supplement (CG). Fecal and pastures samples were collected to assess
dry herbage intake and digestibility. Serial ultrasound measurements from the ovary were performed in both groups to evaluate
follicular dynamics. The heifers were categorized according to their follicular size and presence of a CL. Forage intake and
dry matter digestibility were reduced (P < 0.05) and body condition tended to improve (P = 0.07) in the supplemented heifers,
however, total intake, final weight, daily gain and dorsal back fat were not affected. After the supplementation period, the
percentage of females in the categories < 3 mm and 3 to < 6 mm, was greater (P < 0.05) in CG (25% and 43.7%) that in SG
(0% and 26.6%) but in the follicle category of ≥ 9 mm, the percentage of animals was 60% in SG and 18.8% in CG (P < 0.05).
The percentage of ovulation for the SG and CG was 86.7% and 62.5%, respectively (P < 0.05). The combination of supplementation
with methionine-urea and molasses at the end of the dry season and the anticipated onset of the rainy season favored the establishment
of ovarian activity and follicular dynamics. |
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| Keywords: | Methionine Supplementation Heifers Tropics |
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