Abstract

ROVIRA, P  and  ECHEVERRIA, J. Desempeño productivo de novillos pastoreando sudangras o sorgo forrajero nervadura marrón (BMR) durante el verano. Rev. vet. [online]. 2013, vol.24, n.2, pp.91-96. ISSN 1669-6840.

The use of annual forage crops increases average daily gain of animals and the carrying capacity of the production system during summer. The objectives of this experiment were to characterize the forage produced by two different materials of Sorghum spp. and to evaluate the response in animal production. Fifty four yearling steers (304±44 kg) were randomly assigned to two treatments with two repetitions: 1) sudangrass (Sorghum sudanense) cv. Estanzuela Comiray, 2) brown midrib (BMR) sorghum (Sorghum vulgare) cv. AGT 21. In both cases stocking rate was 6 steers/ha in a rotational grazing system in 4 paddocks. There were no statistical differences (p>0.05) in crop height (93±18 cm) and forage availability of leaves (2342±1208 kg DM/ha), stems (4714±2004 kg DM/ha) and total herbage mass (7078±2410 kg DM/ha) during three grazing cycles. The contribution of leaves to total forage production decreased from 50% (first grazing period) to 25% (third grazing period) for both materials. The leaves of sorghum BMR had lower dry matter (p<0.05) than those from sudangrass (22.2 y 27.4% respectively) and tended (p<0.10) to register higher digestibility (67.7 y 64.5% respectively). The stem fraction of sorghum BMR had more digestibility (70.7%) and less lignin (8.1%) compared with stems of sudangrass (61.5 y 9.3% respectively) (p<0.05). As a result steers grazing sorghum BMR showed a greater (p0.05). The improved forage quality of sorghum BMR, mainly observed in the stem fraction (main plant component during the second and third grazing periods), determined an increase in average daily gain of steers during summer compared to traditional forage materials (sudangrass).

Keywords : Steer; Summer; Sorghum; BMR.

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