ABSTRACT
Increasing levels of concentrate supplementation for heifers (Nellore x Angus) finished on tropical pasture

Tarcísio R. Paixão1, Dorgival M. Lima Júnior2*, Fabiano F. Silva1, João W.D. Silva1, Laize V. Santos1, Lucas S.F. Gomes1, Ana P.G. Silva1, Monique M.O. Garcia1, Beatriz O. Chagas1, Thiago L.A.C. Araújo2, and Robério R. Silva1
 
Concentrate supplementation during the finishing phase in tropical pastures improves the average daily gain and carcass characteristics of the animals. The objective of this study was to evaluate the effects of increasing levels of concentrate supplementation on nutrient intake and digestibility, ruminal fermentation parameters, and the performance of heifers finished on Megathyrsus maximus (Jacq.) B.K. Simon & S.W.L. Jacobs ‘Mombaça’ pasture. Forty heifers (½ Nellore × ½ Angus), with an average body weight of 312.65 ± 17.95 kg and 16 mo age, were distributed in a completely randomized design. To analyze ruminal parameters, four rumen-fistulated heifers were used in a 4×4 Latin square design. Supplementation was provided at four levels: 0.2%, 0.3%, 0.4%, and 0.5% of body weight (BW) over 134 d. A linear increase (P < 0.05) was observed in the intake of total DM, organic matter, crude protein (CP), and non-fibrous carbohydrates with increasing supplementation levels. However, the digestibility of neutral detergent fiber and CP decreased linearly (P < 0.05) and quadratically (P < 0.05), respectively, with increasing supplementation. Greater supplementation levels also reduced (P < 0.05) the concentrations of short chain fatty acids, acetate, and propionate in the rumen. Final body weight (398 kg) and average daily gain (0.64 kg d-1) were not affected (P > 0.05) by supplementation level, but gross feed efficiency declined (P < 0.05) as supplementation increased. Increasing concentrate supplementation from 0.2% to 0.5% BW in ½ Nellore × ½ Angus heifers finished on M. maximus ‘Mombaça’ pasture did not affect average daily gain but reduced feed efficiency. Therefore, lower supplementation levels (0.2% BW) are recommended.
Keywords: Guinea grass, heifer finishing, heifer performance, Megathyrsus maximus, ruminal fermentation.
1Universidade Estadual do Sudoeste da Bahia, 45700-000, Itapetinga, Bahia, Brasil.
2Universidade Federal Rural do Semi-Árido, 59625-900, Mossoró, Rio Grande do Norte, Brasil.
*Corresponding author (juniorzootec@yahoo.com.br).