Autores
Marcela Morelli, Thais Matos Ceacero, Roberta Carrilho Canesin, Renata helena branco
Feed efficiency and reranking of beef cattle at different stages of development
Resumo
The Residual Feed Intake
(RFI) is a measure of feed efficiency usually evaluated post-weaning, and
according to available evidences in the literature is highly correlated to RFI
measured at other ages. The objective of present study was examining the
reclassification of RFI in Nellore
bulls classified in two post-weaning tests. In post-weaning performance test
127 Nellore
males (210 ± 45 days of age) in feedlot collective pens (GrowSafe Systems®)
were evaluated. Data of dry matter intake (DMI, 7.23 ± 1.72 kg/day) and mean
body weight (BW, 306.72 ± 7.54
kg) were collected during 112 days, and the animals were
classified according to RFI. The RFI was estimated as multiple regression error
of DMI on average daily gain (ADG) and metabolic weight (BW0.75).
Thereafter, a sample of 24 animals (408 ± 45 days old), 12 high (2.34 ± 0.24 kg DM/day) and 12 low
RFI animals (-1.48 ± 0.24 kg
DM/day) were reclassified after performance post-weaning test in feedlot for 84
days in individual pens. The diet was offered twice daily, contained corn
silage (53.6% DM), Urochloa hay
(10.0% DM), ground corn (21.8% DM), soybean meal (11.6% DM) and mineral
supplement (3.0% DM). The experimental design was completely randomized. Data
were analyzed using GLM procedure (SAS Inst., Inc., Cary, NC), fitting
a model including the fixed effects of RFI class and the initial weight as
linear covariate. Means were adjusted by the least squares method and compared
by the Tukey test (P<0.01). The 24 animals reclassified in performance post-weaning,
33.3% retained the class of RFI established in the post-weaning performance,
and 66.7% of the animals changed RFI class on 0.5 standard deviation from the
mean. On the other hand, 16.7% of the animals changed from high to low RFI
class, and 12.5% changed from high to medium RFI class (Table 1), showing
improvements in feed efficiency. These results indicate that there is reranking
of RFI in Nellore
young bulls at different stages of development with same diet.
Eficiência alimentar e reclassificação em bovinos de corte em diferentes fases de desenvolvimento
Abstract
Íntegra (PDF)