André Lasmar Guimarães, Maria Eugênia Zerlotti Mercadante, Roberta Carrilho Canesin, Renata Helena Branco, Maria Lucia Pereira Lima, Joslaine Noely dos Santos Gonçalves Cyrillo
The objective of this study was to evaluate the associations between
feed efficiency and feeding behavior, growth and carcass traits in
Senepol cattle. A total of 137 animals were evaluated. Of these animals,
36 males were evaluated in a second test, totaling 173 records (initial
age of 466±96 days and initial weight of 426±104 kg). Residual feed
intake (RFI) was calculated as the difference between observed and
expected dry matter intake, estimated by regression of dry matter intake
on average daily gain and metabolic body weight (BW0.75),
and the animals were classified as negative (high efficiency) and
positive RFI (low efficiency). The mean RFI was -0.838±0.078 and
0.797±0.075 kg DM day-1 for negative and positive RFI animals, respectively, with a difference of 1.63 kg dry matter day-1. The dry matter intake of negative RFI animals, expressed as kg day-1
and percentage of mean body weight, was 11.3% and 13.1% lower than that
of positive RFI animals. Negative RFI animals spent less time at the
feed bunk and ingested less dry matter per visit than positive RFI
animals, but did not differ in terms of chest girth, scrotal
circumference, or hip height. However, negative RFI animals had lower
rump fat deposition (7.13±0.477 mm) than positive RFI animals
(7.83±0.473 mm). The Spearman correlation between RFI estimated in the
first and second tests was 0.69, indicating that RFI is consistent when
evaluated during two different periods of the life of the animal.
Senepol animals with low residual feed intake (high efficiency) deposit
less subcutaneous rump fat, but this reduction is not accompanied by a
reduction in backfat thickness and longissimus muscle area.
Key Words: beef cattle; feed intake; residual feed intake.
Fonte: Revista de Zootecnia, v.46, n.1, p.47-55, 2017.
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