Download Data/hora: 06/05/2017 10:16:45 Biblioteca(s): Embrapa Gado de

Data/hora: 09/06/2017 01:19:50
Biblioteca(s): Embrapa Gado de Corte.
Data corrente: 07/02/2013
Data da última atualização: 07/02/2013
Autoria: ALBERTINI, T. Z.; MEDEIROS, S. R. de; TORRES JUNIOR, R. A. de A.; ZOCHI, S.
S.; OLTJEN, J. W.; STRATHE, A. B.; LANNA, D. P. D.
Afiliação: T. Z. Albertini, USP/ESALQ; SERGIO RAPOSO DE MEDEIROS, CNPGC; ROBERTO
AUGUSTO DE A TORRES JUNIOR, CNPGC; S. S. Zocchi, USP/ESALQ; J. W. Oltjen,
UNIVERSITY OF CALIFORNIA; A. B. Strathe, UNIVERSITY OF CALIFORNIA; D.
P. D. LANNA, USP/ESALQ.
Título: A methodological approach to estimate the lactation curve and net energy and protein
requirements of beef cows using nonlinear mixed-effects modeling.
Ano de publicação: 2012
Fonte/Imprenta: Journal of Animal Science, v.90, n.11, p.3867-3878, Nov. 2012.
Idioma: Inglês
Conteúdo: The objective of this study was to evaluate methods to predict the secretion of milk and
net energy and protein requirements of beef cows (Bos indicus and B. taurus) after
approximately 1 mo postpartum using nonlinear mixed-effect modeling (NLME). Twenty
Caracu × Nellore (CN) and 10 Nellore (NL) cows were inseminated to Red Angus bulls,
and 10 Angus × Nellore (AN) were bred to Canchim bulls. Cows were evaluated from
just after calving (25 ± 11 d) to weaning (220 d). Milk yield was estimated by weighing
calves before and after suckling (WSW) and by machine milking (MM) methods at 25,
52, 80, 109, 136, 164, 193, and 220 ± 11 d of lactation. Brody and simple linear equations
were consecutively fi tted to the data and compared
using information criteria. For the Brody equation, a NLME model was used to estimate
all lactation profiles incorporating different sources of variation (calf sex and breed of
cow, cow as a nested random effect, and within cow auto-correlation). The CV for the
MM method (29%) was less than WSW (45%). Consequently, the WSW method was
responsible for reducing the variance about 1.5 times among individuals, which
minimized the ability to detect differences among cows. As a result, only milk yield MM
data were used in the NLME models. The Brody equation provided the best fi t to this
dataset, and inclusion of a continuous autoregressive process improved fi t (P < 0.01).
Milk, energy and protein yield at the beginning of lactation were affected by cow
genotype and calf sex (P < 0.001). The exponential decay of the lactation curves was
affected only by genotype (P < 0.001). Angus × Nellore cows produced 15 and 48%
more milk than CN and NL during the trial, respectively (P < 0.05). Caracu × Nellore
cows produced 29% more milk than NL (P < 0.05). The net energy and net protein
requirements for milk yield followed a similar ranking. Male calves stimulated their dams
to produce 11.7, 11.4, and 11.9% more milk, energy and protein, respectively (P < 0.05).
The MM method is better than the WSW technique to detect genetic or environmental
differences in milk yield among beef cows. The data obtained by the MM method and
analyzed by NLME models allows the
inclusion of fi xed effects, random effects and an autoregressive process in lactation
equations to describe lactation curves and net energy and protein requirements.
The NLME is a powerful tool to describe differences in the secretion of milk due to
heterosis and cell mammary external stimulus in beef cows.
Palavras-Chave: Bovino de corte; Curva de lactação; Desempenho animal; Nutrição animal; Vaca.
Categoria do assunto: -Registro original: Embrapa Gado de Corte (CNPGC)
Exemplares: CNPGC - (15148-1) - UPC - SP - DD - - - - DIS