03004naa a2200217 a 450000100080000000500110000800800410001910000170006024501110007726000090018850003720019752020100056965000230257965000270260265300190262965300160264865300180266465300220268270000180270477300640272210548442021-06-24       2015    bl uuuu     u00u1 u    #d1 aGOLDBERG, V.  aDescription of the growth curve for Angus pasture-fed cows under extensive systems.h[electronic resource]  c2015  aThis work would not be possible without the support and data from the Uruguayan Aberdeen Angus Breed Society and the Rural Association of Uruguay. Appreciation is expressed to Drs. Ignacio Aguilar, Mario Lema, and Graciela Quintans from INIA for their valuables comments and suggestions. Received April 15, 2015. / Accepted July 10, 2015 / Published September 8, 2015  aABSTRACT.  Growth curves are useful for describing the sigmoid shape of an animal?s weight pattern over time. The purpose of the present study was to describe, for the first time, a complete growth curve for pasture-fed Angus cows in Uruguay and to analyze the major fixed effects that affect the estimation of mature cow weight (CW). A total of 22,743 records from 5,284 cows belonging to 73 herds were used in the statistical analysis. Five nonlinear models (Brody, Gompertz, Von Bertalanffy, logistic, and Richards) and a 3-knot cubic spline function were fitted to model weight change across age. Body weights were recorded at birth, weaning, and 18 mo and as an adult (at 2.3?3.6, 3.6?4.6, 4.6 to 5.6, 5.6 to 6.6, and 6.6 to 8.1 yr). After preliminary analyses, the fixed effects included in the model to estimate CW were BCS, herd, year and month of measurement, and age of dam. The herd and BCS were the major significant sources of variation. The Richards model had the lowest values for Akaike information criterion, Bayesian information criterion, and ?2 log likelihood, with the asymptotic weight being 542 kg. The spline function was the model that fitted the data most closely to the observed weights followed by the Richards function. The Richards model gave better predictions of weights from birth to maturity than the other 4 nonlinear models, because these functions were shown to over- or underestimate weights at different ages in this beef cattle data set. The predicted curve showed that cows reach mature CW after 5 yr of age, which is the age commonly assumed as adult weight in beef cattle. Results form this analysis allowed the estimation of CW and rate of maturing and to take knowledge of the shape of growth curve for Angus females in Uruguay under extensive conditions, helping breeders to take selection decisions. In this way, breeders can optimize the management and efficiency for each production system.  © 2015 American Society of Animal Science. All rights reserved.  aBOVINOS PARA CARNE  aMODELOS DE CRECIMIENTO  aABERDEEN ANGUS  aBEEF CATTLE  aGROWTH MODELS  aMATURE COW WEIGHT1 aRAVAGNOLO, O.  tJournal of Animal Science, 2015gv.93, no. 9, p. 4285-4290.