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Title: Describing dry matter intake and growth patterns in beef steers during the finishing period

Author
item Jurado, N. Vargas - Virginia Polytechnic Institution & State University
item Scaglia, Guillermo - Louisiana State University
item Swecker, Jr., William - Virginia Polytechnic Institution & State University
item Fiske, David - Virginia Polytechnic Institution & State University
item Neel, James - Jim
item Fontenot, Joseph - Virginia Polytechnic Institution & State University
item Lewis, Ron - Virginia Polytechnic Institution & State University

Submitted to: Journal of Animal Science
Publication Type: Proceedings
Publication Acceptance Date: 3/20/2011
Publication Date: 7/11/2011
Citation: Jurado, N., Scaglia, G., Swecker, Jr., W.S., Fiske, D.A., Neel, J.P., Fontenot, J.P., Lewis, R.M. 2011. Describing dry matter intake and growth patterns in beef steers during the finishing period. Journal of Animal Science. 89(1):71.

Interpretive Summary:

Technical Abstract: Feed intake is central to animal production systems, as it impacts efficiency and represents a substantial fraction of the total costs. The objectives of this study were to: (i) assess feed intake, weight gain and feed efficiency in Angus crossbred steers during finishing on a total mixed diet; and, (ii) describe the pattern of their growth using the Brody function. The experiment was conducted at a research farm in western Virginia. Feed intake and BW data were collected on 18, 22 and 11 steers in 2005, 2006, and 2007, respectively. Animals were on average 420 d of age, and weighed 357 kg, when housed in a drylot with access to an individual feeding system (Calan Gate System, American Calan, NH). Across years, steers were fed a similar diet (9.7% CP and 15.6% NDF DM) ad libitum for 90 to 128 d. Daily feed intake (DFI), ADG and feed conversion ratio (FCR) were evaluated. In addition, mature size (A), daily rate of growth (k), and initial body weight at the start of the study (W0), were estimated by fitting the Brody function Wt = A - ((A - W0)*exp( kt)), where Wt is weight at time t. Mean DFI were 15.4 +/- 0.1, 16.6 +/- 0.1 and 17.6 +/- 0.1 kg/d, for 2005, 2006, and 2007, respectively, with significant differences among years (P<0.001). Growth rate was constant (linear) over the finishing period (P<0.001; R2= 0.93). The mean ADG in 2006 (1.25±0.09 kg/d) was less (P<0.01) than in 2005 (1.66 +/- 0.07 kg/d) and 2007 (1.53 +/- 0.13 kg/d). Mean FCR was better (P<0.01) in 2005 (10.0 +/- 0.4) than 2006 (13.1 +/- 0.7), with 2007 intermediate (12.1 +/- 1.1). The estimates of A and k, the two key parameters of the Brody function, were similar across years: A was 742 +/- 158, 734 +/- 298 and 730 +/- 269 kg while k was 0.0065±0.0041, 0.0065 +/- 0.0110 and 0.0072 +/- 0.0092 per d, for 2005, 2006 and 2007, respectively. The correlation between A and k was -0.99, indicating a strong relationship between their estimated values. Differences in intake, ADG and FCR were observed among years although cattle genotype and husbandry were similar. Even with those differences, the Brody function appeared to provide a useful general description of growth in steers during the finishing period.