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Optimum duration of performance testing growing Boer bucks for growth rate, feed intake, and feed efficiency

W. Hu, T. A. Gipson, S. P. Hart, L. J. Dawson, A. L. Goetsch, and T. Sahlu

Journal of Animal Science 88(E-Supplement 2):455. 2010

Central performance testing of meat goats has increased in popularity recently, but minimum test length has not been ascertained. This study was conducted to determine the minimum length of time required for accurate evaluation of growing Boer bucks for ADG, feed intake, and feed efficiency as assessed by ADG:feed intake and residual feed intake. Data were collected from 425 bucks in Langston University tests from 2000 to 2009. Bucks averaged 111 25 d of age and 27 kg BW at the beginning of the test, consumed a pelletized 50% concentrate diet ad libitum, and were weighed weekly. Daily feed intake was determined with Calan feeding gates (American Calan, Inc., Northwood, NH) and automated feeding units (MK3 FIRE, Osborne Industries Inc., Osborne, KS). Weekly data of four performance traits were analyzed using the MIXED procedure of SAS with a repeated-measures model. The first-order ante dependence [ANTE(1)] structure type was selected as the appropriate covariance structure based on goodness-of-fit criteria. Variation relative to that at 84 d (%) was 337, 275, 225, 188, 153, 129, 118, and 107% for ADG, 171, 161, 150, 141, 131, 120, 112, and 106% for feed intake, 415, 303, 223, 165, 135, 122, 111, and 105% for gain:feed intake (g/d), and 154, 138, 129, 116, 106, 101, 101, and 101% for residual feed intake at 28, 35, 42, 49, 56, 63, 70, and 77 d, respectively. Grafted polynomial break-points determined by nonlinear regression indicated that residual variance had stabilized at 64, 64, and 56 d for ADG, ADG:feed intake, and residual feed intake, respectively. A break-point for feed intake was not estimable, although the correlation between ADG at 63 and 84 d was 0.99 (P < 0.01) compared with r of 0.95, 0.96, and 0.97 (P < 0.01) for ADG, ADG:feed intake, and residual feed intake, respectively. In conclusion, the duration of Boer buck performance tests could be decreased from 84 to 63 d with little loss in accuracy.


 

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