Validation of a goat simulation model using performance test information for young fast growing meat bucks

Villaquiran¹, M., T. A. Gipson¹, and H. D. Blackburn²

¹E (Kika) de la Garza American Institute for Goat Research, Langston University, OK and ²USDA/ARS/NPA/NSSL/NAGP, Fort Collins, CO

As part of a regional project, a computer simulation model for goat production is being updated. However, the model was developed before the recent interest in meat goat production. The objective of this study was to test the simulation model to determine if its biological assumptions and equations are representative of a young fast growing meat goat, typified by the Boer breed. Validation data were weekly body weight and daily feed intake of 180 young Boer bucks enrolled in the Langston University Meat Buck Performance Test. Numbers of bucks enrolled in the test per year were 47, 33, 50, and 50, respectively, for years 1999 through 2002. Components of the simulation model tested were BW and feed intake (air-dry) for 15-d periods.

Table 1. Simulated and actual mean BW (kg)

Age (d)	Simulation	1999	2000	2001	2002
120	30.5	31.7 ± 6.7	31.5 ± 6.2	28.8 ± 7.6	29.6 ± 6.4
135	34.0	34.2 ± 6.8	34.6 ± 6.3	32.9 ± 8.6	33.5 ± 7.3
150	37.8	37.5 ± 6.9	38.0 ± 6.4	37.6 ± 9.2	37.8 ± 7.9
165	42.1	42.3 ± 7.5	42.6 ± 6.0	40.8 ± 9.0	41.3 ± 7.9
180	46.0	44.6 ± 7.3	45.3 ± 7.0	44.7 ± 8.9	45.4 ± 8.3
195	51.0		48.5 ± 6.9	49.2 ± 8.9	48.0 ± 8.0

Prior to 165 d of age, simulated BW was intermediate to actual mean BW; however, later the simulation model slightly overestimated BW, with an average difference of 1.0 kg at 180 d and 2.4 kg at 195 d.

Table 2. Simulated and actual cumulative feed intake (kg)

Age (d)	Simulation	1999	2000	2001	2002
120	18.75	20.7 ± 0.18	19.3 ± 0.18	17.4 ± 0.14	18.6 ± 0.20
135	41.25	42.4 ± 0.30	42.5 ± 0.28	39.4 ± 0.25	41.9 ± 0.33
150	68.25	67.6 ± 0.38	66.1 ± 0.40	65.8 ± 0.33	69.8 ± 0.46
165	98.25	95.2 ± 0.40	93.7 ± 0.41	92.3 ± 0.38	99.6 ± 0.58
180	129.75		121.6 ± 0.52	123.2 ± 0.49	128.9 ± 0.81

Prior to 180 d of age, simulated cumulative feed intake was intermediate to actual means, although later predicted values were greater than observed. Average overestimation at 180 d was 5.2 kg. In summary, the existing simulation model produced accurate estimates of BW and feed intake of young fast growing meat goats; however modifications may be required to improve prediction with age greater than 180 d.