|Ngwa, A -|
|Dawson, L -|
|Puchala, R -|
|Detweiler, G -|
|Merkel, R -|
|Wang, Z -|
|Tesfai, K -|
|Sahlu, T -|
|Goetsch, A -|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 18, 2009
Publication Date: September 1, 2009
Citation: Ngwa, A.T., Dawson, L.J., Puchala, R., Detweiler, G.D., Merkel, R.C., Wang, Z., Tesfai, K., Sahlu, T., Ferrell, C.L., Goetsch, A.L. 2009. Effects of Breed and Diet on Growth and Body Composition of Crossbred Boer and Spanish Wether Goats. Journal of Animal Science. 87(9):2913-2923. Interpretive Summary: Boer (3/4) and Spanish wether goats were fed either a 50% concentrate or a hay diet during the growing-finishing period. Growth rates of Boer were greater than those of Spanish when provided the high quality diet. Similar rates of gain for Boer and Spanish goats when provided a grass hay diet indicated the greater growth potential of the Boer goats was not expressed, but there was not a penalty paid for that potential. Measures of gut and liver mass indicated that greater growth potential of Boer goats did not elicit greater energy use by splanchnic tissues unless diet quality was high. Body composition responded to diet as expected, but did not differ substantially between Boer and Spanish goats.
Technical Abstract: Sixty growing 3/4 Boer x 1/4 Spanish (BS) and Spanish (SP) wethers were used to determine influences of diet and breed on growth and body composition. A 50% concentrate pelleted diet (CON) and one based on grass hay (HAY) were fed free-choice. Six wethers of each breed were harvested at 0 wk (total of 12) and 6 of each diet-breed combination were harvested at 14 and 28 wk (24 per time). Initial BW of fed wethers was 21.6 and 18.8 kg for BS and SP, respectively (SEM = 0.67). Average daily gain during the entire experiment was influenced by an interaction (P < 0.05) between breed and diet (199, 142, 44, and 50 g for BS:CON, SP:CON, BS:HAY, and SP:HAY, respectively). Carcass mass was greater (P < 0.05) for CON vs. HAY (56.2, 56.2, 53.2, and 54.0% empty BW for BS:CON, SP:CON, BS:HAY, and SP:HAY, respectively). Mass of the liver (2.11, 1.92, 2.00, and 1.98% empty BW; SEM = 0.048) and gastrointestinal tract (5.50, 4.83, 8.43, and 8.36% empty BW for BS:CON, SP:CON, BS:HAY, and SP:HAY, respectively; SEM = 0.158) tended (P < 0.07) to be influenced by an interaction between breed and diet. Mass of internal fat (12.2, 12.1, 3.4, and 3.4% empty BW for BS:CON, SP:CON, BS:HAY, and SP:HAY, respectively; SEM = 0.28) differed (P < 0.05) between diets. Energy in the carcass (320, 236, 87, and 79 MJ), noncarcass tissues (318, 237, 77, and 72 MJ), and empty body (638, 472, 164, and 150 MJ) ranked (P < 0.05) BS:CON > SP:CON > BS:HAY and SP:HAY. Empty body concentration of fat was 18.3, 17.5, 17.3, and 19.7% (SEM = 0.29) and of protein was 24.0, 23.4, 10.8, and 10.3% for BS:CON, SP:CON, BS:HAY, and SP:HAY, respectively (SEM = 0.59). Energy concentration in accreted tissue was 17.0, 18.7, 16.3, and 6.4 MJ/kg for CON:wk 1-14, CON:wk 15-28, HAY:wk 1-14, and HAY:wk 15-28, respectively (SEM = 1.39). In conclusion, relatively high growth potential of growing Boer goats with a moderate to high nutritional plane does not entail a penalty in realized growth when the nutritional plane is low. Body composition of growing Boer and Spanish goats is fairly similar regardless of growth rate. For growing meat goats other than with a prolonged limited nutritional plane, an average energy concentration in accreted tissue is 17.3 MJ/kg.