Relationships between body composition and shrunk body weight and urea space in growing goats

摘要

Growing Spanish wethers and doelings (31; 3.5 mo) consumed ad libitum diets differing in quality continuously for 18 wk or with an increase m quality after 9 wk. Urea space (US), shrunk body weight (SBW) and chemical composition of the whole body were determined at the beginning, middle and end of the experiment. In addition, at the beginning of the experiment the same determinations were Made with two yearling Boer x Spanish doelings that had consumed a high quality diet ad libitum for 12 wk. Mean, standard error, minimum and maximum values were 20.4, 1.14,, 10.3 and 42.0 leg SBW; 64.0, 1.05, 47.2 and 72.3% water; 15.7, 1.19, 6.0,and 32.3% fat and 17.3, 0.25, 14.0 and 20.9% protein. Regressions Of water, fat and protein concentrations and mosses against US and (or) SBW were performed. Model fit was assessed by R-2, root mean square error (RMSE) and the distribution of residuals (observed - predicted) among predicted values. Overall, SBW explained considerably more variability in body composition than did US, although US slightly improved predictions of water and fat masses and concentrations. Equations explaining greatest variability with acceptable distributions of residuals. were: water, kg = 1.274 (SE = 1.1608) +(0.1546 (SE = 0.05863) x US, kg) + (0.5782 (SE = 0.10861) x SBW, kg) - (0.0043 (SE 0.00205) x. SBW2, kg) [n = 33; R-2 = 0.944; adjusted R-2 = 0.938; RMSE = 2.266], fat, kg = -0.921 (SE = 1.1389) - (0.1520 (SE 0.05753) x US, kg) + (0.1564 (SE = 0.10656) x SBW, kg) + (0.0064, (SE = 0.00201) x SBW2, kg) [n = 33; R-2 = 0.942;. adjusted R-2 = 0.936, RMSE, 0.734]; and protein, % water 34.696 (SE = 3.9913) (0.1175 (SE 0.06192) x predicted water, %) [n = 33; R-2 = 0.101: adjusted R-2 = 0.073; RMSE = 1.983]. In conclusion, such equations may have utility for within experiment treatment comparisons or for assessing changes in composition. However, validation with an independent. animal population is desirable, as well as is future research with larger numbers of animals, different types of goats and procedural considerations.