Relationships between body composition and shrunk body weight and urea space. In growing goats

Abstract

Growing Spanish wethers and doelings (31; 3.5 mo) consumed ad libitum diets differing in quality continuously for 18 wk or with an increase in quality after 9 wk. Urea space (US), shrunk body weight (SBW) and chemical composition of the whole body were determined ai the beginning, iniddle 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 kg 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 masses against US and (or) SBW were performed. Model fit was assessed by R, root mean square error (RMSE) and tele­distribution of residuals (observed - predicted) a inong predicted values. Overall, SBWexpiait led considerably more variability in body composition than did US, although US slightly improued predictions of water and fat masses and concentrations. Equations explaining greatesl 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; R2 = 0.944; adjusted R2 = 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 SBWJ, kg) [n = 33, R2 = 0.942; adjusted R- = 0.936; RMSE = 0.734j; and protein, % water = 34.696 (SE = 3.9913) = (0.1175 (SE = 0.06192) x predicted water, %) [n = 33; R2 = 0.101; adjusted R2 = 0.073; RMSE = 1.983]. In conclusion, suck equations may have utility for within exportaient 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 animais, different types of goats and. procedural cojisiderations. © GSP, India.