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Prediction of metabolizable energy requirements for maintenance, gain, and mohair fiber growth by Angora goats

J. Luo, A. L. Goetsch, and T. Sahlu

E (Kika) de la Garza American Institute for Goat Research, Langston University, Langston, OK

A database was constructed for Angora goats to estimate energy requirements for maintenance, gain, and mohair fiber growth. Treatment mean observations were classified into preweaning, growing, mature (not lactating or pregnant), lactating, and pregnant goats; however, due to limited numbers of observations, data for preweaning, lactating, and pregnant goats were removed. Data set 1 (n = 144) was used to estimate ME requirements for maintenance and whole body gain using simple linear regression analysis; data set 2 (n = 89) was employed to estimate ME requirements for maintenance, tissue gain, and mohair fiber growth using multiple regression analysis. Variables were mean BW (kg), ME intake (MEI, kJ/d), ADG (g), tissue gain adjusted for grease fiber weight (TG, g/d), clean fleece growth rate (CFGR, g/d); all variables in the regression analysis were scaled by kg BW0.75. Because of differences between growing and mature goats in intercepts and regression coefficients of simple and multiple regressions of MEI (P < 0.01 and 0.08 for simple and multiple regressions, respectively), separate regressions were conducted. Linear, quadratic, and cubic effects of ADG on MEI for growing goats were not significant. The simple linear regression equation for mature goats was MEI = 527 (SE = 19.7) + 42.8 (SE = 4.98) × ADG [n = 79; R2 = 0.48]; after removing 2 observations with residuals greater than 2 times the residual standard deviation, the final equation was MEI = 533 (SE = 18.8) + 43.2 (SE = 4.77) × ADG [n = 77; R2 = 0.52]. The coefficient for CFGR in the multiple regression model for growing goats was not significant (P = 0.42). The multiple regression equation for mature goats was MEI = 469 (SE = 52.3) + 33.6 (SE = 7.15) × ADTG + 159 (SE = 55.1) × CFGR [n = 49; R2 = 0.45]. The modified equation after excluding 1 observation with residual greater than 2 times residual standard deviation was MEI = 473 (SE = 49.9) + 37.2 (SE = 6.97) × TG + 157 (SE = 52.5) × CFGR [n = 48; R2 = 0.53]. In conclusion, estimated ME requirements for maintenance of mature Angora goats from simple and multiple regressions were 533 and 473 kJ/kg BW0.75 and ME requirements for whole BW gain, TG, and CFGR were 43.2, 37.2, and 157 kJ/g, respectively.


 

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