Effects of dietary protein concentration (corn:soybean meal ratio) and body weight on nitrogen balance of growing boars, barrows, and gilts: mathematical descriptions
1993
Hansen, B.C. | Lewis, A.J.
The effects of dietary CP level (actually corn:soybean meal ratio) and BW on N intake, N digestibility, the efficiency of utilization of N (apparent biological value), and N retention were measured in 36 pigs: 12 boars five collection periods), 12 barrows (four collection periods), and 12 gilts (nine collection periods). Initial and final BW of the boars, barrows, and gilts were 19, 24, and 27 kg and 80, 69, and 110 kg, respectively. Diets were based on corn and soybean meal and contained 11 to 23% CP. Averaged over all collection periods, N retention was 24.2, 20.0, and 19.8 g/d for boars, barrows, and gilts, respectively. The response of N retention to CP levels was quadratic (P < .15) and cubic (P < .01) for boars, linear (P < .01) and quadratic (P < .05) for barrows, and linear (P < .15) for gilts. Rates of N retention responded quadratically (P < .001) for all sexes as pigs gained weight, reaching a maximum when pigs weighed 55 to 65 kg. Multiple-regression analyses were conducted and equations were developed that described the effects of CP level (or lysine intake) and BW on N retention for each sex. The results indicated that N balance was a function of both CP level (or lysine intake) and BW and that the nature of the response differed for each sex.
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