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Protein levels for growing boars, barrows and gilts
Abstract
The effect of dietary protein (CP) concentrations and live weight (W) on performance, carcass quality and measures of nitrogen (N) balance of growing boars, barrows and gilts was studied in a series of three N balance experiments and three growth experiments. The serial N balance experiments were conducted for each sex (12 pigs) starting at 20 kg. Four CP levels (in two percentage unit increments) were fed ad libitum. The maximum CP levels fed during the grower stage were 17, 13 and 15% for boars, barrows and gilts, respectively. Daily N retention (NR) increased curvilinearly as CP increased (barrows and gilts, P $<$.14; barrows, P $<$.04) and as W increased (all sexes, P $<$.004) to 60 kg and decreased at heavier weights. Overall, NR averaged 24.2, 20.2 and 20.6 g/d for boars, barrows and gilts, respectively. The growth experiments were conducted using a total of 189 pigs (from 19 to 105 kg) ad libitum fed diets ranging from 11 to 23% CP in two percentage unit increments. Performance responded curvilinearly (P $<$.001) as CP levels increased. The rate and efficiency of gain improved as protein levels increased from 11 to 17%. Carcass quality improved curvilinearly (i.e., tenth rib backfat, P $<$.002; longissimus muscle area, P $<$.0001; carcass percentage lean, P $<$.0001) as CP levels increased to 19%. Performance and carcass quality was impaired for swine fed a 23% CP diet. Boars and barrows had similar growth rates, superior to that of gilts (P $<$.0001). Compared to barrows and gilts, boars had a superior feed:gain ratio (P $<$.008). Carcass quality was more seriously impaired for boars fed inadequate CP levels than barrows or gilts. Multiple regression analysis revealed that the linear effect of age accounted for nearly all variance in the models evaluating cumulative feed intake (F) and W. Response patterns were similar among the sexes, but there were differences in magnitude of response when F and W were described as a function of CP and age. Nonlinear regression analysis parameter estimates followed a curvilinear pattern, increasing at a decreasing rate as CP increased. These results indicate that responses of the sexes to increasing CP levels are generally similar, however, the magnitude of the responses differ among the sexes and is dependent upon the response criteria of interest.
Subject Area
Livestock
Recommended Citation
Hansen, Blaine Curt, "Protein levels for growing boars, barrows and gilts" (1988). ETD collection for University of Nebraska-Lincoln. AAI8824930.
https://digitalcommons.unl.edu/dissertations/AAI8824930