Effect of Increasing Dietary Crude Protein Concentration on Growth Performance and Serum Insulin-Like Growth Factor-I Concentration in Barrows and Gilts

postfarrowing. The following sow performance criteria will be collected: litter size (total and live), number and weight of pigs at weaning, and return to estrus (relative to weaning date). Pigs will be weaned at 17 to 21 days post weaning. Daily heat checking will be initiated three days postweaning until expression of estrus. Sows will be bred at the first or second estrus postweaning. Sows that are not bred by day 21 postweaning will be culled. Sows will remain on treatment for a maximum of four consecutive parities. Criteria for gilts to be allocated to treatment and sow culling procedures to be used are described in the Maternal Line National Genetic Evaluation Program Results (NPPC; April, 2000). The economics of sow productivity and lon-gevity will be evaluated using the NPPC Return on Equity (ROE) Model. Based on the MLE, when gilts were developed with the common industry practices, expected differences between P1 and P2 gilts are described in Table 1. We hypothesize that feed restriction (prior to 250 lb) will not adversely affect productivity or health status of the P2 gilt line; however, reduced energy intake during late development will reduce lifetime productivity of the P1 line. A study was conducted to investigate the effects of increasing dietary protein intake on growth performance, carcass composition and serum insulin-like growth factor-I (IGF-I) concentration in growing-finishing barrows and gilts. Seventy crossbred pigs (35 barrows and 35 gilts) with an initial body weight of 75.1 lb were used in a 26-day growth study. The pigs were allocated randomly to one of four dietary treatments. The diets were standard corn soybean meal diets, which were formulated to contain 10, 14, 18, or 22% crude protein by changing the ratio of corn to soybean meal in the diet. At the termination of the experiment , pigs were slaughtered to determine carcass accretion rates of protein, water, fat and ash. Pig and feeder weights were recorded weekly for the determination of average daily gain (ADG), average daily feed intake (ADFI), and calculation of feed efficiency (ADG/ADFI). Weekly blood samples were collected to evaluate dietary effects on plasma urea and IGF-I concentrations. There was no difference (P > 0.10) in ADFI among treatments; however barrows consumed more feed than gilts (3.94 versus 3.70 lb/d; P = 0.01) throughout the 26-day period. Dietary protein concentration had linear and qua-dratic effects on ADG and ADG/ ADFI (P < 0.01). …