Development of a NCR-42 Vitamin-Trace Mineral Mix

also supported by the FFLG data. Serum IGF-I concentrations are presented in Figure 2. Protein concentration had linear and quadratic effects (P < 0.01) on serum IGF-I concentration during weeks 2 and 4 of the experiment. There were no sex effects detected for serum IGF-I concentration, thus the data for barrows and gilts within dietary crude protein concentration were pooled and presented in Figure 2. Pigs fed the diet containing 10% CP had the lowest IGF-I concentration throughout the experiment and pigs fed the 18 and 22% CP had similar IGF-I concentration during weeks 2 and 4 of the experiment. These serum IGF-I concentrations indicate that the production and release of IGF-I into the blood is inhibited by the consumption of a 10 or 14% CP diet. This reduction in serum IGF-I is supported by the reduced fat-free lean accretion rates calculated for the pigs consuming the 10 and 14% crude protein diet. However, pigs fed the 18 and 22% CP diets had numerically similar serum IGF-I concentrations, and pigs fed the 18% CP diet had a significant decrease in FFLG as compared to pigs fed the 22% CP diets. These results suggest that the consumption of a diet marginally deficient in CP (18%) does not inhibit the production of IGF-I. However, the actions of IGF-I (i.e., muscle protein accretion) are partially inhibited. This diminished action of IGF-I is supported by the reduction in FFLG observed for pigs fed the 18% CP diet. Conclusions Results from this experiment demonstrate that growing pigs respond to increased dietary crude protein concentration, which is supported by the improvement in ADG, feed efficiency and fat-free lean gain in pigs fed up to 22% crude protein. A similar effect was detected in plasma urea concentration. Pigs fed the 22% CP diet had an increase concentration of plasma urea compared to the pigs fed the 10, 14, and 18% CP diet, indicating that the CP requirement of gilts in this experiment was > 18% CP. However, serum IGF-I concentrations were decreased in pigs fed the 10 and 14% CP diets, indicating that the consumption of a diet below the pigs dietary crude protein requirement (18%) was not always associated with a reduction in IGF-I serum concentration. Therefore, future research in this area will focus on the relationship between carcass protein accretion and serum IGF-I concentration. Also, the effect of crystalline amino acids will be investigated to …