Sulfur amino acid nutrition of the young pig
Experiments were conducted to study sulfur amino acid (SAA) nutrition of the young pig. Pigs were ad libitum fed in all experiments. A methionine (Met)-deficient feather meal-corn-soybean meal-dried whey basal diet (20% protein, 3250 kcal ME/kg, 0.19% Met, 1.00% cystine (Cys), 0.11% choline) was used to determine the Met and SAA requirements and to evaluate the utilization of Met isomers and analogs. Weight gains of pigs fed the Met-deficient basal diet when fortified adequately with Met were similar to those of pigs fed a 20% protein practical corn-soybean meal-dried whey diet. A series of four experiments estimated that both 5- to 10-kg and 10- to 20-kg pigs had the same Met and SAA requirements, i.e., 0.29% and 0.58% of the diet, respectively. When Met isomers and analogs were added to the Met-deficient basal diet at isomolar levels, growth performance of pigs did not differ in any of the measured parameters. This indicated that pigs utilized L-Met, D-Met, DL-Met and DL-methionine hydroxy analog with the same molar efficiency. A chemically defined amino acid diet (14.77% protein (N X 6.25), 3450 kcal ME/kg, 0.15% choline) in which all nutrients were 100% bioavailable was used to assess the maximal portion of the SAA requirement that could be furnished by Cys and the efficiency of dietary Met utilization. Regardless of whether pigs were fed chemically defined amino acid diets containing a constant level of dietary SAA or sulfur, no more than 50% of the 10- to 20-kg pig's total SAA requirement (wt:wt) could be furnished by Cys. Comparative slaughter methodology was used to estimate efficiency of dietary Met utilization in the presence of excess dietary Cys. Methionine retention was a linear function of Met intake. Regressing Met retention on Met intake resulted in an efficiency of Met retention of 71.7% and an estimated Met maintenance requirement of 57 mg/day for pigs in the weight category 10 to 17 kg. The concentration of Met (and most other indispensable amino acids) in the protein deposited increased as dietary Met concentration increased. These increases occurred at the expense of glycine and proline, which decreased in whole-body protein as Met level increased.
Agriculture, Animal Culture and Nutrition
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign