Dietary amino acid balance and requirements for pigs weaned at 3 weeks of age

Abstract

ABSTRACTNitrogen balance was measured in a series of experiments to determine the optimum balance between lysine, threonine and methionine plus cystine by successive additions of the free amino acids to a basal diet of barley, soya bean meal and tallow. The basal diet had a calculated digestible energy (DE) value of 14·5 MJ/kg and a crude protein content of 146 g/kg. The ranges of total lysine; threonine and methionine plus cystine tested were (g/kg) 6·6 to 11·8, 4·9 to 6·9 and 4·3 to 71, respectively. Latin-square designs were used involving a total of 33 pigs. Nitrogen utilization was optimized in pigs of 3 to 9 weeks of age when each kg of diet contained 10·5 g lysine, 6·4 g threonine and 5·0 g methionine plus cystine, corresponding to a ratio of 100: 61: 48. Thereafter, five diets were formulated in which the same ratio was maintained, but at different protein levels (129 to 192 g/kg). Again the diets were based on barley, soya bean meal and tallow supplemented with free amino acids. These diets were compared, in both nitrogen balance and performance experiments, with a conventional early-weaning diet with a protein content of 240 g/kg. All six diets had the same calculated DE value (14·5 MJ/kg). The N balance experiment was of Latin-square design and involved 18 pigs, and the performance experiment used 36 pigs fed individually from 3 to 9 weeks of age. A diet containing 0·99 g lysine per MJ DE (14·4 g lysine and 192 g balanced protein per kg) was considered to be adequate on the basis of the growth rate and food conversion efficiency results obtained.