Thirty-two male pigs were used to investigate the effects of nine levels of dietary lysine ranging from 0-41 to 1-30 g lysine per MJ gross energy (GE) on the performance of pigs weaned at 1 to 2 days of age and growing between 2 and 7 kg live weight. The nine dietary lysine treatments, which contained similar levels of GE and balance of essential amino acids, were offered to the pigs at a common feeding level of 2-0 MJ GE per kg metabolic live weight (M 075 ) per day. Growth performance and protein deposition rates increased linearly with increasing dietary lysine content up to about 0-97 g lysine per MJ GE and remained relatively constant thereafter. The response of protein deposition (PD, g/day) in the whole body of pigs to dietary lysine (L, g lysine per MJ GE) was described by three models. The respective regression equation for the quadratic function was PD = -14-23 + 87-66 L -36-00 L 2 and maximum protein deposition occurred at 1-22 g lysine per MJ GE. The rectilinear model, which had an ascending linear phase (PD = 1-49 + 40-10 L, R 2 = 0-98, P < 0-001) and a horizontal component representing a mean protein deposition rate of 39-7g/day revealed that maximum protein deposition occurred at 0-95g lysine per MJ GE. Finally, application of the asymptotic model also revealed a highly significant equation: PD = 43-40 -79-99 X 0-0711 1 , R 2 = 0-94, P < 0-001; which indicates a dietary requirement of 1-07 g lysine per MJ GE assuming that the dietary requirement was estimated at 0-90 of the asymptote maximal value. The results indicate that the dietary lysine requirement for pigs during the first 3 weeks of life appears to have changed little over the past 20 years despite substantial changes in genotype.

Effects of dietary protein concentration on the amino acid composition of sow's milk was studied using 10 crossbred first-litter sows. At parturition, diets containing similar concentrations of digestible energy but with either 63 or 238 g crude protein per kg and 4.4 and 15.1 g lysine per kg respectively, were given through lactation (five sows per treatment). The ratios of other amino acids to lysine were in excess of those currently recommended for lactating sows. Dietary protein level significantly affected milk yield, gave higher milk protein output (P&gt; 0.05) but was without significant effect on the proportions of amino acids in the milk.

No abstract