Effects of Dietary Lysine Level on Performance,Serum Indices and Milk Composition of Lactating Sows

This experiment was conducted to investigate the effects of different lysine level in low-protein diets on performance,serum indices and milk composition of lactating sows based on ideal dietary amino acid pattern.Sixty crossbred (Large White × Landrace) sows with 3 to 5 parity,similar body condition and parturition dates were selected and randomly divided into 4 groups with 15 sows per group,and the lactation period was 21 days.Four groups of sows were fed four low-protein diets with different lysine levels of 0.90%,0.95%, 1.00% and 1.05%,respectively,and added synthetic amino acids based on the same digestible amino acid pattern.The results showed as follows: 1) weaning litter weight gain and average daily gain in 0.90% and 0.95% groups were significantly higher than those in 1.00% and 1.05% groups (P0.05); the sowweight loss in 0.90% group was significantly higher than that in the other groups (P0.05),but there were no significant differences in average daily feed intake,weaning to estrus interval and subsequent litter size among 4 groups (P0.05).2) There were no significant differences in the contents of urea nitrogen and glucose in serum among 4 groups (P0.05),the contents of serum estradiol and insulin in 0.90% and 0.95% groups were significantly higher than those in 1.00% and 1.05% groups (P0.05); the contents of serum lysine, threonine,valine and essential amino acids in 0.90% and 0.95% groups were significantly lower than those in 1.00% and 1.05% groups (P0.05).3) The milk total protein content in 0.90% and 0.95% groups was significantly higher than that in 1.05% group (P0.05),the milk solids content in 0.90% and 0.95% groups was significantly higher than that in 1.00% and 1.05% groups (P0.05).In conclusion,based on low-protein diets with ideal amine acid patter,the lactating sows can get the optimal performance when dietary lysine level is 0.90% to 0.95%.