A total of 520 Ross308 broilers (male: female = 1:1) with initial BW of 45.32 ? 0.27g were used to evaluate effects of the dietary threonine: lysine ratio (Thr: Lys) on the growth performance, relative organ weight, blood profile, and meat quality. The broilers were randomly assigned to 4 treatments (10 replications per treatment), the Thr:Lys ratio of diets were set at 0.65 (T65), 0.70 (T70), 0.75 (T75), and 0.80 (T80), respectively. The Lys levels of different phases were fixed at 1.42, 1.24, and 1.13%, respectively. The phases of trial were 0 to 1 week (wk), 1 to 3 wk, and 3 to 4 wk of age. Lys was used as the base value with Thr expressed as the percentage of the Lys content. The body weight gain (BWG) was improved (P < 0.05) without affecting the feed intake and feed conversion ratio in T75 treatment compared with T80 treatment during wk 1 to 3. During the overall period (0 to 4 week), the broilers in T70 and T75 dietary treatments had highest (P < 0.05) BWG among all dietary treatments. The relative organ weight was unaffected (P > 0.05) by dietary Lys:Thr ratio. The blood creatinine concentration was increased in T80 treatment (P < 0.05). The meat quality was unaffected by Thr:Lys among all treatments. In conclusion, the Thr:Lys at 0.70 to 0.80 improved the growth performance in broilers.
Two experiments were conducted to evaluated the effect of different threonine (Thr):lysine (Lys) ratio on growth performance, blood urea nitrogen (BUN) concentration and nitrogen (N) retention in weaned pigs. In experiment (Exp.) 1 (feeding trial), a total of 90 weanling pigs (Landrace ? Yorkshire-Duroc) with an initial average body weight of 6.6 ? 0.53 kg was allocated in 1 of 3 treatments. Each treatment had 6 replicate pens with 5 pigs per pen. The experiment lasted for 35 day (d) and contained 3 phases, including phase 1 (d 0-7), phase 2 (d 7-21), and phase 3 (d 22-35). Diets were formulated with different Thr:Lys ratio of 0.63, 0.65, and 0.67. Dietary Lys and Thr concentrations were 12.4, 12.7, 12.6 and 7.8, 8.2, 8.4 g?kg-1, respectively. Body weight (BW) was measured on d 0, d 7, d 21 and d 35, and feed disappearance was also recorded in each phase and then the average daily gain (ADG), average daily feed intake (ADFI) and feed:gain (F:G) ratio were calculated. Through all the experimental periods, ADG, ADFI, and F:G ratio were not influenced (P > 0.05) by the dietary Thr:Lys ratio. However, on d 35, BUN concentration was increased (P < 0.05) as the dietary Thr:Lys ratio increased. In Exp. 2 (N balance trial), a total of 24 crossed Landrace ? Yorkshire-Duroc weaned pigs (8.57 ? 0.32 kg) was individually housed in metabolic cages and fed for 10 d period. Dietary treatments were same as in Exp. 1. The N intake, N excretion in faeces and urine, and N retention were not influenced (P > 0.05) by dietary Thr:Lys ratio. In conclusion, increasing dietary Thr:Lys ratio (0.63, 0.65 versus 0.67) cannot neither improve the growth performance nor N utilization in weaned pigs.
Eighteen primiparous sow were used to determine the effect of dietary valine (Val):lysine (Lys) ratios on lactational performance in primiparous sows and litter performance. Corn-soybean-wheat based diets were formulated, which contained 0.86 or 0.87% available lysine and 0.69 or 0.73% available Val. The present experiment contained two dietary treatments with Val:Lys ratios of 0.80 or 0.85. The experiment lasted for 24 d. On the end of the experiment, body weight loss, backfat loss ADFI and days to return estrus of sows were not affected (P > 0.05) by different dietary Val:Lys ratio. Furthermore, no difference (P > 0.05) was observed on piglet weaned number, piglet survival rate, weaned litter weight, litter weight gain, piglet weanling body weight, piglet gain and piglet daily gain between two dietary treatments. However, increasing dietary Val:Lys ratio increased (P < 0.05) Arg and Thr concentrations in the milk. In conclusion, dietary Val:Lys ratio of 0.80 and 0.85 does not differ lactational performance of primiparous sow nursing large litters but increasing dietary Val:Lys ratio can increase Arg and Thr concentration in milk.
Two experiments were conducted to determine dietary Lysine (Lys): calorie ratio (g of total dietary Lys/Mcal of DE) for growing barrows and gilts in cool and hot seasons in a commercial environment. In experiment 1 (Exp.1), 96 barrows and 96 gilts were allocated in 1 of the 4 treatments. Each treatment had 12 replicate pens with 4 pigs per pen. The experiment was lasted for 34 days (d) in the cool season (March 12th to April 15th). Diets were based on corn-soybean-wheat meal. Lys:calorie ratios were attained by adjusting the amount of corn and soybean and supplementation of crystalline Lys. In Exp. 1, no difference (P > 0.05) was observed on growth performance in both barrows and gilts among all treatment groups. However, total Lys intake (barrows, 15.1, 16.1, 17.3, and 19.4 g/d; gilts, 14.7, 17.1, 16.9, and 16.0 g/d) and available Lys intake (barrows, 13.0, 13.9, 15.0 and 16.9 g/d; gilts, 12.7, 14.8, 14.7 and 16.0 g/d) were increased (P < 0.05) as dietary Lys:calorie ratio increased. The blood urea nitrogen (BUN) concentration on d 34 for barrows and BUN change for barrows and gilts were linearly increased (P < 0.05) as dietary Lys:calorie ratio increased. For gilts, backfat was decreased and then increased (quadratic, P < 0.05) as increasing dietary Lys:calorie ratio. Exp. 2 had the similar design as Exp.1 with the exception that Exp. 2 was conducted in hot season (June 30th to September 11th) for 42 d. Diet of Exp.2 was same as Exp.1. In Exp. 2, dietary Lys:calorie ratio did not affect (P > 0.05) the growth performance, backfat and lean percentage in both barrows and gilts. However, total Lys intake (barrows, 14.0, 17.0, 17.4 and 19.3 g/d; gilts, 14.3, 16.8, 17.6 and 19.6 g/d) and available Lys intake (barrows, 12.1, 14.7, 15.1and 16.8 g/d; gilts, 12.3, 14.6, 15.3 and 17.1 g/d) were increased (P < 0.05) as dietary Lys:calorie increased. On d 42, the BUN concentration was increased (P < 0.05) in response to the increasing dietary Lys:calorie ratio. Although growth performance was not influenced by dietary Lys:calorie ratio in the present study, we observed that in both experiments barrows had the numerically maximal ADG at the Lys:calorie ratio of 3.0, while gilts had the numerically maximal ADG at the Lys:calorie ratio of 3.3. In conclusion, dietary Lys:calorie ratio of 2.7 can satisfy the requirement of 25- to 50-kg growing pigs. Increasing dietary Lys:calorie ratio can increase BUN concentration in growing pigs.