Estimation of the optimal ratio of standardized ileal digestible tryptophan to lysine for finishing barrows fed low protein diets supplemented with crystalline amino acids

Abstract

Optimum standardized ileal digestible (SID) tryptophan (Trp) to lysine (Lys) ratio was estimated for 67-96 kg barrows fed low protein diets supplemented with crystalline amino acids (AA). One hundred and fifty Yorkshire × Landrace barrows, with an average initial body weight (BW) of 67.3 ± 3.2 kg, were used in a 28-day feeding trial. All dietary treatments were based on corn, wheat bran, and soybean meal and were formulated to provide 10.5% crude protein and 12.6 MJ/kg metabolizable energy. The dietary SID Lys was set at 0.61% ensuring that Lys was marginally deficient for barrows of this weight range. Graded levels of crystalline l-Trp were added to the basal diet to produce diets providing SID Trp to Lys ratios of 0.131, 0.164, 0.197, 0.230, and 0.262. There were improvements in weight gain (linear and quadratic effect P < 0.01) and feed intake (linear effect P = 0.04) with increasing dietary SID Trp to Lys ratio. Increased SID Trp to Lys ratio resulted in a decrease in the serum urea nitrogen (SUN) content (linear and quadratic effect P < 0.01). The serum concentration of Trp increased with increasing dietary SID Trp to Lys ratio (linear effect P = 0.03, quadratic effect P = 0.08). Estimates of the optimum SID Trp to Lys ratios were 0.203, 0.197, and 0.214 for weight gain, feed conversion ratio, and SUN, respectively, using a broken-line model while a quadratic model produced optimum SID Trp to Lys ratios of 0.251, 0.224, and 0.249 for the same parameters. The results of this experiment indicate that the SID Trp to Lys ratio for finishing barrows is at least 0.203, which is higher than the SID ratio of Trp to Lys currently recommended by the National Research Council (NRC, 2012).

Estimation of the standardized ileal digestible valine to lysine ratio required for 25- to 120-kilogram pigs fed low crude protein diets supplemented with crystalline amino acids1

“…However, the requirement was better estimated using the quadratic model than the linear broken-line model. In accordance with this result, both Gaines et al (2011), in estimating the SID Val:Lys ratio of 13-to 32-kg pigs, and Xie et al (2014), in estimating the SID Trp:Lys ratio of finishing barrows, found that the requirements were higher using a quadratic model than a linear broken-line model.…”

“…The SUN concentration can be an indirect indicator of the AA balance in the diet, as a lower SUN indicates a reduced need for deamination and improved AA balance in the diet (Htoo et al, 2014). Therefore, SUN has been used as a rapid response criterion to estimate AA requirements of pigs (Coma et al, 1995;Xie et al, 2014). The SID Val:Lys ratios estimated in Exp.…”

Evaluation of standardized ileal digestible lysine requirement for 8–20 kg pigs fed low crude protein diets

“…Similarly, the reported SID Lys requirement (10.3 g/kg SID Lys) for growing pigs (22–50 kg) (Lu, ) and (7.5 g/kg SID Lys) for finishing pigs (72–100 kg) (Xie et al., ) fed with low CP diets were higher than that of the NRC () values. Likewise, the ideal ratios of SID Thr:Lys and SID Trp:Lys for growing pigs (Zhang et al., , ) and finishing pigs (Xie et al., , ) fed with low CP diets were also higher than the NRC () recommendation. Nutrient requirement estimates can be affected by the regression method used (Kendall et al., ; Pesti, Vedenov, Cason, & Billard, ).…”

Effects of N-acetylcysteine on the energy status and antioxidant capacity in heart and liver of cold-stressed broilers

“…Amino acids in the plasma were analyzed by an automatic amino acid analyzer (S433D, Sykam GmbH, Eresing, Germany) according to Xie et al [16] with minor modifications. Briefly, 1 mL of plasma and salicylsulfonic acid (2%) were mixed thoroughly and then placed in an ice bath for 15 min.…”