Evaluation of increasing standardized ileal digestible valine:lysine ratio on growth performance and plasma urea nitrogen of 21 to 116 kg pigs.

Abstract

Three experiments evaluated the effects of increasing standardized ileal digestible (SID) Val:Lys ratio on growth performance and plasma urea nitrogen (PUN) of pigs from 21 to 116 kg. In Exp. 1, 351 pigs (initially 21.4 ± 0.35 kg) were used in a 21-d study. Pens of pigs were blocked by body weight (BW) and randomly allotted to one of six dietary treatments with five pigs per pen and 12 replications per treatment. The SID Val levels were 60, 63, 66, 69, 72, and 75% of Lys. Pigs were weighed on d 0 and 21 to determine average daily gain (ADG), average daily feed intake (ADFI) and gain:feed ratio (G:F). A blood sample was collected from 2 pigs per pen on d 10 after a 5-h fasting period. Gain:feed ratio increased (linear, P = 0.012) as SID Val:Lys ratio increased, but with little improvement past 69% SID Val:Lys ratio as supported by broken-line analysis. Increasing Val:Lys ratio increased (linear, P = 0.029) PUN but no differences were observed for ADG or ADFI. In Exp. 2, 647 pigs (initially 38.6 ± 0.90 kg) were used in a 27-d experiment. Pens of 8 or 9 pigs were blocked by BW and randomly allotted to one of six dietary treatments with 12 replications per treatment. The SID Val levels were 60, 63, 66, 69, 72, and 75% of Lys. Pigs were weighed on d 0 and 27 and after a 10 h fasting period on d 15, blood was collected from 3 pigs per pen. Final BW, ADG, and ADFI increased (quadratic, P < 0.05) as SID Val:Lys ratio increased. A quadratic polynomial analysis indicated a SID Val:Lys ratio of near 69% maximized ADG. As the SID Val:Lys ratio increased, both G:F and PUN decreased (linear, P < 0.050). After a 30-d common feeding period, the same 647 pigs (initially 90.0 ± 1.86 kg) from Exp. 2 were used in another 27-d experiment (Exp. 3). Pens of pigs were randomly reallotted to one of six dietary treatments and weighed on d 0 and 27. The SID Val levels were 63, 66, 69, 72, 75, and 78% of Lys. On d 15, after a 10-h fasting period, blood was collected from 3 pigs per pen. Average daily gain and ADFI increased (linear, P < 0.05) as SID Val:Lys ratio increased. However, little improvement in ADG was observed when feeding greater than 69% SID Val: Lys ratio. Final BW also tended to increase (linear, P = 0.078) as SID Val:Lys ratio increased; however, there was no evidence of an effect on G:F or PUN. These results indicate a SID Val:Lys ratio of 69% appears to maximize ADG or G:F for 21 to 40 and 38 to 67 kg pigs. In 90 to 116 kg pigs, a ratio of at least 69% SID Val:Lys appeared to be sufficient for growth performance.