Nitrogen metabolism and growth performance of gilts fed standard corn-soybean meal diets or low-crude protein, amino acid-supplemented diets1

Abstract

Two experiments were conducted to determine the CP concentration below which N retention and growth performance are reduced when low-protein, amino acid-supplemented, corn-soybean meal diets are fed. In a N balance trial (Exp. 1), 12 gilts (initial weight 41 kg) were fitted with urinary catheters and fed six different diets during three 7-d periods in an incomplete block design. The diets were: 1) 18% CP; 2) 14% CP + AA, 3) 16% CP; 4) 12% CP + AA; 5) 14% CP; and 6) 10% CP + AA. Amino acids (lysine, threonine, tryptophan, and methionine) were supplemented such that the concentrations in the low-protein diets were equal to those in their standard (4% CP higher) counterparts. Nitrogen retention (g/d) decreased (P < 0.01) as CP decreased, in both standard (27.10, 24.53, and 20.99) and low-protein (21.51, 19.18, and 15.83) diets, but was lower (P < 0.01) in low-protein diets. There were no differences among treatments (P > 0.05) in biological value (68.2% standard vs 71.0% low-protein). In a growth performance trial (Exp. 2), 36 gilts (initial weight 19.5 kg) were penned individually and fed one of six diets for 35 d in a randomized complete block design. Dietary treatments were a 16% CP standard diet and low-protein diets formulated to contain 15, 14, 13, 12, and 11% CP supplemented with crystalline lysine, tryptophan, threonine, and methionine to equal the total concentrations in the standard diet. Protein concentration affected (P < or = 0.05) ADG, ADFI, feed efficiency, fat-free lean gain, longissimus muscle area, plasma urea, and plasma concentrations of most essential AA. For most of these traits, the major difference was poor performance of pigs fed the 11% CP diet. Thus, in Exp. 1, at AA concentrations from deficient to excess, low-protein, amino acid-supplemented diets failed to produce the same N retention as the equivalent corn-soybean meal diets. However in Exp. 2, the same performance was obtained with 16, 15, 14, 13, and 12% CP. Based on these data, we suggest that N balance is more sensitive than growth to amino acid adequacy andthat other AA (e.g., isoleucine and valine) may limit growth performance when the protein concentration is reduced by more than four percentage units.

Effect of low-protein amino acid-supplemented diets on the growth performance, gut morphology, organ weights and digesta characteristics of weaned pigs

“…Low-protein diets for weaned pigs level in weaned pig diets could result in a deficiency of other indispensable AA apart from lysine, methionine1 cysteine, threonine and tryptophan (Figueroa et al, 2002;Stein and Kil, 2006). Since most indispensable AA are not commercially available, formulation of weaned pig diets to be moderately low in CP should be done carefully.…”

Effects of low-protein diets supplemented with indispensable amino acids on growth performance, intestinal morphology and immunological parameters in 13 to 35 kg pigs

“…It is well documented that reducing dietary CP level from 16% to 12%, supplemented with indispensable amino acids (IAA), could maintain similar growth performance as pigs fed control diet (Figueroa et al, 2002 andKerr et al, 2003). In addition, a moderate reduction of dietary CP level has been shown to decrease the harmful microbial metabolites in the digesta such as ammonia N (Nyachoti et al, 2006;Opapeju et al, 2008), as well as improving the villous morphology of weaned piglets (Gu and Li, 2004;Opapeju et al, 2008).…”

Níveis de energia metabolizável em rações formuladas com base no conceito de proteína ideal e suplementadas com fitase para leitões dos 15 aos 35 kg

“…Resultados semelhantes foram encontrados por Figueroa et al (2002). Kerr et al(2003 a,b), em experimento com animais em crescimento, verificaram que rações com baixa proteína bruta suplementadas com aminoácidos es senciais resultaram em menor concentração de uréia no sangue.…”