The response of weaned piglets to dietary valine and leucine

Abstract

Valine (Val) is considered to be the fifth-limiting amino acid in a maize-soyabean meal diet for pigs. Excess leucine (Leu) levels often occur in commercial diets, which may attenuate the effect of Val deficiency because of an increased oxidation of Val. The objective of the present experiment was to determine the effect of increasing concentrations of Leu on the response of young piglets to dietary Val. In all, 75 Large White × Landrace entire male pigs, 44 days of age and with a mean starting weight of 13.5 kg, were used. Three of these were sacrificed at the start to determine their mean initial chemical composition. A summit feed first limiting in Val was serially diluted with a non-protein diluent to produce a series of five digestible Val concentrations of 11.9, 10.1, 8.3, 6.6 and 4.8 g/kg, with a sixth treatment being added to test that the feeds were limiting in Val. Three identical Val series, each with six levels of Val, were supplemented with increasing amounts of Leu (23, 45 and 67 g/kg), thus 18 treatments in total. All pigs were killed at the end of the trial after 18 days for analysis of water, protein, lipid and ash in the carcass. The levels of Val and Leu and their interaction significantly influenced all the measurements taken in the trial. Daily gain in liveweight, water and protein, and feed conversion efficiency all increased with dietary Val content, whereas feed intake decreased as both Val and Leu contents increased. The deleterious effect of increased Leu on feed intake and growth was more marked at lower levels of Val. Supplementing the feed with the lowest Val content with additional Val largely overcame the effect of excess Leu. The efficiency of utilisation of Val for protein growth was unaffected by the level of Leu in the feed, the primary response to excess Leu being a reduction in feed intake. An intake of around 9 g Val/day yielded maximal protein growth during the period from 44 to 62 days of age in pigs of the genotype used in this trial.

Meta-regression analysis to predict the influence of branched-chain and large neutral amino acids on growth performance of pigs1

“…Our equations for ADG and G:F suggest that ADFI is reduced in high Leu diets. Other research also suggests that ADFI is decreased when pigs are fed diets with high Leu or imbalanced BCAA concentrations (Harper et al, 1984;Gloaguen et al, 2011;Millet et al, 2015;Wessels et al, 2016a;Meyer et al, 2017). A possible explanation for this response is the excessive stimulation of the mammalian target for rapamycin (mTOR), a signaling pathway that stimulates protein synthesis and cell growth in the presence of adequate nutrients (Schmelze and Hall, 2000).…”

Effects of soybean meal concentration in lactating sow diets on sow and litter performance and blood criteria1

“…Recently, Millet et al (2015) observed that growing pigs fed increasing levels of Leu had decreased growth and feed intake; however, this was able to be partially recovered by increasing the Val:Leu ratio. Similarly, a Val titration study with weaned pigs observed more severe feed intake reductions when Val:Leu ratios decreased ( Meyer et al, 2017 ).…”

The Optimal Valine to Lysine Ratio for Performance Parameters in Weaned Piglets

“…A reduction of ADFI was seen in diets that were deficient in Val [ 8 , 10 ], but also in Ile deficient diets [ 9 ]. Excess Leu in combination with a low level of Val in the diet had a negative impact on feed intake and consequently on the performance of piglets [ 26 , 27 ]. BCAAs get degraded by the same enzyme system complexes; thus, excess Leu may affect the requirements of Val and Ile [ 12 ] because excess Leu activates the degradation of Val and Ile too.…”