Studies on the tryptophan requirement of lactating sows. Part 2: Estimation of the tryptophan requirement by physiological criteria

Abstract

Mature sows were fed for a total of 72 lactations with diets which provided an adequate supply of energy and nutrients except for tryptophan (Trp). By supplementing a basal diet [native 1.2 g Trp/kg, equivalent to 0.8 g apparent ileal digestible (AID) Trp or 0.9 g true ileal digestible (TID) Trp] with L-Trp, five further diets (2-6) containing 1.5-4.2 g Trp/kg were formulated. The dietary Trp content had no effect on amino acid contents in milk on days 20 and 21 of lactation, but Trp in blood plasma on day 28 of lactation reflected the alimentary Trp supply with an increase from 2.74 +/- 1.14 mg/l (diet 1) to 23.91 +/- 7.53 mg/l (diet 6; p < 0.001). There were no directional differences between the diets with regard to the other amino acids. Concentrations of urea in milk and blood were higher with diet 1 (211 and 272 mg/l, respectively) than with diets 3-6 (183 and 227 mg/l, respectively). Serotonin levels in the blood serum were lower with diet 1 (304 ng/ml) than the average of diets 4-6 (540 ng/ml). This study confirms previously given recommendations for the Trp content in the diet of lactating sows, estimated by means of performance, of 1.9 g AID Trp (equivalent to 2.0 g TID Trp; approximately 2.6 g gross Trp) per kg diet.

Reduced feed intake of lactating primiparous sows is associated with increased insulin resistance during the peripartum period and is not modified through supplementation with dietary tryptophan1

“…These results suggest that Trp could promote the uptake of glucose through increasing insulin sensitivity. The meal tests performed in our experiment showed that the increase in the supply of dietary Trp increased the plasma Trp concentration in agreement with the previous results of Sève et al (1991) and Pampuch et al (2006). The blood concentrations of the other variables measured after the meal did not vary according to the dietary treatment except for the plasma insulin response, which was less in the Trp+ sows than in the Trp− sows at AF.…”

“…A deficient as well as an excessive dietary supply of Trp impairs the appetite of lactating sows (Lewis and Speer, 1974;Paulicks et al, 2006). The actual recommendation for the Trp:Lys ratio in the lactation diet is 18% (Dourmad et al, 1991;NRC, 1998) but was recently estimated at 24% on the basis of feed intake and uremia (Pampuch et al, 2006;Paulicks et al, 2006). However, these authors studied multiparous sows only, and the effect of such a dietary Trp concentration on the performance of lactating primiparous sows remains to be investigated.…”

The threonine requirement of sows increases in late gestation1

“…1 where plasma Thr increased linearly with increasing Thr intake in LG. Plasma AA have been shown to correlate poorly with other estimates of requirement or to respond linearly to all treatments (Mitchell et al, 1968;Sohail et al, 1978;Pampuch et al, 2006) and thus are less reliable dependent variables when estimating AA requirements. The quantitative response of plasma AA to changes in dietary AA reflects the complex interaction of the dynamic equilibrium of the plasma AA pool with the tissue AA pool, protein degradation, and labile nonprotein AA sources (Young and Scrimshaw, 1970).…”

Supplementary Tryptophan Fed to Sows Prior to and after Farrowing to Improve Piglet Growth and Survival

“…Thus, more research should be conducted on the effects of tryptophan supplementation on sow behaviour and serotonin production to understand how tryptophan affects piglet survival. Furthermore, serotonin production may not increase linearly with increasing tryptophan levels [ 21 ]; thus, the similar survival rates seen in both High and Low tryptophan may be attributed to High tryptophan having a plateauing effect on serotonin production.…”

“…Most maternal tryptophan supplementation studies in sows have focussed on sow performance indices such as lactational weight loss and milk yield. Although benefits for piglet survival and weights have been shown [ 10 , 11 , 21 , 22 , 23 ], the impact of tryptophan on piglet viability has yet to be established. Furthermore, increasing levels of calcium and melatonin through tryptophan supplementation has only been studied in cattle, sheep and rats, respectively, and have not been established in sows [ 17 , 18 , 24 ].…”