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Tryptophan Requirement for Reproduction in Swine

Iowa Agriculture and Home Economics Experiment Station, Ames 50011³

Abstract

Twenty-five crossbred gilts were used in an experiment to determine the tryptophan (Trp) requirement for reproduction. L-tryptophan was added to a fortified corn-gelatin diet to attain the five Trp levels of ,64, 1.04, 1.44, 1.84 and 2.24 g per day. These diets were fed at 2 kg daily during pregnancy I and 1.82 kg daily during pregnancies II and III. During each 3-week lactation, all animals were fed the same 10% crude protein diet. Litter size and feed intake were standardized during both lactations.

Five-day nitrogen balance trials were initiated on day 45 and day 90 of pregnancies I and II. As dietary Trp increased, urinary nitrogen decreased and nitrogen retention increased linearly (P<.05). Similarly, plasma urea nitrogen decreased and plasma-total Trp increased linearly (P<.005) as dietary Trp increased.

Litter weights increased linearly (P<01) with increasing Trp. The number of days from weaning to estrus decreased linearly (P<.005) and quadratically (P<.01) as dietary Trp increased. Baby pig weight gains, sow milk yield, sow milk solids and sow milk nitrogen increased linearly (P<.005) with increasing dietary Trp. There were no differences in nitrogen retention among the treatments during day 15 to day 20 of lactation. Sow weight gains during gestation and during the entire experiment increased linearly (P<.005) with increasing dietary Trp.

All sows were slaughtered during pregnancy III, and most of the carcass measurements responded linearly (P<.005) to increasing dietary Trp. Plasma-free and plasma-total Trp and brain Trp increased linearly (P<.005) with increasing dietary Trp. Correlation coefficients for plasma-total Trp, plasma-free Trp and the sum of the competitor amino acids in relation to brain Trp were highest for plasma-total Trp.

It was concluded that 1.44 g of Trp per day satisfied the requirements for reproduction when all the parameters were considered. If synthetic Trp is assumed to be 100% available and that supplied by corn or other ingredients 90% available, a level of 1.53 g per day (.084% at 1.8 kg/day feed intake) would satisfy the requirement for pregnancy.

² Present Address: Cooperative Extension Service, Iowa State University, 5 North 16th St., Fort Dodge 50501.

³ Department of Animal Science.