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Threonine Requirement of the Lactating Sow¹

Iowa Agriculture and Home Economics Experiment Station³, Ames 50010

Abstract

Twenty-five mature Landrace x Yorkshire sows were used in an experiment to estimate the threonine requirement of the sow during the first 3 weeks of lactation. A basal diet consisting of corn and gelatin with added vitamins, minerals and essential amino acids was formulated to satisfy the currently recognized sow requirements for all essential nutrients except threonine. L-threonine was added to this diet to produce five diets containing: .31, .36, .42, .49 and .57% threonine. The sow's threonine requirement was estimated on the basis of milk production and pig weight gain, nitrogen retention, plasma essential amino acid and urea levels, and urea excretion.

Milk yield increased quadratically (P < .07) with increasing levels of threonine, reaching a maximum at .49% threonine. Pig gains also were maximal at this threonine intake. Nitrogen retention and output of milk nitrogen increased as threonine intake increased from .31% to .42%, with little change above this level. Plasma threonine increased quadratically (P < .001) as dietary threonine increased, remaining at a low level until .42% dietary threonine and increasing rapidly at higher threonine intakes. The plasma concentrations of eight of the nine other essential amino acids decreased with increasing dietary threonine, generally reaching a plateau at .42% threonine. This trend also was followed by plasma urea concentrations and urine urea excretions, both of which fell rapidly as threonine intake increased from .31% to .42% with little change above this level.

¹ Journal Paper No. J-7987 of the Iowa Agriculture and Home Economics Experiment Station, Ames. Project No. 2024.

² Present address: Department of Animal Science, University of Nebraska, Lincoln, NB 68503.

³ Department of Animal Science.

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