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Isoleucine Requirement of the Lactating Sow¹

Iowa Agriculture and Home Economics Experiment Station², Ames 50011

Abstract

Twenty-five Landrace x Yorkshire sows (second through seventh parity) were randomly assigned to five dietary treatments in an experiment designed to estimate the isoleucine requirement of the sow during the first 3 weeks of lactation. The basal diet (.20% isoleucine), composed of oat groats, corn sugar, wood cellulose, soybean oil, vitamins, minerals, indispensable amino acids and L-glutamic acid, fulfilled the requirements of the lactating sow for all essential nutrients except isoleucine. L-isoleucine was added to provide levels of .20 (basal), .28, .37, .65 and .92% isoleucine in the five diets. The sows were fed 5.45 kg daily during the 21-day lactation period. The requirement for isoleucine was estimated from the data on milk yield and composition, pig weight gain, nitrogen retention, plasma isoleucine and plasma urea.

Milk yield and pig weight gain responded quadratically (P<.05 and P<.08, respectively) to increasing levels of isoleucine and were maximized at .37% isoleucine. Total solids and protein production in the milk increased quadratically (P<.005 and P<.05, respectively) with increasing isoleucine. There was a rapid increase from .20 to .28% isoleucine, with a maximum obtained at .65% isoleucine for both parameters. Nitrogen retention was maximized at .37% isoleucine (quadratic component, P<05).

Plasma isoleucine moderately increased to .37% isoleucine, then increased sharply at higher isoleucine levels (linear component, P<.001; quadratic component, P<.05). Plasma urea concentration did not respond significantly to the treatments, but the concentration was minimized at .37% isoleucine.

When all parameters are considered, the data suggest that a mature sow consuming 5.45 kg of feed daily and nursing nine pigs require a minimum of .37% dietary isoleucine during the first 3 weeks of lactation for maximum performance. In a diet containing natural ingredients, the requirement would probably be increased to .39% dietary isoleucine.

¹ Journal Paper No. J-8560 of the Iowa Agriculture and Home Economics Experiment Station, Ames. Project N. 2024.

² Department of Animal Science.