Dietary sulfur amino acid level and energy utilization in laying hens

Effects of marginal total sulfur amino acid (TSAA) deficiency and methionine toxicity on energy utilization of laying hens were studied with 7-month-old Single Comb White Leghorn pullets housed in individual cages at constant temperatures of 15.6 and 32.2 C. Diets containing .47, .49, .51, and 3.47% TSAA were fed throughout the 4-week study. Following a 2-week acclimation period, each diet was fed at three levels of intake for 2 weeks. Voluntary feed and metabolizable energy (ME) consumption of nontoxic TSAA diets was significantly reduced at the higher housing temperature, and a further significant reduction was observed with the toxic diet at both temperatures. Energy balance increased from 79.7 to 98.7 kcal/bird per day at 32.2 C and from 117.3 to 142.0 kcal at 15.6 C as dietary TSAA increased from .47 to .51%; energy balance of hens fed 3.47% TSAA was very low at both temperatures. Maintenance ME requirements were unaffected by dietary TSAA up to .51%, ranging from 123.3 to 131.1 and 155.5 to 163.5 kcal/hen per day at 32.2 C and 15.6 C, respectively; the requirement increased about 20 kcal/day at each temperature when the toxic TSAA diet was fed. As the amino acid balance of the diet was improved with methionine supplementation up to .51%, heat increment plus activity decreased from 70.2 to 37.0 kcal/bird per day for hens housed at 32.2 C. Consequently, efficiency of conversion of dietary ME to net energy improved from 52.1% with .47% TSAA to 63.8% with .51% TSAA. Housing temperature did not influence energetic efficiency.(ABSTRACT TRUNCATED AT 250 WORDS)