EDUCATION and TRAINING

B.S. in Animal Science, Cornell University
M.S. in Animal Nutrition, University of Illinois
Ph.D. in Animal Nutrition, University of Illinois

RESEARCH INTERESTS

Focus: Research interests include amino acid, protein, and energy nutrition of nonruminants and the interaction of nutrition and other environmental factors on growth, development, and productivity.

Amino acid nutrition: Research has emphasized amino acid utilization and dietary requirements. I developed a widely used statistical method for determining amino acid requirements for essential amino acids. Using this methodology, we determined that 50% of the growing pig's total phenylalanine requirement can be met with dietary tyrosine, and demonstrated the utility of estimating the pig's dietary lysine requirement using serum urea concentrations as the response variable. In studies with rats, we determined that dietary arginine is an essential amino acid for normal mammary gland development during gestation. And, in a series of studies we accurately determined the efficiency of nutritional utilization of amino acid derivatives which develop during food- and feed-processing, including the cross-linked amino acids, lysinoalanine, lanthionine, and the various oxidized derivatives of the sulfur-containing amino acids, cystiene and methionine; and determined the effect of dietary minerals on amino acid utilization.

Broiler nutrition: Research in broiler nutrition has been focused on factors affecting energy utilization for growth. In studies comparing energy utilization by a slow-growing, lean genotype (leghorn) and a fast-growing genotype (commercial broiler strain), we determined that the higher efficiency of energy utilization in the commercial broiler was due to a lower maintenance energy requirement -- efficiency of energy utilization above maintenance was not different between genotypes. Increasing the levels of dietary energy in broiler diets resulted in increased fat deposition in males independent of the dietary calorie:protein ratio; but in females only when energy was increased in iso-nitrogenous diets (i.e. an increasing calorie:protein ratio). And, we established that a daily period of darkness was essential for normal growth of broilers. Either the absence of a daily dark period or removal of the pineal gland reduced growth and the efficiency of energy retention above maintenance, but had no effect on the bird's maintenance energy requirement.

Broiler breeder management: Research has been directed at development of rearing management regimes to maximize fertile egg production during lay. We determined that there exists both age and body compositional thresholds for onset of egg production in pullets. Egg production is maximized when pullets are reared to begin lay at 24 weeks of age. When reared in short-day, dark-out systems, we determined that pullets should begin photostimulation at 18 weeks of age, and full-feeding no later than 24 weeks of age. However, when reared in natural daylight, photosimulation should commence at 14 weeks of age, and full feeding at 15 weeks of age. We determined that once-a-day, morning feeding vs. twice-a-day, split feeding improved egg production of heat-stressed breeders, but did not improve egg shell quality.