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Dietary Glycine Requirements for Growth and Cellular Development in Chicks^1,2,3,

Department of Poultry Science, University of Maryland, College Park, Maryland 20742 and Protein Nutrition Laboratory, Nutrition Institute, Agricultural Research Service, United States Department of Agriculture, Beltsville, Maryland 20705

The requirement of dietary glycine for the growth and cellular development of approximately 2-week-old male broiler chicks was studied. Chicks fed a corn-casein-amino acid diet (analyzed to have 20.5% protein, 0.34% glycine and 0.56% serine) supplemented with levels of glycine up to 3.2% showed a correlation 1) between glycine consumption and weight gain (r = 0.88), feed conversion (r = 0.92) and uric acid excretion (r = 0.60), and 2) between uric acid excretion and weight gain (r = 0.84) and feed conversion (r = 0.74). In subsequent experiments, serum uric acid and pectoral muscle creatine increased curvilinearly, then plateaued 14 days post-hatching in chicks fed reference amino acid diets containing 1.2% glycine. Dietary glycine depletion significantly reduced body weight, liver weight, mg protein/g wet liver, mg DNA/liver, mg RNA/liver, and mg protein/liver. The mg DNA and RNA/g wet liver were not significantly different in chicks fed either 0 or 1.8% dietary glycine. In terms of mg/g wet liver, there was a significant increase in protein with a small, but significant decrease in RNA and DNA with age (5 to 10 days), respectively, which suggest increased liver growth in chicks after 5 days post-hatching is primarily cell hypertrophy. Livers from chicks fed the glycine depleted diet showed a lack of heavy ribosomal aggregates, an increase in monosomes and a decrease in [U-¹⁴C]L-leucine incorporated liver protein compared with livers from chicks fed the similar diet supplemented with 1.2% glycine. The conclusion is that the deficiency of dietary glycine in young chicks led to the limited synthesis of uric acid, creatine, and protein necessary for optimum growth.

KEY WORDS: • chicks • glycine requirement • uric acid • creatine • DNA • RNA • polysomes • protein synthesis

¹ Scientific Article No. A2247, Contribution No. 5237, of the Maryland Agricultural Experiment Station (Department of Poultry Science).

² Part of these data were presented at the 64th Annual Meeting of the Poultry Science Association. Poultry Science 54, 1800 abstr. (1975). Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture, and does not imply its approval to the exclusion of other products that may also be suitable.

³ Reprint requests should be sent to Department Chairman, Poultry Science Department, University of Maryland, College Park, Md. 20742.

⁴ Present Address: Department of Poultry Science, Cornell University, Ithaca, New York 14850.

⁵ Present Address: Department of Animal Sciences, Washington State University, Pullman, Washington 99164.

Manuscript received 1 September 1976.