Date of Award
Program or Major
Animal and Nutritional Sciences
Doctor of Philosophy
A series of growth experiments was conducted to evaluate the feeding of ruminally undegraded protein alone, or in combination with ruminally protected lysine and methionine. Eighty Holstein heifer calves were blocked by date of birth as they became available at 6 wk of age and assigned to a 2 x 2 factorial arrangement of treatments. Main effects of the 2 x 2 factorial were amount of ruminally undegraded protein in diet dry matter and whether ruminally protected lysine arid methionine were supplemented to diets. Four phases of growth were evaluated: Phase (1) 6 wk to 100 kg; Phase (2) 100 to 175 kg; Phase (3) 175 to 245 kg; Phase (4) 245 to 410 kg. Feeding higher concentration of ruminally undegraded protein during Phase 1 improved average daily gain and feed efficiency, which reduced days on feed. No improvement of skeletal growth was evident by feeding more ruminally undegradable protein. Responses were limited to the young calves; no benefits were observed for heifers greater than 100 kg by feeding higher concentrations of ruminally undegraded protein or ruminally protected lysine and methionine. Results suggest that recommendations for ruminally undegraded protein fed to older heifers may be too generous. No improvements for growth were achieved by feeding ruminally protected lysine and methionine, but responses may have been masked by high intake of total absorbable protein.
Garthwaite, Brian David, "Ruminally undegraded protein and ruminally protected amino acids for dairy heifers" (1997). Doctoral Dissertations. 1992.