Master of Science (MS)


Animal Science (Animal, Dairy, and Poultry Sciences)

Document Type



Eight Holstein calves approximately 6 months of age (mean BW 185.15 + 16.16 kg) were used in a replicated 4 x 4 Latin Square experiment to study effects of protein sources on performance of weaned dairy calves. Dietary treatments consisted of 16% CP diets with three sources of ruminally undegradable protein (RUP). Experimental diets were corn-silage based, with soybean meal (SBM) as the source of ruminally degradable protein (control) and 3 sources of RUP including heat treated soybean meal (SBM) (SoyPLUS®), animal protein blend (PRO-LAK), and extruded-expelled SBM, included at 45% of the dietary CP. The animals were fed their respective diets twice daily ad libitum. Animals were housed in individual stalls for 14 days for dietary adjustment and feed intake measurements. Steers were housed in metabolism crates during the last 4 days of each experimental period for sample collection. Total fecal and urine output was collected, weighed, and sampled for laboratory analysis of nitrogen during the 4-d collection period. On day 4 of the collection period, animals were fitted with jugular catheters. Blood samples were collected at 15-minute intervals for 6 hours for analysis of growth hormone. An additional blood sample was collected at time 0 for plasma urea nitrogen (PUN) and at 30-minute intervals for IGF-I and insulin. On day 18 of each experimental period body weight, wither height, hip height, and body length were measured. Treatment did not affect dry matter intake (P > 0.05). There were also no effects (P > 0.05) of protein source on nitrogen metabolism, PUN, or growth parameters. There was no effect (P > 0.05) of protein source on GH levels. There was no effect of RUP sources on plasma IGF-I concentrations on (P > 0.05). Treatment did not affect (P > 0.05) insulin concentrations. However, there was an affect of time on insulin concentrations (P < 0.05). There was no difference (P >0.05) among treatments in the digestibility of DM, OM, NDF, ADF, or CP. These data suggest that feeding diets with sources of RUP does not improve performance in weaned dairy calves.



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Committee Chair

Cathleen C. Williams