Master of Science (MS)


Dairy Science (Animal, Dairy, and Poultry Sciences)

Document Type



Eight weaned Holstein steers approximately 4 mo of age (mean BW = 119.47 ± 2.65 kg) were used in a replicated 4 x 4 Latin square designed experiment to study the effects of protein source and level on performance and anabolic hormonal status of weaned dairy calves. Treatments consisted of two diets containing either 16 or 20 % crude protein (CP) with or without fish meal (FM). Experimental diets were corn silage based with soybean meal (SBM) as the source of ruminal degradable protein and FM as the source of ruminal undegradable protein. The animals were fed their respective diets twice daily at ad libitum levels during each 10-d adjustment period and 4-d sample collection period. Animals were housed in individual stalls for 10 d and in metabolism crates for 4 d for each experimental period. Feed intake was recorded daily. Total fecal and urine output were collected, weighed and subsampled during the 4-d sample collection period for laboratory analysis of nitrogen. On d 4 of the sample collection period, animals were fitted with indwelling jugular catheters. Blood samples were collected for 6 h at 15-min intervals for analysis of growth hormone (GH) and 30-min intervals for analysis of insulin (INS) and insulin-like growth factor-1 (IGF-1). An initial blood sample was taken at the beginning of the 6-h blood sample period for analysis of plasma urea nitrogen (PUN) and thyroxine (T4). On d 14 of the each experimental period, body weight, wither height, hip height, and body length were measured. Treatment did not affect (P > 0.10) dry matter intake, any of the growth parameters measured, or nitrogen balance. Steers consuming diets containing 20% CP diets tended to have higher plasma INS concentrations (P = 0.07) whereas steers consuming SBM as the protein source tended to have higher mean GH levels (P= 0.07). Thyroxine, IGF-1, and PUN concentrations were not effected by protein level or source (P > 0.10). It is concluded that feeding diets greater than 16% CP with or without FM does not improve performance in weaned dairy calves.



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Committee Chair

Cathleen C. Williams



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Dairy Science Commons