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Abomasal Protein Infusions for Growing Steers Fed Corn Grain Rations¹

Oklahoma Agricultural Experiment Station, Stillwater 74078^,4

Abstract

Casein was abomasally infused into five growing 226-kg steers consuming a urea-supplemented corn grain diet ad libitum. Infusate solutions in the 5x5 Latin square arrangement of treatments contained 0, 20, 40, 80 and 120 g casein made isocaloric and isonitrogenous by the addition of dextrose and urea. Feed intake averaged 5.4 kg dry matter daily and was not altered significantly by abomasal infusions. Apparent digestibility of N decreased from 71.7 to 66.8% as level of casein infusion increased. N retentions (NR) were 40.5, 35.5, 42.8, 35.1 and 32.7 g/d at the five levels of infusion, respectively. A second study was conducted to determine whether level of feed intake influenced the benefit seen from postruminal protein supplementation. Four steers (306 kg) ate ad libitum or were limit-fed (2.5 kg/d) a 1% urea-supplemented corn grain diet in a 4 X 4 Latin square design. These steers were abomasally infused with 120 g casein or an isocaloric, isonitrogenous dextrose-urea mixture. Daily ad libitum feed intake averaged 4.7 kg and was not altered significantly by infusion composition. NR tended to increase with casein infusion at both levels of intake, but, as a percentage, the increase tended to be greater with limit feeding (43 vs 20%). To determine whether supplemental abomasal urea might be beneficial, a third trial was conducted with four 313 kg steers consuming the same diet ad libitum in a crossover design. Infusates consisted of 120 g dextrose or 120 g dextrose plus 42.6 g urea/d. Daily feed intakes were 4.5 and 4.8 kg/d for the steers given the dextrose and the dextrose plus urea infusions, respectively. NR tended to increase with urea infusion (20.9 vs 29.7 g/d). Results suggest that energy, total N or other nutrients, but not postruminal amino acids, limited N balance of young growing steers fed a urea-supplemented, cracked corn diet and gaining weight at. 9 kg daily.

Key Words: Abomasal Infusion • Casein • Protein • Steers • High Concentrate Diets

¹ Journal Article No. 3937 of the Oklahoma Agr. Exp. Sta., Stillwater.

² Present address: Assistant professor, Texas Agr. Exp. Sta., Vernon 76384.

³ Present address: Missouri Farmers Assoc. Inc., 201 S. 7th St., Columbia 65201.

⁴ Anim. Sci. Dept.