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ARS Home » Plains Area » Miles City, Montana » Livestock and Range Research Laboratory » Research » Publications at this Location » Publication #59152
Title: EFFECTS OF GROWTH POTENTIAL AND PROTEIN SUPPLEMENTATION ON STEERS GRAZING FALL PASTURE

Author
item Grings, Elaine
item Short, Robert
item ADAMS, DON - UNIV OF NEBRASKA

Submitted to: Journal of Production Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Regrowth of harvested, irrigated hay fields can provide forage of a quality for fall grazing greater than that of nonirrigated native pastures. The high quality of irrigated pastures may make them suitable for young animals with high nutritional requirements for growth. The protein requirements of 6 to 9 month old calves may be greater than what is available from pasture alone, however. Research showing improvements in weight gain in cattle fed protein supplements along with moderate quality forages has been hypothesized to be related to increased postruminal flow of amino acids. The objective of this study was to evaluate protein supplementation for calves of two growth potentials grazing irrigated pastures in the fall after weaning. A 3-yr study (1990 to 1992) was conducted to evaluate supplemental protein for steers (average weight 471 lbs) of high or moderate genetic potential for growth in the fall after weaning. Each year 22 or 23 steers grazed pastures of a russian wildrye-wheatgrass complex for about 80 days. One-half of the steers were individually fed soybean meal (1 lb/d) 5 d/wk in 1990 and 7 d/wk in 1991 and 1992. Dietary CP averaged 13.2, 12.6, and 10.6 in mid-October and 8.8, 12.3, and 6.0% in mid-December of 1990, 1991, and 1992, respectively. Weight gains of non-supplemented steers were 1.1 lb/d and increased by 0.4 lb/d through the addition of a protein supplement. Cattle of both high and moderate growth potential responded similarly to added protein. Forage requirements can be determined based upon body weight, being an equal percentage of body weight for steers of high or moderate growth potential.

Technical Abstract: A 3-yr study (1990 to 1992) was conducted to evaluate the effects of supplemental protein on steers (average weight 471 lbs) of high (Charolais-sired) or moderate (Hereford-sired) genetic potential for growth. Each year 22 or 23 steers grazed pastures of a russian wildrye-wheatgrass complex. One-half of the steers were individually fed soybean meal (1 lb/d) 5 d/wk in 1990 and 7 d/wk in 1991 & 1992. Dietary CP averaged 15.1, 14.8, and 12.6 in mid-October and 10.5, 14.5, and 7.0% of OM in mid-December of 1990, 1991, and 1992, respectively. Steers of high genetic potential for growth gained 1.4 lb/d compared to 1.2 lb/d for steers of moderate potential for growth (P < 0.05) and protein supplemented steers gained 1.5 compared to 1.1 lb/d for non-supplemented steers (P < 0.01). There were also differences in rate of gain among years. Steers gained only 1.1 lb/d in 1990 compared to 1.5 and 1.4 lb/d in 1991 and 1992. Forage intake was affected by year (P < 0.01) and genetic potential for growth (P < 0.05) and averaged 8.8, 9.5, and 7.5 lb/d for 1990, 1991, and 1992, respectively and 9.0 and 8.1 lb/d for steers having high and moderate genetic potential for growth. Protein supplementation was cost effective for steers grazing irrigated pasture in the fall.