Submitted to: Research Update for Fort Keogh Livestock and Range Research Laboratory
Publication Type: Other
Publication Acceptance Date: 9/1/1997
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: A study was conducted to evaluate the effect of sire growth potential, age, and cow size on intake, growth, and production efficiency in grazing cattle. Data were collected on 24 cow-calf pairs during each of four summers (1989-1992) and on twelve 7-mo-old and 12 yearling steers during three summers (1990-1992). Steers were sired by either high- (Charolais with high EPD for yearling weight) or moderate-growth potential (Line 1 Hereford with average yearling weight ratios) bulls. Forage, but not milk, OMI by suckling calves was influenced (P<.05) by sire growth potential. Milk OM intake decreased from 1029 g/d (10.1 g/kg BW) in June to 696 g/d (3.3 g/ kg BW) in September, while forage OM intake increased from 394 g/d (4.2 g/kg BW) in June to 2311 g/d (10.3 g/kg BW) in September. Older, high growth potential steers tended to consume more OM than moderate growth potential steers (P<.10) when expressed as kg/d but not when expressed as g/kg BW (P>.10). Seven-mo-old steers ate less (P<.01) forage (4.3 kg/d) than yearlings (5.6 kg/d) when expressed as kg/d, but more (P<.01) when expressed as g/kg BW (7-mo-old, 15.9 vs yearling, 14.4 g/kg BW). Cow OM intake was affected by cow size and milk production but not calf growth potential. Milk production but not cow size was a significant covariate for cow efficiency (g calf BW gain/kg forage OMI by cow-calf pair). Calf sire growth potential did not affect cow efficiency. We conclude that growth potential of sire for suckling calves and steers and cow size for cows affected intake of rangeland forage in summer, but did not affect efficiency of production from Northern Great Plains rangelands. The greatest influence on efficiency of cow-calf production was milk production by the cow.