Graduate Thesis Or Dissertation
 

Forage intake and related performance criteria of spring and fall calving cow-calf pairs on summer range

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  • Three studies during three consecutive summers were conducted at the Squaw Butte Experiment Station to estimate relative and quantitative forage intake of spring and fall calving cow-calf pairs on summer range. In a drylot study (experiment 1) individual animal consumption of fescue or meadow hay cut at 2- to 10-day intervals from May 16 to August 22 was determined for 6 spring and 6 fall cow-calf pairs. Spring cows consumed more hay than did fall cows (10. 72 vs. 10.00 kg/day; P = 0.08) and produced more milk (3.73 vs. 2.13 kg /day between June 4 and July 8; P < 0,01). Fall calves consumed more hay than did spring calves (3.48 vs. 1.28 kg/day; P < 0.01), had greater total weight gains (68.2 vs. 50.2 kg; P = 0.05), and required less total feed invested (cow + calf) per unit of gain (20. 16 vs. 24.38 kg feed/kg gain; P = 0.20), Fall pair intake exceeded that for spring (13.48 vs. 12.00 kg/day; P < 0.01), and total feed required per unit of total animal (cow + calf) gain favored the fall treatment (11.66 vs. 14.42 kg feed/kg gain for spring; P = 0.23). Intake estimates for fall pairs (6) on pasture expressed as a percent above spring pair (6) intake (as determined by clipping plots before and after grazing for four, 5- to 10-day periods between May 10 and August 28) were 6, 19, 22, and 24% in May, June, July, and August, respectively (experiment 2)._ Fall cows gained more (85.9 vs. 68.4 kg; P = 0. 13) and produced less milk (1.78 vs. 4.34 kg/day; P < 0.01) than did spring cows. Calf gains between treatments were not different. Measuring individual intake by cows and calves (six pairs per treatment) on pasture using total fecal collection (six, 5-day trials between April 29 and August 30; experiment 3) resulted in higher mean forage intakes for spring cows (11.98 vs. 10.90 kg/day; P = 0.02), higher fall calf intake (4.25 vs. 0.94 kg/day; P < 0.01), and higher fall pair intake (15.19 vs. 12.89 kg/day; P < 0.01) relative to opposing treatments. Fall calves gained more than did spring calves (118.5 vs. 89.8 kg; P < 0.01), and fall cows gained more than did spring cows (116.4 vs. 75.8 kg; P < 0.01) while producing less milk (2.47 vs. 5.24 kg/day; P < 0.01). Fall pair intake, as a percent above spring intake, increased linearly (Y = 1.074X + 5.257, where X = week number beginning May 1) from May through August. Quantitative differences in intake also increased linearly at approximately 0.077 kg/week on pasture from an early May difference of 1.63 kg. Adjustments to account for an early fall calf weaning on July 20 or May 1 gave estimates of fall cow or cow-calf range forage intake, relative to spring, of 100% and 72%, respectively. Relative differences in intake of the two cow groups were comparable in all three studies.
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