Allocating forage to fall-calving cow-calf pairs strip-grazing stockpiled tall fescue

¹ Division of Plant Sciences, University of Missouri, Columbia, 65211

^* To whom correspondence should be addressed. E-mail: kallenbachr{at}missouri.edu.

	Abstract

In a 2-yr study, we evaluated the impact of different forage allocations on the performance of lactating beef cows and their calves grazing stockpiled tall fescue. Allocations of stockpiled tall fescue at 2.25, 3.00, 3.75, and 4.50% of cow-calf pair BW/d were set as experimental treatments. Conventional hay-feeding was also evaluated as a comparison to grazing stockpiled tall fescue. The experiment had a randomized complete block design with 3 replications and was divided into 3 phases each year. From early December to late February (Phase 1) of each year, cows and calves grazed stockpiled tall fescue or were fed hay in the treatments described above. Immediately following Phase 1, cows and calves were commingled and managed as a single group until weaning in April (Phase 2) so residual effects could be documented. Residual effects on cows were measured after calves were weaned in April until mid-July (Phase 3). During Phase 1 of both years, apparent DMI of cow-calf pairs allocated stockpiled tall fescue at 4.50% of BW/d was 31% greater (P < 0.01) than those allocated 2.25% of BW/d. As allocation of stockpiled tall fescue increased from 2.25% to 4.50% of cow-calf BW/d, pasture utilization fell (P < 0.01) from 84 ± 7% to 59 ± 7%. During Phase 1 of both years, cow BW losses increased linearly (P < 0.02) as forage allocations decreased, although the losses in yr 1 were almost double (P < 0.01) those in yr 2. During Phases 2 and 3, few differences were noted across treatment groups, such that by the end of Phase 3, cow BW in all treatments did not differ either year (P > 0.40). Calf ADG in Phase 1 increased linearly (P < 0.01) with forage allocation (y = 0.063x + 0.513; R² = 0.91). However, calf gain/ha decreased linearly (P < 0.01) as stockpiled tall fescue allocations increased (y = -26.5x + 212; R² = 0.97) such that gain/ha for cow-calf pairs allocated stockpiled tall fescue at 4.50% BW/d was nearly 40% less (P < 0.01) than for those allocated 2.25% of BW/d. Allocating cow-calf pairs stockpiled tall fescue at 2.25% of BW/d likely optimizes use, because cow body condition is easily regained in the subsequent spring and summer months, less forage is used during winter and calf gain/ha is maximized.

Key Words: fall-calving, forage allocation, stockpiled tall fescue