PSXI-7 Comparison of Range-Based and Irrigated Cow-Calf Systems – Grazing Season Performance

Abstract

Abstract The objectives were to compare 1) cow performance, 2) cow fertility, and 3) calf performance in a range-based (RAN) or irrigated (IRR) system over 4 yr. Crossbred beef cows were assigned by age, BW, BCS (1 - emaciated to 9 - obese) and productivity to IRR or RAN. Cows in IRR (n = 170/yr) grazed irrigated cool season perennial pastures (May–October) then grazed crop residues (October-December). Cows in RAN (n = 160/yr) grazed sagebrush steppe range (May–December). Cows were provided hay and supplement (January-mid-March) to achieve BCS 5 by calving. Cows were artificially inseminated (AI). AI sires were distributed across IRR and RAN. Natural service bulls were introduced 8 to 14 d after AI. Cow BW and BCS were recorded at branding (April), pregnancy diagnosis, and end of grazing (December). Pregnancy was diagnosed at 60, 100, and 120 d after AI. Calves were weighed at birth, July, August and weaning (September). Data were analyzed using mixed models with main effect of system. Year (n = 4) was the experimental unit. Cows from the IRR (n = 674) and RAN (n = 638) had similar (P = 0.13) BW at branding but RAN BCS was 0.4 BCS less (P < 0.05). At end of grazing, IRR cows were 96 kg heavier (P < 0.001) and 1.8 BCS greater (P < 0.001) than RAN cows. System did not affect calf birth weight (P = 0.30); however, IRR calves were 20.7 kg heavier (P < 0.003) than RAN calves at weaning. Pregnancy rate was similar (P = 0.64) for IRR and RAN cows (94.7% and 93.6%, respectively). RAN resulted in reduced calf weights and returns per cow (- $60.50) compared to the IRR. In conclusion, producers using sagebrush steppe range will need to operate at a lower cost per cow than irrigated ranches.