The impact of long-term precipitation trends on animal performance on the Santa Rita Experimental Rang

Beef production in the arid Southwest depends on range forages. Forage quality and quantity primarily results from amount, intensity and timing of precipitation. Twenty-three years (1978--2000) of precipitation and animal production data were evaluated. Two major questions addressed were: Does rainfall timing affect number and weight of calves weaned? Does grazing system reduce immediate drought impact on calf production? Three grazing systems were evaluated: Year-round grazing, Savory rotational grazing and Santa Rita rotational grazing (50--60hd, 80--150hd and 50--65hd/year respectively). Winter (P < 0.05), summer (P < 0.01) and previous fall (P < 0.01) precipitation affected calf crop. Only summer precipitation (P < 0.01) had a significant effect on weaning weight. Calf crop did vary between grazing systems (P < 0.01). Savory system had the heaviest weaning weight, total production, and lowest maintenance cost; followed by Santa Rita and year-round respectively (P < 0.01). Maintenance cost per kg calf weaned was similar between rotational systems, but higher in year-round (P < 0.01).