Observations on the calcium intake and serum calcium status of grazing ewes during drought

Abstract

The calcium intakes of two flocks of dry Merino ewes grazing a Phalaris tuberosa-white clover pasture stocked at 3 and 15 sheep per acre and a third flock grazing a native pasture stocked at 1.5 sheep per acre, were estimated from December 1964 to July 1965. The calcium content of the diet was highest on the improved pasture stocked at 15 sheep per acre and ranged from 0.84 to 1.67 per cent of the organic matter. The corresponding range for the other flocks was from 0.24 to 0.96 per cent calcium. Calcium intakes were highest on the heavily stocked pastures. Daily calcium intake on all pastures ranged from 2.8 to 13.5 g. Serum calcium values of 170 sheep stocked at varying rates on different pastures and receiving varying amounts of wheat were determined after 21 months of drought. Nine sheep had serum calcium values less than 8.0 mg per 100 ml serum, but no clinical signs of calcium deficiency were observed. It was concluded that sheep would not be deficient in calcium while they had access to paddock roughage but that hypocalcaemia would occur in sheep run at very high stocking rates and supplemented with wheat without limestone for prolonged periods.