The health and performance of the grazing animal in relation to fertilizer nitrogen usage. I. Calves

An experiment was carried out in 1961 and 1962 to test the effect of the application of high levels of fertilizer N to S 23 ryegrass swards on the health and performance of grazing calves. A uniform application of 47 kg. P and 75 kg. K/ha. was used in each year. Nitro-chalk was applied at monthly intervals from February to September, at rates equivalent to 22.4 kg. (Nl) and 112 kg. (N3) per hectare in 1961; in 1962 an intermediate rate (N2) of 67.2 kg./ha./month was also used. The total quantities of N applied per hectare in 1961 were 185 and 1042 kg. and in 1962, 192, 576 and 961 kg. 2. Male calves, 2-6 months old when introduced to the experiment, grazed in rotation round a series of four paddocks on each treatment. In 1961 Friesian, Aberdeen Angus cross and Shorthorn twin calves were used; in 1962 all the calves were unrelated Friesians.