The Effect of Nitrogen, Stocking Rate and Frequency of Grazing by Beef Cattle on the Output of Pasture

Abstract

Two successive grazing experiments were conducted over 12 weeks on perennial ryegrass pastures with 50 and 44 young cattle to study the effect of N fertilizer when applied at a daily rate of 1 or 3 kg N/ha. At each level of N two stocking rates differing hy 20% were imposed. At the liigher N level and stocking rate, three frequencies of grazing were imposed.At the stocking rates imposed N tended to reduce the daily liveweight gain per head, hut increased the total liveweight gain per ha hy from 0-79 to 1-58 kg/kg N. A 20% increase in stocking rate depressed gain per head in hoth years. In the first year it did not improve gain/ha, hut in the second year gain/ha was increased hy 12-17%.There was a tendency for performance per animal and per ha to increase as the grazing cycle was lengthened. In 1969 the highest yield in the whole season was 1880 grazing days and 1260 kg gain/ha. The overall response to N fertilizer was similar to that recorded in other reports, hut it is possihle that a lack of K had limited pasture growth.

The Effect of Nitrogen and Stocking Rate on the Output of Pasture Grazed by Beef Cattle

“…The results in Table 4 show that in the first 12 weeks of each season there was a response of about 1-3 kg gain/kg N, declining to 1-14 and 0-96, respectively, for the 20-week periods of 1970 and 1971. The corresponding values for ME ranged from 27 to 20 Mcal/kg N and in terms of DM from 10-4 to 7-7 kg/kg N. These values are slightly higher than those reported by Escuder et ai (8), but in terms of DM they are about 10% lower than those reported by Reid (15) in cutting experiments over the same range of fertilizer N. In terms of liveweight gain/kg N they exceed the values reported by Tayler (6) and Escuder et al (8), but are similar to those reported by Browne (4,5). They suggest that a response of at least 1 kg gain/kg N applied can be expected from N applications up to 300 kg/ha.…”

“…They are shown for the first 12 weeks in each year, to facilitate comparison with Escuder et al (8), and also for the full 20-week experimental period. In each year further grazing amounted to 100-200 grazing days and 1000-2000 Meal, ME/ha were obtained in the late autumn grazing.…”

“…The soil was heavy Gault clay with adequate reserves of P and K. The treatments are shown in Table 1. The stocking rates were chosen so that NQH compared with N^ in the experiment reported by Escuder et al (8); N, was established at 80% of NoH. Treatment Nj was imposed at the same level as NQH and at three higher levels equivalent to 120, 140 and 160% of the lower level.…”

“…It was considered that these low responses were possibly associated with the high levels of N applied, or with a marginal deficiency of K in the soil. It was accordingly decided to conduct further experiments comparing somewhat lower levels of fertilizer N. Although Escuder et al (8) found •Present address: Department of Agriculture, Nicosia, Cyprus. that a 6-week rotational grazing cycle was marginally superior to one of 4 weeks, it was decided, for simplicity of operation to adopt a 4-week cycle throughout.…”

The Effect of Nitrogen Application to Pasture on Beef Production

“…The smaller liveweight gains made by the bullocks in the last third of the grazing season (Fig. 1) is a feature also noted by Browne and Walshe (8), Escuder et al (11), and Yiakoumettis and Holmes (22). This efFect could be due to a combination of declining digestibihty, increased faecal contami- nation of herbage and change in body condition of the animals.…”