The Effects of Level of Nitrogen Fertilizer on Beef Production From Grazed Perennial–ryegrass/White–clover Pastures

Abstract

The treatments in this summer-grazing experiment were designed as a 2 x 3 factorial, there being two levels of nitrogenous fertilizer (nitro-chalk), supplying 0 and 336 kg of N/ha per annum (NO and N3, respectively) and three stocking rates. The fertilizer was applied in 7 dressings at approximately three-weekly intervals. The animals used were Hereford x Friesian steers; these were slaughtered at the end of the grazing season. The stocking rates were calculated on the basis of expected herbage production. The experiment was laid out in 6 randomized blocks which were grazed in rotation. Two blocks were cut for conservation before grazing each year; up to the end of June only 4 blocks were used for grazing. There was little contamination of the swards with unsown species. With the NO swards the clover contents declined each year, but remained fairly high at over 20% in 1965. Clover contents also declined each year in the N3 swards and by 1965 were only 2 to 4%. The quantities of herbage cut for conservation were higher from the swards receiving N. The live-weight gains of the cattle (per head) were higher at the lower stocking rates, the effect of stocking rate being more noticeable in the July to Oct. period. Live-weight gains per ha increased at the higher stocking rates. In 1963 and 1965, as stocking rates increased carcass weights per animal decreased and carcass quality, as indicated by the commercial grades, was poorer. In 1964, a dry spell from July to Oct. necessitated the removal of cattle from the experiment and the effects of treatment on carcass weight and quality were not apparent.

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

“…The estimated digestibilities were identical in 1971 and 1972 and agreed closely with those estimated by Leaver et al (10), by Yiakoumettis and Holmes (13) and by Alder et al (3).…”

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

“…The results for 1970 which show no difference in gain/head between treatments in weeks 1-^ confirm this view, while the results from weeks 7-12 in the same year show the more normal decline in gain with increased stocking rate which has been demonstrated by Alder, Cowlishaw, Newton and Chambers (3,4) and by Cowlishaw (5).…”

“…These results accord with the conclusions of Mott (14) if it is considered that in 1969 grazing pressure at both levels exceeded the optimum, while in 1970 the two stocking rates imposed were approximately just above and just below the optimum. The results for 1970 which show no difference in gain/head between treatments in weeks 1-^ confirm this view, while the results from weeks 7-12 in the same year show the more normal decline in gain with increased stocking rate which has been demonstrated by Alder, Cowlishaw, Newton and Chambers (3,4) and by Cowlishaw (5).…”

“…Clover developed well in the N^ swards and was not eliminated from the N3 swards. The level of performance of Nj for the whole 1969 season, 1080 grazing days, 1084 kg liveweight gain and 14030 Meal ME/ha was high, exceeding the values previously obtained at this centre (6) and by Alder et al (4). The N responses were therefore calculated above high control values.…”

The Relationship Between Intensity of Grazing and the Herbage Consumption and Growth of Calves

“…calves in their first grazing season (8,20) and from older cattle (3,4). The poor growth of young grazing calves has not been fully explained, but may well be a result of a relatively low level of herbage intake associated with a developing pattern of grazing behaviour (9,16).…”