The production of fattening cattle and extension of autumn grazing following three rates of application of nitrogenous fertilizer to a rye-grass/white clover sward

Abstract

Few experiments on the effect on animal production of varying levels of nitrogenous fertilizer applied to pasture have been reported. Such information is necessary to supplement data derived from small-plot trials. There are several factors in fertilizer usage which the presence of the grazing animal must affect. First, the re-circulation of nitrogen and other elements through dung and urine will add considerably to those applied as fertilizer. Watkin (1954) and Wolton (1955) have shown in this country how important these effects can be. Secondly, biting, treading, palatability and degree of utilization will affect total production of the fertilized swards as well as their rate of botanical change. A third factor is that in any closed grazing area with a fixed stocking rate, a rise or fall in rate of herbage growth has a strong cumulative effect, normally met by the conservation of excess herbage, since adjustment of stock numbers on the farm as a whole can only infrequently be made. Conservation therefore has an influence on total output. Last, but not the least important, is the influence on the grazing animal of herbage varying widely in its chemical composition as a result of the application of nitrogen fertilizer. The attainment of alevel of production per head equal to that from an untreated sward should allay doubts that fertilized herbage is nutritionally less satisfactory, at least in respect of fattening animals which are less sensitive to imbalance of elements than lactating and pregnant stock.With these points in mind, an animal production experiment was carried out at The Grassland Research Institute in 1955 and 1956 to study three rates of application to pasture of a nitrogenous fertilizer. Fattening steers were used to study rates of live-weight gain and carcass production. More fertilizer was applied in late than in early summer in order to obtain a more uniform growth of herbage and to extend the autumn grazing season. METHODSivard and layout. The experiment was conducted on a perennial rye-grass/white clover sward in its fourth and fifth harvest years on afree-draining loam soil overlying Upper Chalk. The seed mixture, sown in 1951, had formed a sward in which S.24 and S.23 rye-grass with white clover predominated; of the other legumes included at sowing only a few plants of lucerne remained.Four blocks, totalling 15 acres, were each permanently divided into four plots of 0-94 acre. Four treatments were allocated at random in each block.Treatments and stock.

The Effect of Nitrogen Application to Pasture on Beef Production

“…Grazing trials on N rates with beef cattle have been reported from Ireland (6,7,8,15,17), southern England (2, 3, II, 18,22) and eastern Scotland (12), and with tbe results recorded here they provide data from 17 different trials and 47 trials x years, over the period 1953 to 1971. There were considerable differences in the number and level of N rates used and in type of stock used.…”

“…The smaller weight gains of the bullocks grazed on high-N pasture compared with those on low-N pasture could have resulted from poorer nutritive value of the grass; from a higher stocking rate relative to the available feed; from an increased faecal contamination of the grass; or from a combination of these factors. While there are several American grazing experiments showing better hveweight gains of cattle from legume pastures than from grassy pastures fertilized with N (4), the results of other British and Irish grazing trials show no clear difference (2,3,6,7,8,II,15,17,18,22). It is difficult to compare the nutritive value of two pastures in grazing trials when expected differences are small, because of the problem of keeping other factors equal.…”

“…The series of experiments was started in 1955 at a time when little information was available on the response in beef production to N application in the grazing situation. Since then, results from 12 experiments in the UK and Ireland (2,3,6,7,8,11,12,15,17,18,22) have been published and these, together with the 5 reported here, have been used to derive regressions of liveweight gain response and profit on rate of N applied. EXPERIMENTAL Five grazing experiments were made during the period 1955 to 1967 on the Edinburgh School of Agriculture farms, 180 m above sea level.…”

Nitrogenous Fertilizer and Seasonal Production*

“…Out-of-season grass, on the other hand, may enable a product to earn a relatively high price, e.g. early spring milk or late autumn beef (14). Also, it would be difficult to overrate the value of a continuous adequate supply of pasture in mid-season.…”

The Effect of White Clover and Nitrogenous Fertilizer on the Production of a Sward

“…In this country most of the evidence presented has been obtained from eut swards. Some data have been obtained where the influence of the animal has been included (20), and Tayler and Rudman (16) discussed experiments where animal output at various levels of N was measured.…”