ESTIMATING THE SOIL CONTENT OF HERBAGE COLLECTED BY FORAGE HARVESTER

A method is described Tor estimating the amount of contamination by soil caused when herbage is collected with a forage harvester. Hand-cut samples of herbage are used as a control. To avoid sub-sampling errors a relatively large sample is used. It is oven-dried and then compressed to facilitate ashing. Acid-insoluble ash ("silica") content is used as a measure of contamination. The Statistical examination of the data is discussed briefly.     

THE USE OF SHEEP FITTED WITH OBSOPHAGEAL FISTULAE IN GRAZING STUDIES

Studies were carried out on the effects of diurnal variation, fasting before sampling, and acclimatization to a sward on the chemical composition and in vitro OM digestibility of samples of extrusa collected from sheep fitted with oesophageal fistulae. The N content of extrusa samples increased markedly during the morning, and tended to decline again in the evening. The diurnal changes in digestibility were similar, but the variation was much smaller. There was no significant correlation between either N content or OM digestibility and grazing speed measured in bites per minute. There were no significant changes in either the N content or OM digestibility of successive samples of extrusa collected after over-night fasting, or after the sheep were introduced to a sward to which they were not accustomed, though the concentration of ash in the extrusa was significantly lower when the sheep were hungry than when they were not. The OM digestibility of the diet selected was approximately two units lower on the first two days after introduction to a new sward than the mean value of samples collected over the next 12 days.     

THE USE OF RUMEN-FISTULATED STEERS IN THE DIRECT DETERMINATION OF NUTRITIVE VALUE OF INGESTED HERBAGE IN GRAZING EXPERIMENTS

A rumen-fistulated steer was used for the manual collection of samples of freshly swallowed herbage, in a grazing-management experiment on a perennial ryegrass sward. Diurnal and seasonal changes in the in vitro digestibility of the herbage selected by the grazing animal were studied under both strip- and continuous-grazing methods of management.
There was no appreciable change in digestibility as the sward was grazed down from upper to lower layers under strip-grazing management in April and May. In June to October a within-day fall in digestibility was found, much of which was attributable to an increase in the amount of old dead herbage grazed from the lower regions of the sward. Dead herbage taken in by the grazing steer was considerably lower in digestibility in August than in May. The in vitro digestibility of herbage samples, cut to ground level before and after grazing in a strip-grazed treatment, fell markedly as the proportion of dead herbage in the sample increased, giving a high negative correlation.
In a continuous-grazing management there was no pattern of diurnal variation, and the seasonal variation in digestibility of the ingested herbage was less than in strip grazing. The implications of these results are discussed in relation to indirect methods of digestibility determination (faecal-index technique), the measurement of herbage intake, and to some aspects of grazing management.     

THE PRODUCTION AND USE OF COCKSFOOT FOGGAGE FOR WINTER GRAZING IN SOUTH-WEST SCOTLAND

The production and use of cocksfoot foggage for winter grazing at the Hannah Dairy Research Institute in the period 1956–61 is described. Two acres of cocksfoot (S37) were sown broadcast in 1956 and two acres were drilled in rows 28 in apart in 1957. The average annual application of fertilizer nutrients was 118 lb. N, 51 1b. P2O5 and 142 lb. K2O per acre.
The mean yield of the broadcast section was 7450 lb. dry matter/acre/annum compared with 6090 lb. from the rowcrop section. Normally two crops of grass were harvested from the field in the summer, and one grazing was made in the winter. The yield of winter herbage dry matter was 28% and 26% of the total annual yield of the broadcast and the rowcrop sections, respectively.
The field was grazed for four successive winters by 5–10 bulling heifers each weighing 650–850 lb. They received no other feed during the grazing period. Grazing started in December and finished in February, March or April in different years. The mean intake of herbage dry matter was only 6 lb./day, and on average the heifers lost 80 lb. liveweight each winter. This loss was regained after 4–6 weeks when the winter grazing finished. Twenty-nine of the 30 heifers held to the first or second service while grazing the winter herbage.
On average the broadcast section gave 340 heifer-grazing-days per acre during the winter and the rowcrop section 260 days. The cost of a heifer-grazing-day was 3id. and 4id. on the broadcast and rowcrop sections, respectively.
The dry matter of the herbage cut on 19 December 1960 had a digestible crude protein content of 59% and a starch equivalent of 34.
It is concluded that on well-drained land the technique of foggage production and of winter grazing can usefully extend the normal grazing season and hence reduce the costs of winter feeding.     

THE USE OF GRAZING CONTROL FOR INTENSIVE FAT-LAMB PRODUCTION

A comparison of 3 systems of creep grazing, at a stocking rate of 6 ewes and 12 lambs per acre, indicated that lambs on a set-stocking management with a lateral creep area grew at a significantly ( P < 0·05) slower rate than lambs folded with a lateral creep area or those rotationally grazed with a forward creep area. A similar difference was apparent in the ability of the managements to maintain the ewes liveweights. However, it is suggested that these results were not the direct outcome of the applied treatments per se . Parasite burdens in the lambs were low on all the treatments and there were no significant differences between them.     

THE USE OF GRAZING CONTROL FOR INTENSIVE FAT-LAMB PRODUCTION

The effects of three stocking rates on fat-lamb production were examined. These stocking rates were imposed upon four grazing systems. The grazing managements had no significant¹ effects upon the rate of liveweight gain or the total liveweight of lamb produced per acre, nor were the ewes' liveweights significantly affected. Reasons are suggested. The lambs' rate of liveweight gain was related negatively and the total liveweight of lamb produced per acre was related positively to stocking rate. The ewes' liveweights were similarly affected, there being the highest losses of liveweight under the high stocking rate. In all cases significant differences existed between the stocking rates and there was a significant linear relationship between them. It is concluded that high stocking rates are essential to obtain the maximum fat-lamb production on a 'per acre' basis.     

THE USE OF GRAZING CONTROL FOR INTENSIVE FAT-LAMB PRODUCTION

Three grazing managements (set stocking, 4-paddock rotation, 8-paddock rotation), each with an undivided lateral creep area, were studied. Each of these managements carried 2 stocking rates (6 ewes and twin lambs per acre, 10 ewes and twin iambs per acre) and the sub-divided managements were grazed at 2 severities of grazing.
Stocking rate had a major effect upon the lambs' liveweights but did not significantly affect the ewes' liveweights. Lambs on set-stocking managements had a significantly higher rate of liveweiglit gain than lambs on managements with sub-divided ewe areas. Under lax grazing, for much of the experimental period, the lambs had a significantly higher rate of liveweight gain and the ewes had significantly higher liveweights than under severe grazing.     

THE EFFECT OF THE BIPYRIDYL HERBICIDES ON HILL COMMUNITIES AND THEIR ROLE IN THE IMPROVEMENT OF HILL GRAZING

The improvement of hill land is important to the national economy of the United Kingdom. An increase in the amount of enclosed productive land results in a greater stock-carrying capacity of a hill farm. Improvement is not always possible by conventional implements, and herbicides are being used to kill the old sward. The bipyridyl herbicides offer a means of destroying or modifying the indigenous vegetation. The application of low doses of paraquat or diquat to an association containing Molinia caerulea, Nardus sfricta and Festuca avina resulted in a change in equilibrium in favour of the fescues. The application of 2 lb paraquat per acre practically eliminates all grass species in a sward and it is then possible to establish desirable pasture species after lightly cultivating the dead surface litter.     

THE PATTERN OF GRAZING IN 'CONTINUOUSLY' GRAZED SWARDS

The frequency and severity of defoliation of small sample areas, 8 × 8 cm, was studied in swards of S37 cocksfoot which were maintained at different levels of leaf-area index by continuous grazing with lambs. By varying the number of lambs grazing a plot, the LAI was maintained at three approximately constant levels, 5.3 (H), 4.1 (M), and 3.0 (L). Any one 8 × 8 cm area was grazed on average once every 36 days in treatment H, 24 days in treatment M and 19 days in treatment L. Approximately 24% of the total length of leaf present per tiller was removed each time a tiller was grazed, under all treatments. The lambs tended to graze patches of herbage about 16 × 16 cm, then move to a different place in the sward. These results are discussed in relation to grazing practices aimed at securing the maximum harvested yield.     

REMOVAL OF THE EFFECTS OF UNEVEN GRAZING IN PASTURE EXPERIMENTS

An experiment is described in which uneven grazing by sheep introduced a bias in a white clover variety trial. The data were adjusted by covariance, using as the independent variable the position of the plots within the paddocks.
Attention is drawn to the errors that may result from uneven grazing and a comparison is made with errors due to transference of fertility. Means of avoiding similar occurrences are suggested.     

FORAGE CONSERVATION IN THE TROPICS*

Under arid tropical conditions the natural grazing provides less than maintenance requirements for 8–9 months of the year. Conservation of natural or sown herbage, either as hay or silage, should be discouraged because of the low nutritive value of the product, and the unfavourable weather usually prevailing during conservation. Of the forage crops, cereal/legume mixtures are the most suitable for ensilage.     

NEW OPPORTUNITIES IN THE ESTABLISHMENT OF GRASS AND FORAGE CROPS*

In the management of British grassland lay there appears to be a marked divergence between the policies advocated by grassland science and general grassland practice. While science places emphasis on monocultures of sown species (mainly perennial ryegrass), heavily fertilized and intensively stocked, grassland farmers for the most part rely on lonstablished or indigenous swards composed of a variety of species and receiving modest applications of fertilizer. Since the gap between the two approaches is both substantial and of long duration the subject appears to be worth fresh attention. The purpose of this paper is to examine the current situation in relation to improvement in botanical composition and to suggest new approaches to that end.     

A TWO-STAGE TECHNIQUE FOR THE IN VITRO DIGESTION OF FORAGE CROPS

A simple technique for the determination in vitro of the dry- or organic-matter digestibility of small (0·5 g) samples of dried forages is described. It involves incubation first with rumen liquor and then with acid pepsin. Using 146 samples of grass, clover and lucerne of known in vivo digestibility ( Y ), the regression equation Y = 0·99 X– 1·01 (S.E. ± 2·31) has been calculated, where X = in vitro dry-matter digestibility. This technique has been used for the study of the digestibilities of plant breeder's material, of the leaf and stem fractions of herbage and of herbage consumed by animals.     

THE INFLUENCE OF NIGHT GRAZING ON THE GROWTH RATES OF ZEBU CATTLE IN EAST AFRICA

Results are reported from a 10-month trial, using 50 oxen, in which growth rates of groups receiving restricted and normal night grazing were compared. The resiriction of night grazing was found to lead to a significant decline of 30% in live-weight gain. This difference was largely attributed to periods of moderate grass shortage (i.e. marginal day grazing) when those animals with the longer grazing period were able to select a diet of superior quality and quantity. Under good, or very bad, grazing conditions the availability of night grazing did not appear to be critical.     

THE SPECIES PREFERENCES OF GRAZING HORSES

Palatability studies of 29 species of grasses, legumes and herbs, and two seeds mixtures, were conducted using three replicates of each species. Crossbred ponies and a few Thoroughbreds were obserred and timed for a total of 260 hours grazing. The results were analysed and sbowed small statistical differences between replicates, between tbe 2 years observed and between horses; and highly significant differences (P<0.001) between certain species. The most palatable was a clover-rich mixture. Tbe pasture varieties of perennial ryegrass were significantly more palatable tban S24, and as palatable as timothy and cocksfoot Alta tall fescue, crested dogs tail and wild white clover were palatable. Some herbs, red clover, brown top, red fescue and meadow foxtail were tbe least palatable. Dandelion, ribgrass and yarrow were palatable herbs.     

THE USE OF GRAZING-ANIMAL OBSERVATIONS IN THE EARLY STAGES OF PASTURE EVALUATION IN THE TROPICS

An observational technique for measuring pasture palatability is described in which a palatability index is constructed to indicate the species selected by stock under specified conditions of choice. The index differentiates these species from others that stock are prepared to eat when opportunities for selection are more limited. The potential usefulness of this index in the initial testing of tropical pasture species is discussed.
Results are reported from two 3-year experiments where the method was used. Coefficients of variationin individualgrazingsranged from 13·5 to 22·2% with experimental meansof 19·2 and 18·3%. Hyparrhenia rufa and Cenchrus ciliaris were found to be the m6st consistently palatable of the grasses offered.     

THE USE OF GRAZING-ANIMAL OBSERVATIONS IN THE EARLY STAGES OF PASTURE EVALUATION IN THE TROPICS

The use of grazing-time records for the estimation of grass species consumption was investigated in the context of two small-plot grazing trials. It was found that sampling errors were significantly lower than those involved in the cutting techniques used and that a high level of repeatability of results could be obtained.
The overall correlations between fresh-weight yield estimates from sample cuts and grazing records for individual plots were found to be 0·57*** and 0·72*** in the two trials. The bias that was introduced into some of the estimates of species yield appeared to be corrected through the use of palatability data.
It is concluded that the use of grazing-time records for yield estimation amongst species of broadly similar growth habit may have a definite potential in tropical Africa, but that the method requires further testing before being widely adopted.     

THE USE OF THE IN VITRO TECHNIQUE IN THE DETERMINATION OF THE DIGESTIBILITY OF GRASS/LEGUME MIXTURES

The in vitro dry-matter digestibility was determined of two samples of Digitaria decumbens , one sample of Medicago sativa , and one sample of Trifolium repens and nine mixtures prepared from these samples.
When the results were compared with in vivo digestibilities the standard errors of the regressions for the three combinations of legume, grass and legume/grass mixtures were ±0.6, ±0.6 and ±1.5 percentage units, respectively.
It is considered that in vivo digestibility of mixtures of grasses and legumes can be estimated by the in vitro technique, provided that suitable grass and legume standards are included.