THE EFFECT OF LENGTH OF SILAGE ON ITS VOLUNTARY INTAKE BY CATTLE

Trials are described in which the intake of silage of varying length was determined. The results indicate that a higher voluntary dry-matter intake occurred as the length of the silage became progressively shorter, but this effect appeared to diminish when the silages were supplemented with concentrates. Data from one trial indicate that reducing the length of hay had no effect on voluntary intake when concentrates were fed.     

THE EFFECT OF PRE-WILTING HERBAGE ON THE COMPOSITION OF SILAGE AND ITS INTAKE BY COWS

Lucerne was ensiled at various dry matter contents, within the range of 19·8% to 39·6%. An increase was found in lactic acid production, with a consequent decrease in volatile acid and volatile base content, up to the level of 33·9% dry matter.
The dry matter intake of cows was increased by feeding silage with a high dry matter content.     

THE EFFECT OF INTRAVENOUS INFUSIONS OF METHIONINE ON THE VOLUNTARY INTAKE OF GRASS SILAGE BY SHEEP

The effect of intravenous supplements of L-methionine on the voluntary intake of a ryegrass silage, prepared using formic acid as an additive, was determined in a 4×4 Latin Square experiment with 4 sheep. Animals receiving no methionine consumed 1061 g DM/day; those receiving 0.8, 1.2 and 2.0 g methionine/day consumed 1015, 1012 and 1078 g DM/day. The concentration of methionine in blood plasma (Y; (_imoles/I) increased with the dose rate of methionine infused (X; g/day) such that Y=36.7 + 38.3X (r=0.80; P<0.001). It is concluded that with a diet of this type methionine may be limiting for protein synthesis in the tissues but is not involved in the control of food intake.     

THE EFFECT OF LEVEL OF PROTEIN IN SILAGE ON THE INTAKE AND PRODUCTION OF DAIRY COWS

Two silages of contrasting protein content were compared in a 16-week winter-feeding experiment with 12 Ayrshire cows. One silage contained 8.2% DCP in its DM and the other 15.9% DCP. The silages were fed ad lib . with a supplement of either barley or barley plus groundnut cake. The DM digestibilities of the low and high protein silages were 74 and 67%, respectively, and the calculated S.E.s 56 and 47. Silage and total DM intakes were highest in the treatments containing low protein silage and in those containing groundnut. The mean daily milk yields for the treatments with and without groundnut were 35.4 and 32.s5 Ib (16.1 and 14.8 kg), respectively, with the high-protein silage, and 38.1 and 35.0 Ib (17.3 and 15.9 kg) with the low-protein silage. The S.N.F. contents of the milk were low and averaged 8.26 and 8.34% on the high- and low-protein silage treatments, respectively, and were not affected significantly by the supplements. It is concluded that the low-protein silage was superior to the high-protein silage as a feed for cows, and that the digestibility of the silage DM was a truer indication of quality than protein content.     

THE ESTIMATION OF FEED INTAKE BY SHEEP ON A SILAGE DIET

The results of nineteen digestibility trials with sheep on different silages have been reported. From these data and from the results of forty trials with sheep carried out by Watson (15) it has been shown that Lancaster's method of calculating feed intake (9) can be applied to silages when the crude protein content is within the range studied (9–24% of the dry matter). For silages in this category, no advantage has been found in taking the nitrogen content of the silage dry matter into account in calculating feed intake.
The digestibility of crude protein and Lancaster's'constant'have both been correlated with the crude protein content of the silage dry matter for the fifty-nine trials considered (r = 0.767 and r = 0.452 respectively). Although it has been found unnecessary to take the protein content of silage into account in calculating dry matter intake when feeds containing 9.24% crude protein in the dry matter are used, evidence is presented which indicates that this factor is of considerable importance when herbage of low protein content is fed. The equation, which has been derived from the silage data considered, has been found to be valid when compared with the results of trials with fresh herbage and well preserved hays of low protein content.
The results of this work indicate that Lancaster's method is a suitable one for estimating the feed intake of animals engaged in self feeding of silage, provided the silage has been well preserved.     

THE INTAKE OF HAY AND SILAGE BY COWS

Three comparisons were made, with non-lactating fistulated cows, of the voluntary intake of silage and hay prepared from similar herbage. On average 28% more dry matter was eaten as hay than as silage. Silage and hay had similar digestibilities, but silage residues tended to remain in the gut longer than those of hay. The amount of digesta in the reticulo-rumen immediately after a meal ad lib . was greater with hay than with silage. The cows spent longer eating and ruminating per kg dry matter of silage than of hay. The results are discussed in relation to possible factors determining the voluntary intake of silage.     

THE EFFECT OF FERTILIZER NITROGEN ON SILAGE FERMENTATION

Direct-cut grass which has been heavily fertilized often produces silage with a poor fermentation. An investigation was carried out to study the effect of rate and timing of N applications to herbage intended for direct-cut silage. A small but consistent increase in silage pH was recorded after high levels of N were applied 7–8 weeks before cutting. The application of additional N fertilizer 10–14 days before cutting the sward had an adverse effect on silage fermentation. Changes in herbage composition following different levels of applied N are outlined.     

FACTORS AFFECTING THE VOLUNTARY INTAKE OF SILAGE AND HAY

Experiments with cows and sheep are described in which the voluntary intakes of hay and silage of differing digestibility were determined. The voluntary intake of hay increased consistently with increasing digestibility, but the relationship was not as well defined for silage. The addition of concentrates depressed the intake of hay, and this effect was more marked for hay with a high digestibility than with poorer quality hay. Concentrates appeared to depress the intake of hay by sheep more than by cows, an effect which was again more marked when the hay had a high digestibility value.     

THE EFFECT OF TEMPERATURE IN THE MASS ON THE CHEMICAL COMPOSITION OF SILAGE

The effect of temperature on silage quality was investigated in a series of trials over a period of three years.
The results indicated that when conditions in the silage were favourable for the formation of lactic acid, either through treatment or because of the herbage itself, low temperatures in the mass had no adverse effect on silage quality.
Some results suggest that, with chopped or lacerated silage, low maximum temperatures are associated with better quality silage. The results, however, were not entirely consistent.
There appeared to be little or no advantage in allowing unchopped silage to heat to 100°F.     

THE EFFECT ON FATTENING STEERS OF SUPPLEMENTING SILAGE WITH DRIED GRASS OR ROLLED BARLEY

Eighteen crossbred Aberdeen-Angus and six Shorthorn steers with an average liveweight of 382 kg were given silage (DM content 22.3%) ad lib., supplemented with 0, 1.2, 2.4 and 3.6 kg artificially dried grass, or 1.8 kg rolled barley, per day. A digestibility study carried out on the silage and dried grass showed that the concentration of the metabolizable energy was 52.7 and 45.6 kcal/100 kcal of food, respectively. Live-weight gain increased with each level of supplementation. Supplementation did not significantly affect the intake of silage DM, but differences in the intake of total DM were significant. The killing-out percentages of the steers were similar. The results suggest that dried grass pellets may be a usefid supplement for a silage diet. It was shown that 1.12 kg of dried grass was equivalent to 1.80 kg rolled barley as a supplement for silage.     

THE AD LIBITUM INTAKE AND DIGESTIBILITY OF DRIED GRASS PELLETS AND SILAGE BY SHEEP

Perennial ryegrass was conserved by ensiling, or by dehydration, grinding and pelleting. the two resultant feeds were given ad lib. to wether sheep, either separately or in different proportions. Pellets were consumed in greater quantities than the silage, but were lower in digestibility. There was a rectilinear relationship between the percentage of pellets in the ration consumed and organic-matter digestibility, but a curvilinear relationship between the percentage of pellets and organic-matter intake. Silage intake was little affected by the feeding of pellets until more than 40% of the ration consisted of pellets. The increase in total intake with an increase in pellets above 60% was small, with the result that intake of digestible organic matter was highest when 65% pellets was fed. the results suggest that dried-grass pellets may be a useful supplement for silage rations.     

THE EFFECT OF TYPE OF CONCENTRATE ON MILK PRODUCTION WHEN SILAGE IS THE ONLY ROUGHAGE OFFERED TO COWS

Trials are described in which barley was compared with a concentrate containing barley and groundnut cake, both concentrates being used to supplement silage. An increase in milk yield was obtained when the compound concentrate was given to the cows, which may be attributable to an inadequate supply of protein in the silage/barley ration or to the effect of supplementary protein on silage intake.     

EFFECT OF SOME GREEN-CROP-DRYING PROCESSES ON THE DIGESTIBILITY AND VOLUNTARY INTAKE OF HERBAGE BY SHEEP

The effect of artificial drying under commercial conditions on the digestibility and voluntary intake of herbage by sheep was studied, using either van den Broek (900°C inlet temperature) or Swiss Combi (1100°C inlet temperature) triple-pass drum-type driers. Organic-matter digestibility of chopped dried herbage was 8·3, 5·8 and 5·3% lower than that of fresh herbage in Experiments 1, 2 and 3, respectively. Packaging chopped dried grass into ‘cobs’ caused a further reduction in OM digestibility of up to 2·8%. Pre-milling plus packaging (i.e. ‘pelleting’) depressed OM digesti bility of chopped dried grass by 5 to 6 percentage units. Digestibility of dried grass in its various physical forms was further reduced when offered ad lib.; the greatest fall (9·4%) occurred with pellets and the smallest fall (0·8?1·3%) with loose chopped material; cobs were intermediate at 4·3?7·0%.     

THE ASSESSMENT OF THE NUTRITIVE VALUE OF SILAGE BY DETERMINATION OF IN VITRO DIGESTIBILITY ON HOMOGENATES PREPARED FROM FRESH UNDRIED SILAGE

A report is presented on studies on the relationship between in vitro digestibility of 18 silage samples and their in vivo digestibilities. Various analytical techniques are compared and the method adopted, on grounds of suitability for routine operation and accuracy of prediction of in vivo data, is based on analysis of homogenates of fresh silage. The homogenates, sufficiently uniform to permit of volumetric subsampling at acceptable error levels, are prepared in a new design of homogenizer. The impact of the % dry matter of the silage, as fed, on the accuracy of in vitrol in vivo relationships is considered and a bivariate regression plane is proposed.     

A PORTABLE-CORRAL TECHNIQUE FOR MEASURING THE EFFECT OF GRAZING INTENSITY ON YIELD, QUALITY AND INTAKE OF HERBAGE

A grazing experiment using four stocking rates of sheep, equivalent to 34, 45, 57 and 68 sheep/ha on an assumed 200-day grazing season, was conducted using a portable grazing corral technique. Plots were subjected to fotir grazing periods between mid May and early September. The effect of stocking rate on herbage yield and quality and the influence of these factors and feed intake on liveweights of the sheep were recorded. The mean daily herbage organic matter available over the trial was 9.6, 5.8, 3.3 and 23% of the total liveweight of the sheep at each of the four stocking rates. The highest grazing pressure led to the production of high-quality herbage, but also led to reduced productivity, low feed intake and liveweight losses. The most lenient grazing pressure failed to provide adequate herbage utilization. Even at the most intensive stocking pressure, only 66% of the herbage available to ground level was utilized in grazings after July. Intake results suggested that sheep of 45 kg liveweight required 1000–1200 g digestible organic matter per day to maintain body weight. Despite the higher in vitro digestibility of herbage on offer at the higher stocking rates, intake was limited through lack of herbage; a high degree of correlation existed between herbage availability and herbage intake over the four stocking rates and at all grazings. It is concluded that the portable corral technique is well suited for grazing studies and the assessment of sward response to varying stocking rates and is particularly useful where facilities for more extensive studies are limited.     

THE INTAKE OF DRINKING WATER BY GRAZING DAIRY COWS. THE EFFECT OF WATER AVAILABILITY

In a 16-week grazing experiment with six spring-calved Ayrshire cows, drinking water was available to the animals in three different ways, and the effect on milk prodnction was studied. The water was available from a water howl in the cowshed for 2.8 h/day in Treatment A, from a trough in the field for 21.2h/day in Treatment B, and from hoth sources for a total of 24 h/day in Treatment C. The cows on all treatments were grazed in individual plots of intensively-managed perennial ryegrass, stocked at the rate of 1 cow/0.22 ha (0.54 ac). The mean daily intakes of drinking water were 10.1, 15.3 and 15.5 kg (2.23, 3.37 and 3.42 gal)/cow, and the mean daily milk yields were 17.0, 17.2 and 16.8 kg (37.5, 37.9 and 37.0 lb)/cow in Treatments A, B and C, respectively; milk yields were not significantly different The herbage had an average DM content of 17.3%, and contained 19.6% crude protein and 66.5% digestible organic matter in the DM. The weight of water drunk was significantly and positively related to the DM percentage of the herbage, the air temperature and the daily hours of sunshine, and negatively related to daily rainfall. It is concluded that when dairy cows are grazing leafy herbage of high digestibility as their sole feed, the time during which drinking water is available may safely be restricted.