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 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 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 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 HISTAMINE ON SILAGE DRY-MATTER INTAKE

The oral introduction of 0·5 g histamine as the diphosphate into the rumen of sheep produced no effect on the physiological condition of the animals. The feeding of histamine, as the dihydrochloride, in levels up to 1 g/day to sheep on silage diets did not affect the dry-matter intake.     

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.     

SOME FACTORS AFFECTING THE INTAKE OF ROUGHAGE BY SHEEP

The dry-matter intake of silage was increased when the silage had a higher dry-matter content and when the time of access to the silage was increased from 3 to 24 h. Concentrate supplementation had a greater influence in depressing the intake of hay than that of silage. Only a small difference was observed in the replacement of hay by concentrates when the concentrates were given with two hays of different dry-matter digestibility. Concentrates with a relatively high protein content depressed roughage intake to a lesser extent than concentrates with a low protein content.     

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 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.     

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 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.     

THE INFLUENCE OF TYPE AND LEVEL OF SUPPLEMENTARY FEED ON INTAKE AND PERFORMANCE OF BEEF CATTLE ON PASTURE

Two experiments, each of 6 weeks dehydration, were conducted in 1972. In Expt 1, 24 cattle were grazed in individnal paddocks during July and August and received one of 4 treatments over a 6-weeks period: no supplements; straw ad lib; 3.3 kgj. day sugar-beet pulp; 4.0 kg/day molasses. Mean daily live weight gains were significantly increased by the sugar-beet pulp and molasses supplements; which also increased OM and DOM intake significantly. The increase in total OM intake per kg OM in the supplement was 0.48 for sugar-beet pulp and 0.67 for molasses. In Expt 2, 18 cattle grazed in groups of 3 during November and December. Two groups each received 0.5, 3.5 or 6.5 kg/day sugar-beet pulp over a 6–weeks period. There was no significant difference in live weight gain between treatments, and no significant difference in total intake. Intake from pasture declined with increasing level of supplement, so that the average increase in OM intake per kg OM in the supplement was 0.28. Hie results are discussed in relation to availability of pasture and the effects of the supplements on intake.     

THE VOLUNTARY INTAKE AND DIGESTIBILITY BY SHEEP OE LEAF AND STEM FRACTIONS OF LOLIUM PERENNE

The leaves of tropical grasses are eaten in larger quantities than stems of similar DM digestibility. To determine whether the same fact applied to a temperate grass, studies were made with leaf and stem fractions of Lolium perenne. The leaves of L. perenne had a 20% higher voluntary intake than the stems, white the DM digestibilities were only slightly higher (67·3%ν. 64·8%). The leaves also had a larger surface area/g, a higher initial (12 h) fermentation rate in vitro, larger content of pepsin-soluble DM, and a smaller energy require ment to grind I g DM in a laboratory mill compared with the stems. The difference in voluntary intake between the leaves and stems of L. perenne was smaller than that for a number of tropical grasses.     

THE EFFECT OF PHYSIOLOGICAL STATUS ON DIET SELECTION BY GRAZING EWES

The effect of the physiological status of grazing ewes on diet selection was studied, using ewes with oesophageal fistulae. The diets of dry ewes grazing Phalaris annual grasses and subterranean clover pastures, over a range of availabilities, were compared with those of ewes in various stages of pregnancy and lactation. There were no significant differences at any stage of reproduction in the botanical composition of the diets. However, small differences in diet digestibility, soluble carbohydrate and nitrogen content were found during pregnancy and lactation. These occurred at all levels of availability of pasture. The differences did not appear to have nutritional significance in the particular pasture ecosystems studied because levels of N, soluble carbohydrates and digestibility of the diet were such that selection for survival was unlikely to be necessary.
It is concluded that dry fistulated ewes can be used to obtain samples for assessing diet N and soluble carbohydrate contents for ewes in other physiological states. The use of in vitro digestibility tests of diets of dry ewes to assess diet digestibility for ewes in other physiological states may be subject to error.     

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.     

THE INFLUENCE OF SUPPLEMENTS OF FLAKED MAIZE ON THE DIGESTIBILITY BY STEERS OF SILAGE, FRESH LUCERNE AND LUCERNE HAY

Three experiments examine the effects of giving small supplements of flaked maize to steers on the digestibility and retention of nutrients from rations of grass silage, lucerne hay and fresh lucerne. The digestibility of the dry matter, crude fibre and crude protein of the silage ration was depressed by the successive additions of 1, 2 or 3 Ib flaked maize per day. There was a tendency for the steers to retain more nitrogen as the level of starch supplementation increased, in spite of a lowered crude-protein digestibility. The digestibilities of the constituents of lucerne hay and fresh lucerne were slightly increased by the addition of 2 and 4 Ib flaked maize per day. The reasons are discussed for the different effect of the supplemental starch on the digestibility of the crude fibre from grass silage and from fresh or cured lucerne. Attention is drawn to the increase in the retention of N following the supplementation of silage with starch.     

A STUDY OF THE INTAKE OF DRINKING WATER BY DAIRY COWS AT GRASS

The average daily intake of drinking water of two groups of 10 spring-calved Ayrshire cows, one gronp on a paddock and the other on a Wye College system of grazing, was measured on 4 days/week for 20 weeks. Trends in water intake were similar on both systems, the average daily intake being 23.0 ±8.5 kg (5.1 ± 1.9 gal)/cow. The average DM content of the herbage was 17.8% and the mean air temperature 134°C (56 1°F). The weight of water drunk was positively related to the daily milk yield and the DM percentage of the herbage, and negatively related to daily rainfall and relative humidity. All of these relationships were significant. Possible changes in the provision of water for dairy cows at grass are discussed.