1.A primary growth of perennial ryegrass was cut on 8 to 11 May (early) or on 12 June (late) for comparison with the primary growth of a tetraploid red clover, which was cut either on 1 or 2 June (early) or on 28 June (late). The crops were ensiled, after wilting for about 4h, with the addition of formic acid at 2-21/t fresh crop. The silages were given ad libitum alone or with rolled barley at 11-5 g dry matter per kg live weight to 40 British Friesian steers initially 3 months old and 108 kg live weight. 2. On average there was no significant difference in digestibility between perennial ryegrass and red clover.However, the rate of decline in digestibility with time was greater with perennial ryegrass than with red clover. 3. Calves given silage of red clover as the sole feed ate more dry matter and grew faster than calves given grass silage (P<0-001) but supplementation with barley reduced the intake of red clover silage to a greater extent than that of perennial ryegrass silage. Barley supplementation increased live-weight gain of calves given perennial ryegrass from 0-32 to 0-83 kg/day and that of calves given red clover from 0-63 to 0-99 kg/day (interaction P<005). The results did not indicate a higher net efficiency of utilization of the legume. Date of cut had no significant effect on dry-matter intake but earlier cutting resulted in an increase in live-weight gain from a mean of 0-61 to 0-77 kg/day (P<0-001). 4. The results show that high rates of live-weight gain (0-74 kg/day) can be achieved by calves given silage of red clover and that earlier cutting of herbage for silage does not always result in higher intakes of dry matter. Supplementation of silages with barley can reduce markedly the difference in intake and live-weight gain apparent when the silages are given as sole feeds.
Experiments were conducted in 1967 and 1968 in which Hereford X Friesian (Experiment 1) and Friesian (Experiment 2) steer calves horn in AprO were turned out to graze at one week or 3 months of age, respectively, and maintained at three stocking densities in the ratio 1:2:3 animals per unit area. The calves grazed paddocks of S23 perennial ryegrass in rotation, and were moved when the height of grazed stuhhle at the medium stocking density was reduced to 8 cm. The rate of liveweight gain and herhage intake per head declined as stocking rate increased. When the results of the two experiments were compared, the weight gain of the calves was more closely related to the weight of herhage residues than to the height of the grazed sward. The rate of liveweight gain was depressed when the amount of herhage left after grazing fell helow 2000-2500 kg OM/ha (1800-2250 lh/ac).
The vuluntary Intake of dried forage by yoong cattle rises with increasing D value and with increasing proportions of fine particles in the compressed package (wafer, coh, or pellet). Higher intakes are accompanied hy higher liveweight gains per day and per unit of food consumed.When different amounts of pellets or cobs of dried forage of high D value or protein content are fed with silage of high digestibility, maximum liveweight gains at lowest food cost have been ohtained with 35-50% dried forage in the diet. The dried forage gave results comparable with alternative supplements of energy or protein fed with the same silage.Hie application of the results of ^ort-term experiments in systems of heef production is discussed.
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.
Six silages were prepared from a primary growth of red clover using additives of 2 1 formic acid/t fresh crop together with formaldehyde at 0, 16, 34, 52, 77 or 117 g/kg crude protein (CP) in the crop. These silages were offered to appetite, either alone or with a urea supplement at 19-4 g/kg total dietary dry matter (D.M.), to 60 British Friesian steer calves with an initial mean live weight of 106 kg.Formaldehyde treatment restricted silage fermentation, the effect increasing with level of application. However, butyric acid and 2,3-butanediol content increased at intermediate levels of application. Protein degradation in the silages was reduced by formaldehyde treatment, as evidenced by a decline in ammonia-N and an increase in insoluble-N content with increasing level of formaldehyde application. The recovery of applied formaldehyde in the silages was low (less than 13 %) but increased with level of application.Intake, live-weight gain and feed conversion ratio followed quadratic trends, with formaldehyde having a deleterious effect at high levels of application. The decline in these production measurements was associated with declines in the apparent digestibility of D.M., organic matter (OM), N and energy with increasing level of formaldehyde application, although there was no effect of formaldehyde on cellulose digestibility. Urea supplementation tended to increase intake and live-weight gain at formaldehyde levels greater than 34 g/kg CP, and apart from the expected increase in N digestibility, did not affect the digestibility of other dietary components. As urea supplementation did not overcome the adverse effects of high levels of formaldehyde application on intake, live-weight gain and digestibility, it appears that the supply of rumen-degradable N was not the major limiting factor on these diets. N retention followed a quadratic trend with level of formaldehyde application, increasing at intermediate levels (30-50 g/kg CP) and then declining markedly at the highest level of application. A similar trend was evident when N retention was expressed as a proportion of live-weight gain, suggesting possible formaldehyde effects on carcass composition. However, carcass composition data did not confirm any formaldehyde effect. Urea supplementation did not affect N retention, and N balance data indicated poor utilization of the supplementary urea N.When considering the use of formaldehyde, relative to a formic acid control, in additives applied to red olover at ensiling, these data demonstrate little advantage in favour of formaldehyde and serious disadvantages when large quantities of formaldehyde are applied.
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