ALBERT

Description: SUMMARYThree silages were prepared from a second cut of perennial ryegrass, using additives of 2 l formic acid/t fresh crop together with formaldehyde at either 0, 47 or 100 g/kg crude protein (CP) in the crop. The silages were offered to appetite either alone, or with supplements of maize starch or maize starch + urea, to 18 British Friesian steer calves, half of which were rumen-cannulated. The maize starch and urea supplements were provided at 184·4 and 18·9 g/kg total dietary dry matter (D.M.) respectively.The low contents of volatile fatty acids and ammonia N in each silage indicated that they were well preserved. Formaldehyde treatment reduced protein degradation in the silages and reduced total acid content. There was a small increase in butyric acid content at the low application of formaldehyde, and the content of 2,3·butanediol increased with formaldehyde application.Formaldehyde treatment depressed intake, although the decline at the high level of application was less when calves were given the starch + urea supplement. Supplementation with starch reduced silage D.M. intake, although total D.M. intake was unaffected, and increased digestible organic matter (OM) intake. The addition of urea to the supplement further increased total D.M., digestible OM and digestible energy intakes. The apparent digestibilities of D.M., OM, N, cellulose and energy were depressed by formaldehyde treatment. Starch supplementation increased the apparent digestibility of D.M. and OM but depressed that of N and cellulose. The deleterious effect on cellulose digestibility was most evident at the high application of formaldehyde. Starch + urea supplementation further increased the digestibility of D.M. and OM, and increased N digestibility. Both supplements increased energy digestibility.N retention was improved by formaldehyde treatment, particularly when the starchfurea supplement was provided. Supplementation with starch did not improve the utilization of dietary N, but reduced N retention on the formaldehyde-treated silages.Within the rumen, ammonia-N concentration declined with increasing application of formaldehyde, and was increased by starch + urea supplementation. There was a tendency for the molar proportion of acetate to increase, and that of propionate and butyrate to decrease with increasing application of formaldehyde. Starch supplementation resulted in a small increase in the molar proportion of butyrate.The apparent rate of digestion of silage in nylon bags in the rumen was reduced by the high application of formaldehyde. On this silage diet, rate of digestion was further depressed by supplementation with starch, but improved by supplementation with starch + urea. The apparent rate of digestion was also depressed when a reference silage (the control) was incubated in the rumens of calves on the high formaldehyde silage, indicating that the adverse effect of formaldehyde was partly due to an effect on the rumen environment. However, it is also possible that formaldehyde reacted with cell wall components, inhibiting fibre digestion.It was concluded that formaldehyde treatment, but not starch supplementation.

Description: SUMMARYIn a 3 × 3 latin-square design experiment, 12 British Friesian steer calves with rumen cannulae were offered three red clover silages to appetite, either alone or with a urea supplement of 18.9 g/kg total dietary dry matter (D.M.). The silages were prepared from a second cut of red clover using additives of 2·11 formic acid/t fresh crop together with formaldehyde at 0, 31 or 123 g/kg crude protein (CP) in the crop.The control silage was well preserved, as indicated by a low content of volatile fatty acids and ammonia N. Formaldehyde treatment generally restricted silage fermentation, although there was an increase in the content of butyric acid at the intermediate level of application, and an increase in 2, 3-butanediol content at the high level of application. A decline in ammonia-N content and an increase in insoluble-N content, with increasing level of formaldehyde application, indicated that formaldehyde had been effective in reducing protein degradation in the silages.Formaldehyde treatment depressed intake, the apparent digestibility of D.M., organic matter (OM), N, cellulose and energy, and N retention, the effect being particularly evident at the high level of application. Behavioural observations showed an increase in eating time on the formaldehyde-treated silages. Urea supplementation increased intake of the formaldehyde-treated silages, but did not influence intake of the control silage, and increased N retention on all silage diets. Apart from an improvement in apparent N digestibility, urea supplementation did not influence the digestibility of other dietary components.Within the rumen, formaldehyde treatment reduced ammonia-N concentration and the molar proportions of propionate and butyrate, and increased the molar proportion of acetate. The rate of D.M. and cellulose disappearance from treatment silages suspended in the rumen in nylon bags was reduced by formaldehyde treatment, the effect being most evident at the high level of formaldehyde application. A similar effect on rate of D.M. disappearance was observed when the control silage was placed in nylon bags, indicating that the adverse effect of formaldehyde was probably due to an effect on the rumen environment. Urea supplementation increased rumen ammonia-N concentrations, although this effect was not as great on the high formaldehyde silage, and increased the rate of D.M. and cellulose disappearance from silage in nylon bags.It appears that the lower intake and the poorer utilization of dietary N on the high formaldehyde silage may have been due to a reduction in the rate of digestion within the rumen. While there was some response to urea supplementation, it could not restore the apparent rate of digestion in the rumen to levels observed on the control diet. Hence, factors other than the supply of rumen-degradable N in the diet must have been responsible for the depression of digestion within the rumen.

Description: SUMMARYSix silages were prepared from a primary growth of red clover using additives of 21 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.