ALBERT

Description: SummaryThe pre-weaning and post-weaning gain, oaroass production and stomach development of oalves fed four levels of whole milk (8%, 10%, 12% and 14% of live weight daily) was studied in two experiments. Calves had access to pasture at all times and were weaned at 12 weeks. Pre-weaning gain, weaning live weight, and carcass weight at weaning all increased as the quantity of milk increased. At the 14% level, male calves reached heavier weaning live weights and produced heavier carcasses than females. Reticulo-rumen weight, when expressed as a percentage of total stomach weight, was significantly reduced with increased milk feeding. Calves reared on the higher quantities of milk gained more slowly after weaning, this being attributed to their poorer reticulo-rumen development at weaning.

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: SummaryThe leaf growth, carrying capacity and dairy production of four summer-growing pastures were measured in a subtropical area of Australia. The growing season was subdivided into ten 4-week periods and the production was estimated for each period. Carrying capacities were determined by rotationally grazing four paddocks of each pasture over the 4-week period, and varying the stocking density so that a target weight of leaf material remained on the pasture at the conclusion of each grazing.A non-limiting rate of nitrogen fertilizer increased total leaf production of kikuyu by 97% over a control treatment without nitrogen, but the response was not evenly distributed throughout the season. It fell to 50% during autumn when growth on the nitrogen-fertilized pastures was restricted following heavy defoliation during late summer. The use of the tropical legumes, siratro and glycine, in a mixed sward with kikuyu, did not increase leaf production over a kikuyu control pasture. The legumes grew poorly and this appeared to be due to the combined effects of their poor adaptability to the krasnozem soil, a high plant mortality especially during the first winter after sowing, the 4-week grazing interval and strong grass competition.The carrying capacity of the nitrogen-fertilized pasture was 1·3–5·3 cows/ha at the beginning (September–October) and end (April–mid June) of the growing season, and increased to a peak of 7·4–9·7 cows/ha during February-mid March. Nitrogen fertilizer increased the carrying capacity by an average of 131% over that on a kikuyu pasture without nitrogen. The carrying capacities were similar on kikuyu and on a mixed carpet grass-kikuyu pasture, both without nitrogen, but were less on a tropical legume-kikuyu pasture which was grazed at a lighter grazing intensity during autumn to aid legume persistence.Reflecting the experimental method of adjusting the stocking density according to the pasture available, differences in dairy production per cow were small relative to differences in the carrying capacity. Consequently seasonal variation in total dairy production/ha mirrored the carrying capacity. Nitrogen fertilizer increased the average production of 4% fat-corrected milk to 13·2 t/ha/40 weeks, an increase of 133% over the control without nitrogen.The results illustrate the marked seasonal imbalance in growth and carrying capacity for a given pasture, and emphasize the need to use mixed feeding systems to provide a uniform level of nutrition for a fixed number of cows.

Description: SummaryRelations were developed between the carrying capacity or production of fat-corrected milk (FCM)/ha and various measures of pasture growth for six pasture treatments grown in a subtropical environment. The pasture and animal production variables were obtained from pastures grazed on a weekly rotation using stocking densities which were varied so that a target weight of leaf material remained on the pasture at the conclusion of each grazing.Within a treatment, there was a curvilinear relation between the rate of leaf growth and carrying capacity, with the greatest efficiency of conversion at the lowest leaf growth rates. This relation generally varied between pasture treatments because of differences in grazing intensity. There was little variation in the production of FCM per cow between grazing periods within a treatment, reflecting the experimental technique of matching the stocking density to the amount of forage. Consequently FCM/ha largely mirrored the stocking density with some adjustment for differences in production per cow caused by differences in grazing intensity between treatments. Production of FCM/ha was affected more by a unit change in residue leaf yield than by a unit change in leaf yield before grazing.Using the rate of leaf removal (intake plus grazing losses) per cow as an inverse index of grazing intensity, it was apparent that the use of variable stocking densities to obtain specified residue yields after grazing did not necessarily equalize the grazing intensity because the rate of leaf removal per cow varied according to the before-grazing leaf yield. Also soiling by dung caused differences in the acceptability of forage for grazing, resulting in differences in grazing intensity between pastures with the same yield and stocking density.

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.