An experiment using herds of ~20 cows (farmlets) assessed the effects of high stocking rates on production and profitability of feeding systems based on dryland and irrigated perennial ryegrass-based pastures in a Mediterranean environment in South Australia over 4 years. A target level of milk production of 7000 L/cow.year was set, based on predicted intakes of 2.7 t DM/cow.year as concentrates, pasture intakes from 1.5 to 2.7 t/cow.year and purchased fodder. In years 1 and 2, up to 1.5 t DM/cow.year of purchased fodder was used and in years 3 and 4 the amounts were increased if necessary to enable levels of milk production per cow to be maintained at target levels. Cows in dryland farmlets calved in March to May inclusive and were stocked at 2.5, 2.9, 3.3, 3.6 and 4.1 cows/ha, while those in irrigated farmlets calved in August to October inclusive and were stocked at 4.1, 5.2, 6.3 and 7.4 cows/ha. In the first 2 years, when inputs of purchased fodder were limited, milk production per cow was reduced with higher stocking rates (P < 0.01), but in years 3 and 4 there were no differences. Mean production was 7149 kg/cow.year in years 1 and 2, and 8162 kg/cow.year in years 3 and 4. Production per hectare was very closely related to stocking rate in all years (P < 0.01), increasing from 18 to 34 t milk/ha.year for dryland farmlets (1300 to 2200 kg milk solids/ha) and from 30 to 60 t milk/ha.year for irrigated farmlets (2200 to 4100 kg milk solids/ha). Almost all of these increases were attributed to the increases in grain and purchased fodder inputs associated with the increases in stocking rate. Net pasture accumulation rates and pasture harvest were generally not altered with stocking rate, though as stocking rate increased there was a change to more of the pasture being grazed and less conserved in both dryland and irrigated farmlets. Total pasture harvest averaged ~8 and 14 t DM/ha.year for dryland and irrigated pastures, respectively. An exception was at the highest stocking rate under irrigation, where pugging during winter was associated with a 14% reduction in annual pasture growth. There were several indications that these high stocking rates may not be sustainable without substantial changes in management practice. There were large and positive nutrient balances and associated increases in soil mineral content (P < 0.01), especially for phosphorus and nitrate nitrogen, with both stocking rate and succeeding years. Levels under irrigation were considerably higher (up to 90 and 240 mg/kg of soil for nitrate nitrogen and phosphorus, respectively) than under dryland pastures (60 and 140 mg/kg, respectively). Soil organic carbon levels did not change with stocking rate, indicating a high level of utilisation of forage grown. Weed ingress was also high (to 22% DM) in all treatments and especially in heavily stocked irrigated pastures during winter. It was concluded the higher stocking rates used exceeded those that are feasible for Mediterranean pastures in this environment and upper levels of stocking are suggested to be 2.5 cows/ha for dryland pastures and 5.2 cows/ha for irrigated pastures. To sustain these suggested stocking rates will require further development of management practices to avoid large increases in soil minerals and weed invasion of pastures.
Formaldehyde-treated silage, formic acid-treated silage, formaldehyde-formic acid-treated silage, untreated silage, and lucerne hay were made from a lucerne sward and offered to Merino wethers. The formaldehyde was applied at a rate of 0.9 % of the weight of the dry matter and formic acid at 0.5 % of the fresh weight of the lucerne. Formaldehyde-treated silage and formaldehyde-formic acid-treated silage had significantly lower concentrations of ammonia nitrogen and total and individual organic acids than untreated silage. Formic acid-treated silage had a similar degree of fermentation to untreated silage, but more acetic acid and less lactic acid were produced than in untreated silage. However, when formic acid was applied in combination with formaldehyde, the ensiling fermentation was inhibited more than when formaldehyde was applied alone. There was some apparent protection of protein by the formaldehyde treatment. Treatment with formic acid significantly increased the in vivo digestibility of both nitrogen and dry matter, but did not increase ad libitum intake or wool growth by sheep offered this silage. Compared to untreated silage, treatment with formaldehyde significantly reduced the in vivo digestibility of nitrogen, produced a non-significant increase in intake, and significantly increased wool growth. The treatment of lucerne with both formaldehyde and formic acid significantly increased in vivo digestibility of dry matter, ad libitum intake, and wool growth compared with untreated silage. The treatment of lucerne with a mixture of formaldehyde (0.9% of the dry matter) and formic acid (0.5% of the fresh weight) was a suitable method of controlling the ensiling fermentation in order to increase the ad libitum intake of lucerne silage by sheep and their subsequent wool production. However, the intake and wool production of sheep offered such silage was still significantly less than that of sheep offered lucerne hay.
Formaldehyde-treated silages, frozen lucerne, and untreated silage were prepared from a lucerne stand and offered to Merino wethers. Formalin was applied at rates of 16.6, 24.9, and 33.1 g formaldehyde per 100 g crude protein. Formaldehyde-treated silages had significantly lower concentrations of ammonia nitrogen and total and individual organic acids than did untreated silage, and hence the ensiling fermentation was inhibited by formaldehyde. Formaldehyde treatment of lucerne partly protected plant proteins against microbial degradation during in vitro rumen liquor digestion and so reduced ammonia nitrogen concentrations in the supernatant. Ad libitum dry matter intakes and in vivo dry matter and nitrogen digestibilities were significantly lower for the treated silages than for frozen lucerne or untreated silage. The treatment of lucerne with formaldehyde at concentrations of 16.6 g formaldehyde per 100 g crude protein and above was not a suitable method of controlling the ensiling fermentation to increase the voluntary consumption of lucerne silage by sheep.
Milk production and composition were measured for 49 days in early lactation in 40 Holstein-Friesian cows fed 8 kg/day (fresh weight) of 1:1 mixtures of either rolled barley-lupin grain (Lupinus angustifolius L. cv. Gungurru) or barley-common vetch grain (Vicia sativa L. cv. Blanche Fleur). All cows were fed 1 kg/day of a pelleted concentrate containing minerals and vitamins, and wilted perennial ryegrass-subterranean clover pasture silage was available ad libitum with restricted grazing of perennial ryegrass-subterranean clover pasture. Cows ate all of the barley-lupin grain and barley-vetch grain mixtures. Mean daily dry matter intakes of silage (kg/cow.day) were 9.9 and 9.8 for cows fed the barley-lupin grain and barley-vetch grain mixtures respectively. Estimated pasture DM intake was 3.0 kg/cow.day. Mean daily yields of milk (L), fat (kg) and protein (kg) were significantly (P<0.001) greater for cows fed the barley-lupin grain mixture (30.3, 1.30 and 0.92 respectively) than for those fed the barley-vetch grain mixture (27.7, 1.23 and 0.87 respectively). Cows fed the barley-vetch grain mixture gained 0.2 kg/day more liveweight than those fed the barley-lupin grain mixture. Although both common vetch grain and lupin grain were readily eaten by dairy cows, when fed as protein supplements to a high quality silage and pasture-based diet in early lactation, cows fed the vetch grain produced less milk and milk components. This may be related to the greater partitioning of nutrients to liveweight gain rather than to toxicity problems in the cows fed vetch grain.
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