Four trials with a total of 1750 Perendale ewes were conducted to determine the effect of feeding lucerne on ovulation rate and lambing performance. Levels of up to 600 ppm coumestans in lucerne leaf, associated with fungal infection, depressed ovnlation rate and lambing by 34% and 14.6% respectively. In the absence of fungal infestation no coumestans were found and stage of regrowth had 110 effect on lambing performance. A negative linear relationship between coumestan ccntent of the diet (x) and ovulation rate (y) was determined (y = 1.382 -O.004x). Levels of coumestans as low as 25 ppm in the diet depressed the ovulation rate of ewes fed lucerne pellets for 35 days. The depression in ovulation rate of ewes fed a high (100 ppm) level of coumestans was overcome by treatment with pregnant mare's serum gonadotrophin. It is suggested that coumestans exert their effect by interference with the release of follicle stimulating hormone from the pituitary gland.

In two experiments lucerne was ensiled with the addition of 8S% formic acid at rates ranging from 0 to 8 lit. In tests made 8 months later, nitrogen, pH, and butyric acid values-vere similar in all formic acid-treated silages and lower than those in untreated ones. With increasing amounts of formic acid, ammonia levels decreased but water-soluble carbohydrate and water-insoluble nitrogen increased. In a quadratic relationship between lactic acid content and level of added formic acid the lactic acid maximum corresponded to a formic acid level of 4 lit. Organic matter digestibility. voluntary intake, and live-weight gain of sheep increased with increasing formic acid. Over the practical range of lamb carcass values and formic acid costs the optimum level of formic acid was shown to be 5-6 lit. lSI

No abstract

Pairs of lucerne silage stacks were made on six occasions starting spring 1970. One of each pair received formic acid at about 4 lit. The other was untreated. The effects of formic acid on the resultant silage were assessed in terms of chemical analysis, digestibility, voluntary intake by sheep, and live-weight gain by sheep and cattle fed the silages as sole diets. Formic acid silages contained more organic matter (85.7 v. 82.6°iO) and digestible organic matter (56.4 v. 48.7%) and less fibre (35.9 v. 40.4°;/c,) than untreated silages, but had lower levels of ammonia (9.4 v. 24.2 %), pH (4.36 v. 5.22), and total volatile fatty acids (3.1 v. 7.6°iO).

Lucerne and lucerne/prairie grass swards were compared at three stocking rates using yearling beef cattle. A 35 day rotational grazing system was used and the experiment ran for 130 days from early October, 1976. Pasture DM yields were higher on the mixed sward but animal production was greater on the lucerne only sward, particularly from December onwards. Increasing stocking rate tended to reduce herbage DM yield and per-animal production. There was no significant interaction between sward type and stocking rate on either sward or animal yield. Lucerne and lucerne/ prairie grass swards on pumice soil compared favourably with fertile Waikato permanent pastures in terms of carcass gain per hectare over the grazing period.