Stylosanthes viscosa and S. scabra cvv. Fitzroy and Seca have previously been shown to trap host-seeking larvae of the cattle tick Boophilus microplus and could provide a means of controlling cattle ticks in improved pastures. We assessed the ability of 229 accessions from 22 species of the genus Stylosanthes to trap larvae of B. microplus or to prevent them from ascending plant stems. The 3 species that were most effective were S. viscosa, S. scabra and S. guianensis. Only accessions which produced sticky secretions were able to trap tick larvae, but the extent of this ability was related primarily to the density and length of bristles on the stems rather than to the degree of stickiness. The highest percentages of larvae were trapped when stylo stems had short, dense bristles of average stickiness or long sticky bristles of average density. These features were also most effective at preventing larvae from ascending stems. A high density of fine, non-glandular hairs, in conjunction with average stickiness, also prevented larvae from ascending stems.
Groups of Polwarth ewes which 1. were barren, 2, were pregnant but aborted with prostaglandins in early pregnancy, 3. lambed and reared a single lamb and 4. lambed but had their single lamb removed soon after birth, were used to estimate the effects of pregnancy and lactation on wool and Iiveweight. Pregnancy plus lactation reduced liveweight (17 per cent), wool growth rate (9 per cent) and clean fleece weight (11 per cent) ; pregnancy alone reduced liveweight (10 per cent), wool growth rate (7 per cent) and clean fleece weight (10 per cent) and its effects were greater than those of lactation in each of the characters studied.
Each of 411 Polwarth ewes was given prostaglandin (125 micrograms cloprostenol) by injection on 2 occasions 10 days apart. Ewes were not mated at either prostaglandin induced oestrus, but field mated at the first natural oestrus thereafter. As a result 97.1% mated in a 12 day period (82% in 4 days). From a selected group of 270 ewes, presumed to have been pregnant (by non-return to sevice), 90 were given prostaglandin (125 micrograms cloprostenol) as an abortifacient, at 22-23 days post service, the remaining 180 acting as lambing controls. Pregnancy was finally determined by ultrasonic fetometer at 106-107 days post mating. A 100% accuracy was achieved being confirmed by lambing observations. Most (98.9%) of the control, as expected, proved to be pregnant and subsequently lambed. By contrast only 33 (36.7%) of the prostaglandin treated ewes were pregnant. Thus, although prostaglandin aborted 63.3% of pregnant ewes, its efficacy was much less than might have been expected. The authors then discuss the efficacy of prostaglandin as an abortifacient at various stages of gestation.
Three groups of 135 ewe weaners were grazed for twelve months following weaning in December at high, medium or low stocking rates. No attempt was made to limit growth of any groups during the spring pasture flush. At 16 months of age three adult stocking rate groups were formed by proportional representation from the weaner groups. The weaner phase treatments induced marked differences in patterns of growth and wool production in the weaner phase. The low plane and high plane weaners differed by 10.3 kg liveweight at the end of July and by 5.0 kg at the end of the weaner phase (December). Weaner wool production differed among groups by 0.8 kg (Clean). In the following year residual effects of weaner nutrition on liveweight were small, but statistically significant for the first eight months. However, weaner nutrition had no subsequent effect on the production of wool or lambs.
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