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Beyond the Bale : March 2015
ON FARM 51 head/day greater than the average weight gain on biserrula alone suggesting presence of other species in the pasture, even at relatively low levels, gives improved growth performance. Thus, there may be merit in deliberately using biserrula in a mixed pasture rather than in a monoculture for improved livestock performance. PHOTOSENSITISATION Neither the on-farm trial or the controlled trial at CSU were without incidence of photosensitisation with clinical signs observed in sheep grazing both cultivars. At Beckom 4% of lambs in the on-farm grazing experiment showed evidence of mild photosensitisation (mild skin lesions primarily on the ears). At the time of final weighing, these lambs were resolving; importantly their body weight was no different to the average of the unaffected lambs. At Wagga a gradation of effect was observed due to the very high proportion of biserrula in some plots (>98%). Where biserrula contributed more than 95% of the feed on offer, mild (superficial tissue loss and swelling of ears / and or muzzle) to moderate (more persistent lesions of the ears) photosensitisation was observed in up to 100% of Merino ewes. Interestingly, on the same plots only very mild changes were noted in the Merino lambs, and in only 50% or less of these animals. In those plots with greater than 10% volunteer species, virtually no animals were affected, and those few (<10% identified) showed only very mild clinical signs; again only Merino ewes were affected. It is also important to note that, in all but the most pure biserrula plots, Merino ewes showed a significantly lower incidence of photosensitisation than crossbred animals grazing the same pastures. This breed specific difference is possibly due to greater fleece coverage in the Merino breed giving enhanced protection from UV rays for both ewes and lambs. CONCLUSION The ability to achieve high liveweight gains on biserrula is an important finding and suggests that photosensitisation is not adversely affecting production in most animals, providing clinical signs are mild. The enhanced weight gain in Merino ewes observed in the study gives producers the ability to grow replacement ewes out to joining weight more rapidly and where Merino wether lambs are to be sold or farmers are joining their ewes to terminal sires, there is capacity to get these animals to target weights rapidly on a pasture that thrives in low rainfall zones. From the older breeding ewe perspective, biserrula has the capacity to be used strategically to maintain higher liveweight/ body condition score through the lactation period, potentially allowing more rapid return to oestrus, or in the case of cull or cast-for- age ewes, enabling turn off of surplus stock sooner and at higher weights than ewes on volunteer pasture. Regardless of age or breed, all animals grazing biserrula when it is green and actively growing should be monitored carefully for signs of photosensitisation. This helps limit any adverse production effects if moderate to severe clinical effects were noted. Overall, these trials suggest that: • biserrula can enhance growth rates for both wool and meat sheep • the most optimal grazing option is biserrula mixed pastures • the effects of photosensitisation can be greatly reduced in mixed pastures, even where contribution to other species to total feed on offer is relatively small. MORE INFORMATION Dr Belinda Hackney E firstname.lastname@example.org P (02) 6330 1200 ‘Casbah’ variety of biserrula with green seed pods.