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South Australia worms, flies and lice update - December 2014

Adelaide: Colin Trengove, Sheep Health Lecturer (UA Roseworthy campus) (trengovet@icloud.com)

Rainfall for most of the state has been around the 20th percentile (lowest 20% of rainfall on record) for the past 6 months and 5th percentile (lowest 5% rainfall on record) for the past 3 months highlighting the extended and marked dry period experienced. This has not been good for pasture growth or worm survival. The lack of pasture growth combined with a dry outlook indicates extended supplementary feeding over summer/autumn. Provided the nutritional needs of livestock are met, this provides minimal opportunity for parasites to impact production. However, it is important to monitor to ensure that worms are not limiting the utilisation of the scarce feed sources available.

Worm egg counts should be done by or during December to check and prevent unexpected worm burdens over summer. While worms are unlikely to present a problem in these extended dry periods one can never assume that to be the case.  There is certainly no need to drench if worm egg counts indicate low parasite loads, but recent monitoring does indicate that especially weaners and hoggets can still become wormy even in dry times.

Stubbles provide a useful break from grazing worm contaminated pastures and there is no need to drench into stubbles unless WECs exceed 100 eggs per gram. Even then it is better to delay moving stock onto stubbles for a week after drenching to limit the risk of encouraging drench resistance to develop.

The nutritional benefit of stubbles is limited in the absence of summer rainfall as it is often the green summer weeds that provide significant nourishment to grazing livestock in stubbles given the efficiency of harvesters leaving little grain behind. Checking for grain in stubbles is essential in estimating their feed value and there are charts available to assist this, e.g. 28 grains of wheat or 25 grains of barley per quadrat (0.1 square metre) indicates approximately 100 kg grain per hectare.

A dry or early pregnant ewe needs the equivalent of 300–500 gm cereal grain/day for maintenance assuming similar intake of stubble. Once the leaves have been consumed in the first 2–3 weeks of grazing stubble the remaining stalks are essentially providing limited potential organic matter plus reduced wind erosion and little else. And so monitoring WECs and condition score followed by adjustment to supplementary feeding regimes is essential to ensure optimum weaner survival and ewe reproductive efficiencies are maintained.  Refer to Life Time Ewe Management and High Performance Weaner course manuals for more details.

All the best for a relaxed family Christmas and look forward to prosperity in 2015.