Autumn rains bring with them the promise of high livestock growth rates, but this not always the case and it can be difficult to know why.
Beef + Lamb New Zealand recently held an Autumn ill thrift webinar where Charlotte Westwood, a Veterinary Nutritionist with PGG Wrightson Seeds, and Marlborough vet Mary Bowron tackled this multi-faceted issue.
Charlotte says a number of factors can contribute to autumn ill thrift including poor pasture quality, abrupt dietary changes (from poor quality to high quality forage) stock water, feed budgeting challenges, low drymatter pastures, Facial Eczema, mycotoxins, ryegrass endophytes, internal parasites, subclinical disease, trace element deficiencies and abrupt changes in feed supply and demand.
In the webinar, Charlotte and Mary step through each of these issues, with Charlotte focusing on nutrition and internal parasites while Mary discusses trace elements.
Throughout the webinar, Charlotte stresses the need to allow autumn pastures to build mass before grazing for both nutritional and animal health (internal parasites, Facial Eczema, mycotoxins) reasons.
She explains that new pasture growth in autumn is typically low in drymatter, so it is easy to over-estimate the pasture mass on offer and therefore easy to inadvertently underfeed stock.
After a very dry summer, stock in extensively grazed areas can walk long distances to find the green pick after autumn rain. This in itself uses energy. Using sub-divided areas and/or supplementary feeding for longer, will allow pastures covers to build and will prevent this.
Building more pasture mass after the first autumn rains will also favour the survival of perennial pasture species.
Post-rain autumn pastures can be low in drymatter and fibre, yet high in protein and water-soluble carbohydrates. Rumen and other gastrointestinal changes need to be made before an animal can make the best use of this feed.
There is also a degree of harvest inefficiency, because compared with summer pasture, each mouthful the animal is ingesting is lower in drymatter.
Lambs will compensate by taking more bites per day but cattle wont.
Again, pasture mass should be allowed to build before grazing, so at grazing, animals are getting more feed with every mouthful.
If young stock suddenly shift from a low to high protein diet, it can create a sudden burst of rumen ammonia. This makes lambs feel unwell and intakes will be reduced until the rumen adjusts over days or sometimes weeks.
This adjustment will be faster if there is not such a big difference in the quality of summer and autumn pasture, as will be the case in many regions this year.
Baleage and hay will help with the transition between a low and high protein diet and high pre-grazing pasture covers will have more drymatter and will be lower in protein and will make the transition easier.
Internal parasites can be a big issue in autumn with high populations of L3 larvae in pastures. Internal parasites should always be considered in cases of ill-thrift.
Marlborough vet Mary Bowron talked about trace elements and minerals, the important ones for sheep being selenium, iodine and cobalt (Vitamin B12) while cattle require copper and selenium, iodine sometimes and cobalt should be kept in the back of the mind.
She says vets are seeing fewer clinical signs of trace element deficiencies, however, farmers are pushing the boundaries of productivity so animals need have sufficient trace elements to help them perform at an optimum level.
Adult sheep and hoggets need selenium and iodine pre-mating while retained lambs may need selenium and cobalt at this time of year.
In the webinar, Mary outlines the signs of deficiencies, how to test and methods of supplementation.
The videos and podcasts of the Autumn ill thrift webinar are available on the Knowledge-Hub here.