While this country’s temperate climate allows farmers to operate world-class grass-based outdoor farming systems – which have significant animal health and welfare benefits – adverse weather is inevitable. But there are a number of measures farmers can take to minimise the impact of weather on livestock, particularly over lambing and calving.
Feeding is the most critical factor. Lambs born to well-fed ewes will have energy stored as fat reserves and are better able to survive times of reduced feed such as during windy or wet conditions or in extreme weather.
According to resources on Beef + lamb New Zealand’s Knowledge hub, a well-fed ewe is considered the best shelter a lamb can have, but protecting ewes from bad weather by providing shelter before lambing will contribute significantly to the chances of good lamb birthweights and survival.
Speaking at a recent B+LNZ seminar, StockCare vet Pete Anderson said it is critical that ewes are set-stocked at a Body Condition of 3. Lambs from a ewe with a lower Body Condition have poor vigour, take longer to stand, the ewe is less interested in her lambs and has a poorly developed udder.
Lamb survival falls by five per cent for every .5BCS lost between scanning and lambing.
Windchill is a major threat to livestock welfare and lamb survival. The ambient temperature experienced by a new-born lamb depends on the air temperature and windchill which is directly determined by wind speed. The greater the windchill, the greater an animal’s heat loss.
Any type of shelter slows the wind speed and reduces windchill. Critical extra minutes of a lamb’s life may be gained by providing shelter during which time a ewe could return to her lamb after lambing and get it to suckle.
This shelter may include trees, hedges, bushes, tussocks or rocks, although topography, slope, aspect and microclimate also play a role and some paddocks can be sheltered without any vegetation.
Multiple lambs typically result in lighter lambs. These lambs are more vulnerable to heat loss as they have lower fat reserves than heavier lambs and a higher surface area to bodyweight ratio, increasing heat loss.
Providing shelter for ewes known to be carrying multiple lambs should be a priority both to protect the ewes before lambing and give lambs a better chance of survival once born.
In extreme weather, even well-fed, well bonded lambs may succumb to extreme cold and weak lambs can be given a 20% mix of Dextrose directly into the abdomen. This can give the lamb the energy boost it needs to survive.
Orphan lambs are inevitable, irrespective of the weather, and there are a number of resources on rearing orphan lambs on the B+LNZ website.