Genetics Key to Lifting Dairy Productivity in New Zealand
Genetics plays a central role in helping farmers lift per-cow productivity over time.
If managed appropriately hogget breeding can not only increase the number of lambs weaned on a farm in a given year, but also increase lifetime performance. However, if poorly planned and managed there can be negative effects, not only in the year the hogget is bred but also throughout her lifetime.
According to Professor Paul Kenyon, from the International Sheep Centre at Massey University, “there are a few simple rules farmers need to follow if hogget breeding is to be successful”.
The first rule is, a hogget needs to be a minimum of 40kg liveweight at breeding (for a flock with a mature ewe breeding weight of 65kg). This is an individual minimum, not a flock average, which is often assumed by farmers. Using body condition scoring, hoggets should be BCS 2.5 minimum, Kenyon says.
BCS is likely a better indicator of reproductive maturity, and thus suitability for breeding as a hogget, than live weight. “Farmers should be weighing their ewe hoggets regularly prior to breeding to get an understanding of how they are tracking so that changes in their nutrition can be made, if they are falling behind liveweight target.”
Another rule to help ensure better lambing from hoggets is exposing them to vasectomised rams (teasers) in mid-late March. This can increase the numbers of ewe hoggets bred early in the breeding period. It also has the flow-on effect of resulting in more lambs being born early in the lambing period, which should result in older and thus heavier lambs at a given weaning date.
“The important rule for teasing is, introduce the teasers to the hoggets 17 days -- and 17 days’ only -- prior to the first day of breeding,” Kenyon explains. “The optimum teaser-to-hogget ratio is 1:70, though a response of 1:200 has been reported. Teasers should not be used as a short-term fix when hoggets are well below the 40kg minimum at breeding.”
Hoggets need to gain about 20kg total weight during pregnancy (including the weight of the placenta, fetus and associated fluids). This requires an average daily gain of 130g/day during both the breeding period and throughout pregnancy. This ensures the hogget grows as does the fetus(es).
With mature ewes, the traditional approach has been to maintain liveweight in early pregnancy and then to feed them well in late pregnancy, to ensure nutritional requirements of the pregnancy are met. This approach will not work with hoggets and will result in poor lambing success and below optimum liveweight two-tooths.
“Just feeding hoggets well in late pregnancy will result in most of the nutrition being partitioned towards fetal growth and the young hogget herself will not grow,” Kenyon adds. “This is likely to result in more birthing difficulties (as she would not have grown out) and she will be lighter than planned at weaning.”
Therefore farmers need to be planning how they are going to feed their ewe hoggets appropriately throughout pregnancy.
“April is the time for farmers to look at their present pasture covers and to consider their likely pasture growth rates when deciding how many hoggets they should breed,” Kenyon explains.
“If covers are low, as they might be on many New Zealand farms after a dry summer, farmers may be wise to either reduce the number of hoggets to be mated or consider not breeding hoggets at all.”
In the meantime, the International Sheep Research Centre team at Massey University, with funding from Beef and Lamb NZ and the C Alma Baker trust, is continuing to work on strategies to improve the performance of hoggets.
Dr Anne Ridler is leading a team examining the perennial issue of lost pregnancies in ewe hoggets. And Dr Rene Corner-Thomas is examining nutritional strategies in lactation, using alternative herbages to improve the liveweight of the hogget at weaning and the weight of her lambs.
