Through the study, Kate also wanted to initiate a standard scoring system for udder health. She shared the early results of the trial at two B+LNZ Farming for Profit days in Canterbury recently.
The study involved 1200 two and four-tooth commercial Romney ewes run on a Massey University farm. These ewes were followed for three years and had their udders examined and scored for factors such as defects, symmetry, appearance and teat positioning four times a year; at pre-mating, set-stocking, tailing and weaning.
Lambs were matched to the dams and data such as lamb weights and survival to weaning was also collected.
As part of the study, a number of commercial farmers and vets were also surveyed about their experiences with udder health.
Kate said that while 85 per cent of the farmers surveyed as part of the trial were actively examining ewe udders, the time, the method of examination and the factors upon which culling decisions were very diverse.
While studies are on-going, Kate says preliminary results show that udder defects are very important and lambs born to ewes with lumps or hard udders are three to five times more likely to die.
There was also a 5-35gm/day decrease in lamb growth rates in ewes with diseased udders.
Kate says pre-mating is a critical time to palpate udders and as part of the study, an udder score given to each ewe proved to be a good predictor of lamb survival to weaning.
Lambs born to ewes with hard udders had a 30% chance of mortality while lambs born to ewes with lumps in their udders had a 40% chance of mortality.
By comparison, lambs born to ewes with normal udders had a 12% chance of dying.
This means there were much higher lamb mortality rates in ewes that were found to have defective udders at their pre-mating check.
Kate says that unlike dairy cows, sheep don’t respond that well to treatment for udder problems so at this stage, culling is the best option.
There is some suggestion that some udder problems are developing in the dry-off period post-weaning, so areas for further investigation include weaning management – particularly in early –weaning and the impact of high lamb growth rates and alternative forages on udder health.
The study found that 88% of ewes that were found to have udder defects at weaning still had those defects four to eight weeks later, but more defects also appeared in the flock and this highlighted the need to carry out a pre-mating udder and teat palpation to identify which ewes are likely to have poorer performing lambs.
Cull: Ewes with black mastitis, ewes with big lumps in the udder – especially at the bottom of the udder and ewes with rock hard udders.
Don’t cull: Superficial lumps near the udder but not part of the udder (they can be golf-ball size lumps in front of the udder). These lumps are quite common at weaning (affecting 3.3% of ewes in the study) but disappeared post-weaning.
In the future the study will look at the change in udder scores in subsequent seasons, the economic cost of keeping or culling ewes with different udder scores, milk quantity and quality and histology of ewes with diseased udders and the economic viability of different treatment options. Look out for future information about udder scoring and trial results as they become available.
This study was funded by Beef + Lamb New Zealand, Massey University and The C.Alma Baker Trust.