A project by the University of Warwick and funded by AHDB Beef and Lamb monitored 10 flocks in a bid to find out more about mastitis in sheep. Farmers Guardian reports.
Mastitis in ewes is a complex disease and many of the theories on how to prevent it are based on anecdotal evidence alone.
A common practice among farmers is to go through the flock at weaning or pre-tupping and examine udders. A ewe may be added to the cull list if her udder is damaged, misshapen or lumpy.
But does this practice really help reduce the incidence of mastitis in a flock, improve overall flock udder health and increase productivity?
Researchers monitored 10 flocks for two years and all ewes were examined, both during pregnancy and lactation, each year. The body condition score (BCS), udder conformation and presence of lumps in the udder of 4,500 ewes was recorded. Once first detected, udder lumps were not always present on subsequent examinations, but if a ewe had a lump in her udder at examination, she was more likely to have a lump in the future.
Udder lumps are typically caused by abscesses which go through a cycle of maturing, rupturing and reforming, enabling the bacteria in them to spread.
Lumps from udders of cull ewes were dissected and all were found to be abscesses. More than 25 bacteria species were isolated from these and Staphylococcus aureus was most common.
Acute mastitis is when there are changes detected in the udder and milk of a ewe. It is likely farmers are not identifying all cases of mastitis, possibly because some are mild and difficult to detect.
Ewes in flocks with a high rate of udder lumps in pregnancy had a greater risk of having a lump in the udder at lactation, suggesting ewes with udder lumps are a source of infection for other ewes in the flock.
Older ewes were more likely to have udder lumps than first-time lambers, probably because they have been exposed to more mastitis pathogens over the course of several lactations.
Worryingly, the study also found underfeeding energy to lactating ewes was common, especially to ewes rearing two or more lambs.
Dr Liz Genever, AHDB senior sheep scientist says: “Feeding energy and protein at recommended levels in pregnancy and lactation is vital for udder health. Ewes must receive adequate energy, either from good quality forages or other sources, such as cereals. If a ewe’s energy requirements are not met then they are more likely to develop udder lumps.
“Farmers should aim to have ewes at BCS 3-3.5 at lambing and provide sufficient feed to minimise condition loss in the first six weeks post-lambing. This will involve planning ahead so there is feed available to ewes if grass growth is poor, supplementing diets of older or thinner ewes and creep feeding lambs where necessary.”
Adequate protein is vital for milk supply. Not providing enough protein in a ewe’s diet can mean a four-fold increase in acute mastitis risk but, unlike energy, underfeeding protein was not found to be common.
Mastitis risk is reduced if ewes are not expected to rear more than two lambs, and first-time lambers only rear singles. There is a cost associated with artificially rearing lambs, but it will be lower than losing or having to cull young sheep due to mastitis.
Dr Genever says: “Conformation of the udder is important for suckling lambs and maintaining udder health. Udders should have teats placed at four and eight o’clock and drop halfway between the abdomen and hock.”
Most ewes in the study had good udder conformation.
Udders with teats which pointed forwards or downwards and udders which fell at or below the hock had an increased incidence of teat lesions, udder lumps or acute mastitis. These were rare and, like udder lumps, tended to be in older ewes. The best advice is to cull or not select offspring from ewes with extreme udder conformation as necessary.
“The practice of examining ewes pre-tupping and culling those with lumpy udders almost certainly does help to reduce the incidence of acute mastitis and udder lumps in a flock.
“If culling ewes in a flocks is not an option, then an alternative would be to run two separate flocks, one with healthy udders and one with lumpy udders, and to select replacement ewes from the healthy udder flock only. Over time, this would increase the overall udder health of the flock and decrease its susceptibility to mastitis,” says Dr Genever.
“A focus on good nutrition could reduce cases of mastitis by half in some flocks and selecting replacement ewes and rams from mothers which have not had acute mastitis or udder lumps will increase resilience to mastitis.”