Investigation of high barren rates at scanning

 

It is common to see sheep scanner’s trailers on the road just now for earlier lambing flocks. Hopefully early indications of scans are good, but the check list below which we issued two years ago is a useful reminder if called to investigate problems with poorer scans through this winter and put in plans to manage this going forward.

One other consideration to bear in mind, particularly for earlier lambing flocks is was the new tup(s) purchased after experiencing heat stress either at a sale or during transport – there were some sales on hot days earlier this year. If so, there is an increased risk of poorer semen quality for six to eight weeks after a heat stress event, so consider this in the context of any semen sampling that may be undertaken.

Questions To Ask When Investigating High Barren Rates In Ewes

 

• Is the problem evenly spread across all groups and ages or can you narrow it down?
  If Toxoplasmosis or Border disease is endemic in a flock early embryonic death is more likely to occur in younger ewes.

 

• Are homebred and/or purchased ewes affected?
  Either group could infect the other with a pathogen they haven’t encountered before.

 

• What type of land are they grazing on? Are there ticks?
  Purchased tups and ewes may be naïve to tick borne fever with consequent poor fertility or early embryonic death. Gimmers that are grazed away from home for long periods could also be naïve. Homebred ewes could be impacted if changes in land management have increased tick challenge. Ticks are present on many land types (eg in-bye ground) as well more traditional hill ground.

 

• Have they had access to brassicas/red clover?
  Oestrogenic feeds can affect fertility, although there have been recent published articles showing no effects on fertility.

 

• What was ewe body condition like at tupping and now?
  Ewes that were too thin at tupping or have lost a lot of condition can scan poorly. Overfat ewes also carry fewer lambs.

 

• How well is liver fluke controlled?
  In addition to effects on body condition anything that causes significant liver damage could affect the maintenance of pregnancy.

 

• Has there been an issue with lameness or sheep scab?
  Significant loss of body condition and/or hypoalbuminaemia could affect scanning percentages.

 

• What date did the tups go out and how long were they out for?
  Has there been a change to previous years?

 

• Is there any suspicion of poor tup fertility or tups not working?
  Were tups examined before being turned out with the ewes? Were they all seen to serve ewes? Was the tup:ewe ratio appropriate particularly if tup lambs were used?

 

• Were all the ewes marked and did they hold to the first service?
  Were the ewes cycling at the time the tups were introduced? Were ewes tupped repeatedly or did embryo loss occur after the tups were removed?

 

• Were there any issues with abortions in 2023?
  Was Border disease or toxoplasmosis suspected or diagnosed?

 

• Was there any evidence of foetal death/resorptions at scanning? How many sheep were affected?
  Can help differentiate conception failure from foetal loss.

 

• Could there be an issue with selenium +/- iodine deficiency?
  Is trace element status known? Is routine supplementation given?

 

• Are they vaccinated against Toxoplasmosis?

 

• Have they had contact with cattle – could there be a BVD risk?

 

• Were they gathered for any stressful procedures after tupping?

 

It is often difficult to confirm the cause of high barren rates and a useful next step is to investigate any abortions that occur.

Possible testing indicated by the answers to the above questions could include border disease and toxoplasma serology, GSHPX and pooled iodine. EDTA bloods could be tested for TBF by PCR. We are always happy to discuss these cases, so please don’t hesitate to get in touch.

Posted by SRUC Veterinary Services on 04/12/2023