Breeding and feeding

This week’s Focus on sheep breeding deals with some of the potential consequences of drought on breeding preparations. Grass supplies are recovering in the west and north but are still slow to pick up in the east and southeast. This is creating immediate problems for early-lamb producers targeting a lambing date of early January. Many farmers in such circumstances have been feeding ewes meal in the run-up to breeding to ensure animals are on a rising plane of nutrition. It is important to ensure that this preferential feeding is continued for at least the first three weeks post-conception to deliver optimum conditions for embryo attachment. A standard cereal-based ration or supplement such as soya hulls or beet pulp will suffice with energy intake the limiting factor at present. Where ewes have access to some forage, a top-up of 0.3kg to 0.4kg concentrate should suffice, but where grass supplies are limiting, this may need to be doubled or even a little higher.

Abortion causing infectious agents

Reports of an increased incidence of abortion-causing diseases – toxoplasmosis and enzootic abortion – continue to rise annually. The two diseases cause abortion but differ significantly. Enzootic abortion can spread sheep-to-sheep during lambing while toxoplasmosis does not spread sheep-to-sheep and is picked up via contaminated feed. Once an animal contracts toxoplasmosis, it will develop natural immunity. A ewe that suffers abortion from enzootic abortion will also develop immunity but the big difference here is that she will continue to shed the infection throughout the flock.

Once enzootic abortion enters a flock, it is hard to eliminate the disease entirely with vaccination (Enzovax) the only form of control outside of complete culling and repopulating with a disease-free flock, which is likely to be impractical and still presents a risk. Veterinary advice includes vaccinating the entire flock and thereafter continuing to vaccinate replacements. Vaccination may not immediately prevent further abortion with some latent infection possible for a few years after a vaccination programme has begun. One vaccination is generally sufficient for lifetime cover and it is important to note that vaccination needs to be administered at least four weeks before the start of the breeding season. Where a flock is clean of infection, buying in latently infected sheep is the principal entry route. Therefore, great care must be taken when sourcing replacements. If progressing down the vaccination route to control toxoplasmosis, the vaccine available, Toxovax, must be administered at least three weeks before the start of the breeding season. One vaccination is sufficient for lifetime control, meaning that once a flock is vaccinated, only replacements will require vaccination thereafter.

Fertiliser application

It is important to take every opportunity to get back on track in terms of replenishing grass supplies. Growth rates in a normal year fall off significantly once you progress into September. Therefore, applying fertiliser as soon as conditions are suitable will deliver a much greater return on investment and help get the farm back on track much quicker. For highly stocked farms, the advice is to apply 25 to 30 units with a lower application sufficient on lowly stocked farms. There is also a good opportunity on these lower-stocked farms, however, to apply a higher volume than required to help build winter forage supplies.