SHEEP MANAGEMENT - PRE-MATING: Nutrition and Body Condition

The body condition of rams and especially ewes at the start of the mating season, is of utmost importance to optimize reproduction. In sheep it is even more important than in cattle due to the fact that multiples are possible/desirable in sheep and nutrition and condition play an important role in this.

 Rams

The condition of the ram during the mating season is just as important as that of the ewe. During the mating season, rams have limited grazing time and spend a lot of energy chasing and mating ewes in heat. (In between, they usually fight with each other too!) This depletes his reserves and if the ram's condition is not right at the start of the mating season, it will adversely affect his working capacity and fertility.

It is important that the condition of the rams is determined 8 weeks before the start of the mating season and adjusted if necessary. Spermatogenesis (development of the sperm to maturity) takes approximately 50 days. A condition score of 3 that builds to 3.5 at the start of the mating season is desirable to ensure that spermatogenesis and semen volume are optimal at the start of the mating season.

However, be careful not to feed rams too much high-energy concentrates too quickly in the run-up to the mating season. Firstly, this can lead to subclinical acidosis which can be detrimental to sperm development. Secondly, it can lead to the accumulation of fat at the neck of the scrotum, which is detrimental to fertility as it affects temperature regulation. If supplementation is given, the intake should be increased gradually. In addition, the supplement should contain good quality protein to optimize sperm development.

If new rams are purchased, this should preferably take place 90 days and not shorter than 60 days before the start of the mating season. Rams purchased at auctions are usually in very (too) good condition (4+) and too fat to be put among the ewes immediately! The condition of these rams should be gradually adjusted downwards over at least 4 weeks, to a condition score of no more than 4. If rams lose condition too quickly, they may become infertile during the mating season.

Rams that are overconditioned and unfit can start off with a bang to mate ewes, but quickly lose steam (get tired). If rams with auction fat are placed with the ewes, they will most likely “fall apart” as they are used/adapted to a high-energy diet (for finishing for the auction), and now exposed to a roughage based diet (grass/crop residues) when they are with the ewes. The rumen microbes must first “adapt” to be able to digest more roughage (the numbers of roughage-digesting microbes must first increase), instead of the microbes that dominate in an easily digestible, high-energy diet. This adaptation can take up to 21 days.

Ewes

More than 70% of the reproductive rate of a herd of ewe is determined by nutrition. Nutrition has a particularly large influence on the number of multiples born. 8 Weeks before the start of the mating season, in the different production systems that are commonly followed, has varying implications e.g.

• In an eight-month (accelerated - lambing 3 times in 2 years) lambing system - this is 1 month after the ewes have lambed. Especially ewes with multiple lambs are now under immense pressure and milk production reaches a peak. Feeding ewes at this time is critical to minimize the loss of condition. Therefore, it is of utmost importance that these ewes lamb in optimal condition - which must be monitored and adjusted in the late pregnancy phase

• In a 12-month lambing system where ewes lamb once-a-year, the ewes are no longer lactating and the lambs have already been weaned. The ewes should therefore be in an acceptable condition of 3, building up to at least 3.5 to even 4 at the start of the mating season.

The season, grazing conditions (quality and quantity of grazing), as well as the condition of the ewes will determine which supplementary feeding strategy will be most appropriate, to ensure that the ewes will be in optimal condition at the onset of mating season.

Regardless of the production system, ewes that have a condition score of <2.5 by this time (6-8 weeks before mating) will need special attention. Provide better grazing and/or a production lick with the correct intake to make a significant difference in condition. Remember that every 1kg increase in mating mass can lead to a 1.5% increase in lambing percentage.

The role of  flush feeding:

Flush feeding is not so much aimed at improving the conception of ewes (it can play a small role), but mainly at increasing the number of multiple births (fecundity) in highly fertile ewes. With the correct supplementation, the provision of flush feeding, even in ewes in good condition, can be economical, provided that the ewes are highly fertile and have the genetic capacity for multiple ovulations. Stimulating feeding should be started 3 weeks before the start of the mating season and continued for at least 42 days (after the start of the mating season). This will ensure that the embryos attach properly in the uterus. If ewes lose condition shortly after conception, this may lead to resorptions or the death of one or both fetuses.

NB.  With sheep, it is important to physically examine (feel) the animals to determine the condition score more accurately! This is especially applicable to wool-bearing breeds with wool of 6 months and longer, where the condition can easily be misjudged if it is only evaluated from a distance.