Feeding ewes for optimal production and reproduction

Dr Vlok Ferreira

National Technical Manager of Ruminants, RCL Foods

Cycle of the ewe

Flush feeding is a management practice that should be put in place roughly three weeks before the mating season. The ideal body condition score (BCS) for a ewe at mating should be about 3.5, where 1 is very thin and 5 is overfat. The goal of flush feeding is to increase the weight and condition of ewes, which will increase the ovulation and conception rate of ewes that have been mated, and results in a higher lambing percentage. For every 1 kg of weight that the ewe gains to be at her ideal BCS of 3.5, her lambing percentage increases by 1.5 – 2%

Ewes that have a BCS of 2 – 2.5 should be fed separately from ewes already in a good condition, as ewes that are already in a good condition will not benefit as much from flush feeding. Flush feeding in ewes with this lower BCS should be implemented 4 – 6 weeks before mating, and should be maintained until at least 3 weeks after mating. The reason behind this is to keep the level of nutrition consistent, so that ewes do not reabsorb the embryo due to stress.

During the first three-quarters of gestation, placenta growth mainly takes place, which contributes to approximately 1 kg of the weight. It is critical that the ewe is not allowed to become overfat during this time, and a good way to manage this is to increase the amount of roughage in their diets and supplement it with a maintenance lick.

75% of the foetal growth takes place during late gestation — the last 6 weeks before parturition. During this period, it is suggested that a bypass protein and production lick is supplied to the ewe to ensure optimal udder development and milk production. During early lactation, the ewe’s protein requirements increase drastically and she will need about 3 times more protein than at maintenance level. About 63% of the lamb’s growth will be influenced by milk production in early lactation, and only 37% of its growth will be influenced by genetics.

The only nutrition that a lamb receives for roughly six weeks after it has been born is milk, and this will correlate directly to its weight gain. For every 5 kg of milk that a lamb drinks, it will gain about 1 kg of weight. It is highly important to supply creep feed to the lamb if the ewe’s milk production is limited.

Weight loss during the first six weeks of lactation

Weight loss during early lactation has been found to delay estrus based on how much weight the ewe has lost. It takes 6 months for the ovum to mature, and this maturation is dependent on the ewe’s level of nutrition and body condition.

An experiment in Australia was conducted with Merinos, which correlated the loss of weight during lactation with the delayed estrus in the next mating season. In Queensland it was found that when a ewe lost about 8 kg during lactation (14% of her mature liveweight), her estrus was delayed by 20 days, but when she lost 4 kg (7% of her mature liveweight), it was found that this delay was only 5 days. Experiments in Victoria revealed the same results.

Weight loss during the first six weeks of lactation

The aim of creep feeding is to ensure that lambs obtain 50% of their year-old weight within the first three months. It also helps to develop the wool and reproductive potential of a lamb. An added bonus is that it helps to relieve the pressure on the ewe so that the amount of weight and condition that she loses is reduced, which in turn increases her conception rate.

Look out for part 3 of this series, where we discuss how nutrition influences the quality and quantity of wool growth.