Late pregnancy concentrate - be aware of ingredient composition

Most ewes are offered concentrate supplement during late pregnancy to provide additional nutrients to meet the demands of the growing foetuses and for colostrum production. Dr. Tim Keady summarises research results from Athenry on the effects of concentrate composition during late pregnancy.

Main Messages

• Offer concentrate to ewe during late pregnancy that contains 19% protein.
• When purchasing concentrate select on ingredient composition and not solely on price.
• Purchase a concentrate formulated using good ingredients
• Use a concentrate that uses soyabean as its protein source

Introduction

Most ewes are offered concentrate supplement during late pregnancy to provide additional nutrients to meet the demands of the growing foetuses and for colostrum production. The level of concentrate offered depends on expected litter size, expected lambing date and forage feed value. Ingredient composition of the concentrate should also be considered when purchasing concentrate to offer to ewes during late pregnancy.

The objective in this paper is to summarise research results from Athenry on the effects of concentrate composition during late pregnancy on ewe and lamb performance.

Concentrate protein

Concentrate offered to ewes during late pregnancy should be formulated to contain 19% crude protein (i.e., 190 g of crude protein per kilogram as fed) as the grass silage on many sheep farms has a low protein concentration. Sometimes it is suggested to formulate 2 concentrates; a 14% protein concentrate for weeks 6 to 4 pre lambing and 19% for week 3 prior to lambing to lambing. Considering the size of most sheep flocks in Ireland, and the fact that ewes require low levels of concentrate during the first 2 to 3 weeks of supplementation, together with the low protein concentration of grass silage on most sheep farms the savings from using 2 different concentrates is, at best, marginal. For example, whilst relative to a 19% crude protein concentrate the cost of formulating a14% crude protein concentrate is lower by approximately €30/t, this equates to only 1 cent per ewe daily during the first few weeks of supplementation, when ewes are offered between 0.2 and 0.4 kg/ewe daily.  For every 100 ewes in a flock 1 tonne of concentrate will last for 50 and 25 days, respectively, when ewes receive a daily concentrate allowance of 0.2 and 0.4 kg/head. Therefore, for most farms there is no benefit to animal production, logistics or financial outcome from offering a low protein concentrate during the first weeks of concentrate supplementation.

Where maize silage is offered as the forage during late pregnancy then concentrate crude protein concentration should be increased to 23% and mineral and vitamin supplementation should be increased by approximately 50%.

Concentrate protein source

The effects of concentrate protein source offered during late pregnancy on the performance of ewes and their progeny was evaluated at Athenry and results are summarised in Table 1. Two rations were formulated to have the same metabolizable energy (12.4 MJ/kg DM) and protein concentrations (18% as offered). The protein sources in the concentrates were either soyabean meal or a mixture of by-products (rapeseed, maize distillers and maize gluten). Lambs born to ewes that had been offered the soyabean-based concentrate were 0.3 kg and 0.9 kg heavier at birth and weaning, respectively, than lambs born to ewes offered concentrate that contained by-products as the protein source. The increase in the weaning weight of lambs from ewes offered the soyabean-based concentrate in late pregnancy (extra cost ~ €0.50/ewe) is similar to the response obtained from offering each lamb 6 kg of creep concentrate until weaning (cost ~ €3.50/ewe per set of twins).

Table 1.  Effect of concentrate protein source on ewe weight and lamb performance

Concentrate at Athenry

The ingredient composition of the concentrate being offered to ewes during late pregnancy at Athenry in 2020 is presented in Table 2. The concentrate was formulated to contain 19% protein using good protein (soya, rapeseed), energy (maize, barley) and fibre (beet pulp, soya hulls) sources. When offering similar levels of concentrate to ewes during late pregnancy as is offered at Athenry, a reduction in concentrate price of €20/t equates to a saving equivalent of only 45 cents per ewe. Therefore, when purchasing concentrate it is important to be aware of its ingredient composition rather than basing the decision on which concentrate to purchase solely on price alone.

Table 2. Ingredient composition of the concentrate that will be offered to ewes at Athenry this year.