Evaluating metabolisable protein supply

Results:

1. The desk study indicated that MP requirements for terminal sire mated, prolific ewes are likely to be 20-30% greater than AFRC (1993) estimates, largely due to heavier lambs. Calculations showed sensitivity of intestinal amino acid supply to DUP content, suggesting that protein quality, i.e. essential amino acid composition, is increasingly important for high DUP diets.
2. Using SBM and xylose-treated SBM (SoyPass®) as models, we observed that early lactation production responses were only modestly more sensitive to DUP than to ERDP.
3. The desk study summarised several protein protection technologies; especially browning with xylose and formaldehyde treatment show great opportunities to more than double DUP content.
4. Novel high-DUP concentrate supplements (up to 56 g DUP/kg), resulting from increased levels of SoyPass®, xylose-treated rapeseed meal (RaPass®), micronized field beans, and mixtures thereof, doubled daily DUP supply in rations with different forage backgrounds but failed to increase lamb weaning BW. The absence of effect of protein source supports the view that home grown protein sources can be used to reduce reliance on SBM in ewe diets.
5. The outcomes of this programme of work is informing the revision of the “Feeding the ewe” booklet, currently underway with support from AHDB Beef & Lamb, and have been used in a number of end-user activities (Farmer Discussion Groups, Open Days, Farm Trials).
6. To feed high DUP pellets in lactation post turnout (~22% DUP), we tested “3-in-1 feeders”, systems that allow 24-h access to supplements but restrict intake by making ewes work hard to extract grains from a narrow aperture. Despite sustained efforts, pellets could not be made hard enough to avoid them absorbing environmental water inside the feeder, resulting in bridging and blocking the flow. Indirectly, this project contributed to the development of high DUP feed blocks based on protected SBM, now available to farmers wishing to supplement DUP at grass
7. When ewes were managed to reduce body CS by 0.5 units during mid-pregnancy, benefits of DUP supplementation on ewe performance were observed; for thin ewes, additional DUP supply increased lamb birth weight, colostrum component yields, and subsequent lamb performance to a larger extent than for fit ewes.
8. Body condition scoring provides a good subjective indication of back-fat depth. The strong relationship between back-fat and eye-muscle depth suggest that composition and energy value of ewe BW change remains relatively constant across a range of CS. Further work is required to clarify relationships between CS, scanning results and nutrient balance in different breeds.
9. It was observed that ewe DUP supplementation did improve litter weaning BW when ewes were exposed to worm challenge upon turn out following periparturient housing in the absence of worm challenge. Unexpectedly, this was not the case for ewes who were under continued challenge during the periparturient period.
10. Building on earlier trial work demonstrating that daily volume of SBM can be reduced by 50% when using protected SBM (Sopralin®), farm trials carried out showed that feeding daily protected SBM can be replaced with 3x weekly feeding without impact on ewe productivity. Both outcomes are providing farmers opportunities to reduce costs, save labour and trough space

The problem:

The nutritional recommendations used for formulating ewe rations were developed in the 1970s. However, the breeds being used, ewe weights, productivity and birthweights have changed, and it is not certain whether the recommendations are still fit for purpose. Also since the banning of fishmeal, ewe diets have been reliant on soya to provide enough bypass protein.   This has issues in terms of sustainability and carbon footprint on sheep production.

Project Aims:

• To determine the metabolisable protein (MP) requirement of prolific ewes during late pregnancy and into lactation
• To investigate the use of protein protection technologies to enhance MP supply from home grown protein sources
• To design concentrate supplements using home grown protein sources to satisfy the MP requirements of prolific ewes offered different basal forages
• To provide guidelines and recommendations on the use of home grown protein sources and protein protection technologies to optimise protein nutrition and ewe performance in different feeding systems
• To design and test novel concentrate delivery system for supplementation at grass‘

Approach:

A desktop review will be done on the use of home grown protein sources and to identify novel protein protection technologies. Experiments looking at different forages (straw, hay, grass silage, maize silage and lucerne), protein source (protected and unprotected soya bean meal, rapeseed meal, field beans or peas) and level of MP supply will be conducted at Harper and SAC over two seasons.

Deliverables:

This work will provide updated information on the MP requirements of pregnant and lactating ewes. The overall aim is to provide evidence of how substituting some of the soya bean meal in ewe rations with protected home-grown protein sources (rape, beans and peas) can be done without affecting performance.