Feed into lamb (FIL)

Results:

Development of updated maintenance energy requirements for the current sheep flocks

Energy intake and out data (n = 131) used were collated from five experiments with sheep (5 to 18 months old and 29.0 to 69.8 kg BW) undertaken at this Institute from 2013 to 2017. These data were analysed using the REML analysis to develop the linear relationship between energy balance (Eg) or heat production (HP) and ME intake, with the effects of a range of dietary and animal factors removed. The net energy (NEm) and ME (MEm) requirements for maintenance derived from the linear relationship between Eg and ME intake were 0.358 and 0.486 MJ/kg0.75, respectively, which are 40% to 53% higher than those recommended in energy feeding systems currently used to ration sheep in the USA, France and the UK. Further analysis of the current dataset revealed that concentrate supplement, sire type or physiological stage had no significant effect on the derived NEm values. However, female lambs had a significantly higher NEm (0.352 vs. 0.306 or 0.288 MJ/kg0.75) or MEm (0.507 vs. 0.441 or 0.415 MJ/kg0.75) than those for male or castrated lambs.

The present results indicate that using present energy feeding systems in the UK developed over 40 years ago to ration the current sheep flocks could underestimate maintenance energy requirements. There is an urgent need to update these systems to reflect the higher metabolic rates of the current sheep flocks.

The Problem:

Current feeding standards for breeding ewes in the UK are largely determined from the Technical Committee on Responses to Nutrients (TCORN) Report published by the Agriculture and Food Research Council (AFRC, 1993).  In the 20 years since its publication, there have been no attempts to update or refine these recommendations.  This is in contrast to the dairy sector where concerns over feeding recommendations, especially for high yielding dairy cows, were largely addressed by the Feed Into Milk (FiM) Project.

Several well-documented concerns over the UK feeding standards for sheep have been highlighted, particularly in relation to the prediction of metabolisable energy requirements for maintenance, and the contribution of fat mobilization to these requirements, particularly in the pregnant ewe.  There is a need to investigate the maintenance energy requirements of sheep and to update current feeding standards accordingly, particularly for breeding ewes.  There is also a need to better understand the feed requirements for growing replacement ewes.

Aims and Objectives:

1. To review and update the current UK feeding standards for sheep, in terms of their metabolisable energy requirements, particularly in relation to age, degree of maturity and both current and historical nutritional status
2. To assess the consequences of changes in these feeding standards on the associated environmental footprint of sheep production systems

Approach:

Calorimetry studies will be used to investigate metabolisable energy requirements for maintenance in growing and adult animals, and the effects of breed, sex/status, and historical nutrition status (change in body condition) on both metabolisable energy requirements and the associated environmental footprint.  These data will be used to develop new improved models for prediction of the energy requirements of sheep toward developing a robust and precise energy feeding system for sustainable sheep production.

A literature review will be produced by March 2016 and an experiment of adult ewes will be conducted in 2017 and one for growing animals in 2018.  The final results will be available by December 2018.