Unlocking the feeding secrets of sheep

The first step of a unique trial to understand more about the intricacies of sheep feeding is complete, but Invermay-based scientists who lead the work say it’s just the beginning of an exciting four years’ research.

Feed efficiency – the measure of how much feed an animal actually eats, versus what it should need to eat for maintenance and growth – is being integrated into many worldwide breeding schemes for both beef and dairy cattle and has been shown to be moderately heritable. Given its importance in these species it is likely to also be important in sheep too, says Tricia Johnson, a senior scientist from the Animal Genomics team.

While feed efficiency continues to be ranked in the top 10 traits in the “Industry Needs Analysis” carried out by Beef + Lamb New Zealand Genetics there is currently no data available in New Zealand that investigates the genetics associated with it in New Zealand maternal sheep breeds. In fact, there’s very little relevant overseas data either.

A recent trial near Invermay is the first step of the Beef + Lamb New Zealand Genetics-funded programme.

“What we’re aiming to do is collect sufficient data over a four-year time period to provide first estimates of the heritability of the trait and genetic correlations between it and other important production traits.  Such data will be able to inform decisions about its integration in to maternal breeding programmes,” says Tricia.

But, investigation of this trait required the development of automated feed intake machines capable of real time recording of individual feeding events of sheep in a mob situation using EID technology to differentiate animals.

Whilst there are a number of ‘off the shelf’ machines that could have been purchased from commercial companies, all had been designed for use in cattle or pigs and all had limitations for use with sheep.

Instead, 20 automated feeders specifically designed for sheep were built by AgResearch’s Engineering Team at Lincoln and installed, ready for use, in early July.

The feeders are designed to record the number and size of feeding events each day, from which total feed consumed per day can be calculated. They allow real-time access to the loggers, as well as receive text alerts and a daily summary table of data collected per animal, noting any outlier animals which means that the data is equally being analysed in real time.

The feeders are also portable, meaning they can be utilised at other sites if required.

At the beginning of July the first 200 ewe hoggets from the Woodlands Central Progeny Test, and the genetically-linked Woodlands Coopworth Progeny Test entered the facility.

Additional measurements that are being made include full spiral computed tomography (CT) imaging of the animals at the conclusion of their time in the facility because significant relationships between feed efficiency and body fatness have been observed in overseas cattle studies.  This data will also provide insight in to the variability in to the genetics of fat distribution (subcutaneous vs intermuscular vs internal fat reserves).

An additional aspect of the programme will investigate correlated measurements including heart rate; body temperature (measured using thermal imaging) and  methane output (measured using Portable Accumulation Chambers (PAC)), if any are proven to be correlated to feed efficiency, in the long term they will allow for more rapid screening of feed efficient sheep.

This trial will be repeated again at the same time next year.  A first look at the data was undertaken in preparation for the Association for the Advancement of Animal Breeding and Genetics Conference in Lorne, Victoria in September, says Tricia.

“Overall the trial went better than we could have hoped for embarking on such a large scale project involving the technology. This first look at the data is pointing towards significant animal variation in the trait of feed efficiency, with some sire variation also existing.  There is also very interesting feeding behaviour evident too, with some consistent grazers and gutsy sheep.”