A recent onfarm trial researching the links between feed, breed and gender on saleable meat yield found there was more profit in separating lambs by sex.
A group of 15 North Island farmers, who supply lambs to Progressive Meats, used Beef + Lamb New Zealand farmer-initiated technology transfer funding to analyse the records for 42,000 lambs across two seasons.
The project, facilitated by geneticist Aimee Charteris, looked for patterns and insights into onfarm factors influencing saleable meat yield as well as carcase weight and fatness.
Lambs from the 15 properties were involved in the trial, which ran over the 2011-12 and 2012-13 seasons.
Information was recorded onfarm before processing then compared to each individual animal’s carcase weight, fatness levels and saleable meat yield.
Results were consistent over the two seasons.
Group spokesperson, Horizon Farming general manager Stuart Ellingham said the analysis reinforced the importance of treating sexes of lambs differently.
“The main message I took out of the trial was that farmers tend to treat lambs as lambs.
“They don't separate out different sexes and recognise what the different sexes are doing at different times of the year.”
That management method was particularly noticeable in terminal-sired lambs, where both sexes tended to be treated the same.
An entire male lamb was different from a wether lamb which was different from a cryptorchid which was different from a ewe lamb, Ellingham said.
The differences were notable in autumn when lambs reached sexual maturity.
“If we are going to leave male lambs entire we need to process them by February to optimise their meat characteristics, that is, the dressing out percentage and saleable meat yield. Both are important.
“When it comes to female lambs, you don't want to be killing them in March or April. Their meat quality characteristics that you are paid for, depending on your processor, drop right off over that period so process before or after that.”
Other gender differences resulted from single-born lambs, breed and feed.
At the same age ewe lambs were fatter, on average, than male lambs but there was no significant difference between carcase weight and saleable meat yield.
Ewe lambs should therefore be processed earlier than male lambs if the processing specifications demanded lower fat cover.
Identifying different sexes, particularly of terminal-sired lambs, and adjusting their feeding regime and timing of processing could improve the bottom line.
To avoid ewe lambs having a lower saleable meat yield they could be separated at weaning, condition score monitored and processed earlier at lower liveweights than males.
Castrating small male lambs at docking and leaving bigger male lambs entire, to be processed pre-autumn, avoided a drop in saleable meat yield during autumn.
Single-born lambs were heavier, fatter and had lower saleable meat yields compared to twin lambs.
Single-born lambs should be processed earlier to achieve better saleable meat yields, although further investigation was needed to determine the optimal age.
There might also be a need to easily identify single-born lambs, at drafting time.
Breed differences for carcase weight, fatness and saleable meat yields were recorded and were consistent with industry experience.
There were significant differences in carcase weight and fatness and meat yield across the lambs when fed different feed types but the results were not consistent over the season.
A more structured trial on feed differences was planned for next year, Charteris said.
“So we can make sure we identify exactly what the effect is and the size of effect and ensure it absolutely is the feed type that is causing the significant differences.”
Throughout the supply season, October to September, there were considerable decreases in saleable meat yield, particularly through March and April, and across both seasons.
The variations were linked to a combination of declining feed quality and lambs reaching sexual maturity.
The group found it was financially worthwhile for individual farmers to evaluate their own systems to identify opportunities to address the March-April yield drop, Charteris said.
More work was needed to understand breed and feed variations before onfarm changes could be recommended.
There was also potential to investigate the correlation between dressing out percentage and saleable meat yield.
A copy of the full project report can be found at beeflambnz.co.nz.
