High energy concentrates deliver better results than extra protein
Where forage is being offered indoors to finish store lambs in addition to concentrate supplementation, the research indicates that only high quality forages should be included in the diet.
The exception to this is where the forage is merely serving as a source of fibre to promote rumen function with 90pc plus of the animal's energy requirements coming from concentrates.
Work from Dr Tim Keady in Athenry shows that 75pc DMD silage offered ad lib and supplemented with 0.8kg of concentrates delivers daily carcase gains of 114grams per day.
Yet in the same study ad lib concentrates supported daily carcase gains of 157 grams per day.
It took 9.1kg drymatter (DM) of concentrates to deliver 1kg of carcase gain.
Assuming a concentrate cost of €0.30/kgDM, this works out at a cost of €2.73 for the concentrates required to achieve 1kg carcase gain.
This is obviously only one of the many costs associated with a concentrate feeding system, but with 1kg of carcase worth €4.50 to €4.70, value can be added through high level concentrate feeding systems, compared to forage based indoor systems.
Yet, when we are feeding any animal particular attention must be paid to what the animal actually requires in terms of their energy and protein requirements.
The intake, energy and protein requirements required to support different levels of growth are detailed in Table 1. below.
As animals age, the make-up of their body changes, along with their nutrient requirements. They move from relatively high protein requirements to lower protein requirements.
This is due to the fact that as animals age and become heavier, fat makes a relatively higher contribution to total carcase weight when compared to the protein or lean tissue portion of the carcase.
In the Teagasc study, increasing concentrate crude protein concentration from 13pc to 18pc did not lead to improvements in lamb performance, carcase conformation or fat score.
This is due to the fact that the finishing lamb is limited in the quantity of protein they require.
Energy to support carcase fat cover is more important, so high energy concentrate ingredients are required. In a concentrate-only feeding system a slightly higher crude protein content of 15pc would be recommended.
There is a high energy requirement to deposit fat on a carcase.
In addition to other physiological changes taking place, a March-born lamb in November/December will require three times as much energy to achieve 1 kg of growth as a three month old lamb.
If we were to compare a lamb of 10kg liveweight with a lamb of 40kg liveweight the energy cost per kilo of gain in the 40kg lamb is 2.75 times higher.
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