Monday, 12 October 2015

Breast is best

We have had a couple of cases of mastitis recently, and so have had to bottle feed two or three lambs. In some cases this is complete substitution (the mother had no milk) and in others it has been an addition to their diet.

I compared the live weight of lambs with the meat weight - i.e. the carcass processed by the butcher. The carcass includes just the bone and muscle structure, not the internal organs, skin or contents of the body cavity.

Here is the result:


Date Live Weight at Slaughter (kg) Meat weight (kg) % Meat /Live Bottle Fed
31/10/2015 23.5 9.2 39.15% Yes
03/05/2015 21.1 9.8 46.45% Yes
31/03/2015 27 15.1 55.93% No
17/08/2015 19.2 8.8 45.83% No
17/08/2015 21 10.99 52.33% No

The ratio of meat to live weight seems - this is a very, very small sample - to be higher in the lambs that fed naturally. Naturally feeding lambs had an average 51.4% meat:live weight ratio, while bottle fed lambs had an average 42.8%.

There are some published papers on this, for example this paper on milk source and body weight [1] but none, that I know of, on Ripollesa sheep.

Time for more research, methinks!

Joaquim Casellas at the Autonomous University of Barcelona has confirmed that there are no studies of this issue in Ripollesas. He has pointed me to this useful study on goats which shows that maternal milk vs milk powder does cause differences in fatty acid composition. 

This leads me to think that one possible explanation of the differences in meat weight:live weight is that bottle fed lambs may build up more body cavity fat (which is discarded in the butchering process) than ewe-fed.

1 Hernández-Castellano, L. E., I. Moreno-Indias, A. Morales-delaNuez, D. Sánchez-Macías, A. Torres, J. Capote, A. Argüello, and N. Castro. ‘The Effect of Milk Source on Body Weight and Immune Status of Lambs’. Livestock Science 175 (May 2015): 70–76. doi:10.1016/j.livsci.2015.02.011.

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