Triplesire

Almost every year I have a ewe or two that delivers an unplanned breeding. Either due to a ram breakout too early in the fall, or perhaps she lost a pregnancy early-on, and re-bred once all the rams were all together with the we group. Often I don’t care who the sire is, I just mark it down as “UNK” (unknown). Then, the lamb either goes to the slaughter channel, or I sell at a discount the mystery ewelambs as 50% recorded ewes.

This time, with those January triplets, I was interested in the parentage. The mother is a good ewe and I’d like to register them. So, I DNA tested them. I already had DNA banked on all my adult rams, and the cost is $18 per lamb to match them up with the appropriate sire. Er, sires.

 

The Central Tendency of Twinning

In Katahdins, there is generally a preference for breeding ewes which have twinning genetics. We know that ewes ovulating more than one egg per cycle is heritable; and that when we select for it, we shift the bell curve toward the right: toward multiple births. So, some consider this a by-product of twinning selection, that we often get triplets or quads. This phenomenon, in itself, is a bell curve; with most ewes in a given season offering twins, and a smaller percentage having singles or triplets (and rarely, four or more). A 200% crop is fairly standard in our breed.

Because of this focus, it is considered a best practice when selecting breeding stock, to take into consideration whether the animal has twinning genetics, or not. For most people, the tendency is to ask about a particular animal “is she a twin?” This is a good start, but I’d like to illustrate why this “is a” descriptor is not as good as knowing the entire history of the dam’s twinning record. Or, better yet, her family’s entire history of twinning.

 

2014 Lamb Birth Weight Trends

Lambing is almost over here, I have one late ewe left to deliver whom I think is due next weekend. Total count so far is 64 lambs, which is low, but not terrible. I have eight open ewes, six of which are yearlings. So now it’s time to pour over data and start making decisions about which sheep to keep, sell, and cull; as well as decisions about management changes for next year.

 

Culling Decisions

I wanted to write a bit about culling decisions, it’s been on my mind due to a lot of discussions on sheep discussion groups I read. For this discussion, I won’t differentiate between sending an animal to slaughter versus selling it to someone else. The former is typically done when it wouldn’t be ethical to pass on a compromised animal to someone else. Selling, however, can be fine if the animal doesn’t meet our own goals, but may be a good fit in someone else’s system; as long as the perceived detractors are disclosed, and the animal is discounted appropriately. Either way, there are times when we may decide that an animal will not be retained in the herd because she’s not passing muster.

 

Statistical Correlations in Lamb Birth Weights

In the last year, I’ve completed Green Belt certification, which is a portion of Lean Six Sigma training. I loved the coursework, and though it was for work and surely I’ll apply these skills to engineering, I couldn’t help but relish the fact that they are also really useful for sheep! And supposedly, Lean Six Sigma credits some of its origin to Agriculture, and it’s early use of statistical analysis in breeding improvements. So here is some fun tinkering with statistical analysis of factors which may affect birth weight in my lambs.