Monday, 1 October 2012

Nutrition and Breeding

This is a topic that has come up for me several times in recent weeks, so I thought I'd put a few notes on (virtual) paper.  Specifically, the conversations have ranged around the topic of how nutrition relates to EPDs and bull (or cow) selection.

Expected progeny difference, or EPDs are a tool used in the cattle industry to measure genetic potential.  They are a prediction of how the progeny of an animal are expected to perform relative to the progeny of other animals in the same index.  Each breed produces their own EPDs and they can't be compared between breeds without some extra math.  It sounds a bit confusing at first, but they are a great tool.

As an example: if Bull A has a weaning weight EPD of +60 and Bull B is +75, then you would expect the calves from Bull B to weigh 15 pounds more at weaning on average (this assumes comparable maternal genetics between the two calf groups).

So, where does nutrition play into this?  Well, in order for those calves from Bull B to live up to their potential they are going to need the right nutrition.  If Bull A's calves are our on lush pasture, crepe fed, and the dams are producing lots of milk, they'll grow great.  If at the same time Bull B's calves are out on poorly maintained fields with low quality grasses, the mother's milk production is going to be lower and the calves aren't going to be getting the nutrients they need to grow thier very best.  It is very asy to waste genetic potential by providing poor nutrition.

Set them both up right by balancing
genetics and nutrition.
Now, that doesn't mean that everyone needs to have perfect pastures and management.  As our extension reproduction specialist says "I don't care what your nutrition plan is, but be honest about it and pick the appropriate bull"  If I know that I'm not going to supplement my cows and calves with grain, then I choose bulls with lower frame scores, lower weaning weights, and lower milk productions (if keeping the heifers as replacements).  They don't have to be bottom of the barrel, just appropriate.  Said another way:  There is no single best bull, only the best one for each situation.

Questions?  Comments?  I'd love to hear your thoughts on the relationship between nutrition and genetics.

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