Do your metrics for animal selection meet the test of common sense?
Selecting genetics that are profitable for commercial flocks
By: James Morgan, PhD
Would you buy a guardian dog for your sheep flock based on whether it fits in your carrier? Not likely; most shepherds would be more concerned about the dog’s aptitude/instinct/training for guarding sheep than size. Would you bet on a race horse for the Kentucky Derby (1.25 mile race) based on its ten mile race time? No, the best evaluation would be based on the horse’s time for a 1.25 mile race.
These don’t meet the test of common sense. Most livestock selection parameters are not as absurd as these examples, but many producers use criteria that don’t make common sense when selecting a flock sire or replacements. If the flock goal is to produce functional sheep for commercial producers, the metrics should mesh two fold: The metric should match the commercially relevant trait and mesh with flock breeding objectives.
Before going on, if you don’t have breeding objectives, make a quick list of your performance selection traits.
First, a shepherd needs to define the traits that lead to increased profit in their market. Different production systems require different criteria. Let’s look at two examples and rank selection criteria for their importance:
The most important predictor of profit for a commercial producer in this system is the number of lambs marketed and secondarily the weight of the lambs marketed (this discussion will not include annual cost of producing the lambs, which is a different article). Therefore in order of importance, the ranking would B, C, D, F, A and E. Number weaned is the most important. Number born is of similar importance since lambs have to be born before they can be weaned or marketed. Weight at 60-90 days is more important than weight of the sire or dam at a year of age or matures size, because the commercial market is buying lambs at that age and not at 12 months of age. It doesn’t meet the test of common sense to select first on sire weight at 12 months of age.
Producers do not need heavy yearling or mature weights to produce a 60-80 pound lamb. In fact, moderate weights at older ages will result in increased efficiency, being able to maintain more ewes on the same acreage or on the same amount of hay and/or grain. Fewer pounds of ewe to feed over the winter will result in decreased feed costs and more profit. The general rule of thumb is that a lamb at market/finish weight should be 60 to 70% of the mature ewe weight. Thus if your market is for 80 pound lambs, a 120-130 pound ewe is sufficient.
For our second example, let’s look at a shepherd who has a primary market of heavier lambs at 120 pounds. It can be scored in two different ways based on how exact the market is. If the shepherd only receives payment for lambs that are 120 pounds, then A is most important since weight at 135-180 days of age is a reasonable target to reach 120 pounds in most nutritional systems (forage only will most likely take longer). E is outside the target age for marketing. Most need lambs marketed before a year of age. D would help strengthen the rate of growth. Either of the following two rankings have merit: A,B,C,D,E,F or A,D,B,C,E,F. Currently mature rams sell at $50 to $80 per 100 pounds and lambs sell at $150 to $250 per l00 pounds at the sale barn. Mature weight does not make the test of common sense for commercial lamb market selection.
In most marketing scenarios, when a shepherd can market lighter lambs, even if they don’t make the target of 120 pounds, selecting on weaning/reproductive rate would produce more income and profit than selecting only on 120 pound lambs that could result from only weaning singles. The ranking in this second case would be: B, C, A, D, E, F. In summary, traits for selection need to make common sense. Just as betting on a horse because of his ten mile race time in the Kentucky Derby (1.25 miles), it does not make sense to select flock sire based on their mature weight when marketing 60, 80 or 120 pound lambs. Keep your metrics for animal selection age appropriate.