1 Goal Oriented Use of Genetic Prediction Mark Johnson Inheritance of Quantitative Traits P = G + E Phenotype = Genotype + Environment Genotype Additive due to individual genes Non-additive due to combinations or pairs of genes Heritability A good indication of the ease by which genetic improvement can be accomplished by selecting one animal over another animal for a specific trait An indication of the proportion of the superiority in an individual or in a group of individuals that can be passed on to their offspring Used to estimate breeding value 1
2 Heritability Traits h 2 Magnitude Reproductive <.2 Low Growth.2-.4 Moderate Carcass.4-.6 High Few traits have h 2 >.6 Estimated Breeding Value Actual genetic merit never known Estimate breeding value based upon: - Individual performance - Performance of relatives - DNA testing genomically enhanced Expected Progeny Difference Values (EPDs) Best estimate of genetic merit Based on: Individual performance in relation to contemporary group average Trait Heritability Correlation with other traits 2
3 Expected Progeny Difference Values (EPDs) Production Traits Calving Ease Direct Birth weight Weaning Weight Yearling Weight Residual Average Daily Gain Dry Matter Intake Scrotal Circumference Docility Expected Progeny Difference (EPDs) Maternal Traits Heifer Pregnancy Milk Mature Weight Mature Height Calving Ease Maternal Cow Energy Value 3
4 Expected Progeny Difference (EPDs) Carcass Traits (based on carcass & ultrasound measures) Carcass Weight Rib-eye Area Fat Thickness Marbling Tenderness $ Value Indexes Based on the concept of an Economic Selection Index Weaned Calf Value ($W) Cow Energy Value ($EN) Feedlot Value ($F) Grid Value ($G) Beef Value ($B) Potential New EPDs Health Foot Scoring 4
5 Use of EPDs Comparison between individuals Bull A Bull B WW EPD Expect the progeny of Bull A to weigh 20 lbs. more at weaning that the progeny of Bull B Accuracy Measure of confidence in an estimate of the EPD Range of possible values 0 to 1 Depending upon amount of information available on the individual and the individuals relatives and offspring EPDs & $Values of Economic Importance to you depend on: -Your Mating System (how you use the bull) - Your Marketing Plan for calves 5
6 Goal Oriented Use of Genetic Prediction 1. If looking for an Angus bull to use on virgin heifers as a terminal sire and all calves will be sold at weaning, what are the three most important EPDs to consider? 2. If looking for an Angus bull to use as a terminal sire on mature cows, and all offspring will be owned through finishing and sold on a carcass value basis, list the single most important $Value Index that you should consider? 3. If looking for a bull to use as a rotational sire and uncertain about when you might sell the non replacement offspring: a. List the EPDs you should consider? b. List one $Value index you should consider? c. What traits or EPDs should be considered in rotational sire selection that will result in lower maintenance, more reproductively efficient cows? 4. The following two bulls are available for private treaty purchase: EPDs No. Price BW WW YW RADG Milk Doc Marb. REA $B 1 $ $ a. If sell all your calves as yearlings and the bull you select will sire an average of 26 calves a year for 5 calf crops, and a pound of pay weight will have an average value $1.50 over that time span, which bull is a better return on the initial purchase price?
7 5. An Oklahoma cow calf operator recently called you to share the following information about his operation. This cattlemen is seeking your advice. This operation has used Angus bulls as rotational sires for the past 30 years. This operation runs 500 cows and (after replacement heifers were selected), has historically marketed remainder of the calf crop as either weaned calves or yearlings. The marketing point has been determined each fall by the status of the wheat crop; if late summer and fall rains were sufficient to allow adequate winter grazing, the calves were sold as yearlings. Bull selection has historically been based on three EPDs: yearling weight, marbling and milk. Bulls excelling in these three genetic predictors have been purchased from the leading Angus programs from across the nation. Current mature cow herd weighs 1450 lb. in body condition score 5, it has been increasingly difficult in the past 10 years to keep cows at a BCS of 5. Supplemental feed cost has driven the annual cow maintenance cost to $850 per cow. Average weaning weight has been 600 Currently 65% of cows exposed to bulls are raising a calf to weaning. This breaks down to approximately 67.7% of cows exposed to a bull getting bred and 96% of calves born being raised to weaning. Herd health, de worming, vaccination program and management is excellent in this operation. No creep feeding. This operation is currently looking to replace its herd bulls. It intends to continue to use bulls as rotational sires and generate its own herd replacements. Address possible ways to improve profitability of this operation from a standpoint of: a. Bull Selection: Should other breeds be considered? What are the long term consequences of selection based on high YW, Marbling & Milk EPDs? What other EPDs should be considered? b. Marketing: Is there a different marketing strategy that might be more profitable? c. Management: Is there a better plan?