Using EPDs in Selection Edited by: Jessica Hawley & Brandon Freel Originally compiled by Colorado Agriscience Curriculum

Objectives Define Expected Progeny Difference. Interpret EPD categories. Analyze EPD variations within breeds. Recognize the importance of EPD use in selection. Apply EPD concepts. EPD Video

Selection of livestock Two Ways Phenotype – The appearance of an animal. Genotype – What genes are present and how they are combined.

Breeding Values (EPD) Expected Progeny Difference – A measurement of genetic potential based on the performance of relatives. (ACC) Accuracy is an important term used in understanding EPDs. It is a measure of expected change in the EPD as additional young are born to the sire. A high accuracy value is better as the chances of the EPD being correct rise.

Common EPD’s Common EPDs: Performance-based, Carcass-based, and Ultrasound. Performance-based EPDs – Are based on a measurement of how well the bull’s offspring perform. Examples of performance-based EPDs are birth weight, weaning weight, milk and yearling weight. Carcass-based – Are based on how well the bull’s offspring have performed on the rail. Examples of carcass-based EPDs are Rib-eye Area, Fat (Outer), Retail Product, and % Intramuscular Fat. Ultrasound EPDs – Done from an ultrasound of the actual bull. Examples of ultrasound EP’s are Rib-eye Area, Fat (Outer), and % Retail Product.

How to Compare EPDs BW WW Milk YW Marb REA FAT %IMF RE %RP Bull A -0.5 +61 +15 +111 +.20 +.19 +.017 +.50 +.22 +.004 +.28 Bull B +0.1 +50 +21 +51 +.44 +.26 +.66 -.046 How much more will Bull B weigh at birth than Bull A? Answer: .6 pounds. How much more will bull A weigh at weaning than Bull B? Answer: 11 pounds Which bull would be a better bull for heifers? Answer: Both would be fine. But smaller calves would come from A. Which bull has a bigger Rib-eye Area? Answer: Bull B

Selection of Cattle Should include both visual and genetic appraisal Valuable genetic traits Depends on producers goal Culling – Cows should be culled from the herd based on the productivity of their calves. Evaluation – Cows should be culled based on evaluation of the udders, eyes, skeleton and teeth.

Selection of Heifers Try to select heifers that will conceive early in the breeding season, calve easily, produce a good supply of milk, wean a heavy calf, make a desirable genetic contribution to your cow herd, and have calves with desirable carcass traits.

Accuracy and Herd EPD’s Accuracy - The reliability that can be placed on the EPD. Accuracy of close to 1.0 indicates higher reliability. Herd- Indicate the number of herds from which daughters are reported. The reliability that can be placed on the EPD. Accuracy of close to 1.0 indicates higher reliability. Do you think accuracy would decrease or increase as the number of calves sired by that bull and measured for particular traits increases? Why? It would increase because we know our average comes from a larger population. If you flip a coin six times and you get 5 heads and 1 tail is that as accurate a representation of the possibility of flipping either a heads or a tails as flipping it 100 times? No. So, it’s important when we look at EPD’s to see how accurate these estimates are. Herd- Indicate the number of herds from which daughters are reported. Why is it important how many herds a bull has been bred to? It increases the accuracy of our data. 9

Birth Weight Predictor of a sire’s ability to transmit birth weight to his progeny, compared to the progeny of an average bull for a specific breed; expressed in pounds. Predictor of a sire's ability to transmit birth weight to his progeny, compared to the progeny of an average bull for a specific breed; expressed in pounds. Why would we want to know the average birth weight of a bull’s calves? In smaller or first calf heifers, the bigger the calf the more liker the cow is to have calving problems. 10

Weaning Weight Predictor of a sire's ability to transmit weaning growth to his progeny, compared to the progeny of an average bull for a specific breed; expressed in pounds. Predictor of a sire's ability to transmit weaning growth to his progeny, compared to the progeny of an average bull for a specific breed; expressed in pounds. Why is weaning weight important? If a producer sells his calves at weaning he wants to know about how many pounds above or below the breed std. his calves will probably weigh. Remember, cattle producers are paid by the pound. Also, later on he can subtract his calves weaning weight from its yearling weight to determine its average daily gain. Why would a producer want to know how much his calves can gain daily? 11

Yearling Weight Predictor of a sire's ability to transmit yearling weight, compared to the progeny of an average sire for a specific breed; expressed in pounds. Predictor of a sire's ability to transmit yearling weight, compared to the progeny of an average sire for a specific breed; expressed in pounds. Why is this important? Producers want calves that can put on weight fast because the more they weigh the more they’ll get paid at the auction barn. 12

Maternal Milk Predictor of a sire's genetic merit for that part of weaning weight attributed to milk and mothering ability. It is compared to daughters of an average bull for a specific breed. Predictor of a sire's genetic merit for that part of weaning weight attributed to milk and mothering ability. It is compared to daughters of an average bull for a specific breed. Who would want this trait in a bull? Someone who would keep replacement heifers from that bull. 13

Scrotal Circumference Predictor of the difference in transmitting ability for scrotal size, compared to the progeny of an average bull for a specific breed; expressed in centimeters. Predictor of the difference in transmitting ability for scrotal size, compared to the progeny of an average bull for a specific breed; expressed in centimeters. Scrotal circumference is important because it has been shown to sometimes indicate how early a bulls daughters will reach puberty. Bulls with larger scrotal circumference have daughters that reach puberty earlier than those with smaller scrotal circumference. If a producer is breeding for replacement heifers, he wants them to have calves as soon as possible to keep his costs down. 14

You are a rancher looking to improve your herd overall You are a rancher looking to improve your herd overall. This requires you to look at all traits and choose the bull you think will offer the most multi-trait excellence. Please right a paragraph discussing why you chose a specific bull.

Objectives Define Expected Progeny Difference. Interpret EPD categories. Analyze EPD variations within breeds. Recognize the importance of EPD use in selection. Apply EPD concepts Objectives