Efficiency & some of its issues relevant to genetic evaluation Dorian Garrick Lush Chair in Animal Breeding & Genetics Progeny mean 9 4 2 1 Consider choosing among sires evaluated from a large cohort of their collective progeny Which bull(s) would you want to use as parent? In what direction would you want to shift the average? CIAG 2 4 Progeny mean 9 4 Points form a tilted ellipse 2 Extent of elongation and angle of tilt 1 depends upon genetic correlation (recall these are progeny means) 2 4 9 4 2 1 2 4 9 9 4 2 1 65 lb gain 4 lb intake 4 2 1 65 lbs gain 2 4 2 4
9 9 Selection for Production 4 2 65 lbs gain 4 2 65 lbs gain 1 1 2 4 2 4 Efficiency Efficiency typically measures output divided by input Big numbers are desirable lbs gain per lbs feed (eg 1/6 =.16 lb/lb) Alternative is feed conversion rate input over output Small numbers are desirable lbs feed per lb gain (eg 6 lb/lb) Rankings are equivalent 9 4 2 1 2 4 65 lb / 4 lb.1625 9 9 4 2 1 488 lb / lb.1625 65 lb / 4 lb.1625 4 2 1 488 lb / lb.1625 814 lb / lb.1625 65 lb / 4 lb.1625 2 4 2 4
9 Iso-efficiency Line Iso-efficiency 4 2 1 488 lb / lb.1625 814 lb / lb.1625 65 lb / 4 lb.1625 All animals on the line have the same efficiency If efficiency was your goal, you would be equally happy with any of those animals 2 4 9 9 Selection for Efficiency 4 2 1 Increasing Efficiency Takes no account of feed cost or beef returns 4 2 1 Increasing Efficiency Takes no account of feed cost or beef returns 2 4 2 4 s 9 More productive animals tend to require more feed This relationship can be quantified by analytical techniques, such as regression 4 2 1 production in relation to average feed intake (eg from regression of production on feed intake) 2 4
Residual Intake Analysis of large bodies of data allows us to compute how much feed average animals requires to produce at average levels of performance Some animals eat more than expected for their level of production and have positive residual feed intake (RFI) thers (desirable animals) eat less than expected, having negative RFI 9 4 2 1 2 4 RFI= 9 Consider an unusual animal 9 4 2 4 2 1 1 2 4 2 4 9 9 4 2 1 Expected 4 2 1 Actual Expected 2 4 2 4
9 4 2 1 -ve RFI (eat < expected) Actual Expected 9 4 2 1 -ve RFI (eat < expected) Iso-RFI RFI= 2 4 2 4 9 4 2 1 -ve RFI (eat < expected) desirable RFI= undesirable +ve RFI (eat > expected) 9 4 2 1 Improving RFI -ve RFI (eat < expected) desirable RFI= undesirable +ve RFI (eat > expected) Takes no account of feed cost or beef returns 2 4 2 4 9 4 2 1 Improving RFI Selection for RFI desirable RFI= undesirable Takes no account of feed cost or beef returns ther ptions We have considered efficiency (or feed conversion) Residual Intake What about an economic approach? 2 4
9 9 4 2 4 2 Increased Sale weight Increases Revenue $.86/lb BWT $1/116 lb 1 Where do you want to move the average? 1 2 4 2 4 9 Decreased feed costs $5.7 per 1 lb DM 175 lb costs $1 9 4 2 Increased Sale weight Increases Revenue $.86/lb BWT $1/116 lb 4 2 1 Where do you want to move the average? 1 2 4 2 4 9 9 4 Iso-income line 2 1 2 4 4 2 1 Increasing Profit 2 4 Sold on lot (lb dry matter) Totally driven by the (future) ratio of beef returns to feed cost
9 Selection for Profit 9 4 2 1 Increasing Profit 2 4 Sold on lot (lb dry matter) Totally driven by the (future) ratio of beef returns to feed cost 4 2 1 2 4 9 9 4 2 Worst RFI 4 2 Worst RFI 1 1 2 4 2 4 9 productive 9 productive 4 2 1 productive Worst RFI 2 4 4 2 1 productive Worst RFI 2 4 Do you want output, efficiency, residual feed intake or profitability? They represent different sectors of the ellipse
9 4 2 1 profitable efficient 2 4 productive The most profitable approach is the only consideration that takes any account of beef returns relative to feed cost