Page 13 - Loonan Stock Farm 46th Annual Production Sale, Red Angus, Simmental, F1 Cross – Feb. 6, 2021

Simmental Herdsires

UNDERSTANDING AND USING ASA’S SELECTION INDICES

By Wade Schafer Ph.D.
API. The API evaluates sires being used on the entire cowherd (bred to in most breeding programs. Though increasing growth is invariably
both Angus fi rst-calf heifers and mature cows) with a portion of their a good thing in terminal sires, its strong association with mature size
daughters being retained for breeding and the steers and remaining makes it less desirable in replacement female sires, as increasing ma-
heifers being put on feed and sold grade and yield. All EPDs, with the ture size increases cowherd maintenance requirements. Keep in mind
exception of tenderness, are taken into consideration in this index. that the positive benefi ts of increased growth in sires’ steers and cull
females are accounted for in the API. Nevertheless, the index is telling
API puts heavy emphasis on bulls with good STAY (an estimate of the us that the extra cost of maintaining larger cows outweighs the benefi t
likelihood of a bull’s daughters staying in the herd). This should come of increased growth in other areas of the system.
as no surprise; research has consistently shown that reproduction
trumps all else in economic importance. STAY improves your bottom Even so, the API is evidently fi nding sires with more carcass weight
line by lessening the need for replacement females. Reducing your than would be expected given their growth potential. (The top 25 aver-
requirement for replacements allows you to market more young, high- age in the 95th and 90th percentiles for weaning and yearling weight,
value females, cuts your costs for heifer development and changes while reaching the 70th percentile for carcass weight.)
your herd’s age structure so a larger portion of your females are in their
most productive years (5 through 10). From the top 25, it is evident that more weight is placed on marbling
than yield grade. This is likely because there is no fi nancial incentive
Direct and maternal calving ease also get substantial weighting in the to improving yield grade unless there is a problem (i.e. yield grades
API. This is because they are strongly associated to calf survivability reach 4); for the most part, due to Simmentals superior yielding ability,
and, to a lesser degree, female longevity. Given that milk is essentially SimAngus half-bloods see few discounts for yield grade.
neutral in the index (the top 25 API bulls are only in the top 40% for
milk), we can conclude that the benefi ts of increased weaning weight TI. The TI is designed for evaluating sires’ economic merit in situations
due to milk is negated by the additional cost associated with increased where they are bred to mature Angus cows and all offspring are placed
milk production. in the feedlot and sold grade and yield. Consequently, maternal traits
such as milk, stayability and maternal calving ease are not considered
It may be diffi cult for breeders to accept that the API places downward in the index.
selection pressure on growth, as it is counter to the direction taken

CE BW WW ADG YW MCE MK MWW ST DOC CW YG MARB BF REA API TI
CURRENT BREED AVERAGES: 10.0 1.8 67.8 0.2 100.6 5.2 21.6 55.6 17.4 10.5 28.3 -0.46 0.01 -0.11 0.82 123.77 68.93

RFS CLINT C45 0.3 6.7 82.4 120.2 0.24 0.3 16.7 57.8 13.5 3.4 24.5 -0.54 0 -0.126 0.88 96.6 68.9
Accuracy 0.52 0.67 0.63 0.61 0.61 0.29 0.26 0.37 0.28 0.29 0.51 0.4 0.41 0.37 0.51
#3040615 Breed Rank 99% 99% 30% 35% 50% 99% 95% 70% 85% 99% 70% 5% 85% 2% 50% 99% 85%

KBHR ALL ALONG E082 6.6 4.8 103.4 153.5 0.31 3.5 22.3 74 13.3 15.6 64.7 -0.43 0.3 -0.11 1.2 132.3 93
Accuracy 0.33 0.59 0.56 0.53 0.53 0.27 0.22 0.32 0.22 0.3 0.47 0.33 0.34 0.32 0.4
#3312076 Breed Rank 95% 99% 1% 2% 10% 90% 60% 10% 85% 10% 1% 50% 15% 20% 4% 40% 4%

DKSR MR RED NATION E73 10.7 1 95.4 129.4 0.21 4 31 78.7 17.6 10.7 38.4 -0.36 0.03 -0.106 0.69 132.2 86.4
Accuracy 0.24 0.52 0.47 0.45 0.45 0.17 0.17 0.28 0.13 0.25 0.33 0.23 0.22 0.18 0.29
#3330840 Breed Rank 50% 35% 3% 20% 75% 85% 10% 2% 35% 60% 20% 85% 75% 20% 90% 40% 15%

CE = Calving Ease MCE = Maternal Calving Ease DOC = Docility REA = Ribeye Area
BW = Birthweight MM = Daughter’s Milk CW = Carcass Weight SHR = Shear Force
WW = Weaning Weight MWW = YG = Yield Grade API = All-Purpose Index
YW = Yearling Weight Maternal Weaning Weights Marb = Marbling Score TI = Terminal Index
ADG = Average Daily Gain ST = Stayability BF = 12th Rib Back Fat

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