Simmental – Profit Through Science


For Simmental and Simmental influenced cattle, we can see from this illustration what is weighted the most in computing the numbers.

API: All Purpose Index — Evaluates sires for use on the entire cow herd (bred to both Angus first-calf heifers and mature cows) with the portion of their daughters required to maintain herd size retained and the remaining heifers and steers put on feed and sold grade and yield.

Taken from Understanding ASA’s Indexes  

All EPDs, with the exception of tenderness,are taken into consideration in this index.

As you can see, the API puts heavy emphasis on bulls with good STAY (an estimate of the likelihood of a bull’s daughters staying in the herd). This should come as no surprise; research has consistently shown that reproduction trumps all else in economic importance.
STAY improves your bottom line by lessening the need for replacement females. Reducing your requirement for replacements allows you to market more young, high-value females, cuts your costs for heifer development and changes your herd’s age structure so a larger portion of your females are in their most productive years (5 through 10).
Direct and maternal calving ease also get substantial weighting in the API.This is because they are strongly associated to calf survivability and, to a lesser degree, female longevity.
Given that milk is essentially neutral in the index (the top 25 API bulls are only in the top 40% for milk), we can conclude that the benefits of increased weaning weight due to milk is negated by the additional cost associated with increased milk production.
It may be difficult for breeders to accept that the API places downward selection pressure on growth, as it is counter to the direction taken in most breeding programs.

Though increasing growth is invariably a good thing in terminal sires, its strong association with mature size makes it less desirable in replacement female sires, as increasing mature size increases cowherd maintenance requirements. Keep in mind that the positive benefits of increased growth in sires’ steers and cull females are accounted for in the API.

Nevertheless, the index is telling us that the extra cost of maintaining larger cows outweighs the benefit of increased growth in other areas of the system. Even so, the API is evidently finding sires with more carcass weight than would be expected given their growth potential. (The top 25 average in the 95 and 90th percentiles for weaning and yearling weight, while reaching the 70th percentile for carcass weight.)

From the top 25, it is evident that more weight is placed on marbling than yield grade. This is likely because there is no financial incentive to improving yield grade unless there is a problem (i.e. yield grades reach 4); for the most part, due to Simmentals superior yielding ability, SimAngus half-bloods see few discounts for yield grade.

TI. The TI is designed for evaluating sires’ economic merit in situations where they are bred to mature Angus cows and all offspring are placed in the feedlot and sold grade and yield. Consequently, maternal traits such as milk, stay-ability and maternal calving ease are not considered in the index






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