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Which is better: big cows or little cows? It depends

Heavier-milking, bigger cows are more efficient in some situations, while 
moderate, lighter-milking cows are more efficient in others

Marketing cows because they are open, calved late or their conformation is breaking down are easy decisions. Marketing cows or retaining heifers based on productive efficiency definitely requires more thought.

Biological efficiency is not always the same as economic efficiency. In a cattle production system, efficiency is often a combination of those two. How we optimize efficiency will depend on:

  • The genetic potential of the cow herd,
  • The environment in which the cattle are raised, and
  • Marketing strategy.

Selection for the type of cattle that perform best in the feedlot (i.e. produce the most beef in the shortest period) may not produce the ideal replacement animals in a grazing environment, yet selection for improved growth rates has increased average mature cow weights from 1,000 lbs. to 1,400 lbs. over the last 30 years. Almost all producers underestimate the size of their cows, unless or until they weigh them.

Maintaining herd performance records can take some of the guesswork out of defining which cows are efficient producers. Adjusted 205-day weaning weights remove the age bias and are quite useful in a tight calving period. However, during long, drawn-out calving seasons (which are inherently inefficient), adjusted weaning weights will tend to favour light, late-born calves which may or may not continue to grow the way the adjustment predicts.

Bigger cow, more feed

Determining cow productive efficiency by using weaning weight as a percentage of cow body weight is definitely biased towards smaller cows, and not a true measure of efficiency. A 1,100-lb. cow weaning 60 per cent of her body weight weans a 660-lb. calf. A 1,400-lb. cow that weans at 50 per cent of her body weight is weaning a calf that is 40 lbs. heavier. Heavier cows tend to wean heavier calves, and a heavier cow will bring more at auction when it is time to ship her.

But a heavier cow means increased maintenance requirements for feed, and the same amount of pasture will carry fewer big cows than smaller cows. This is not a linear relationship, however. Increasing cow weight by 27 per cent (from 1,100 lbs. to 1,400 lbs., assuming a high lactation level for both weight classes) only increases maintenance requirements by 20 per cent. For that reason, 78, 1,400-lb. cows require about the same amount of feed for maintenance as 93, 1,100-lb. cows.

The total feed energy required increases as cows get bigger, but the amount of energy required per lb. of body weight actually decreases, making a 1,400-lb. cow 5.5 per cent more efficient than a 1,100-lb. cow, assuming similar milk production. Perhaps obviously, cows with higher genetic potential for milk production will have increased maintenance requirements, but also produce a heavier calf at weaning.

Pencilling it out

What needs to be pencilled out is whether the potential increases in weaning weight and salvage value from larger, heavier-milking cows offset the costs of increased feed and decreased carrying capacity. The answer here depends almost entirely on the environment (quality and quantity of forage resources), cost of supplemental winter feed, and marketing strategy.

In the table, we can see that heavier-milking, bigger cows are more efficient in some situations, while moderate, lighter-milking cows are more efficient in others. A similar table can be found in the latest Beef Improvement Federation Guidelines.

Environments such as the shortgrass parts of the country favour small to moderate cows without extreme milk production, while the Parkland region tends to favour larger, heavier milking cows. An early Agriculture Canada study illustrates this point. In Brandon, Man., a fertile area where feed resources were abundant, heavy milkers were the most profitable cows. However, in the Manyberries, Alta. area, where feed resources were more limited and the environment more stressful, light to moderate milkers proved to be the most profitable.

Feed efficiency is one trait that has the ability to dramatically influence the type of cows you match to the environment. A big cow may eat the same as a smaller cow while raising the same-size calf and maintaining the same reproductive cycle and body condition. The way that cows utilize feed (especially in pasture or forage situations) has not been studied to the same extent as feed efficiency in feeder animals.

A project funded by the Alberta Beef Producers (ABP) intends to provide a reliable method of measuring feed efficiency in replacement heifers by comparing residual feed intake (RFI) measurements in confinement and on pasture, while also quantifying the relationship of RFI with first-calving fertility and productivity.

Another project funded by ABP and the Beef Cattle Research Council (BCRC) under the second Beef Cattle Industry Science Cluster aims to demonstrate how to build a feed-efficient cow herd without sacrificing reproductive performance and maintaining or improving progeny carcass traits. Results are expected in 2016.

There is more to cow efficiency than size, and while bigger is not always better, it might be in some situations. Selecting cows that are the best fit for their environment, available resources, and your marketing strategy will optimize production efficiency and improve profitability.

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