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Three profit points to genetics and reproduction

R. Kraig Peel and Emma Huff Published on 24 July 2012

Profitability will always be the primary driver behind all cattle operations.

We all know that we have to have successful reproduction in order to be profitable.

Recent genetic advances have led to many questions regarding the genetic influences behind reproduction and whether we can estimate or predict a cow’s reproductive performance.

While the genetics industry has made significant strides in the predictability of certain traits, reproduction is too easily influenced by nutrition to be able to use genetics as a primary predictor.

However, genetics will play an indirect role in reproduction as we focus on breeding the correct-size cow for the environment and continually selecting bulls that reinforce our mature cow size objectives.

Some of the traits that are being examined by researchers currently are herd fertility, heifer pregnancy and stayability.

Cow and calf

1. Herd fertility

This is a complex trait that is not easily utilized for selection purposes but has significant influence on the biological and economical efficiencies of a cow-calf operation.

The main focus of the National Cattle Evaluation in previous years has been on production traits such as growth and carcass.

The primary reason these traits have been used is because there has been a tremendous amount of data generated and collected for all breeds that has increased the accuracy of the predictions of these traits.

Reproductive traits are much more difficult to measure and the information that is relevant takes a lifetime to compile. Reproductive traits have been proven to be lowly heritable which means that they are not easily passed to their offspring. It is difficult to measure herd fertility consistently.

Heifer pregnancy is a trait normally included within a breeding objective and is most often really a measure of sexual maturity.

Heifer pregnancy is the probability that an exposed heifer will be pregnant before she becomes a 2-year-old and that the pregnancy is maintained.

For this to happen, the heifer would have to realize pubertal onset and settle a successful pregnancy by 12 to 15 months old so that she will calve at 2 years old.

Even though heifer pregnancy is considered a trait that is low to moderately heritable, it is an important aspect of any cattle operation.

2. Heifer pregnancy

Heifer pregnancy will largely be determined by the feed resources that are invested in order for her to realize at least 65 percent of her mature size.

Research has been conclusive that heifers that have achieved that threshold prior to breeding are much more likely to become pregnant.

If a producer is selecting mature cow sizes that fit their environment, the feed investment to achieve 65 percent of her mature body size should be minimized.

The ability to raise replacements and have them calve as 2-year-olds is important to the economic success of the operation.

A heifer’s ability to retain a pregnancy and calve as a 2-year-old can be used as an indicator for her future success within the herd. A heifer that conceives early in her first breeding season tends to have greater lifetime calf production.

If that heifer can breed early in the breeding season, she has more time to recover from the nutritional demands of lactation and growth, which increases her chances of getting pregnant with her second calf, which is the time of greatest reproductive failure.

3. Stayability

Stayability or longevity is the probability that a cow will survive to a specific age if she is given the opportunity to reach that age. Stayability is a trait that is affected by many things, with reproduction having the biggest influence.

Most cows are culled because they fail to become pregnant within the normal breeding season. Most breed associations that use stayability as a trait require that, for a cow to receive a positive stayability observation, she must have calved at 2 years old and remain productive in the herd by not missing more than two consecutive seasons without calving.

Stayability has a wide range of heritability estimates, from 0.02 to 0.23, depending on the end age point and the definition of stayability that is utilized. In order to get reliable heritability and EPD estimates for stayability, data must be collected on a cow basis through total herd reporting.

The average longevity of the herd is going to influence the overall economic returns of the production system and potentially increase profits as cows stay in the herd longer.

There are many reasons for this potential increase in profits, with the most obvious being that, by keeping a greater amount of older cows, there are fewer replacements that need to be saved, therefore increasing the amount of animals available for sale.

Total herd production will increase due to the tendency of mature cows to have less calving difficulties, to wean heavier calves and require a lower total energy requirement.

Another benefit of keeping a greater number of mature cows in the herd is the ability to increase selection intensity on replacement heifers. If we need fewer replacements, then we can increase the selection pressure on the heifers we keep.

Stayability may be an important indicator in a cowherd if the information is collected properly. The drawback to developing a stayability EPD is the amount of time required to collect enough data to increase accuracy.

If a sire is used as a yearling, his first calves are born when he is 2 – and by the time his daughters have reached the age of 6, in order for them to have the opportunity to receive a stayability observation, the bull is 8 years old.

By the time the bull has had a chance to gain a high-accuracy stayability EPD, that bull will most likely not be in use.

There are alternatives to increase accuracy by using stayability observations from younger ages that are highly correlated to the 6-year mark. This technology is continuing to evolve and be improved.

The bottom line is that there is an effort to develop EPDs that will predict reproductive efficiency in cattle.

The problem is that they are not to the point of being useable for making selection decisions. Until this technology is improved, it is best to provide adequate nutrition, breed heifers early to give them extra time to recover and try to get the bulk of your cows bred early in the breeding season.

You have significant control over the reproductive efficiency of your cows by making good management decisions.  end_mark

Emma Huff is a graduate student of breeding and genetics.

PHOTO

Reproductive traits are lowly heritable, making them difficult to measure consistently in herd fertility. Photo courtsey of Progressive Cattleman staff.

kraig peel


R. Kraig Peel, Ph.D.

Animal Sciences Professor
Colorado State University

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