Cattle Today

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Dr. Joel Yelich is associate professor for reproductive physiology with the University of Florida. His research and teachings here helped identify ways to enhance and improve the reproductive efficiency of beef cattle, particularly in the Southeast. Cattle Today recently interviewed Yelich about how cattle producers can improve their breeding programs. Here's what he had to say:

In what ways does the South's intense humidity and heat impact cow reproduction?

“Heat and humidity can have negative effects on both the males and females. Increased temperature and humidity can have a negative effect on early embryonic embryo survival. Furthermore, increased heat can have negative effects on overall production of the cow/calf unit. Similar negative effects are observed in bulls, such as decreased semen quality as well as decreased libido of breeding bulls, which ultimately has a negative effect on breeding season pregnancy rates of the cowherd. In general, these negative effects are amplified as the percentage of Bos indicus breeding decreases and Bos taurus breeding increases.”

As a southern producer, how can you ensure your cow herd is reproductively sound and ready for the breeding season?

“Just like most areas of the United States, the challenge is to make sure cows are in good body condition at calving and body condition losses are kept to a minimum after calving until the start of the breeding season. Providing supplemental feed resources, with energy being the limiting factor most often, is essential during times of low forage availability. Obtaining excellent reproductive results in beef cattle is pretty much dependent on the level of nutrition cattle are kept on particularly after calving. However, with that said, I think this is a major concern for producers in how they try to maintain low input nutritional cost while still maintaining a high level of production. To complicate the issue how you approach this is different across all the different environmental regions of the Southeastern US where there are numerous types of forages and available feed byproducts.”

What steps should you take to ensure your bulls are in good physical condition and reproductively sound prior to turn-out?

“Producers have to make sure that the bulls are acclimated to the warm temperatures of the southeast. For bulls born and raised in the southeast it is usually not a problem but it can be a problem for bulls purchased from cooler climates and moved into the southeast. Therefore, it is important to bring bulls into the southeast from northern climates during early fall, which can serve as an adaptation period before the breeding season starts. With that said, some cattle never acclimate to the hot and humid environment. Second, it is important to have bulls in good body condition but no overly fat as this can have negative effects on breeding ability and fertility. Breeding soundness exams conducted 40 to 50 days before the breeding season can also help to identify any sub-fertile bulls.”

Are there ways for producers to analyze forage/pasture quality for improved nutrition and cow reproductive performance?

“Yes. Producers can analyze forage samples to determine pasture quality but this is usually impractical because our forage grows so quickly. Therefore, some producers will utilize intensive grazing management systems in an attempt to stay ahead of forage growth to prevent the forage from getting old in its growth stage where it is not eaten by cattle. If the forage does get ahead of the cows' ability to graze it, producers should mow the grass, particularly on improved pastures. But stockpiling forage cannot be done in many parts of the Southeast, so we have to use it effectively when it is available.”

In what ways should southern producers approach AI and synchronization programs differently than their counterparts in cooler climates?

“Producers need to identify the genotype of cattle they want to synchronize. Do they want all Bos taurus genetics our do they want Bos indicus cattle? If they are all Bos taurus breeding, they can probably use synchronization systems that are typically used in cooler climates as well as use a timed-AI system and still achieve acceptable results. However, if cattle are of Bos indicus breeding, they will need to incorporate estrous detection with timed-AI into their synchronization programs. The reason for this is that cattle of Bos indicus breeding tend to have a compromised estrous response as well as an estrous response that is less synchronized compared to Bos taurus cattle, which makes timed-AI difficult to implement in Bos indicus cattle. Therefore, we encourage producers to use at least three days of estrous detection combined with timed-AI for cattle that do not exhibit estrus by the third day. We use this protocol with a majority of the synchronization protocols commonly used today in both cows and heifers.”

How do southern producers construct a cost-effective AI/synchronization program that can allow them to utilize top genetics and remain competitive?

“First, I think that they have to pay attention to both nutrition and the genetics of their cowherd. The cattle must have the proper genetics to survive in their environment with minimal supplemental nutrition. However, for estrous synchronization systems to be effective, cattle must be in good body condition and a high percentage of cattle must be cycling at the start of the breeding season. Second, producers must place emphasis on selecting for reproduction in their cowherd. This would include such things as: breeding heifers at 14 months of age with a breeding season that is less than 50 days, cull all cows and heifers that do not get pregnant during the breeding season, and select bulls that have a large scrotal circumference at a year of age. Third, I think small producers also have to be active in some type of marketing program to make sure that they actually get paid for the superior genetics that they are producing, since their input costs are probably going to be a little greater per cow than it will be for some of the larger producers.”

Do you believe AI is more important or less important to smaller producers than it is to larger producers?

It is probably more important for smaller producers to use A.I. First, it is easier for smaller producers to implement AI than larger producers since they have fewer cattle to work. Second, many smaller producers are reluctant to pay and/or can't afford to pay the money necessary to purchase top quality genetics. By using AI, smaller producers can actually decrease the number of bulls needed for natural service and use the savings to purchase better bulls. Third, it allows producers greater flexibility to take advantage of sires that can be used for calving ease, generating replacements, or for terminal sire programs.

How do southern producers take steps to ensure the genetics they use in their cow herds also meet consumer demands for quality and tender beef?

“There are some genetic markers available to assist in evaluating quality and tenderness issues in cattle. However, these tests are still too expensive to do large numbers of cattle. Once this becomes cost effective, it may serve to be very beneficial to producers with predominantly Bos indicus genetics. However, we have to be careful not to get caught up in single-trait selection or placing too much emphasis on only a couple of traits, since it can have dramatic and negative effects on cow herd productivity. Producers have to balance growth and carcass related traits with reproduction and cow efficiency. We must also remember that the primary job of a cow is to convert forage into pounds of gain and she must be able to wean a calf every year.”


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