Ron Torell with his wife, Jackie.
Cow Camp Chatter
Consider the postpartum anestrous period.
The structure and function of a cow's uterus is fascinating. It accepts the calf, a substance that is completely foreign to it, while blocking the body's normal defense mechanism designed to destroy foreign invaders. The uterus nourishes, protects and sustains the developing calf while growing up to 24 inches or more in diameter.
When the time is right, the uterus receives a signal from the calf and transforms itself into a delivery system, forcibly expelling the calf.
It then begins the amazing process of preparing itself for a repeat of the whole cycle. The recovery process between calving and a cow's next pregnancy is critical to a profitable beef enterprise and is quite frequently misunderstood.
The stage of reproductive inactivity that follows calving is known as the anestrous period. The amount of time that the cow remains in anestrus until her first estrous cycle is the postpartum interval. The rate of involution — a term that encompasses uterine shrinkage, fluid loss and tissue repair following calving — is largely determined by nutrition, lactation rate, age, health and condition of the cow.
During the anestrous period, the cow's reproductive abilities are put on hold while uterine involution occurs and her body builds up enough energy reserves to allow her to become reproductively active again.
Anestrous factors
Reducing the length of the postpartum anestrous period is the first basic principal of reproductive management. This can be accomplished by incorporating better management practices.
The postpartum anestrous period is the highest nutrient-demanding phase of the cow. By banking fat reserves during the stages of her biological cycle that are less demanding nutritionally, the cow has a nutrient source of energy to draw from during the periods of higher nutrient demand in both the last trimester and the anestrous period.
Nutritional and body reserve deficiencies are the first place to look when noncycling cows are encountered as a result of an extended postpartum anestrous period. Chances are, it could take months for a cow to rebreed if she is in poor condition and lactating. If she is a 2- or 3-year-old cow, large-framed or heavy-milking, she may not breed back at all. It is important to note that reproductive diseases and bull fertility may also play a role in open cows.
Reducing anestrous period
If the goal is to have a cow calve at the same time next year, the postpartum anestrous period should not exceed 83 days. In order for this to happen, management of the anestrous period needs to be a 12-month effort. This can be done by managing the body condition of the cow.
Adequately addressing the nutritional needs of the cow and using body condition score (BCS) as a management tool will help the cow prevail over anestrus. Consider BCS management to monitor the condition of cattle, particularly in the fall after weaning and a few months before calving.
Generally, cows are assigned scores from 1 to 9, with the thinnest possible score being 1 and the fleshiest possible being 9. Having a BCS of 5 is considered to be the optimum breeding condition for mature cows, while a BCS of a 5 or 6 is suggested for first-calf heifers. If you do not have these body reserves at the minimal level, your cows may not reproduce. (For examples of Angus cows at the various condition scores, visit www.cowbcs.info.)
Evaluating body condition is not enough. You need to take action on your assessment. In dry years and as body condition is reduced below a 5, management changes must be made, such as supplementation, weaning or moving cattle to better feed. If you do not act on a group of cattle that is low in body condition, they will continue to lose weight. It is easier and cheaper to preserve body condition than it is to bring a thin cow back into condition.
Cows that experience difficulty during calving often have more difficulty overcoming the effects of anestrus and take longer to rebreed. The cervix acts as a valve that seals the uterine interior from the outside environment and opens wide at calving to allow the calf to pass.
This open valve may lead to a contaminated uterus when human assistance is required at the time of calving by admitting whatever bugs are in the neighborhood.
Subsequently, the cow may develop a uterine infection. Minimizing calving difficulty and employing sanitary practices when assisting births in a timely manner may help save calves and attain higher rebreeding rates the following breeding season.
Additional management practices that may help reduce the anestrous period include calving heifers prior to the mature cows, utilizing certain estrous-synchronization protocols, employing teaser bulls during the anestrous period, implementing strategic weaning methods, grazing or winter-feeding classes of cattle separately, and feeding energy pre- and postpartum.
When all is said and done, never underestimate the power of genetics. Selecting bulls for high reproductive efficiency and those that are of moderate frame and milk is an additional long-term aid to shortening the anestrous period.
That's enough for this month. A special thanks to my wife, Jackie, for her part in writing "Cow Camp Chatter." As always, if you would like to discuss this article or simply want to talk cows, do not hesitate to contact me at 775-385-7665 or e-mail me.
