High Reproduction Rate is Essential to Financial Success in Cattle Business

February 2004
Lochrane A. Gary - Hardee County Extension, Director/Livestock Agent

The most common cause of reproductive failure in cattle has been identified. It can be stated in two words - poor management. Poor management of a cattle operation is responsible for poor nutrition, failure to detect low fertility bulls, for not preventing diseases and their spread, for keeping subfertile cows in the herd and for mating large bull breeds to small or young females. Yes, poor management is primarily responsible for poor reproductive performance.

How Can My Management Be Improved?

  • Purchase structurally sound, free moving growthy bulls with well developed testicles, short sheaths which have passed a fertility test by a qualified bovine practitioner.
  • Cull all cows which fail to calve; calve irregularly; calve late in the season; have teeth, eye, udder or feet problems; have prolapsed the previous calving season or are continuously in poor body condition.
  • Provide one mature, sound fertile bull for every thirty cows or one young, sound fertile bull for every twenty cows. Do not mix young and old bulls in the same breeding pasture. The older more mature bulls will have social dominance and will intimidate the younger less experienced bulls.
  • Design the breeding season so calving occurs when the most nutritious grass is available. Provide a level of nutrition that will keep the cattle in a thrifty condition and provide minerals containing calcium and phosphorus on a year round basis.
  • Observe breeding activity early in the breeding season and make notes on active and inactive bulls. Write it down. Replace non-breeders immediately. Note breeding dates and check for repeat cycling following breeding. Repeated cycling by several cows spells trouble.
  • Use a restricted breeding season so bulls may be given a breeding soundness exam (BSE) and a fertility test periodically and cows can be checked accurately for pregnancy. Pregnancy checking should be accomplished sixty days after the end of the breeding season.
  • Cull sterile or subfertile bulls and cows that fail to breed and conceive during the breeding season.
  • Design a herd health program and immunization schedule with the advice of a veterinarian.

Ingredients of a Good Herd Health Program

A good herd health program will contain the following:

  • A good relationship with a local veterinarian. Don't introduce yourself to him/her at midnight during an emergency.
  • Vaccination or immunization schedule for nursing, weaned and yearling cattle, replacement heifers, brood cows and bulls with specifications for products to be used.
  • Recommendations for isolating sick and newly purchased cattle.
  • An internal parasite control program. (Stomach worms and liver flukes)
  • An external parasite control program. (Flies, mosquitoes and lice)
  • Emergency procedures to use in the event of a disease outbreak such as calf scours, grass tetany or anaplasmosis.
  • A procedure for handling abortions and determining their cause.
  • Recommendations for coping with calving problems.

Can I Expect a Calf from Each Cow Every Year?

Probably not. It's possible, but not very likely. Pregnancy rates will range from sixty to ninety-five percent. The better managed herds will always have the higher pregnancy rates despite droughts, flooding, freezing weather and other environmental stresses. Pregnancy percentage is expressed as the number of cows becoming pregnant compared to the number of cows exposed to the bull(s) for breeding. For example, if forty out of fifty cows become pregnant during the breeding season, the pregnancy rate is eighty percent. It is imperative that calving percentages and weaning rates be as high as possible. In beef cattle operations a weaning rate (number calves of weaned per number of cows exposed for breeding) in excess of eighty percent and weaning weights in excess of 450 pounds are necessary to break even.

Not All Cows Calve Every Year

Some cattle will fail to come into heat. Some will breed and not conceive, while others will become pregnant and fail to carry the pregnancy to term. The failure to breed, especially during a restricted breeding season, and embryonic mortality are common causes of poor reproductive performance. Many cows fail to cycle (come into heat) while they are nursing a calf. This is called lactational anestrus. This is normally due to inadequate nutrition (energy). A normal, healthy cow will come into heat every 21 days (within a range of 17 to 24 days). Her heat period (estrus) will last from 10 to 18 hours and is followed by ovulation or release of the egg from the ovary. Natural mating occurs only during the heat period. If a cow experiences no heat period, she will not breed.

Failure to Cycle

Most cows failing to come into heat every 21 days are experiencing insufficient nutrition. When adequate amounts of energy, protein, vitamins and minerals are not available, the heat cycle is interrupted. With poor nutrition body weight and bodily functions decrease and poor reproductive performance will be experienced. A body condition score (BCS) of 5 or 6 is conducive to cycling. Failure to cycle may also be caused by physiological abnormalities such as cystic ovaries and hormone imbalances. The stress associated with a difficult calving (dystocia) may also delay or prevent cycling.

Not all cows which breed will become pregnant. The bull may have been sterile or the cow may have failed to ovulate a viable egg to be fertilized. Even though most matings result in pregnancies, factors such as low bull fertility, environmental heat stress, high body temperatures and reproductive diseases can reduce the number of pregnancies in a cow herd.

Poor Bull Fertility

Complete sterility (permanent) is much less common than infertility (temporary). Small or abnormal testicles, testicular infection or inflammation, abnormal or injured reproductive organs, high body temperature for a sustained period of time, diseases, inadequate nutrition or just a plain lack of interest in the female are some causes of poor fertility. Some bulls have abnormal or injured sexual organs and cannot make physical contact with cows during a mating attempt. Poor bull fertility can be as simple as a management error resulting from too few bulls being placed with the number of cows involved. Rough or wide open country may require a higher bull to cow ratio than smaller improved pastures.

Embryo Mortality, Premature Births and Stillborn Calves

Diseases such as brucellosis (Bangs), vibriosis, leptospirosis and viral diseases like IBR, BVD and PI-3 are the most common and will cause embryonic mortality and abortions. Toxic plants and other substances can also be responsible for poor calving percentages. Inadequate nutrition will increase the percentage of still births. Calving difficulty caused by large birth weights and or small pelvic areas will cause still births and subsequent lowered female fertility.

Ideal Breeding Season

There are two seasons that work well in south Florida. Breeding from December 15 to March 15 will produce calves from September 20 to December 20 (fall calves). Breeding from April 15 to July 15 will produce calves from January 24 to April 24 (spring calves). The choice of the season depends upon the individual rancher. Cows with fall calves require more and better quality winter feed than cows nursing spring born calves.

Avoid summer calves. They seldom grow well and are extremely light at sale time. Their value will seldom cover annual cow costs.

Producers with a large number of cows may wish to have calves born in both seasons. This will allow more efficient use of bulls and spread the calves over a longer period of time, thus tending to average the effects of good and bad markets.

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