Beef Cattle Reproduction for Small Producers

April 2004
Sonja C. Crawford - Hendry County Extension, 4-H Coordinator/Livestock Agent II

Many ranchette landowners are trying to find a way to utilize their property for livestock production as a secondary income or as a hobby. These landowners, as seen through the 2004 Small Farms Livestock Conference, are interested in learning all facets of livestock production pertaining to the commodity they are raising. Understanding the reproductive system, its hormones as well as many other aspects of reproductive management will assist in ones success in the operation of the class of livestock concerned.

For example the goal to success in the beef cattle operation is producing a live, healthy calf from all productive cows and heifers every year. To do this one must take into consideration proper nutrition of the brood cow, it's body condition score, health program of the herd, minimizing death losses, using fertile bulls, culling non-breeding brood cows, and breeding heifers 21 days earlier than the mature cow herd.

The body condition scoring system is based on a scale of from 1 to 9. Body Condition Score 1 is characterized as emaciated where the bone structure of shoulder, ribs, back, hooks and pins are sharp to touch and easily visible and little evidence of fat deposits or muscling. Body Condition Score 9 is associated with extreme fat with the bone structure not seen or easily felt and with the tail head buried in fat. The optimum body condition score for a brood cow to conceive is between 5 and 7. The thinner the brood cow or the fatter the brood cow the lower the conception rate.

The reproductive system is composed of a vulva, vagina, cervix, uterus, oviducts, and ovaries. All of these serve different functions. The vulva is the exterior portion of the reproductive tract which provides signs of heat. The vagina lies between the vulva and the cervix and is the birth canal as well as the semen deposit area with the cervix being the opening to the uterus. During pregnancy the cervix becomes blocked with a mucous plug to prevent infection. At birth the cervix stretches to allow the calf to pass. The uterus contains a body and two uterine horns. The right or left uterine horn is where implantation of the fetus takes place. The oviduct is where conception occurs and the ovaries are the female sex cells that possess large number of eggs in all stages of development. The ovaries also produce the hormones, estrogen and progesterone.

It is very important to understand the reproductive cycle is especially if the producer has plans for a successful artificial insemination. Estrous, ovulation and pregnancy are controlled by hormones. The length of the estrous cycle is 21 days and the length of estrus (heat) is 14 to 18 hours. The female is receptive to the male during estrus. Females show external signs during estrus. The primary sign of estrus is standing for mounting. Secondary signs may consist of mounting other cows, a roughened tailhead, being nervous and restless, clear mucus from the vagina, or swollen vulva. During diestrus the female is not receptive to the male. Ovulation takes place 30 hours after heat begins. The estrous cycle stops after conception and begins soon after birth. If the egg is not fertilized, pregnancy does not occur and the cycle will repeat itself. The gestational period (time from conception to birth) is approximately 283 days with an additional non-cycling period of 40 plus days after birth.

One of the questions that is frequently asked at the Small Farms Livestock Conference is should "I purchase a bull for my herd or should I artificially inseminate." Deciding upon which is better depends on the facilities and the number of brood cows. Normally, bulls are not run with the brood cows all year around. If this occurs, calves will be born all year around and not during a set calving season. A 90 day breeding season is normal for small ranchette producers, then the bulls must be placed in a separate pasture. The rule of thumb is twenty-five cows per bull. One bull will contribute 50% of the genetics to the next generation of cows. Successful Artificial Insemination (A.I.) is obtained through adequate facilities, proper equipment, a good herd health program, sound nutritional program, and a well trained and experienced A.I. technician. Artificial Insemination (A.I.) is also performed by many veterinarians. Depending on the number of brood cows, A.I. may be cheaper in the long run than owning a bull that is adequate for the brood cow herd because owning a bull is not a one-time investment.

Puberty in heifers begins between 11 and 12 months of age. Most heifers need to cycle at least two times before breeding and should be bred by the age of 15 months. Heifers should be cycling normally by the time they reach two-thirds of their mature body weight (refer to table below). Heifers calving at two years of age are more prone to calving problems due to the calf being too large for the birth canal. Reviewing the Estimated Progeny Difference (EPDs) before purchasing bulls will help decide if the birth weight and calving ease are satisfactory for the herd.

Breeds and Weights at Puberty

Breed Weight (lbs)
Herefords 600 - 650
Angus 575 - 650
Charolais Crosses 675 - 725
Simmental Crosses 650 - 700
Brahman Crosses 700 - 750
Limousin Crosses 650 - 700
Gelbvieh Crosses 600 - 650

For more information regarding reproductive management contact your local livestock extension agent or refer to the Florida Cow-Calf Management Handbook. The handbook may be purchased through the IFAS Bookstore (800-226-1764) or through the South Florida Beef Forage Agents Group.

Return to top