SAN ANTONIO, Texas – Millions of heifers enter breeding herds each year, but few have been properly developed for good lifetime reproduction.
Heifer development studies show these young females need a higher level of nutrition than cows because they are still growing.
“The alteration of the nutrition plane up to the breeding or prior to breeding can actually kick animals onto cycling,” said Rick Funston, an animal physiologist from the University of Nebraska.
However, they may not need to be pampered.
Read Also
Agriculture ministers agree to AgriStability changes
federal government proposed several months ago to increase the compensation rate from 80 to 90 per cent and double the maximum payment from $3 million to $6 million
“Those heifers that were taught or exposed to an environment in which they were going to have to exist as cows, they actually had better preg rates later in life,” he told a cow reproduction seminar held during the recent National Cattlemen’s Beef Association meeting in San Antonio.
Heifers need to reach 65 percent of their total adult body weight before breeding starts.
Gary Williams of Texas A & M University said they also need to score a five at the time of breeding on a body condition score scale of one to nine where one is emaciated and nine is obese. The cost associated with continuous rates of gain is one of the reasons cattle producers do not adopt this advice.
“Only a small percentage of U.S. cattlemen do this,” Williams said.
Sexual maturation first starts in the lower part of the brain called the hypothalamus, triggering puberty and allowing animals to ovulate and become pregnant.
Williams said heifers should be allowed to have several estrus cycles before becoming pregnant.
Puberty delays can be caused by inadequate nutrition.
As well, high-energy diets can accelerate maturity, especially among larger breed types. Heifers that gain less than a pound a day after weaning are likely to have delayed puberty.
Williams recommended weaning heifers at seven to nine months and then placing them on a nutrition program where they gain 1.5 to two pounds per day so they can achieve puberty when 12 to 14 months old.
Early weaning and early life exposure to a high concentrate, high-energy diet may encourage an earlier puberty at less than 10 months of age. Growing too fast could suppress other genes needed for proper development.
“We really don’t want precocious puberty because we don’t want a bull breeding heifers in the pasture too early,” Williams said.
Producers often overlook the need for a physical exam conducted by a qualified person who knows how to palpate the reproductive tract and monitor the progress of the female’s sexual development.
Few measure the size of the pelvis, which should be 172 sq. centimetres.
Heifers with unacceptable pelvic areas should be culled because calving problems may result.
Heifers may also be placed in an estrus synchronization program.
Progestins, a natural or man-made substance with properties similar to natural progesterone, induce puberty in beef heifers and prevent the expression of behavioural estrus, said Dave Patterson, an animal scientist from the University of Missouri.
The feed additive MGA has been a preferred method of synchronizing estrus in heifers at a rate of half a milligram once a day for 14 days.
Do not top dress it on silage because it will sink down to the bottom.
“If it is fed first thing in the morning, you will probably get good intake and get the best outcome,” he said.
