Developing Heifers for Long-Term Success

By Laura Handke

Research conducted in the past decade is helping to shed light on new heifer development strategies, with management beginning early in the life of a heifer calf. Today, there is much focus on nutritional management strategies that can be applied at strategic times in a heifer’s early life. The importance of timing in attaining puberty is critical, research is proving, and nutrition is an essential component of long-term reproductive performance.

To maximize lifetime productivity, heifers need to become pregnant by 15 months of age, meaning they have to reach puberty by 12-13 months of age. Additionally, heifers need 2-3 cycles to become sexually mature.

“Longstanding research shows that heifers bred on their third estrus cycle have greater pregnancy rates than those bred on their first,” says Philipe Moriel, University of Florida, associate professor of beef cattle nutrition and management in a recent Beef Reproductive Task Force webinar.

In a recent study, researchers looked at heifers that reached puberty before breeding season and heifers that reached puberty during breeding season; 100% of heifers had the opportunity to settle, the only difference was when they came into estrus for the first time.

“What we see is a very consistent response from heifers that reach puberty before the breeding season versus those that reach puberty after breeding season has begun,” Moriel says. “We can see the negative effects of later puberty on long-term reproductive performance and calving distribution.” Not only the number of heifers that settle are of concern, but the effect that a later conception has on calving distribution can be costly. Longevity is also a concern – heifers that calve within the first 21 days of their first calving season have greater pregnancy rates in the next six generations, allowing a producer more time to absorb the costs of developing a heifer and realizing profit from her calves.

And, obviously, heifers that calve earlier typically wean heavier calves.

Focus on Calfhood Opportunities

“Feed efficiency is greatest in calfhood, the younger the calf, the more feed efficient they are. Calves are also more susceptible to environmental effects early in life. Both environment and nutrition experienced early in a heifer’s life can influence her metabolic performance throughout her lifetime,” Moriel says.

Metabolic imprinting is an early adaptation to nutritional stress/stimulus that permanently changes physiology and metabolism. These changes continue to be expressed even in the absence of the stress/stimulus that initiated them.

Puberty attainment is susceptible to metabolic imprinting and is influenced most between the first two to six months of a calf’s life.

Recent data shows that when you enhance nutrition between the first two to six months of a heifer’s life, she is able to achieve puberty sooner. Even better, new data has shown enhanced nutritional response and subsequent puberty attainment is possible to a greater extent when the nutrition is provided at earlier periods in the heifers life and even in the gestational phase of her dam.

The study looked at heifers that were assigned to a high average daily gain (ADG) from 3-21 weeks of age and a group of heifers that were assigned a moderate ADG (.5 kilo/1 pound) from 3-21 weeks of age. What they saw was that that those heifers on a higher ADG had better developed reproductive tracts as a percentage of body weight.

“By boosting nutrition in the early stages of life, we are able to help those heifers reach puberty sooner,” Moriel says of the opportunities early high average daily gains provide in heifer development. Nutritional Strategies

Early weaning, between two and three months of age, on the first day of breeding season for their mothers, is a tool that researchers are investigating. This strategy to increase reproductive performance of the cows, especially first calf heifers, is one that is proving to be effective.

“You can significantly increase a cow’s pregnancy rates when you early wean their calf on the first day of the breeding season,” Moriel says, “This strategy also allows you to modulate 100% of the calf’s intake at a time when calves are very young, achieve the greatest feed efficiency, and are in the critical phase of puberty attainment.”

A 2006 study looked at puberty attainment in beef heifers that were either early weaned at 100 days of age or regularly weaned at 200 days of age. What they found was that when heifers were early weaned at 100 days and immediately put on a high concentrated diet, their puberty attainment was significantly increased. In the study, 100 percent of the heifers in that group reached puberty before the end of the study.

The graph below shows the percentage of heifer calves that reached puberty before the end of the study in relation to the nutrition that they received. It also indicates that early weaning was not a driver in the attainment of early puberty, but rather the application of a high concentration diet immediately after weaning – boosting their intake of energy and protein at an early age – indicated the most significant results in attaining puberty.

Another strategy that is currently being reviewed for use in commercial herds, but isn’t available at this time, is the injection of bSt prior to weaning. This proof-ofconcept work is showing promise in modulating growth and attaining early puberty at the same success rate as those heifer calves that are early weaned and put on a high concentrate diet immediately after weaning. In cows, an injection of bSt increases milk production, however an injection of bSt in growing animals increases average daily gain and concentration of insulin growth factor 1 (IGF-1).

“This strategy has the potential to be very beneficial in a beef system. It is very convenient,” Moriel says.

The third, and most easily applied, strategy is the use of creep feeding.

“Most creep feeding is done later in a heifer’s growth and development, closer to weaning,” says Moriel, “What researchers are looking at is implementing creep feeding much earlier in the heifer calf’s life.”

One study looked at offering creep feed at 68 days of age when calves are very efficient, providing supplementation for a very short amount of time, just 50 days. So the investment in supplementation is very low, and the timing is strategic because the heifer calves are at a development stage that allows them to be metabolically imprinted. What they saw was that during the imprinting, the 50 days that the creep feed was offered, those heifers gained more through weaning. They also collected tissue samples throughout the study, which showed that physiological changes, higher concentrations of IGF-1, were present in those heifers that were metabolically imprinted.

Maternal diets can also change the reproductive performance of the heifer calf. A 2012 study showed that heifers born from cows that had an energy restricted diet had smaller ovaries, showing that a change in diet effects reproductive performance.

Another study looked at two groups of beef cows, one offered no supplementation and the other offered one pound of protein supplement during the last trimester of gestation, both groups were subsequently managed exactly the same. What researchers learned was that heifers born from cows that received the one pound of protein supplementation in the last trimester of gestation were heavier at weaning, attained puberty sooner, had greater pregnancy rates and also had a higher percentage of calving during the first 21 days of their calving season.

What all of these studies show is that there is great opportunity for this type of research and that a relatively small investment in supplementation can pay great dividends in heifer development. FF