Recommendations for heifer reproduction shared
The Beef Reproduction Task Force Applied Reproductive Strategies in Beef Cattle webinar series kicked off Nov. 4 with a session focused on cows and heifers.
Dr. Phillipe Moriel, assistant professor at the University of Florida and researcher at the Range Cattle Research and Education Center presented information for enhancing long-term growth and reproduction of beef heifers focused on mechanisms and the importance of timing on puberty attainment, as well as nutritional strategies to achieve puberty sooner with greater body weight.
Optimizing reproductive management
“Optimal heifer management maximizes lifetime productivity,” says Moriel. “Heifers reach puberty by 12 to 13 months of age and should be pregnant by 15 months of age. Heifers need three cycles to be considered sexually mature, and those heifers bred in the third cycle, rather than the first, have shown to be more productive.”
Boosting puberty attainment is beneficial to producers as heifers reaching puberty before the breeding season are more productive than those reaching puberty during the breeding season, notes Moriel. Earlier maturing heifers also calve earlier, wean heavier calves and tend to remain in the herd longer.
Moriel mentions pre-weaning strategies have more potential for attaining puberty, as opposed to post-weaning strategies, while also offering an opportunity to minimize feed costs. Young cattle, Moriel explains, are susceptible to metabolic imprinting, or nutritional and environmental impacts of productivity and growth, which follow the animal through its life.
Recent studies have suggested enhanced nutrition in heifer developmental stages, particularly between two and six months of age, can help heifers to reach puberty sooner. One study Moriel cited in particular, suggests heifers consuming higher-quality nutrition have greater reproductive tract development as well.
He explains four different nutritional strategies to promote greater nutrition during development. The first strategy is early weaning.
“Weaning calves at two to three months of age or on the first day of their mother’s return to the breeding season allows full nutritional control over calves and boosts growth directly after weaning,” says Moriel. “It is not so much the actual early weaning strategy, but we are immediately applying a high concentrate diet to increase average daily gain (ADG) and heifer size at puberty.”
The second strategy is pre-weaning injections of the exogenous growth hormone bovine somatotrophin (bST). Although bST is not currently on the market for early injection for commercial operations, research has shown the hormone increased ADG and increased levels of the hormone, insulin-like growth factor (IGF-1).
Creep feed supplementation is Moriel’s third pre-weaning strategy, providing calves supplementation without allowing cows access.
“A study started creep-feeding much sooner than normal, starting at 68 days of age,” Moriel explains. “Supplemented heifers gained more during the metabolic imprinting phase, and heifers had higher levels of IGF-1, but there was no difference in time to pubertal attainment.”
He notes when calves are small and don’t eat much, producer investment in supplementation is low, and this is a cost-efficient way to boost heifer ADG to reach a greater body size by puberty.
The fourth strategy is focusing on maternal diet during gestation. Research has shown heifers born from cows with restricted diets have smaller ovaries and a smaller corpus luteum, showing gestational nutrition has the ability to increase reproductive organ development, according to Moriel.
“Cows supplemented in the third trimester tend to have heavier calves, and those heifer calves have a greater first-calf pregnancy rate and calved during the first 21 days of the calving season,” notes Moriel. “Heifers born to cows offered 100 percent to 125 percent of maintenance requirements also calved in the first 21 days of the calving season and had higher calving percentages.”
Body condition score also matters when it comes to the second and third trimesters, he says, as higher body score could protect the calf’s performance after birth from negative changes to the diet during pregnancy.
Averi Hales is the editor of the Wyoming Livestock Roundup. Send comments on this article to firstname.lastname@example.org.