Medical breakthrough could boost beef production

A recent breakthrough in human medicine research could help a Texas A&M Animal Science Department researcher find a way to boost beef production to meet the demands of global population growth.

Bos indicus cattle breeds are very important to world beef production due to their adaptability to tropical and subtropical climates, including in Texas and other southern US states .

But the big problem or disadvantage of Bos indicus cattle, or the Brahman breed, is that their overall reproductive performance is lower than that of the Bos taurus cattle breeds, such as the Angus and Hereford, that predominate in the Midwest and Northern states.

Rodolfo Cardoso, DVM, PhD, Associate Professor and Reproductive Physiologist in the Department of Animal Science, College of Agriculture and Life Sciences, is leading a four-year project funded by a $500,000 grant from the USDA.

Cardoso said revolutionary advances in neuroendocrine research have identified the mechanisms that control the secretion of the gonadotropin-releasing hormone, GnRH. He believes the new insights could help his team identify neuroendocrine differences between the genotypes of Bos taurus and Bos indicus cattle and use this to improve the reproductive efficiency of Bos indicus-influenced cattle.

“More recently, there has been an important breakthrough in our understanding of how GnRH secretion is regulated in rodents and primates,” he said. “Our preliminary study suggests that similar mechanisms are also important in cattle and may explain differences in reproductive performance between Bos taurus and Bos indicus animals. If confirmed, these findings may have practical implications for managing the reproductive function of Bos indicus cattle. Several pharmacological strategies have already been developed in medicine to improve fertility in women based on these new findings.”

Calving time matters

As many as 70% of the world's cattle are raised in tropical and subtropical regions, and approximately 30% of US beef herds have some Bos indicus influence, especially in the southern and southeastern regions.

One of the main problems is that Bos indicus and Bos indicus cattle reach sexual maturity much later than Bos taurus breeds. This late puberty essentially means one less calf in a cow's life and also creates problems when breeders try to synchronize oestrus cycles for the annual breeding season.

Cardoso said that typically Bos taurus heifers reach sexual maturity at 10 to 12 months of age, while Bos indicus heifers often do not reach sexual maturity until 15 to 17 months of age.

“This five-month delay results in them not reaching sexual maturity for their first breeding season, and so farmers have to wait another full year to get their first calf,” Cardoso said.

Cardoso said heifers who calve for the first time at two years of age produce about 300 pounds more weight per calf, or $500 more, than heifers who calve at three years of age.

This project will use recent findings to determine whether the apparent differences observed in reproductive function between the Bos indicus and Bos taurus breeds can be explained by functional differences in the area of ​​the brain that controls GnRH hormone secretion.

Predefined breeding seasons are the key to efficiency

The predetermined breeding season typically lasts 45 to 90 days, Cardoso says, and allows beef cattle to be managed more effectively.

"You can have a very uniform crop of calves, which makes it much easier to care for them - vaccinate and follow all HEALTH protocols in a timely manner," he said. “You can wean and sell calves at the same time because you have a homogeneous group, which makes cow management much more efficient. It also allows for the culling of animals that are ineffective.”

In addition to better understanding bovine reproductive function, a second goal of the pharmacological strategy is to develop timing protocols for artificial insemination adapted for Bos indicus heifers, Cardoso says. Most of the protocols currently in use in the US have been developed specifically for Bos taurus breeds.

“Bos indicus heifers already at 12-14 months of age have the skeletal size and maturity needed to ensure a safe and healthy pregnancy,” he said. “There is no doubt about that. We don't want heifers to reach what we call precocious puberty (puberty before 10 months of age)."

Cardoso says a key benefit of more effective breeding season timing is the ability to use artificial insemination more frequently in cattle affected by Bos indicus.

“Artificial insemination is the most powerful tool we have to improve the genetics of beef herds,” he said. “Artificial insemination is a way that a beef producer can start improving herd genetics over time.”

But at present, the ability of breeders to synchronize Bos indicus-influenced animals for artificial insemination is not optimal, Cardoso said.

“We hope that by the end of this four-year project we will have a very good understanding of the neuroendocrine differences between Bos taurus and Bos indicus heifers,” he said. "And more importantly, we think at this point we will have good strategies for the pharmacological control of the estrus cycle in Bos indicus heifers."