Hill Climbers versus Bottom Feeders

John Maday, Editor, Bovine Veterinarian ( Lori Hays )

The following commentary does not necessarily reflect the views of AgWeb or Farm Journal. The opinions expressed below are the author's own.

While the “nature versus nurture” debate persists, we continue to gain understanding of genetic influences in virtually every aspect of livestock production. Beyond the familiar physical traits, scientists now explore the role of genes in more difficult-to-measure, but economically important traits, such as disease susceptibility, feed efficiency and even grazing behavior.

As ruminants, cattle have one key production advantage over pigs and chickens: their ability to graze and thrive on a forage-based diet. For ranchers, more efficient forage utilization can mean heavier stocking rates, more beef production per acre and higher returns over fixed costs. Toward that goal, ranchers routinely drive their herds away from over-used bottomlands and onto fresh forage, often on steep slopes and further from water.

So, a “nurture” strategy can improve resource utilization, but what if we could rely more on nature, and reduce the labor associated with herding cattle? It turns out we probably can. During the recent Beef Improvement Federation’s annual research symposium, New Mexico State University grazing specialist Derek Bailey, PhD, discussed development of grazing distribution phenotypes. Colorado State University animal scientist Milt Thomas, PhD, followed with a presentation on genomic approaches to improve grazing distribution.

Bailey outlined his work using electronic GPS tracking systems, allowing researchers to track and map grazing patterns for individual cows over several months on Western rangeland. Their results clearly show that some cows – the bottom feeders – spend all their time in the valleys, near water sources. Other cows – the hill climbers – are more adventurous, climbing the steep mountain sides and venturing further from water in search of fresh, underutilized forage.

More hill climbers in a herd could allow ranchers, especially in the Mountain West, to increase stocking rates or grazing periods on public lands, generate higher returns on their forage assets and prevent overgrazing on sensitive riparian areas. And, the researchers say, grazing behavior is a heritable trait and a potential target for data-based genetic selection.

As with many traits, multiple genes influence grazing behavior, as do non-genetic environmental factors, Thomas says. There is no single gene that separates the hill climbers from the bottom feeders. However, he adds, whole-genome sequencing could allow researchers to develop molecular breeding values for grazing behavior and incorporate predictions into selection indices.

More work needs to be done before we can use genomic ratings for grazing habits in selecting bulls or replacement heifers, but ongoing advancements in technology will keep expanding the possibilities for genetic progress. Whole-genome sequencing and genetic testing play a key role, while other advancements such as affordable GPS tracking, more sensitive disease diagnostics, radio-frequency identification and others provide the tools we need to quantify differences in genetic traits previously difficult to measure.

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