Embryonic deaths cut calf crop

Embryonic deaths cut calf crop

BEEF herd owners would be shocked to learn that they'd lost 25% of cow pregnancies in two weeks, but it happens all the time without owners ever knowing it.

"Huge losses occur before farmers know their cows are pregnant," said Mike Smith, University of Missouri animal scientist. "Many losses occur before the cows know they are pregnant."

Pregnancy checks in University of Missouri research herds have shown that three days after breeding, 95% of all cows bred are pregnant. However, 14-16 days later, only 70% are pregnant.

Early embryonic death loss cuts calf crops, Smith said. Late embryonic death pushes losses higher: By day 30, pregnancy rates have dropped to 65%. Another 5-10% can be lost later in gestation.

Preventing pregnancy losses offers profit potential to the beef industry. Research on that subject continues at the University of Missouri's College of Agriculture, Food & Natural Resources.

New tools developed at the university allow for early detection of pregnancies.

"Genetic defects cause one-third of early losses. Those losses clear birth defects and genetic abnormalities," Smith said. "That leaves two-thirds of losses to stress and other factors in cows."

Herd managers can reduce the stress on cows, he added.

"We don't know what causes all of these early embryonic losses," Smith acknowledged, noting, however, that "there are ways to save more calves through management."

Transportation and heat stress cause losses. Loading cows on a truck and moving them after breeding creates stress. The timing and method of transportation affect loss rates. Heat stresses come from the sun and from toxic endophyte-infected fescue grass.


Fall pasture

Cattle producers who want to promote a healthier pasture next spring may want to take steps now to prevent overgrazing their pastures in fall, according to Rory Lewandowski, a forage expert from The Ohio State University's College of Food, Agricultural & Environmental Sciences.

To promote a healthier pasture next spring, producers need to start planning for the end of the season now and help their plants prepare for fall, which is an important time for pasture management, said Lewandowski, an agriculture and natural resources educator for Ohio State University Extension.

"Producers need to start thinking about what these plants are doing to get ready for the end of the season and should match their grazing practice with what the plant is trying to accomplish, which is to build up root reserves," Lewandowski said. "Producers need to be looking and planning ahead.

"Although pasture growth this year has been good and has left most producers in a better position than last year, hopefully, the 2012 drought and its impacts are still in their memory, so they will realize how important the fall period is and will work to protect that pasture from overgrazing," he added.

During autumn, particularly in September and October, pastures must be managed so that grass and legume plants are able to build up and store carbohydrate reserves for the winter period, which keeps a root system living over the winter months, he said.

While the leaf tissue dies during the winter, the buds and roots of the plant remain as living tissues over the winter and continue to respire and burn energy, Lewandowski said.

"If the root reserves are insufficient, the plant may die over the winter," he said. "If the plant survives but root reserves are low, spring regrowth and vigor of the plant are reduced. In order to build up carbohydrate reserves, there must be adequate leaf area so that the plant can maximize the photosynthetic process."

To accomplish this, producers should ensure that they don't overgraze their pastures.

"Growth rate slows down in the fall, so it's harder to recover from overgrazing mistakes in September," Lewandowski said. "Other benefits to keeping higher grazing residual include conserving soil moisture so the plants will continue to grow. Overall, it's really about keeping enough leaf area on the plant so producers get quicker green-up in the spring and better, more vigorous spring plant growth in the long run."


Understanding bovine TB

The use of whole bacterial genome sequencing will allow scientists to inexpensively track how bovine tuberculosis (TB) is transmitted from farm to farm, according to research presented last week at the Society of General Microbiology's Autumn Conference.

Bovine TB is primarily a disease of cattle caused by the bacterium Mycobacterium bovis.

Researchers from the University of Glasgow in Scotland, working in collaboration with the Agri-Food & Biosciences Institute and the Northern Ireland Department of Agriculture & Rural Development, sequenced the genomes of 147 M. bovis samples that had been collected over a decade of outbreaks in Northern Ireland. By combining the genomic sequences of the bacteria with information about when and where the sample was isolated, in addition to data on the movement of cattle from farm to farm, the researchers were able to build a detailed forensic map of bovine TB spread.

The results showed that, even on a scale of a few kilometers, M. bovis samples from neighboring farms were more closely genetically related than geographically distant farms that had had cattle moved among them. This finding confirms that, while long-distance spread via cattle movements plays a role, local transmission mechanisms appear to drive the spread of the disease, although the researchers were unable to determine what those vectors were.

Hannah Trewby, who presented the research, said, "The inclusion of whole-genome information in our data will give us unprecedented insight into how bovine TB spreads and will help us to develop better control methods for the disease."

In the U.K., the role infected wild badgers play in spreading bovine TB remains a controversial topic. This work will help clarify any part badgers may have in spreading the disease and continue to build a sound, scientific evidence base on which control measures can be built. The U.K. government has proposed a badger cull to try to control the spread of bovine TB.

University of Glasgow mathematical biologist and principle investigator Rowland Kao explained, "Our results suggest that the establishment and local persistence of the pathogen in cattle has a distinct spatial signature. We believe that explaining this signature is the key to quantifying the role that badgers play in the persistence of bovine TB in Britain and Ireland.

"While we do not yet have sufficient data to be definitive, it is clear that whole-genome sequencing of the bacterium will play an important part in solving this puzzle. Given the extensive collection of samples already collected from cattle and badgers, we are optimistic that this approach will help in accumulating the right scientific evidence over the coming years to tackle this important problem," Kao added.

Volume:85 Issue:38

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