Earlier this month, a beef-type cow in Florida was identified as having bovine spongiform encephalopathy (BSE), also called mad cow disease. For those old enough to remember, BSE was the cause of death (by disease and culling) of many thousands of cattle—most heavily in the United Kingdom—in the late 1980s through early 2000s. Worse yet, it caused the deaths of a couple hundred people who had consumed beef from infected cattle (in humans, this is called variant Creutzfeld-Jakob disease).
The caused-many-deaths BSE is referred to as classical BSE, where the route of infection was due to ingestion by cattle of the infectious agent: a nasty little misfolded protein called a prion, specifically a prion designated PrPSc. Infection with PrPSc came from affected animals that were recycled into meat and bone meal and fed to other cattle. When the molecules of PrPSc get into the body, they go around refolding the native, normal PrPC proteins into the abnormal PrPSc proteins (see figure). As the disease progresses (over years), normal brain tissue becomes decidedly abnormal, and the animal’s behavior follows suit. Key symptoms of BSE include nervousness or aggression, abnormal posture, and lack of coordination. Cattle exhibiting such behaviors are not allowed in the food chain and are automatically tested for BSE.
Due to bans on the recycling of higher-risk tissues into feed, identified cases of classical BSE have fallen to essentially zero worldwide. What surveillance programs have picked up are a very few cases of what is called atypical BSE. The prions detected in these cases are slightly different at the molecular level from that in classical BSE. Atypical BSE arises from a spontaneous mutation in the gene that encodes the native PrP protein with the result that they start to misfold into a PrPSc-like shape. Like the atypical BSE-affected cow recently identified in Florida, these cases are not caused by infection from the outside.
Discovery of this “mad” cow (and the five others over the last 28 years) demonstrates that the surveillance procedures conducted by USDA are effective. At this point, USDA is testing about 25,000 cattle a year, and those are largely sampled from older or ill animals. USDA estimates the prevalence of BSE in the US at 1 in 1 million cattle.
Bottom line: we will occasionally see cases of atypical BSE pop up due to nature (mutations happen!) and our well-functioning surveillance system, but risk to the health of people and other cattle is exceedingly low.
Educational seminars (maximizing corn silage quality, effects of drought stress on digestibility, water conservation) and free lunch(!) are at the University of Idaho Kimberly Research and Extension Center. The field day is September 13, 2018, 10:00-2:00.
For additional details and to RSVP (by September 10), click here to open the flyer.
So what’s all this business about A2 milk? How is it different from A1 milk? Is it hooey? What do these codes refer to anyway?
Starting with the last question first, A1 and A2 refer to “versions” of the beta-casein gene. In this case, the gene in question encodes the protein beta-casein, one of three casein proteins, which is, of course, a key component of cheese. The A2 version of this protein varies just a little bit in its structure from the A1 version. An individual cow’s genotype could be A1A1, A2A2, or A1A2 for the beta-casein gene; her milk would then contain whichever protein versions her genes dictate.
The a2 Milk Company claims that A2-only milk is easier on digestion. A recent study has suggested that in milk-sensitive individuals, milk containing A1 protein may be associated with symptoms of discomfort after milk consumption, and with strictly A2 milk those symptoms may be lessened. Also, gastrointestinal transit time appears to be slower with A1 milk consumption but, contrarily, yielding softer stools. Additional studies to provide replication of these findings are needed. Early studies on A1 and A2 milk that suggested a link between A1 milk and several diseases have been unsupported by subsequent investigations. That is, there is no evidence that consuming milk containing A1 protein carries any disease risk.
So, should breeding decisions be made on the basis of beta-casein genotype? Or perhaps the question is, is A2 milk a fad or a legitimate, long-term slice of the market? Does A1 vs. A2 matter for yogurt or cheese making? There is a lot we still don’t know about the biology of milk. However, there would seem to be little risk in choosing A2A2 bulls. There are quite of few of them out there, although the number varies by breed. The most comprehensive and recent documentation of beta-casein genotype by breed has been compiled by the Canadian Dairy Network (see table).
Available data from U.S. cattle are more limited in number and over 20 years old. Interestingly, Zebu- or Brahman-type cattle have a very high frequency of A2A2.
Bottom line, don’t compromise your primary genetic objectives for your herd just to chase an A2A2 genotype, but there’s likely no harm in moving that direction if it makes sense for your market of the future.
For a deeper dive into the biology of A1 and A2, read on.
A1 and A2 refer to types of gene variants of the beta-casein gene. A gene variant (an allele, for those who remember their biology) is when we have a difference in the DNA sequence for a particular gene. The A2 gene variant encodes a proline (a particular amino acid; you’ll recall that amino acids are the building blocks of proteins) at position 67 in the 209-amino acid chain that forms beta-casein (see figure below). The A1 gene variant encodes a histidine at position 67.
The A1 beta-casein protein is thought likely to be cleaved (cut) during gastrointestinal digestion at the position 67 histidine, while A2 beta-caseins are less likely to be cleaved there. Cleavage at amino acid 67 generates a short protein (a peptide) called beta-casomorphin-7 (abbreviated BCM7). BCM7 has opioid properties. Now, no need for concern. We all know that while milk is tasty, it is not a very effective painkiller nor brain manipulator. It is possible though, that BCM7 may have some effect on processes in the gut, such as slowing the rate of passage. Also, all milk contains additional types of opioid peptides. Other foods (from animals and plants) do as well.
Are too many heifers on your farm showing up with mastitis early in that first lactation? You may want to examine your prevention strategies. A review paper that examined the effectiveness of various precalving treatments in heifers was published earlier this summer. Here are the key take-a-ways:
- When the infection is caused by contagious bacteria (e.g., Streptococcus agalactiae, Staphylococcus aureus), antibiotics, teat sealants, and vaccines can improve udder health outcomes.
- Particularly if you are considering using antimicrobial treatments, culture quarter milk so you know who the enemy is. We want to minimize the development of antibiotic resistance.
- When environmental pathogens (e.g., Escherichia coli, non-agalactiae streptococci) are the problem, teat sealants and combination therapies are effective at reducing mastitis risk.
- When coagulase-negative staphs (CNS) are infecting heifer udders, antibiotics, teat-sealants, and combination therapies offer the most help.
- When employing any of these treatment options, be sure they are delivered by a well-trained person.
- On farms with effective fly control and that minimize stress for late-gestation heifers, there may be little benefit from preventative medical treatment.
The paper: Naqvi, Nobrega, Ronksley, & Barkema. June 2018. Effectiveness of precalving treatment on postcalving udder health in nulliparous dairy heifers: A systematic review and meta-analysis. Journal of Dairy Science 101:4707-4728.
Another good resource is the National Mastitis Council’s Heifer Mastitis Prevention and Control Plan.
Researchers from Oregon State University investigated the blood serum profiles of Holstein cows before and after calving and compared those that developed clinical mastitis with those that did not. To do so, they used ultra-performance liquid chromatography high resolution mass spectrometry plus statistics to identify differences in concentration of metabolites, lipids, minerals, and inflammatory markers in blood serum. It’s OK if you read that last sentence and went, “Huh?” The short version is that they ran blood serum samples from dry cows through some fancy laboratory equipment to see if there were any indicators associated with developing clinical mastitis after calving. And yes, there are!
For example, alpha-tocopherol (a form of vitamin E) levels were significantly higher in the blood of cows that did not develop clinical mastitis compared to those that did (Figure 1). Another difference was in the overall profile of metabolites (molecules that participate in or are produced during metabolism); they were quite different for cows that remained healthy and those with post-calving mastitis (Figure 2).
While no dairies have liquid chromatography mass spec technology in their on-farm lab, these results may lead the way to identifying one or two highly reliable blood markers that could be easily measured on the dairy. And forewarned is forearmed, right? Knowing which cows were likely to develop mastitis could allow proactive treatment to prevent the more expensive and damaging clinical mastitis.
The paper: F. Zandkarimi, J. Vanegas, X. Fern, C.S. Maier, G. Bobe. Metabotypes with elevated protein and lipid catabolism and inflammation precede clinical mastitis in prepartal transition dairy cows. Journal of Dairy Science, June 2018, 101:5531–5548
Significant changes to the Margin Protection Program for dairy producers were made in the Bipartisan Budget Act of 2018. The Farm Service Agency has recently announced new implementation rules to accommodate the changes. Mark Stephenson and Andrew Novakovic, from the University of Wisconsin and Cornell University, will conduct a webinar to walk you through these changes and to assess impacts on producers who participate.
The webinar will be hosted by Farm Credit East at 10:00 AM PDT on Monday, April 9. It will be limited to the first 500 registered attendees. You can register for the webinar at https://DairyMarkets.org/register/ The webinar will be recorded and made available as an online stream after it is presented live.
Oregon Junior Holstein Sale
5 Holstein heifers & 1 Brown Swiss heifer selling.
Open to all interested 4H & FFA members.
The Sale Catalog is available on Facebook (https://www.facebook.com/oregonjuniorholsteinassociation/), in pdf form here: Junior Holstein Sale Catalog 2018, or can be mailed upon request.
The sale is April 7, 2018, starting at noon, at
4900 Cook RD SE
Turner, OR 97392
Any questions: 503-559-7222 Megan; 503-932-7129 Brian
The Oregon State University Dairy Club is hosting its bi-annual
Beaver Dairy Youth Day
on Saturday, April 14, 2018
at the OSU Dairy,
for kids in grades 4-12.
Dairy club members, along with industry experts, will be teaching youth about dairy judging and pedigree reading. After lunch, there will be a dairy judging competition for all levels of experience. Cattle for the event will be provided by the OSU Dairy. Lunch and snacks will be provided. However, if a student requires a special diet, please bring it from home. Event t-shirts, lunch, and awards are all included in the cost. Please preregister by March 28. Click on the link below for the registration form and additional information.
Join the Polk SWCD staff as they host forage seed growers from our region to learn about the many seed resources grown in our region. Livestock and horse owners will learn about the many grass, legume, and other kinds of seed available for high quality forage production. Factors such as suitability to soil type and moisture, hardiness, and livestock dietary need will be discussed by our panel of growers and seed company representatives. Bring a tag from a pasture seed mix bag or other list for discussion.
RSVP by February 20 to Claudia.Ingham@PolkSWCD.com or 503-623-9680 ext. 101 to ensure your light dinner at 5pm.
February 22, 2018 5-7pm
Polk County Fairgrounds, Building B
520 S Pacific Hwy W, Rickreall, OR 97371