cows in field

Recent ODairy Discussions – May, 2021

By Liz Bawden, NODPA Board Co-President

A farmer had two “healthy young animals die overnight without any clear explanation”. Both were grassfed heifers in good condition due shortly with their first calves. The farmer’s vet was called to perform an autopsy, and the results were inconclusive. After a great exchange of ideas from several vets on the list, it was agreed that the most likely scenario is they had both died from positional bloat, commonly called “casting”.

One vet described it as: “a cow or heifer that's heavy with calf will sometimes lay down on their right side and get tipped slightly back so the rumen "pins" the animal down and they can't get righted (a bit like a turtle on its back) - Jerseys are more prone to this and sometimes the depression is surprisingly minor -nearly level and shallow. The inability of the cow to right itself keeps the rumen outlet (esophageal opening) blocked and bloat quickly suffocates the animal.” Another farmer has experienced the same challenges and makes it a practice to patrol his pastures and barnyards throughout the day to look for animals that need to be rolled back up.

The topic of the cast heifers brought up other threads of discussion on causes for sudden death in animals. One farmer experienced the sudden death of several heifers; the autopsy found the appearance of unusually red lungs. They found it was due to clostridia perfringens, a soil borne pathogen. Once it is on the farm in the soil, it’s there forever. So they began to vaccinate with Ultrabac 7, and continue to this day to vaccinate after weaning. A vet shared a story of a shorthorn cow that died suddenly due to nitrate toxicosis. This disorder occurs when feed is high in nitrates (often from drought stress) and the nitrates prevent the blood from carrying enough oxygen. Another vet identified clostridial enteritis as a quick and fatal condition: ”there will be an area (sometimes quite short ~4-6") of the intestine that is discolored (red to black), gas-filled and containing putrid gas - the overgrowth of the clostridium bacteria produces a powerfully lethal toxin. That condition is most common in situations where cattle are getting a lot of grain.” And tragically, sometimes a cow in late pregnancy will tear the uterine artery (at the point where it attaches to the aorta). This causes sudden death with no outward signs but as soon as one opens the abdomen there will be blood all around the viscera.

A producer asked for recommendations for a pre-milking sanitizer. Recommendations included peroxyacetic acid (from De Laval or IBA) and peracetic acid (small cubes from IBA). Another producer uses an iodine bath to sanitize milking units between cows, and asked if another product would work to minimize possible pathogen transfer without getting traces of iodine in the milk. A Chlorine dioxide product and IBA’s Supersan (peroxyacetic acid) were both suggested.