Daffodils are not the only things emerging this Spring
As we start to welcome Spring and warmer weather, so too do the parasites that have been hibernating in the guts of your calves over the winter. We still don’t know the cues that worms use to know when to awake but we do know that they start emerging from the stomach lining at about this time of year causing gut damage, inappetence and poorer growth rates. The stomach worm, Ostertagia, causes the most gut damage, but in calves under 15-18 months of age a mixed infection with Cooperia also is highly likely.
Once the parasites emerge from hibernation within the gut they start mating and producing eggs. These eggs exit the calf in the dung where they hatch into larvae and, over time, can heavily contaminate your pasture. It’s a tactical move to drench calves early in the season in order to kill these hibernated worms and therefore prevent heavy contamination of your pasture. There will be larvae on the pasture from the previous season that has survived the winter that, unfortunately, you can’t do anything about and regular drenching throughout the season is usually necessary. Never drench a mob and move them to a new paddock. There will always be a few worms that survive a drench and produce larvae that contain this survival gene – you don’t want a new pasture full of these. The old pasture will still have larvae on it that don’t contain this gene, so leave your calves on here for a few days to mix up the gene pool before you move them on.
When worms start emerging from the gut lining, the calf’s own immune system works hard to try to eliminate the parasite from the gut. Parasites have been evolving for millions of years to live in this environment and so they are good at evading the body’s attack. The immune system has to work hard and long and, in order for the immune system to function properly, it requires protein and energy. If feed is tight and the animal requires protein and energy to grow, as well as to mount an immune response, growth rates can suffer. Most farmers are aiming for calves to be 60% of their adult body weight at 15 months of age (mating). Calves that hit these targets have greater longevity in the herd, produce more milk in their first two lactations and are more likely to conceive. Being free from disease (BVD/worms etc.), having adequate copper, selenium and B12 and, most importantly, good quality feed means a healthier, productive future herd.