Calves: Any calves that were dosed in May with a long-acting worm dose will be due another dose in the coming weeks as the cover period of four months comes to an end. Most farmers will use either a short-acting ivermectin-type product or a white drench as opposed to a long-acting dose again to allow animals build up some resistance to worms and because of cost. Contrary to some opinion, there should be no issue with resistance when using ivermectin products provided that the correct time interval between doses is adhered to and the right amount of product is used. Dose rates depend on weight. Time can be saved by using a pour-on dose and, instead, use the time to weigh the calves while they are in the crush.
Get your hands on a weighing scales or a weighband and weigh the lot and separate the lightest. February-born calves should be 33% of their mature body weight now, so Holstein Friesian calves should be between 190kg and 200kg, while smaller crossbred type calves should be between 180kg and 190kg. Many of the farmers in the Heifer Rearer of the Year competition will be starting back feeding meal to the on-target heifers over the coming weeks as grass growth slows and the weather becomes more changeable. In a Moorepark study from a few years ago, it was found that heifers too heavy at mating produced less milk solids and had poorer fertility in their first lactation than those on target weight at mating, so there’s no point in pushing them on too hard for the sake of it. Just get them to the target weight and keep them at it.