As a rule, dairy heifers need to grow around 0.5 - 0.7 kg/day between weaning and mating. Good feeding, nutrition, and a managed parasite control programme is necessary for calves post weaning through to entry into the milking herd.

Target:

• 30% of mature live-weight at 6 months.
• 60% of mature live-weight at 15 months (mating).
• 90% of mature live-weight at 22 months.

	3 Months	6 Months	9 Months	12 Months	15 Months	22 Months
Jersey	70kg	120kg	160kg	200kg	240kg	360kg
Jersey x Fresian	80kg	135kg	180kg	225kg	270kg	405kg
Fresian	90kg	150kg	200kg	250kg	300kg	450kg

Achieving target calf weights

Good rearing, feed, and nutrition is Key. An effective drench programme to manage internal parasites will be crucial to help calves achieve target weights.

Younger animals have low immunity to parasite infections - left uncontrolled infections quickly escalate, resulting in diminished health and live-weight gains. As calves mature natural immunity becomes increasingly robust, and animals are more capable of managing worm burdens.

As a general guideline the following drench programme will be necessary for dairy calves:

Age	Treatment Frequency
Weaning - 6 months	Every 4 - 6 weeks
6 - 15 months	Every 6 - 8 weeks
12 - 24 months	As required pre/post winter

Why worms matter

In extreme cases worm burden causes severe illness and death. More commonly a worm burden will reduce feed intake and energy utilisation efficiency - your animals will eat less and grow less from what they do eat. Over time this will affect calves reaching target weight.

1. Heifers that are underweight at mating are less likely to cycle and get in calf, more likely to be late calvers, and will probably produce less milk.
2. The hidden cost of worms is the eggs they shed via faeces on to pasture. Infected animals leave paddocks loaded with worm eggs ready to infect the next group of animals to graze. This is problematic where calves are grazing the same paddocks year after year.

Which drench products to use

With the rapid increase in resistance of Cooperia to the endectocide (macrocyclic lactone or mectin) drench family in cattle, use of single active endectocides as the only drench for young cattle is no longer recommended.

Levamisole (clear drench) remains highly effective in controlling Cooperia, though can be less effective in controlling Ostertagia, especially inhibited Ostertagia larvae.

Current best-practice recommendation is to use combination drenches containing levamisole in calves up to 12-18 months of age (Cooperia become less of an issue in cattle above this age). There has been very little resistance to combination drenches reported in cattle.

The choice of which product to use will be determined by cost, stock management, preferred method of application, and stock handling facilities.

We recommend drenching calves regularly from weaning through to at least 15 months with an oral combination product.

• Combo™ Low Dose is a good option. A broad spectrum, low dose combination of oxfendazole + levamisole.
• Integrate Abamectin™ Pour On each alternate drenching for targeted control of Ostertagia in spring/summer as a rule, or more often if FEC dictates.
• Moximax® Pour On should be used strategically where high worm burdens are present on pasture (eg spring & autumn). Moximax has persistent activity of 28, 35, and 42 days respectively for susceptible Trichostrongylus, Ostertagia and Lungworm. Can be a useful tool as a strategic single action option.

For young stock, we strongly recommended that you undertake regular pre and post drench Faecal Egg Counts to confirm the efficacy of each drench treatment. FEC tests after 18 months are unlikely to be of value in cattle due to natural immunity suppressing worm egg output