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Quick answer: give a calf its first deworming dose at about 7–14 days of age, repeat it every month until the calf is 6 months old, and then move it onto the adult herd plan (twice a year, at the start and end of the rains). NDDB gives the first dose at 7–10 days and the Dairy Knowledge Portal and NDDB's new-born calf guidance say 10–14 days. The reason it starts so early is the calf roundworm Toxocara vitulorum. The calf picks it up from its mother's milk in the first days of life, and buffalo calves are hit hardest. Dose by the calf's weight on the day, using a dewormer and dose your veterinarian chooses, and weigh or tape the calf every time, because it grows fast.
| Calf age | What to do | Why |
|---|---|---|
| Day 0–1 | Colostrum within the first hour, navel dipped in tincture of iodine. No dewormer yet. | Colostrum protects the calf in its first weeks. See colostrum management for newborn calves. |
| 7–14 days | First dose, by weight, with a dewormer your vet confirms is effective against immature roundworms | Kills the roundworm larvae the calf got through milk before they mature and start laying eggs (from about 3 weeks of age) |
| 1, 2, 3, 4, 5 and 6 months | Repeat monthly, re-weighing the calf each time | Calves under 6 months keep picking up worms from the shed, soil and the dam's udder |
| 6–12 months | Join the herd plan: twice a year (start and end of the rains), plus fluke treatment in snail areas. Heavily grazed calves may need a dose every 2–3 months, guided by a dung test and your vet | Grazing calves now meet stomach worms and flukes, as adults do |
| Dam (mother) | Deworm near calving and again about 6–7 weeks after calving (NDDB) | Reduces the worm load passed to the calf and the eggs dropped in the shed |
This calf schedule fits inside our full deworming schedule for cattle and buffalo in India, which covers adult animals, the pre- and post-monsoon rounds and drug rotation.
The large calf roundworm, Toxocara vitulorum, is different from the worms adult cattle carry. Its larvae rest in the tissues of the cow or buffalo. Around calving they become active and pass into the milk, so the calf is infected while it suckles. The MSD Veterinary Manual notes that the worm matures in the calf's gut and eggs can appear in the dung from about 3 weeks of age. Calves under about 6 months are the ones affected.
A classic study in buffalo calves (Roberts, 1989) found that transmission through milk happened in all calves in the first 2 days after birth. It fell to about 2% from day 10 onwards. So treating at about 10–16 days, with a drug that kills immature worms, catches almost the whole infection before the worms grow and lay eggs. In that study pyrantel and levamisole killed about 97% of immature worms. Some older drugs worked much less well. This is why the first dose should never be skipped or delayed to "when the calf looks wormy". By then the damage and egg-laying have already started.
Diarrhoea in a young calf has many causes, not only worms. If a calf is scouring, weak or dehydrated, treat it as an emergency: see calf scours: prevention and management and call your vet. A dung test (faecal egg count) by your vet is the reliable way to know what worms are present and whether the dewormer worked.
Underdosing is the most common mistake. Calves grow fast in the first months, so a dose that was right at 2 weeks is too low at 2 months. Weigh the calf, or estimate weight with a girth (heart-girth) tape, before every dose, and follow the dewormer's label or your vet's dose per kg. NDDB's guidance is clear: the drug must be given in adequate dosage, so consult a qualified person.
NDDB's productivity manual lists fenbendazole and albendazole for calf roundworms. Pyrantel and levamisole have good evidence against immature T. vitulorum. Piperazine is also used, although in the buffalo-calf study it killed fewer immature worms (about 42%). Your vet will pick the drug based on the calf's age and the worms found. Do not use the same molecule every month for the whole year. NDDB advises against repeating the same drug, to slow resistance.
Drench slowly onto the back of the tongue, not into the cheek or the front of the mouth, so the dose is swallowed and does not go down the wrong way. Hold the head level, not high. Never drench a calf that is too weak to swallow.
NDDB advises deworming 2–3 weeks before vaccination for a better immune response. Plan the monthly calf dose so it falls before, not on the same day as, your calf's vaccine dates. See the cattle vaccination schedule.
Once calves start grazing, the worms change. Stomach worms such as Haemonchus, and in canal or pond areas liver fluke and rumen fluke, become the main problem. From about 6 months, deworm with the herd twice a year, at the start and end of the rainy season. Add fluke treatment where snails are present, on your vet's advice. Read about liver fluke in cattle and buffalo and rumen fluke (amphistomiasis).
For older calves, heifers and adults in fluke areas, vets may use a combined fluke-and-roundworm dewormer. Cattle Remedies Criloxy-S Suspension contains oxyclozanide 6%, levamisole hydrochloride 3% and silymarin 0.4%. Its label dose for cattle, buffalo, sheep and goats is 1 ml per 4 kg body weight orally, or as advised by the veterinarian. It is a chemical dewormer, so use it only on your vet's advice, dosed by weight, and observe any withdrawal period your vet advises.
Deworming removes the worms, but a calf that carried a heavy load needs good milk or milk replacer, clean water, a calf starter as it begins to eat solids, and a mineral mixture suited to calves. A liver tonic can support appetite and recovery after a heavy worm or fluke load. Cattle Remedies HEPRICH™ is a polyherbal liver tonic. Its label calf dose is 20–25 ml twice daily, or as advised by the veterinarian. It is also available on Amazon. To compare options, see our guide to choosing a liver tonic for cattle. Healthy, worm-free calves reach breeding weight on time. Read raising calves into profitable heifers.
At about 7–14 days of age. NDDB says 7–10 days and the Dairy Knowledge Portal says 10–14 days. Research in buffalo calves supports treating at 10–16 days, when milk-borne transmission of the calf roundworm has mostly stopped but the worms have not yet matured.
Every month from the first dose until 6 months of age. After that, twice a year with the adult herd (start and end of the rains), plus fluke treatment in snail areas as your vet advises.
No. In the first days the priority is colostrum, navel care and warmth. The calf roundworm is still being passed through milk in the first days of life, so a very early dose is wasted. Give the first dose at 7–14 days.
It depends on the drug and the calf's weight, so there is no single number. Weigh or tape the calf, then follow the product label or your veterinarian's mg-per-kg dose. Re-weigh before every monthly dose because calves grow quickly.
The schedule is the same, but be stricter with buffalo calves. The calf roundworm is especially common and dangerous in them, so do not skip or delay the first dose, and keep pens and wallow areas clean.
More in this series: deworming schedule for cattle and buffalo; the hidden burden of worm infections; calf pneumonia: signs and first aid; which Cattle Remedies product for which problem.
Reviewed for accuracy against the sources above on 26 October 2026. This article is general educational information for dairy farmers and is not a substitute for veterinary advice. Choice of dewormer, dose and timing must be decided with a qualified veterinarian, and label withdrawal periods must be followed. Cattle Remedies HEPRICH™ is supportive care and works best alongside correct deworming, feeding and hygiene.
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