Controlling Worms in Dairy Goats: A Challenge
Dr. Steve Hart
Control of worms (internal parasites; gastrointestinal nematodes) in dairy goats presents some unique challenges. The first limitation is that some dewormers (Cydectin® and ivermectin) have a long milk withdrawal period (period between administering the drug and time that milk is safe for human consumption). There are a few drugs with short withdrawal periods so that there is minimal loss of milk for human consumption.
Another problem in lactating dairy goats are that they are very susceptible to worms due to lactating depressing the immune system and the additional stress caused by a high level of milk production. For these reasons, lactating dairy does must be monitored closely for parasite problems. Does can become wormy very rapidly and if they become badly infected (FAMACHA© 4+) they may need to be dried up to recover.
During the warm season, the goats are likely infected with the barber pole worm which causes anemia as well as depressed animal production and may cause bottle jaw (a collection of fluid causing a bulge under the jaw), which is edema. Milk production will be reduced and the animal will lose excessive body weight. This worm can be detected by FAMACHA© scoring the doe which measures the degree of anemia.
During cooler times of the year, the predominant worm species may be the bankrupt worm or the brown stomach worm. These worms do not cause anemia. The brown stomach worm may cause bottlejaw. There may also be other worms present. Basically, these worms will cause diarrhea, loss of appetite and poor milk production and excessive loss of weight. Worms can be monitored by fecal egg counts.
Management is the first line of defense against worms. Eggs hatch under conditions of warmth and moisture. Moist areas such as a wet area around a water trough may increase risk for worms. The eggs hatch and develop into infective larvae in about 5 days under good conditions. The larvae is trapped in the pellet by the hard skin on the pellet and cannot get out until there is significant rain (two inches in a month’s time) or several days of heavy dew. The larvae follow the moisture up the grass about 3 inches. Therefore, do not graze closer than 4" from the ground to keep goats from picking up infective larvae. Goats grazing brush pick up very few infective larvae.
The larvae may only live 35 days in hot weather, but 6 months in cool weather. Therefore, rotation grazing helps where you move animals away from the infective larvae and allow a long rest period. Horses and cattle can graze the area and vacuum up the infective larva since the larvae will not infect them. Haying will also clean the area up. Trees increase risk for worms because the goats collect under the same tree which equals more goat pellets and more eggs to hatch. The tree shades pellets from the sun and increases humidity, providing a good egg hatching environment. The grass is grazed close under the trees so goats pick up many infective larvae.
The only time one should blanket deworm the whole herd is around kidding time. The rest of the time, only deworm the animals that need it as determined by FAMACHA© (deworm heavy lactating dairy does that have a FAMACHA©
score of 3 or greater) or animals with symptoms of being wormy as described above. Fecal egg counts can be useful and one should utilize their local veterinarian or other experienced person to interpret fecal egg counts.
Panacur® and Safeguard® can be given orally to dairy does at twice the sheep dose with a 96 hour withdrawal. These drugs have the highest level of dewormer resistance and may not be effective against your worms. Valbazen® may also be given orally at double the sheep dose and has a 120 hour withdrawal. It is more potent than Panacur® or Safeguard® but some worms are resistant to it. Rumatel which is a dewormer that is mixed in the feed at the feed mill can be effective and has a zero day drug withdrawal. There are some commercially available feeds such as Positive Pellet Dewormer that contain Rumatel.
Prohibit® (also known as Levasole or Tramisol) may be used at twice the sheep dose with a 4 day drug withdrawal for milk. The only other dewormer suitable for use during lactation is Eprinex® which may be poured on the back of the doe at twice the cattle dose and it has a zero day milk withdrawal in Europe when used at this dose as a pour-on. Ivomec®, administered orally at double the sheep dose has a 9 day milk withdrawal time. Most of the other dewormers of the ivermectin family have long drug withdrawals such as Cydectin® with a 56 day milk withdrawal and should not be used during lactation. At least once a year, one should do a fecal egg count 7-14 days after deworming to see if the dewormer was effective at reducing fecal egg count to a low level.
Use good animal and pasture management to prevent worms, monitor animals for worms using FAMACHA© and the 5 point FAMACHA© check and use an effective dewormer and do not use the milk for human consumption during the withdrawal period. Good parasite management is important if the doe is going to produce milk to her potential.