Livestock Management RANCHING
Parasite Control on a Cow-Calf Herd By David Bechtol, D.V.M.
Internal parasites cause numerous problems including depressed immune systems and increased disease susceptibility. They sup- press appetites while limiting nutrient intake and absorption, which results in reduced feed effi ciency, reduced rate of gain and reproduction and lower immune re- sponse to vaccinations.
M
ETHODS OF CONTROLLING INTERNAL AND EXTERNAL parasites have changed very little over the years, with the possible exception of the
introduction of broad-spectrum anthelmintics. Yet, resistance has started showing up across the country to many of the anthelmintics. This makes developing a strategic deworming program even harder in this extremely important management problem, no matter where you live or how you raise your cattle.
External parasites • Include biting and non-biting fl ies, myiasis-producing fl ies (maggots), mosquitoes, biting and sucking lice, ticks and mites
• The most serious threat to production and econom- ics since they feed on body tissues such as skin, blood and hair, often resulting in discomfort and irritation for the animals
• Live year-round in the southern warmer climate • Irritate animals and may transmit diseases from infected animals to healthy ones
Flies Flies have many families affecting livestock. Some are blood suckers, while other are just plain pesky.
44 The Cattleman June 2014
Most come in contact with the animals for only a short period of time, making control diffi cult.
Lice Lice spend their entire lives on the host. Several
species of lice are present in the South. Many are blood-sucking, but one is merely a biting louse, which feeds on skin and hair causing itching, irritation and hair loss. Lice cause most of their damage in the colder weather months of late fall and early winter.
Mites Mites feed on the surface or burrow just beneath
the skin, making very slender winding tunnels and secreting fl uid. A toxin is also secreted which causes intense irritation and itching. Infested animals rub and scratch continuously, causing infl amed areas with only scattered hairs remaining. Infestations are contagious and treatment of all animals in the herd is essential in preventing spread.
Ticks Ticks are blood-sucking and drop off the host after
feeding to lay their eggs. Their effects include infl am- mation, itching and swelling at the bite site, blood
thecattlemanmagazine.com
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