Controlling External Parasites on Cattle

By Jerad Jaborek

External parasites that feed on the blood of cattle, including flies, ticks and lice, pose a serious threat to cattle health due to the possible transmission of various pathogens that can negatively impact animal well-being and reduce growth and reproductive performance. Controlling these parasites in your herd will help keep your herd healthy and improve their well-being.

Flies

There are several types of flies associated with annoying and stressing cattle, including horn flies, stable flies, house flies, heel flies, horse flies and deer flies. Fly season in the upper Midwest begins in the spring months (March–May) as the temperatures begin to warm up. The stress caused by flies can lead to reduced weight gain and milk production of impacted cattle. Face flies can cause eye irritation and spread pinkeye (Moraxella bovis) between cattle. Additionally, biting flies can cause skin irritation, hide damage and the spread of various blood-borne diseases. Some flies can lead to fly strike, where flies infiltrate wounds and deposit eggs for the hatched maggots to feed on once hatched. However, a majority of fly species lay eggs in the manure of cattle. Depending on the fly species, it can take from half a week to three weeks to complete the life cycle from egg to adult.

Lice

There are a couple species of lice that can be bothersome to cattle. Among lice, there are biting or sucking lice depending on the morphology of their mouth and what they choose to feed on (i.e., blood, skin, hair). Animals affected by lice appear less thrifty and can suffer from reduced performance and anemia as well. These affected cattle display signs of itching or may be missing patches of hair from scratching. Lice infestations are most common in late fall through the spring and typically decline in the summer.