A study of Nematode parasitism in hill-country breeding ewes

Abstract

A two-year study of Nematode parasitism has been carried out on Romney breeding ewes run at stocking rates ranging from three to seven ewes per acre. Total egg numbers of the ewes at the low stocking rates were consistently lower than those at the high stocking rates, but results indicated that egg numbers rarely reached a level considered to be detrimental to sheep health (i.e.. above 2,000 eggs per g faeces moist weight). A post-parturient rise in egg numbers occurred at high but not at low stocking rates. Ostertagia spp. were mainly responsible for this rise but Bunostomum trigonocephalum predominated in the egg counts throughout the rest of the year. Some large numbers of B. trigonocephalum worms were found in a few dead or extremely emaciated sheep. Bunostomum egg numbers were significantly higher in the ewes at high stocking rates without cattle than at low stocking rates. Numbers in ewes at high stocking rates with cattle were intermediate.