Influence of physiological stage
The influence of the physiological stage of a Blackbelly flock against natural infection by gastrointestinal parasitic nematodes (GIN) was investigated by Mexican researchers. The two most abundant GIN species identified were Haemonchus contortus (91%) and Trichostrongylus colubriformis (81%).
Data were recorded in 51 sheep for 6 months. The flock was divided based on their physiological stage as follows: a) pregnant ewes, b) lactating ewes, c) non-pregnant ewes, d) pre-weaning lambs, e) growing lambs and f) replacement sheep. Additionally, sheep were classified based on the parasite infection as stabled or grazing management system as follows: g) non-infected stabled sheep, h) infected and stabled sheep and i) infected grazing sheep. Feces and blood samples were collected every fifteen days.
Results showed high FEC in stabled lactating ewes (2764 epg) and in growing lambs (2950-4550 epg). Pregnant ewes had higher packed cell volumes (PCV; 27%) than lactating ewes (23.5%). Infected lambs showed low PCV (28.5%) and high plasma protein (PP) values (5.9 g/dL) compared with non-infected lambs (31% PCV and 5.6 g/dL PP). The group of infected lactating ewes and lambs showed susceptibility to GIN more than the other groups, including the pregnant ewes.