Seasonal variations of nematode infection in Small East African goats and their crosses with Boer and Saanen reared under extensive and semi-intensive systems

Abstract

A study was conducted in Turiani (sub-humid environment) and Mlali (semi-arid environment) to assess the seasonal variation of nematode infection in Small East African (SEA) goats and F₁ crosses of SAE with Saanen and Boer. The SEA goats were kept under extensive system while the crossbreds were kept under semi-intensive system. In Mlali 37 SEA goats and 30 SEA x Boer crosses while in Turiani 30 SEA goats and 33 SEA x Saanen crosses were included in the study. Worm burden was assessed using faecal egg count (FEC) and packed cell volume (PCV) as indicator traits. Faecal and blood samples were collected at the end of dry season, mid and end of rain season. The dominant worm species were identified by faecal culture. The results indicated that fewer animals (30 – 66.7%) were infected at the end of the dry season than at the mid and end of the rain season (69.7 – 100%). The FEC values differed significantly between periods of the year (P< 0.001) and between locations (P<0.05). The geometric mean faecal egg count (GFEC) ranged from 71.3 to 200.9, 185.8 to 516.4 and 273.5 to 924.7 eggs per gram (epg) at the end of dry season, mid and end of rain season, respectively. The GFEC values of SEA goats reared under extensive system were slightly higher (80.5 – 924.7 epg) than those of crossbred goats (71.3 – 690.2 epg) reared under semi-intensive system. The PCV values differed significantly (P<0.001) between locations, periods of the year and breeds. In Mlali, the PCV values ranged from 18 to 45% while in Turiani, the values ranged from 10 to 43%. The dominant parasite in the study areas was Haemonchus spp and accounted for 47.5 and 48.9% of total worms in Turiani and Mlali, respectively. This was followed by Trichostrongylus spp (21.3 and 19.8% in Mlali and Turiani, respectively) and Oesophagostomum spp (18.2 and 20.7% in Turiani and Mlali, respectively). The proportions of Strongyloides spp (6%), Bunostomum spp (4%) and Cooperia spp (3%) were small in all periods and locations. It is concluded that the level of nematode infection is highest at the end of the rain season and low during the dry season. The crossbred goats kept under semi-intensive grazing system had lower level of nematode infection than the local goats kept under the free-range grazing system.