Grazing with heifers and sows alone or mixed: herbage quality, sward structure and animal weight gain

The aim of the present study was to compare the effect of mixed grazing (MI) by sows and heifers with alternate grazing (AL) or grazing heifers (HN) and sows (SN) alone on animal weight gain, sward structure, herbage quality and composition, and selection during grazing. Mixed or alternate grazing consistently improved the weight gain in both heifers and sows, compared with grazing one species alone, but the positive effect was statistically significant only for heifers. The herbage quality of the MI and AL systems was better compared with the SN system, but not clearly better compared with the HN system. The total animal weight gain (heifers+sows) and estimated herbage intake per hectare were also higher in the MI and AL systems compared with SN and HN systems. The sows grazed selectively as they preferred clover rather than grass and grass leaves rather than grass stem. Only few turnovers of the sward by the sows were observed. Animal behaviour was not systematically surveyed, but no adverse behaviour was observed between the two animal species. Herbage quality, proportion of rejected herbage and the load of gastro-intestinal nematodes in heifers could have positively influenced animal weight gain per day and hectare in the MI and AL systems in this study

Epidemiological studies of parasitic gastrointestinal nematodes, cestodes and coccidia infections in cattle in the highveld and lowveld communal grazing areas of Zimbabwe

Between January 1999 and December 2000 faecal samples from 16 264 cattle at 12 dipping sites in the highveld and nine in the lowveld communal grazing areas of Zimbabwe were examined for gastrointestinal (GI) nematode and cestodes eggs, and coccidia oocysts. Strongyle larvae were identified following culture of pooled faecal samples collected at monthly intervals. The effects of region, age, sex and season on the prevalence of GI nematodes, cestodes and coccidia were determined. Faecal egg and oocyst counts showed an overall prevalence of GI nematodes of 43 %, coccidia 19.8 % and cestodes 4.8 %. A significantly higher prevalence of infection with GI nematodes, cestodes and coccidia was recorded in calves (P < 0.01) than in adults. Pregnant and lactating cows had significantly higher prevalences than bulls, oxen and non-lactating (dry cows) (P < 0.01). The general trend of eggs per gram (epg) of faeces and oocysts per gram (opg) of faeces was associated with the rainfall pattern in the two regions, with high epg and opg being recorded during the wet months. The most prevalent genera of GI nematodes were Cooperia, Haemonchus and Trichostrongylus in that order. Strongyloides papillosus was found exclusively in calves. Haemonchus was significantly more prevalent during the wet season than the dry season (P < 0.01). In contrast, Trichostrongylus was present in significantly (P < 0.01) higher numbers during the dry months than the wet months, while Cooperia and Oesophagostomum revealed no significant differences between the wet and dry season. These findings are discussed with reference to their relevance for strategic control of GI parasites in cattle in communal grazing areas of Zimbabwe