Pasture populations of cattle nematode larvae in Guadeloupe (French West Indies)

Effects of stocking rates on gastrointestinal nematode infection levels in a goat/cattle rotational stocking system

Gastrointestinal nematodes (GIN) are increasingly resistant to anthelmintic drugs worldwide, so integrated control methods are more and more needed for the sustainability of small ruminant farming. Such methods rely on knowledge in epidemiology, physiology, and genetics. Ecological studies have highlighted the effect of host density on parasite populations, and in the humid tropics, rotational grazing systems were designed according to the survival of GIN free-living stages. This study aimed to assess the effects of mixed stocking and host stocking rate on host GIN infection level. Four groups of 15-17 Creole male kids were raised on irrigated pasture from weaning (about 3 months) until the age of 7 months, at four partial stocking rates (pSR): 100% (control), 75% (G75), 50% (G50), and 25% (G25) of the total stocking rate of the pasture. The last three groups were associated with weaned Creole heifers to obtain the same overall stocking rate as the control. Animals grazed in a 'leader' goat and 'follower' cattle design: the G25, G50, and G75 paddocks were split into six plots; each plot was grazed by goats for 1 week and by heifers the following week. The pasture then rested for 4 weeks before the animals were returned for a new grazing sequence. Five control plots were grazed rotationally for 1 week, and rested for 4 weeks. This design was repeated three times a year for a total of 10 repetitions. Average faecal egg counts (FEC) decreased according to a power function of the pSR: FEC=1829pSR(3.7). The observed death rate decreased significantly with the pSR (27.6%, 16.4%, 11.9%, and 12.2%). The kids grew faster in G25 (51 g d(-1)) than in G50 (43 g d(-1)) and G75 or control (32 g d(-1), p<0.05). Heifers were not significantly infected with GIN and grew normally (about 0.48 kg d(-1)). Reducing the pSR by associating a non-host species in a rotational stocking system may be a very promising component of integrated GIN control, at least for the humid tropics.

Comparative efficacy of the nematode-trapping fungus Duddingtonia flagrans against Haemonchus contortus, Teladorsagia circumcincta and Trichostrongylus colubriformis in goat faeces: influence of the duration and of the temperature of coproculture

Amongst the alternative strategies to the use of anthelmintics, the administration of Duddingtonia flagrans spores has already proved its efficacy in reducing the number of developing larvae of several nematode species in goat faeces. In this trial, the efficacy of this fungus against the larvae of the three major nematode species of goats was compared in various conditions of coproculture. Twelve strongyle free goats were experimentally infected with either Trichostrongylus colubriformis, Teladorsagia circumcincta or Haemonchus contortus larvae. Half of the animals received an oral dose of 5x10(5) Duddingtonia chlamydospores/kg BW daily for 27 days, whereas the remaining was kept as control goats. From the 7th day of administration onwards, individual coproscopical examinations as well as coprocultures, which were incubated 4, 7, 10 or 14 days at 21 or 28 degrees C, were performed. The reduction in developing larvae due to the activity of Duddingtonia ranged from 62.8 to 99.5% compared to control. The trapping efficacy depended on temperature (better activity of the fungus at 21 than at 28 degrees C) and on duration (larval reductions lower after 4 days than after 7, 10 and 14 days of coproculture). Teladorsagia larvae were the least trapped, and Haemonchus larvae were the most trapped.

The role of parasite epidemiology in the management of grazing cattle

Epidemiology of ruminant helminths is the foundation on which strategic parasite control programmes are designed. Without this information one is not able to use anthelmintics to provide the optimal benefits for controlling both the adult worm and the pasture larval populations. The absence of strategic programmes generally results in using anthelmintics at the convenience of the producer, which may have little if any impact on parasite populations. The design of a strategic parasite control programme requires a knowledge of the dynamics of egg shedding from the host and the resulting pasture larval populations. It is important to know if larvae are available when animals are turned out onto pasture, when larval populations reach their maximal numbers and when they are induced to become hypobiotic. The goal is to keep pasture larval populations as low as possible. The use of pasture rotation adds another dimension to control programmes. The longer a pasture is allowed to remain fallow, the lower the pasture larval burden will be when it is grazed next. However, when we use intensive rotational grazing, animals may return to the pasture about 28 days later, when the larvae resulting from the eggs shed in the previous grazing are infective. This practice forces cattle to eat all of the forage available, including the grass closest to the faecal pat, where most of the infective larvae are available. If we treated cattle before turning them onto a clean rotationally grazed pasture, we should be able to control parasitism. Using a long-acting anthelmintic should enhance helminth control in rotationally grazed pastures and actually help to clean the pastures. Another grazing management practice is to alternately graze different species. This programme with the strategic use of anthelmintics should reduce parasitism in both host species.

Gastro-intestinal parasitism of cattle in native pasture grazing system in Guadeloupe (French West Indies)

Gastro-intestinal parasitism of creole cows and calves, Limousin x creole cross calves and Brahman x creole cross calves was recorded during seasons of calving in a native grazing system in Guadeloupe, a wet tropical area. Calvings were pooled during the dry season for two herds and during the rainy season for two other herds. For each calving season, calves of one herd were drenched monthly with anthelmintic. A marked periparturient rise in egg excretion was observed in cows. Coccidial infection was always present in calves, but no clinical signs were observed. The main parasites during the first 2 months of life were Strongyloides papillosus and Toxocara vitulorum. Then, Haemonchus placei, Trichostrongylus spp. and Cooperia spp. were the dominant species encountered. Brahman cross calves were the most heavily infested animals. There was no clear relationship between third stage larvae (L3) population size on pasture and worm burdens in calves, except during the second month of life. Despite medium levels of infestation, parasitism inhibited the growth of creole calves: -10.5 kg of bodyweight at weaning (-59 g day-1 of daily bodyweight gain from birth to weaning). The pathological effects of subclinical parasitism were confirmed by a lower packed cell volume and albuminaemia in parasitized calves than in treated calves.

Population evolution of the free-living stage of goat gastrointestinal nematodes on herbage under tropical conditions in Guadeloupe (French West Indies)

In Guadeloupe (French West Indies), paddocks were contaminated with gastrointestinal helminth eggs by young goats during the rainy season and the dry season. The evolution of L3 population size on herbage was followed over a period of 56 days. The major genera were Haemonchus and Trichostrongylus. It was shown that the L3 appeared on herbage 7-14 days after the beginning of contamination (DAC), and the L3 population sizes were maximal between the 14th and the 21st DAC. The maximum duration of larval survival ranged between 49 and 56 days. There was a marked depressive effect by the dry season on eggs hatching and L3 development with some arrested egg hatching in Trichostrongylus. The climatic events and the amount of dry matter on pastures during the grazing period appeared as the main important factors which could interfere with the overall evolution of the L3 population size and there was no preferential direction of L3 migration from faeces to herbage.