Influence of grazing regimes on cattle nutrition and performance and vegetation dynamics in Sahelian rangelands

In the West African Sahel, common herd management practices such as night grazing and corralling influence time available for grazing. When animals are used to deposit manure in the cropping fields, conflicts often arise between the need for animals to graze long enough for adequate feed intake, especially in the dry season, and the need to collect manure.

Grazing trials were carried out in Sadoré (13 ^o14'N and 2 ^o16'E) and Toukounous (14 ^o30'N and 3 ^o17'E), Niger, to determine the effects of timing (day or day-and-night) and duration of grazing on cattle nutrition and performance, and to quantify the short-term effects of grazing by cattle on vegetation dynamics in Sahelian rangelands. In addition, a survey was conducted among livestock herders in two villages of Niger, Kodey and Toukounous, on their perceptions of night grazing with the aim of identifying constraints to the practice of night grazing and opportunities to apply relevant experimental results in the management of herds in the region.

There were no differences in the quality of the diet selected during the day and at night, but the quality of the available and ingested forage declined as the season progressed from wet to dry. During the dry season, there was a trend for day-and-night grazing cattle to be more selective during the day, than animals that grazed only during the day. Animals that had additional grazing time in the night consistently had higher forage intake and consequently, higher average daily gain than those that grazed only during the day in all seasons.

However, additional grazing at night reduced the amount of manure that could be collected for crop fields. When animals are supplemented, night grazing appears less relevant as the length of night grazing time did not significantly affect average daily gain in the critical late dry season. Annual herbage production of four paddocks used in Toukounous was 1893 kg DM ha ^-1. Of this amount, consumption by cattle accounted for 48% on a year-round basis. The quality of the diet selected by the animals was consistently higher than that of the herbage grazed in all seasons. These results indicate that grazing ruminants tend to make better use of Sahelian rangelands than often predicted on the basis of pasture evaluation alone.

The response of herders interviewed on their perceptions of night grazing indicates that ethnic group and herd size are critical characteristics for the decision on the practice of night grazing. Herders' perceptions of night grazing with respect to animal production parameters such as weight development, water consumption, faecal output and feeding behaviour are consistent with available experimental results. Therefore, the herders' current knowledge and herd management strategies need to be considered in the development of any animal or ecological innovation.