333 Animal Science 2000, 71: 333-340 1357-7298/00/96710333$20·00 © 2000 British Society of Animal Science Effect of nocturnal grazing and supplementation on diet selection, eating time, forage intake and weight changes of cattle A. A. Ayantunde 1,2 , S. Fernández-Rivera 1 , P. H. Y. Hiernaux 1 , H. van Keulen 3 , H. M. J. Udo 4 and M. Chanono 5 1 International Livestock Research Institute (ILRI), ILRI/ICRISAT, B P 12404, Niamey, Niger 2 Institute for Animal Science and Health (ID-DLO), Department of Ruminant Nutrition, Runderweg 2, PO Box 65, 8200 AB Lelystad, The Netherlands 3 Research Institute for Agrobiology and Soil Fertility (AB-DLO ) , PO Box 14, 6700 AA Wageningen, The Netherlands 4 Animal Production Systems Group, Wageningen Institute of Animal Sciences, PO Box 338, 6700 AH Wageningen, The Netherlands 5 Ministére de l’Agriculture et l’Elevage, Centre du Multiplication de Betail, Toukounous, Niger Abstract Sixty-four Azawak male calves were used to study the effect of nocturnal grazing (NG) and supplementation (S) in the dry season on forage and water intake, faecal output, eating time and weight changes of cattle in the Sahel. Treatments were factorial combinations of four levels of NG (0, 2, 4 and 6 h/day) and two levels of S (0 and 608 g dry matter (DM) per animal per day). All animals were allowed to graze 10 h during the day and were weighed every 2 weeks during the 70-day experimental period. Eight oesophageally fistulated steers were used in a cross-over design to sample the diet (forage) selected during the day and at night by supplemented and non-supplemented animals. Extrusa crude protein and in vitro organic matter digestibility were not influenced by supplementation (P > 0·05). Time spent eating during the day or at night were not affected by supplementation but total eating time increased by 39·4 (s.e. 2·1) min/h of NG. Forage intake increased with increase in NG, while total food intake (forage + supplement) increased with supplementation (82·4 v. 92·1 (s.e. 2·4) g DM per kg M 0·75 per day). The supplemented animals also drank more water than the non-supplemented (26·2 v. 24·8 l per animal per day). Average live-weight change (LWC) increased by 24·4 (s.e. 8·7) and 9·3 (s.e. 6·2) g/h of NG in non-supplemented and supplemented animals, respectively. Supplementation improved LWC (–107 v. 99 g/day, s.e. 14, P < 0·05). Night grazing improves dry season performance and its effect decreases when cattle are supplemented. Keywords: cattle, feeding behaviour, food intake, noctural activity, supplementary feeding. Introduction Nocturnal grazing and night-time corralling of cattle are alternative herd management practices in the west African Sahel (Dicko-Touré, 1980; Fernández- Rivera et al., 1995; Powell et al., 1996). Results from previous studies (Fernández-Rivera et al., 1996; Ayantunde, 1998) demonstrated that when cattle are corralled (i.e. no night grazing) at night during the dry season to collect manure, forage intake decreased, and weight losses increased. Therefore, night corralling increased the need for supplementation. On the other hand, night grazing improved animal performance (King, 1983; Khombe et al., 1992) but it reduced the amount of collectable manure for cropping (Ayantunde, 1998). In addressing this conflict of interest it is necessary to determine the interactions between night grazing and supplementation. The objective of this study was to determine the effect of night grazing and supplementation on diet selection, forage intake, faecal output, water intake, eating time and weight changes of cattle. Material and methods Study site A grazing trial was carried out for 70 days in the late dry season between April and June 1997 at Toukounous, Niger (14º30' N and 3º17' E). The paddock used was a fenced area of 75 ha. The soil was predominantly sandy while alluvial clay plain