A study was carried out in the dry season, from October 1993 to May 1994 at an institutional farm in Niono (14º5’N, 6ºE, 295 m), on the Sahelian border of Mali with a semi-arid climate. Thirty-four local Sahelian goats in their first to fifth lactation weighing about 27 kg were used. Eleven of them suckled twin and 23 suckled single kids. The does were herded on natural rangeland for 8 to 9 h/day and received no food supplements. Dry season forage mass, intake and nutritive value of diets selected by goats, milk yield and effects on kids’ growth were measured.
The vegetation cover consisted of a herbaceous stratum dominated by annual gramineae plants and a woody stratum composed of 26 species of plants, whose relative abundance varied according to the topography and soil type. The goats spent between 0·126 (early dry season) and 0·004 (late dry season) of grazing time on herbaceous cover and the remaining time on consuming leaves, flowers and fruits of woody plants. The phytomass decreased as the dry season advanced. However, nutrient intake was relatively constant during the course of the study period, as the goats compensated for low biomass by walking more and grazing larger areas and for longer periods. On average, goats selected diets with 121 g crude protein and 7·6 MJ metabolizable energy per kg dry matter.
The milk yield and milk fat were measured weekly for 29 weeks but data for only 12 weeks are interpreted and discussed. Mean daily actual and fat-corrected milk (40 g fat per kg milk) production for the first 12 weeks of lactation was 692 (s.e. 139) g and 627 (s.e. 73) g respectively. The milk yield was maximum in the 1st week of lactation followed by a gradual decline. Milk yield was affected by litter size, number of lactation, weight and age of does at parturition. The does with twin kids produced significantly more milk (762 (s.e. 110) g/day) than the does with singles (656 (s.e. 158) g/day) (P < 0·05). The milk yield increased from the first lactation (542 (s.e. 49) g/day) to the third lactation (739 (s.e. 49) g/day) (P < 0·05) with no difference between the third and fifth lactation. Does over 27 kg produced more milk than those under 27 kg (P < 0·001) and does over 2·5 years produced more milk than younger does (P < 0·01). Milk fat was inversely related to milk production. Kids born as singles were heavier (2194 (s.e. 76) g) than those born as twins (1966 (s.e. 78) g) (P < 0·05). The kid growth rate was affected by birth weight (P < 0·001) and milk yield of dams (P < 0·01). Within litter size (single or twins), sex had no significant effect on the growth rate of kids, however the singles grew faster than twins (P < 0·001) throughout the 12 weeks of measurement. Single kids were 1·41 times as heavy as twins at 12 weeks.
It is concluded that, the milk yield of does and weight gain of kids under the precarious feeding conditions of the study indicate that the local goats monitored were adapted to local harsh conditions. Nutrition has been regarded as the main constraint to goat production from the range in the dry season. Further specific studies are needed to overcome the dry season nutritional stress and to improve goat production.
