Effects of stocking rate of goats and stage of crop growth when grazed on grain yield and goat production from pigeonpea (Cajanus cajan)

Abstract

An early-maturing, photoperiod-insensitive cultivar of pigeonpea, Cajanus cajan (cv. QPL4), was grown in two experiments. In the first experiment, grazing began at different times by goats with a mean weight of 14 kg. On different plots grazing started 24 days (before flowering), 57 days (flowering), 98 days (50% pod fill) and 141 days (after harvest) after plant emergence. The crop was then allowed to grow unchecked to pod maturity at 139 or 154 days after emergence and was harvested on 5 April 1982 to compare the effects of time of grazing on phenology, growth and yield. Ratoons were harvested on 9 August 1982. Grain yields of main crop plus ratoons were: the ungrazed control 1920 plus 403 kg/ha, pre-flowering 8 15 plus 107 kg/ha; 50% flowering 1210 plus 3 kg/ha, pod fill 0 plus 428 kg/ha and post-harvest grazing 1250 plus 24 kg/ha. In the second experiment, young feral doe goats (mean weight 16 kg) grazed pigeonpea at 25, 50, 75 and 100 goats/ha. Grazing commenced when 50% of plants were in flower (11 January 1982). Mean daily liveweight gains per animal (over 42 days) were: 25 goats/ha, 68 g; 50 goats/ha, 49 g; 75 goats/ha, 58 g; 100 goats/ha, 35 g. Grain harvested on 14 May 1982 was 1085, 530,80, and 0 kg/ha for goat stocking rates of 25, 50,75, and 100 goats/ha. Compared with the ungrazed control, grazing in both experiments had marked effects on plant populations and dry matter yields and reduced grain yields. Pigeonpea does not seem to be a good forage, perhaps because of its low energy content; therefore, there seems little point in grazing the crop during growth because of the marked reduction in yield of grain.