Nutrient intake, digestibility and growth performance of Washera lambs supplemented with graded levels of sweet blue lupin (Lupinus angustifolius L.) seed

•Effect of supplementing hay with graded levels of sweet lupin seed (SLS) was evaluated.•Supplementation with SLS significantly increased intake, digestibility of nutrients; lamb performance and feed conversion efficiency.•Sweet lupin seed is a promising protein supplement in the tropics and subtropics.•Enhancement in productivity of ruminants through SLS supplementation could improve the livelihood of smallholder farmers in the tropics and subtropics.

The experiment was conducted to evaluate nutrient intake, digestibility and growth performance of Washera lambs fed natural pasture hay-based diet supplemented with graded levels of sweet blue lupin (Lupinus angustifolius L.) seed. Twenty male intact Washera lambs with average age of four months and initial body weight of 16.9 ± 0.32 kg (mean ± SD) were used in 90 days feeding trial followed by 10 days digestibility trial. The design of the experiment was randomized complete block design (RCBD) with five replications. The four supplement feeds were;150 g wheat bran (WB) (control-T1), 150 g WB + 195 g sweet lupin seed (SLS) (T2), 150 g WB + 245 g SLS (T3) and 150 g WB and 295 g SLS (T4). Natural pasture hay was offered ad libitum. Digestibility trial was conducted at the end of the growth trial. Data were analyzed using the General Linear Model (GLM) procedures of SAS (version 9.2). Means were separated using Duncan's Multiple Range test. Correlation between nutrient intake, digestibility of nutrients and weight gain were analyzed using Pearson correlation procedure. Results showed that supplementation of SLS significantly increased total dry matter, crude protein and organic matter intakes. Supplementation of SLS improved the digestibility of dry matter and organic matter (P < 0.05) and crude protein (P < 0.001). However, the digestibility of NDF and ADF were not affected by supplementation (P > 0.05). Average daily gain (ADG) was higher (P < 0.001) for the SLS supplemented groups (61.8–89.1 g/day). It was concluded that sweet blue lupin seed could serve as alternative CP supplement in natural pasture hay-based feeding of Washera sheep. Based on the biological performance of the experimental lambs (ADG and FCE values), T3 could be recommended for practical feeding of lambs if optimum performance is targeted.