Influence of Acacia tortilis leaf meal-based diets on growth performance of pigs

The objectives of the study were to assess the nutritive value of Acacia leaf meals and to determine the optimum inclusion level of Acacia tortilis leaf meal in finishing pigs. Five dominant leguminous leaf meals namely, Acacia tortilis, Acacia robusta, Acacia nilotica, Acacia nigrescens and Acacia xanthophloea, were individually hand-harvested and analyzed for their chemical and physical properties. Although the crude protein content of A. xanthophloea and A. tortilis were similar, the latter was incorporated into the experimental diets as it had the lowest water-holding capacity and swelling capacity and moderate levels of condensed tannins. A. tortilis was also the most abundant in the locality. Thirty finishing male F1 hybrid (Landrace x Large White) pigs with an initial weight of 60.6 (s.d. = 0.94) kg were randomly allotted to six diets containing 0, 50, 100, 150, 200, 250 g/kg DM inclusion levels of A. tortilis leaf meal. Each diet was offered ad libitum to five pigs in individual pens for 21 d. Average daily feed intake (ADFI), average daily gain (ADG), and gain:feed (G:F) ratio were measured every week. There was an increase in both ADFI and ADG (P < 0.001) as A. tortilis leaf meal increased, before they started to decrease. An increase in A. tortilis leaf meal levels in the diets caused a quadratic decrease (P < 0.01) in the G:F ratio. The change in ADFI, ADG, and G:F ratio during each week of successive feeding decreased (P < 0.05) with incremental levels of A. tortilis in the diets. Using piecewise regression (broken-stick analyses), it was observed that A. tortilis leaf meal can be included up to 129 g/kg DM in finishing pig feeds without negatively affecting the G:F ratio. The ability with which pigs utilize leaf meal-based diets improves with duration of exposure to such diets.