The effects of a multiple-enzyme combination in maize-soya diets for broiler chickens
Thesis (MscAgric (Animal Sciences))--University of Stellenbosch, 2007.
The effect of a multiple-enzyme combination in mash and pelleted vegetarian maize-soya diets for broilers was evaluated in terms of apparent excreta- and ileal nitrogen- and amino acid digestibility and production performance. Two separate digestibility trials and one performance trial were conducted. For Trial 1, the apparent nitrogen (N) - and amino acid (AA) digestibility was determined by the collection of the excreta (total collection method) and in Trial 2 from digesta collected at the terminal ileum (ileal digestibility method). Production performance was also recorded in Trial 1. In Trial 3, the effect of the multipleenzyme combination in potentially improving performance of broilers in commercial conditions was evaluated. Broilers were fed a balanced- and low apparent energy (AME) vegetarian maize-soya diet with the addition of the multiple-enzyme combination. The addition of enzymes improved the apparent excreta- and ileal N digestibility of the mash diets during the period 14-21 d, and the ileal N-digestibility of the pelleted diets at 28 and 35 d of age. Conflicting results with regard to apparent excreta- and ileal AA digestibility were found. By both methods the digestibilities of threonine (Thr), methionine (Met) and phenylalanine (Phe) (14-21 d) and Cys (22-28 d and 29-35 d) were improved by the addition of the enzyme combination to the mash diets. Over the entire experimental period (14-35 d) the ileal digestibilities of histidine (His), Cys and leucine (Leu)of the mash diets were improved by 0.2 %, 0.2 % and 1.9 % respectively, following enzyme addition. By both methods the digestibilities of Thr, arginine (Arg), Met, Cys, Phe and Leu (14-21 d), serine (Ser), Arg, glutamic acid (Glu), Val, His, aspartic acid (Asp), lysine (Lys), proline (Pro), Met, tyrosine (Tyr), Phe and Leu (22-28 d), and Pro (29-35 d) were improved by the combination of enzymes and pelleting. For the entire experimental period (21-35 d), the ileal digestibilities of Ser, His, Lys, Met, Tyr, Cys, Phe and Leu was improved by the combination of enzymes and pelleting, indicating enzymatic activity was not destroyed by cold pelleting at 60 - 80º. The improvements in apparent nitrogen- and AA digestibilities were, in most cases, not reflected in production performance, although the combination of enzymes and pelleting resulted in improved body weight gain (BWG) for the first two weeks of chicks life and significantly improved the feed conversion ratio (FCR) during the second week of the chicks’ life. The effect of the multiple-enzyme combination on the production performance of broilers on a low AME- and commercial diet was mostly non-significant except for a significantly lower feed iii intake of the balanced diet for the fourth and fifth week of chick’s life following enzyme addition. A financial calculation showed, however, that the enzyme combination might increase profitability of a nutritionally balanced vegetarian maize-soya diet for broilers.