Abstract
Polyethylene glycol (PEG 4000), Browse PlusTM (BP), wood ash (WA) and boiling water were evaluated as tannin deactivation methods on tannins in Acacia nilotica fruits. Twenty four Matebele goats of mean body mass, 38.7 ± 3.12 kg, were used in a digestibility and nitrogen balance trial. A completely randomized design was used, and the initial weight was used as a covariate in data analysis. The goats were randomly allocated to the treatments and were fed for 28 days on a basal diet of hay and A. nilotica fruits treated with PEG (MW 4000), BP, WA or boiling water. Acacia nilotica fruits had 4.39% catechin equivalents of condensed tannins, thus the amount of PEG, BP and WA used to treat the fruits was 1.5 parts per part of condensed tannin in the fruits. It was hypothesized that treating the fruits would deactivate the tannins in them and increase intake, digestibility and nitrogen retention. Treating the fruits for condensed tannins had no effect on hay and fruit intake. None of the treatments had an effect on the apparent digestibility of dry matter, organic matter, neutral and acid detergent fibre and nitrogen retention in the goats. The goats that were fed on the boiled fruits had a negative N retention of –1.03 g/day. It was concluded that none of the detannification methods improved feed intake, apparent nutrient digestibility and nitrogen retention. It is recommended that each detannification method should be tested on different types of tannins and at different concentrations before totally dismissing the treatments as not useful.Keywords: Boiling, Browse Plus, pods, proanthocyanidins, PEG, wood ash
Highlights
Shortage of good-quality feed, especially during the long dry season in tropical and subtropical areas, has increased the need to provide supplementary feed to maintain livestock condition (Hove et al, 2001)
The objective of the study was to determine the efficacy of wood ash (WA), Browse PlusTM (BP), PEG and boiling on the reduction of the effects of condensed tannins in A. nilotica fruits on feed intake and digestibility
The vegetation is characterized by thorny Acacia species, mostly A. karroo and A. nilotica with an understorey layer dominated by perennial grasses with occasional annuals (Ward et al, 1979)
Summary
Shortage of good-quality feed, especially during the long dry season in tropical and subtropical areas, has increased the need to provide supplementary feed to maintain livestock condition (Hove et al, 2001). Few communal farmers can afford to buy supplementary feed for livestock, and some have resorted to collecting tree fruits and feeding them to livestock as protein supplements, especially during the dry season (Kindness et al, 1999; Sikosana et al, 2002). Tree fruits are especially valuable because they ripen and fall on the ground in the dry season when there is no green forage (Timberlake et al, 1999). Many trees produce potentially nutritious fruits containing up to 200 g crude protein/kg (Tanner et al, 1990). A. nilotica has been reported to contain condensed tannins that reduce browse utilization efficiency by herbivores (Tanner et al, 1990; Phale&Madibela, 2006; Nsahlai et al, 2011).
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