The effect of wattle tannin on intake, digestibility, nitrogen retention and growth performance of goats in South Africa
Institut d'Economie Rurale (1ER), BP 258, Bamako, Mali; School of Agricultural Science and Agribusiness, University of KwaZulu- Natal, P/Bag X01 Scottsville, Pietermaritzburg 3209, South Africa
Bengaly, K., Institut d'Economie Rurale (1ER), BP 258, Bamako, Mali; Mhlongo, S., School of Agricultural Science and Agribusiness, University of KwaZulu- Natal, P/Bag X01 Scottsville, Pietermaritzburg 3209, South Africa; Nsahlai, I.V., School of Agricultural Science and Agribusiness, University of KwaZulu- Natal, P/Bag X01 Scottsville, Pietermaritzburg 3209, South Africa
This study was conducted to determine the effect of wattle tannin extract (WTE) on protein utilisation by goats in a metabolism and a growth trial. Iso-nitrogenous diets (18% CP) with the following ingredients: filler, sunflower cake, molasses, hominy chop, vitamin-mineral mix and lucerne hay were formulated and mixed with 0,7.5,15,22.5 and 30 g WTE/kg dry matter (DM). The diets were fed to goats supplemented with 20% (w/w) native pasture hay. In the metabolism trial eighteen male (5 Nguni and 13 Boer) goats, within a live weight range of 21.5 to 37.5 kg (with a mean of 28.6, S.D. = 4.88), were blocked by weight and randomly assigned to the five treatment rations. Incremental levels of WTE in the diet resulted to small and non-significant increases (P>0.05) of total intake (g/day) of dry matter (DM) (mean 1089 ±58.6), organic matter (OM) (mean 902 ± 48.3), and nitrogen (N) (mean 32 ± 1.8) but the intake of neutral detergent fibre (NDF) (mean 351 ± 17.6) significantly increased linearly (P<0.05) with increasing WTE dosage. The apparent digestibility (g/kg) of DM (mean (661 ± 17.9) did not change (P>0.05)across treatments. Microbial N supply (g/day) and its efficiency of synthesis were similar across dietary treatments. N digestibility was adversely (P<0.05) affected by the levels of WTE. In response to supplementation with WTE, faecal N (mean 8 ± 0.4 g/day) rose while urinary N excretion (mean 13 ± 1.0 g/day) was not affected, and neither was N retention (mean 10 ± 0.7 g/day). In the growth trial, South African indigenous Nguni and Boer goats (n = 26) were used. Goats were about at 8-24 months of age with live weights ranging from 11 to 28 kg (mean 17.8, S.D. = 3.80 kg). Boer goats converted feed significantly more efficiently than Nguni goats (0.21 vs. 0.17 g gain/g feed, P<0.001). These results indicate that WTE given as dietary supplement is unlikely to improve the protein status and therefore growth performance of goats to a considerable degree. Condensed tannin, goat, growth, nutrient digestibility, protein, wattle.