ORANGE-FLESHED SWEETPOTATO ROOTS AS ENERGY AND PROVITAMIN A SOURCES FOR LAYING HENS

Abstract

Orange-fleshed Sweetpotato Root (OSR) is a potent energy feedstuff for laying hens due to its high energy and carotenoid content. However, OSR’s high perishability and dustiness in finished feeds are limitations, which could be addressed by high-temperature-short-time extrusion. There is scarce information on the effect of extrusion on the nutritional quality of OSR, the pigmenting abilities of OSR carotenoids and their interconversion to vitamin A in poultry. Therefore, this study was designed to assess the effect of extrusion on metabolisable energy of OSR-based concentrates, pigmenting abilities and the interconversion of OSR carotenoids to vitamin A in laying hens. Concentrates: OSR and Corn Bran at 3:2 (OSR-CB), extruded at 65-70℃ (Elow) and 100- 110℃ (Ehigh) in a single screw extruder, were assayed for Water Solubility Index-WSI, Water Absorption Index-WAI, and Provitamin A (PVA) carotenoids using standard procedures. Twenty-nine-week-old ISA Brown hens (n=96, 1.9±0.1kg) were randomly allotted to 12 diets containing unextruded, Elow and Ehigh OSR-CB each at 0, 10, 20 or 30% as substitute for glucose monohydrate, for seven days (r=4). The nitrogen corrected Apparent Metabolisable Energy (AMEn, kcal/kg) of the concentrates were estimated using standard methods. Carotenoid-depleted hens at 42-week-old (n=96, 2.2±0.1kg) were randomly assigned to White Maize-Soybean Meal (WM+SBM, control), WM+SBM + apo- ester, OSR-CB+SBM or Yellow Maize -SBM (YM+SBM) based diet in four replicates for 84 days. Eggs were collected for yolk quality assessment, PVA carotenoids (μg/g) and retinol (μg/100g) at day 0, 28, 56 and 84 using standard procedures. Liver was biopsied at day 0, 28, 56, and 84, and assayed for retinol (μg/g). Data were analysed using descriptive statistics and ANOVA at ἀ0.05. Extrusion significantly decreased WSI by 4.05% (23.67±0.47) and 16.21% (20.67±0.47) in Elow and Ehigh OSR-CB, respectively, compared to unextruded OSR-CB (24.67±0.47). A significantly higher WAI of 5.39±0.21 was recorded in Ehigh OSR-CB, while unextruded and Elow OSR-CB were similar. The PVA carotenoids decreased significantly from 228.04±0.05 in unextruded OSR-CB to 152.32±0.16 in Elow and 148.37±0.53 in Ehigh OSR- CB. Extrusion significantly enhanced AMEn of Elow and Ehigh OSR-CB by 16.47% iv (4051.15±0.05) and 14.11% (3968.82± 0.06), respectively over unextruded OSR-CB (3478.13± 0.08). Colour intensity of egg yolk at day 28 ranked: 74.07±0.18 (WM+SBM + apo-ester) > 70.97±0.04 (YM+SBM) > 63.41±0.03 (OSR-CB+SBM) > 53.68±0.09 (WM+SBM), with similar trends at 56 and 84 days. The PVA carotenoids in egg yolk on day 84 was significantly higher in OSR-CB+SBM (2.80±0.04) and YM+SBM (1.13±0.02) than WM+SBM (0.52±0.03) and WM+SBM + apo-ester (0.33±0.02) fed hens. Egg yolk retinol increased by 709.56% (77.88±0.04) and 20.06% (11.55±0.03), in OSR-CP+SBM and YM+SBM fed hens, respectively compared to the control (9.62±0.08) at day 28, with similar trend at 56 and 84 days. Liver retinol at day 28 was significantly higher in OSR- CB+SBM (996.26±0.04) and YM+SBM (367.64±0.05) and similar in WM+SBM (136.30±0.02) and WM+SBM + apo-ester (126.80±0.06) fed hens with same trend observed at 56 and 84 days. Extruded Orange-fleshed sweetpotato root based concentrate at low temperature improved energy availability, egg yolk pigmentation and vitamin A in laying hens.