Alginate increases water stability whilst maintaining diet digestibility in farmed saltwater crocodiles (Crocodylus porosus)

作者：Francis M; Morel P C H; Wilkinson B H P; Wester T J^*

来源：Journal of Animal Science, 2017, 95(2): 820-826.

DOI：10.2527/jas2016.0908

• alginate
• Crocodylus porosus
• digestibility
• ileal amino acid digestibility

Saltwater crocodile (Crocodylus porosus) farming in Papua New Guinea is an emerging industry that supplies high-quality skins to the fashion industry. Crocodiles are semiaquatic and fed highquality feed made from extrudated animal byproducts (i.e., forced through a die at low pressure but not heat treated); however, it disintegrates on contact with water, and this leads to low utilization. Alginate is used extensively in food and pharmaceutical processes because it quickly forms a gel at room temperature; however, its effects on nutrient availability are equivocal, and its utility in crocodile diets is unknown. Extrudated chicken byproduct-based crocodile diets were formulated (asfed) with and without 1.7 and 3.3% Na alginate with either CaCl2 or CaCO3 to cross-link. After immersion in water at 30 degrees C for 24 h, feed retained on a 0.5-mm screen was measured to determine DM retention (DMR). Regardless of inclusion level, alginate addition resulted in a 13-fold increase in DMR (P < 0.05) when CaCO3 was used as a Ca+ 2 source; however, CaCl2 use resulted in a much lower DMR. In a digestibility trial, 10 juvenile crocodiles (2.2 to 2.4 yr of age; 1.2 to 1.9 kg BW) were chosen from farm-raised stocks and fed extrudated chicken byproduct-based diets with and without 1.5% Na alginate and 1.9% CaCO3. Animals fed 2% BW for 12 d and with excreta collected the last 5 d were slaughtered and had digesta sampled from the ileum. There were no differences in apparent ileal digestibilities of any AA, N (65.0 vs. 55.8%, SE = 12.2%), and OM (46.8 vs. 39.6%, SE = 12.8%) between diets with and without alginate, respectively. Total-tract digestibilities of OM (69.8 vs. 39.2%, SE = 9.1%) and energy (72.2 vs. 44.4%, SE = 8.3%), however, were greater in alginate-containing diets (P < 0.05). Our study showed that alginate addition to crocodile feed improved its stability in water and did not impair nutrient digestion. Application of these findings should greatly decrease feed wastage, which ultimately will benefit Papua New Guinea by simultaneously increasing economic returns and decreasing environmental impacts.

• 出版日期2017-2