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Abstract：
A suitable feed size has a positive effect on animal feeding. For aquatic larvae, the correct feed size is very important for their growth. This experiment analyzed and compared the effect of different particle sizes of feed for larval stages on the growth performance, whole body composition, and muscle amino acid and fatty acid composition of crayfish. Five larval crayfish diets of different particle sizes, namely < 0.40 mm (Group A, control group), 0.40-0.50 mm (Group B), 0.71-0.85 mm (Group C), 0.90-1.00 mm (Group D) and 1.5 mm (Group E), were fed to 2000 crayfish (initial weight 0.0786 ± 0.0031 g) for 100 d. The results showed that as the particle size increased, final weight, weight gain (WG, p = 0.001) and specific growth rate (SGR, p = 0.000) of the crayfish tended to increase and then leveled off, with the control group being the lowest. The feed conversion ratio (FCR, p = 0.000) showed a decreasing and then equalizing trend with increasing particle size, but there was no significant difference between the groups except the control group. Broken-line regression analysis showed that the critical values for the appropriate particle feed size for crayfish larvae were 0.55 mm and 0.537 mm using SGR and FCR as indicators. Groups B, C and D had the highest crude protein content and were significantly higher than the control group (p = 0.001). Group E had the highest umami amino acid (UAA) and was significantly higher than the control group (p = 0.026). The content of isoleucine (Ile, p = 0.038) and phenylalanine (Phe, p = 0.038) was highest in group C and significantly higher than in the control group. Through principal component analysis, groups C and D were shown to contain leucine (Leu), glutamic (Glu), methionine (Met), valine (Val), histidine (His), Phe, and Ile levels significantly induced. The content of linoleic acid (C18:2n6, p = 0.000), linolenic acid (C18:3n3, p = 0.000), saturated fatty acid (SFA, p = 0.000), monounsaturated fatty acid (MUFA, p = 0.001), polyunsaturated fatty acid (PUFA, p = 0.000) and n-6 PUFA (p = 0.000) in group C was the highest and significantly higher than the control group. Principal component analysis showed that group C significantly induced the levels of C18:2n6, C18:3n3, DHA, EPA, n-3 PUFA and n-6 PUFA in muscle. Therefore, our results suggest that appropriate feed particle size can improve the growth performance and nutrient composition of crayfish. Based on the broken-line regression analysis of SGR and FCR, the critical values of optimal particle size for crayfish are 0.55 mm and 0.537 mm, and when the particle size exceeds these critical values (not more than 1.5 mm commercial feed), growth performance and FCR of the crayfish are no longer changed. Nevertheless, group C has high protein and low lipid content, as well as better nutrition with amino acids and fatty acids. Overall, combined with growth performance and nutrient composition, it is recommended that the particle size of the diet at the larval stage for crayfish is between 0.71 and 0.85 mm.
摘要：
合适的饲料尺寸对动物喂养具有积极作用。对于水生幼虫，正确的饲料大小对它们的生长非常重要。本试验分析比较了不同粒度饲料对幼虫期生长性能的影响,全身成分，小龙虾的肌肉氨基酸和脂肪酸组成。五种不同粒度的幼体小龙虾日粮，即<0.40mm(A组，对照组)，0.40-0.50mm（B组），0.71-0.85mm（C组），0.90-1.00mm（D组）和1.5mm（E组），饲喂2000小龙虾(初始重量0.0786±0.0031g)100d。结果表明，随着颗粒尺寸的增加，最终重量,体重增加(WG，p=0.001)和比增长率(SGR，p=0.000）的小龙虾趋于增加，然后趋于平稳，对照组最低。饲料转化率(FCR，p=0.000)显示出随着颗粒尺寸的增加而减小然后相等的趋势，但除对照组外，各组间无显著差异。断线回归分析表明，以SGR和FCR为指标，小龙虾幼虫适宜颗粒饲料大小的临界值分别为0.55mm和0.537mm。B组,C和D组的粗蛋白含量最高,均显著高于对照组(p=0.001)。E组的鲜味氨基酸（UAA）最高，且明显高于对照组（p=0.026）。异亮氨酸的含量(Ile，p=0.038)和苯丙氨酸(Phe，p=0.038）在C组中最高，并显着高于对照组。通过主成分分析,C组和D组显示含有亮氨酸（Leu），谷氨酸（Glu），蛋氨酸（Met），缬氨酸(Val),组氨酸(His),Phe,和Ile水平显著诱导。亚油酸含量(C18:2n6,p=0.000),亚麻酸（C18：3n3，p=0.000），饱和脂肪酸(SFA，p=0.000)，单不饱和脂肪酸(MUFA，p=0.001),多不饱和脂肪酸(PUFA，p=0.000）和n-6PUFA（p=0.000）在C组中最高，且明显高于对照组。主成分分析显示,C组显著诱导C18:2n6、C18:3n3、DHA、EPA,肌肉中的n-3PUFA和n-6PUFA。因此,我们的结果表明，适当的饲料粒度可以改善小龙虾的生长性能和营养成分。基于SGR和FCR的折线回归分析,小龙虾的最佳粒度临界值为0.55mm和0.537mm，当颗粒尺寸超过这些临界值时（不超过1.5毫米的商业饲料），小龙虾的生长性能和FCR不再改变。然而，C组蛋白质含量高，脂质含量低，以及氨基酸和脂肪酸更好的营养。总的来说,结合生长性能和营养成分，建议小龙虾幼体阶段日粮的粒度在0.71至0.85毫米之间。
