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飼料添加微藻蝦紅素對熱緊迫下蛋雞產蛋性能、蛋品質及蝦紅素蓄積量之影響
Effect of dietary supplementation of astaxanthin on egg production, egg quality, and astaxanthin deposition in laying hens under heat stress
摘要
蝦紅素（Astaxanthin, AST）屬於類胡蘿蔔素，富有抗氧化特性並可做為蛋黃紅色色素的天然來源，可透過添加藻類作為蛋雞之飼料添加物與強化雞蛋營養，但添加劑量對熱緊迫環境下蛋雞生產性能、蛋品質及蛋黃蝦紅素濃度之影響，報告尚少。本研究於亞熱帶夏季進行，每日最高溫和最低溫平均分別為32.0和28.9℃。選用192隻30週齡商業品種之羅曼褐殼蛋雞，逢機分配至三個處理組，分別為添加0（對照組）、10及20 mg/kg蝦紅素，蝦紅素由商業來源之雨生紅球藻（Haematococcus pluvialis）供應。每處理組4欄，每欄16隻，飼於放置巢箱且鋪有粗糠之水泥地面上，以4週為1周期單位分析產蛋性能，並於第4及8週結束當天，每欄逢機選取2顆蛋置於室溫下7天，分析蛋品質、蛋黃顏色及蛋黃蝦紅素濃度。試驗結果顯示，飼料添加20 mg/kg顯著較其他二組增加平均蛋重（P<0.01），但試驗處理不影響ADFI、產蛋率、產蛋量或飼料換蛋率（P>0.05）。飼料添加10和20 mg/kg蝦紅素降低蛋殼厚度（P<0.05），其中添加10 mg/kg蝦紅素具有增加蛋白比例之趨勢（P=0.10），但不影響蛋殼強度或霍氏單位。隨著飼料蝦紅素添加濃度提高，呈現曲直線增加蛋黃之羅氏比色扇數值和紅色色度（a*），但同時也會降低蛋黃光澤（L*）（P<0.01）。蛋黃之蝦紅素蓄積量依飼料蝦紅素添加量增加而提高，但其蓄積效率卻隨蝦紅素添加量增加而降低（P<0.01）。總結發現，飼料添加蝦紅素可以增加蛋重、蛋黃之紅色色度及蝦紅素蓄積量，但仍需留意添加20 mg/kg蝦紅素對蛋殼厚度之不利影響。
並列摘要
Astaxanthin (AST), a carotenoids and a potent antioxidant, is a popular dietary additive for laying hen to enhance yolk reddish color. Yet, the supplementary dosage of AST has not been established and with this aim, this study was designed to investigate the effects of different levels of dietary AST supplementation on the egg production and quality, as well as yolk AST content under heat stress. This study was conducted in subtropical summer with a daily temperature fluctuation from 32.0 to 28.9°C. A total of 192 laying hens aged 30-weeks were randomly allocated into 12 pens in combination with microalgal (Haematococcus pluvialis) AST at 0 (control), 10, and 20 mg/kg. Each treatment consisted of 4 pens × 16 hens fed on a floor with bedding for 8 weeks. Production performance was recorded weekly, and 2 eggs per pen were randomly collected every 4 weeks for egg quality and yolk AST content analysis after seven-day storage at room temperature. The results showed that the dietary supplementation of 10 mg/kg AST had no effect on egg weight, but 20 mg/kg AST significantly increased egg weight (P < 0.01). All AST treatments did not affect egg production, egg mass, feed intake, or feed conversion ratio. Both 10 and 20 mg/kg AST decreased shell thickness and 10 mg/kg AST tended to increase the albumen height (P = 0.10), but exerted no significantly effects on the shell strength and Haugh unit. Yolk redness was improved by AST supplementation in a dose-dependent manner which was in consistence with increasing Roche yolk color fan score by 1 to 3 (P < 0.01). The yolk AST content was significantly increased by dietary AST inclusion in a dose-dependent manner in accompany with reducing light reflectance. In conclusion, dietary supplementation of AST increased egg weight, redness of the yolk, and yolk AST enrichment under heat stress in laying hens. Despite an adverse effect on eggshell thickness, 20 mg/kg supplementation of AST apparently was acceptable.