果皮在家禽飼料中的價(jià)值

發(fā)布單位:天津瑞孚農(nóng)牧科技集團(tuán)有限公司

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時(shí)間：2019-11-29

最近爆發(fā)的非洲豬瘟對(duì)豬群造成了一定程度的損害，為了尋求其他可替代的肉類產(chǎn)品，全球家禽的需求量將會(huì)上升。對(duì)家禽產(chǎn)品的更高需求可能導(dǎo)致全球家禽價(jià)格上漲。為了維持全球家禽類價(jià)格，可替代/低成本的飼料原料將是維持家禽飼料壓力的關(guān)鍵。考慮到人們對(duì)低抗?fàn)I養(yǎng)因子的作物越來(lái)越感興趣，外加先進(jìn)的加工技術(shù)以及酶產(chǎn)品和抗?fàn)I養(yǎng)結(jié)合劑在飼料市場(chǎng)的有效性，根莖類植物的外皮以及水果果肉可能是很有價(jià)值的飼料成分。
替代能量來(lái)源
家禽生產(chǎn)的預(yù)期增長(zhǎng)直接影響到飼料的供應(yīng)和價(jià)格。根據(jù)美國(guó)農(nóng)業(yè)部（2015）的數(shù)據(jù)，從2005年到2015年，玉米價(jià)格上漲了71%。這表明了尋找可替代能量來(lái)源替代家禽飼料中常規(guī)使用的能源物質(zhì)的重要性。食品和工業(yè)中根莖類植物和水果加工過(guò)程中產(chǎn)生了大量經(jīng)濟(jì)價(jià)值低的果皮和果肉加工剩余物，有效的利用這些剩余物對(duì)環(huán)境來(lái)說(shuō)也是積極有利的。
富含淀粉的根莖類植物是重要的糧食作物，估計(jì)全球年產(chǎn)量為8.36億噸（FAO，2013年），而果皮重量占到塊莖重量的15%～20%；此外，大多數(shù)水果的果皮產(chǎn)量更高于根莖類植物，如木瓜和香蕉的果皮產(chǎn)量分別為31%和40%。此外，大量的水果可能會(huì)被浪費(fèi)，約30～40%的香蕉由于缺陷和損壞而被淘汰（FAO，2012）。柑桔榨汁后留下的果肉殘?jiān)?，占水果重量?0%～70%。

1 果皮作為飼料成分的優(yōu)點(diǎn)
1.1 木薯
木薯皮的成分受品種、成熟期、農(nóng)藝和環(huán)境等因素的影響。有研究報(bào)道稱，木薯皮粉的蛋白質(zhì)含量為30～60 g/kg，其中精氨酸含量較高；纖維含量更高（主要是NSPs）， 為140～340 g/kg。木薯中主要的抗?fàn)I養(yǎng)因子是氫氰酸，氰化物是高度熱不穩(wěn)定的，可以通過(guò)日曬降低到有毒水平以下。
1.2 山藥
山藥皮是一種能量來(lái)源，其代謝能量值為11.3～12.6 MJ/kg不等；蛋白質(zhì)含量為91.4 ~ 127 g/kg。有研究報(bào)道表明，山藥皮淀粉含量高，淀粉消化率高。
1.3 紅薯
紅薯皮能量高，蛋白質(zhì)含量適中，粗纖維含量低。研究表明，其粗蛋白含量為36～46 g/kg，粗纖維為38～70 g/kg，代謝能值為11.25 MJ/kg。不同顏色的紅薯是類胡蘿卜素的良好來(lái)源，為可以使正常的雞蛋和皮膚色素沉著對(duì)色素的需求減少補(bǔ)充量。也有相關(guān)報(bào)道描述了紅薯皮中酚類化合物的研究。

1.4 柑橘

柑橘渣是柑橘汁工業(yè)的副產(chǎn)品，由柑橘果皮、果肉和種子按不同比例混合而成。柑橘品種和榨汁方法的不同影響著柑橘渣的成分，柑橘渣的能量值相對(duì)較高 （11.4 MJ/kg）和纖維含量高（123～135 g/kg 干物質(zhì)），蛋白質(zhì)含量在620～740 g/kg 干物質(zhì)之間。在柑橘皮中發(fā)現(xiàn)了低濃度的蛋白酶抑制劑、植酸鹽和單寧。果肉中含有大量的酚類化合物，具有很強(qiáng)的抗氧化能力。

1.5 香蕉

有研究顯示香蕉的粗蛋白含量為5%或10%，在生和熟的香蕉皮中代謝能分別為11.6 ~ 14.0 MJ/Kg。果皮中含有兒茶酚，具有抗氧化、抗菌和降膽固醇的作用，單寧已被報(bào)道為香蕉皮中主要的抗?fàn)I養(yǎng)因子。

1.6 甜菜渣

甜菜渣（SBP）也是另一種潛在的家禽飼料原料，但其用途受到低代謝能、高纖維和纖維的高持水能力的限制。研究發(fā)現(xiàn)SBP含有3 MJ ME/kg，9.6%粗蛋白，19%粗纖維 （主要為NSPs形式）。

1.7 木瓜

木瓜皮蛋白質(zhì)與玉米相似，但纖維含量較高，脂肪含量較低。有研究報(bào)道，木瓜含有高濃度的蛋白水解酶（木瓜蛋白酶和木瓜凝乳蛋白酶）、維生素、礦物質(zhì)和β-胡蘿卜素。由于多酚類物質(zhì)的存在，木瓜皮被報(bào)道具有驅(qū)蟲(chóng)劑、抗菌和抗球蟲(chóng)活性?？?fàn)I養(yǎng)因子包括單寧、生物堿、皂苷和黃酮類化合物。

2 果皮在肉雞和蛋雞日糧中的應(yīng)用

有幾項(xiàng)關(guān)于家禽果皮飼料喂養(yǎng)的研究，但建議各不相同。若干因素，包括果皮成分的差異（營(yíng)養(yǎng)成分和抗?fàn)I養(yǎng)組分）、加工方法、雞只年齡和日糧成分，都可能影響家禽對(duì)果皮的利用。以下是來(lái)自不同研究的一些建議的摘要：

2.1 木薯皮

飼料中加入200g/kg木薯皮并不影響肉雞的生長(zhǎng)。也有研究稱，與對(duì)照相比，飼喂500g/kg日糧干木薯皮的肉雞體重增加和飼料效率有所提高；低氫氰酸含量（< 4mg kg）的木薯品種可以在不影響性能的情況下添加到500～600 g/kg。最近，有研究觀察到，添加154g/kg日糧的木薯皮粉會(huì)對(duì)肉雞的生產(chǎn)性能產(chǎn)生負(fù)面影響，但這可以通過(guò)添加脂肪和酶來(lái)克服。

2.2 山藥皮

添加量為150g/kg山藥皮時(shí)，肉雞雛雞的生長(zhǎng)沒(méi)有受到影響。有研究觀察到250g/kg的山藥皮粉添加量對(duì)肉雞生長(zhǎng)和胴體性狀產(chǎn)生最佳效應(yīng)；在育雛期和育成期分別推薦添加68和224 g/kg的山藥紅薯皮混合物（1:1）效果最佳。有報(bào)道稱，山藥-紅薯皮混合物在肉雞育雛期和育成期可替代日糧中15%和45%玉米，且對(duì)肉雞生長(zhǎng)、血液學(xué)指標(biāo)和胴體測(cè)定無(wú)不良影響。

2.3 紅薯皮

紅薯皮能量高，蛋白質(zhì)含量適中，粗纖維含量低。有研究者建議，不應(yīng)將紅薯皮粉添加到肉雞育雛期飼料中，但可以在育成期飼糧中添加高達(dá)310g/kg；最近有學(xué)者建議150g/kg的添加量。

2.4 甜菜渣

2015年的一項(xiàng)研究發(fā)現(xiàn)，23g/kg是最適合肉雞生長(zhǎng)的添加量，而最近的一項(xiàng)試驗(yàn)發(fā)現(xiàn)，在肉雞中補(bǔ)充酶可以使添加量達(dá)到75g/kg。

2.5 柑橘渣

報(bào)道稱添加20g/kg的柑桔渣對(duì)肉雞的生產(chǎn)性能和健康狀況有改善作用。試驗(yàn)表明，在肉雞日糧中添加50g/kg的柑橘皮，可使肉雞的生長(zhǎng)性能與玉米對(duì)照組相似。另一項(xiàng)試驗(yàn)報(bào)道，在肉雞日糧中添加柑橘皮可達(dá)到79.2g/kg，且不影響肉雞的生產(chǎn)性能。

2.6 香蕉皮
有研究推薦，在肉雞日糧中添加100g/kg香蕉皮粉。此外，有學(xué)者觀察到，同時(shí)添加酶補(bǔ)充物可使香蕉皮粉的使用達(dá)到340g/kg。此外，用干香蕉皮代替15%、30%或45%的黃玉米對(duì)生長(zhǎng)性能、胴體特征和血液學(xué)參數(shù)沒(méi)有影響。
2.7 木瓜皮
120g/kg木瓜皮粉對(duì)肉雞生長(zhǎng)無(wú)不良影響。在蛋雞飼糧方面，木薯皮的來(lái)源、加工和雞只年齡等因素都可能影響木薯皮的成分及其在飼糧中的使用。

3 果皮的未來(lái)
為滿足世界對(duì)食品和工業(yè)用途日益增長(zhǎng)的需求，世界大量生產(chǎn)塊莖類和水果作物，這也表明，如果有適當(dāng)?shù)眉庸ず蛢?chǔ)存技術(shù)，果皮是很容易獲得的。果皮含有適量的營(yíng)養(yǎng)成分，這使它們成為家禽飼料的潛在原料成分，將這些廢棄物用于家禽飼料也可降低飼料成本和潛在的環(huán)境風(fēng)險(xiǎn)。再加上減少抗?fàn)I養(yǎng)因子的加工技術(shù)的進(jìn)步，將使果皮作為家禽飼料的價(jià)值更突出。
除了營(yíng)養(yǎng)成分外，果皮還具有多種功能特性（抗氧化、抗菌、降膽固醇等），隨著飼料添加劑（外源酶產(chǎn)品、氨基酸、抗氧化劑、抗?fàn)I養(yǎng)結(jié)合劑)市場(chǎng)的不斷擴(kuò)大和飼料工業(yè)對(duì)植物生物制劑的研究興趣的增加，果皮的應(yīng)用前景更加廣闊。

The value of peels in poultry diets
The recent outbreaks of African Swine Fever have damaged pig populations, especially in China. As a result, global poultry demand will rise as consumers seek out other meats as an alternative. The higher demand for poultry products might lead to a rise in global poultry prices during 2019. Less costly alternative feed ingredients will be crucial to sustain the pressure on poultry feedstuffs. Peels from roots and tubers as well as fruit pulps might be valuable feed ingredients, considering the increasing interest in breeding crops for low anti-nutritional factors, advanced processing technologies and availability of enzyme products and anti-nutrient binding agents in the feed market.
Alternative energy sources
The expected increase in poultry production has a direct effect on the availability and price of feed. From 2005 to 2015 the price of maize has increased by 71%, according to USDA (2015). This indicates the importance of alternative energy sources to replace the regularly used sources in poultry diets. The processing of roots and tubers and fruits for food and industrial uses results in the disposal of the low economic value residues in the form of peels and pulps. Utilisation of these residues as feedstuffs will also have a positive impact on the environment.
Starch-rich roots and tubers are important food crops with an estimated global annual production of 836 million tonnes (FAO, 2013). With peel weight accounting for 15–20% of the tuber weight one can estimate the amount of peels that can be produced from the processing of these crops. Peel yield is still higher in most fruits than roots and tubers. Peel yields of 31% and 40% have been reported in papaya and bananas, respectively. In addition, huge quantities of these fruits may be wasted, about 30–40% of bananas are rejected due to defects and damage (FAO, 2012). Citrus pulp, the residue left after juice extraction, represents up to 50–70% of the fruit weight.
The benefits of selected peels
Cassava – The composition of cassava peel is affected by several factors including cultivar, stage of maturity and agronomic practices and environmental factors. Adesehinwa et al. (2011) reported a protein content of cassava peel meal of 30–60 g/kg, with the protein content being high in arginine. The peel is high in fibre (mainly NSPs), 140 to 340 g/kg. The major anti-nutritional factor in cassava is hydrocyanic acid, however, cyanide is highly heat labile and can be reduced below toxic levels by sun-drying.
Yam – Yam peel is an average source of energy with metabolisable energy values ranging from 11.3 to 12.6 MJ/kg. The protein content ranges from 91.4 to 127 g/kg. High starch content and higher starch digestibility have been reported in yam peel.
Sweet potato – Sweet potato peel is high in energy, moderate in protein and low in crude fibre. Abdel- Hafeez et al. (2018) found the value of crude protein and crude fibre to be 36–46 g/kg and 38–70 g/kg, respectively, and a metabolisable energy of 11.25 MJ/kg. Coloured varieties of sweet potato are good sources of carotenoids, this can reduce the need of pigment supplements for normal egg and skin pigmentation. Phenolic compounds have also been reported in sweet potato peels.
Citrus – Citrus pulp is a by-product of the citrus juice industry consisting of a mixture of citrus peel, pulp and seeds in different proportions. The cultivar of citrus and differences in juice extraction methods affect the composition of citrus pulp. It has a relatively high energy (11.4 MJ/kg) content and high fibre ranging from 123-135 g/kg DM. Protein content ranges from 620-740 g/kg DM. Low concentrations of protease inhibitors, phytate and tannins have been reported in citrus peel. The pulp has high levels of phenolic compounds which demonstrate strong antioxidant capability.
Banana – Diarra et al. (2018) found CP of 5% while Blandon et al. (2015) found 10% CP. The metabolisable energy content of banana peel ranges from 11.6-14.0 MJ/Kg in the unripe and ripe peels, respectively. The peel contains catechins which possess antioxidant, antimicrobial and cholesterolemic activities. Tannins have been reported to be the major anti-nutritional factor in banana peel.
Sugar beet pulp – Sugar beet pulp (SBP) is also another potential feed ingredient for poultry feeding but its utilisation is limited by the low ME and high fibre content and high water-holding capacity of the fibre. Abdel- Hafeez et al. (2018) found a content of about 3 MJ ME/kg, 9.6% crude protein and 19% crude fibre (mainly in the form of NSPs).
Papaya – Papaya peel protein is like that of maize, but it is relatively high in fibre and low in fat. High concentrations of proteolytic enzyme (papain and chymopapain), vitamins, minerals and β-carotene have been reported in papaya. Due to presence of polyphenols, papaya peel is reported to have anthelmintic, antibacterial and anticoccidial activities. Anti- nutritional factors include tannins, alkaloids, saponins and flavonoids. Table 1 shows the nutrient composition of the peels drawn from different sources.
Peels in broiler and layer diets
There are several studies on the feeding of peel meals to poultry, but recommendations have been quite variable. Several factors including differences in the composition of the peel (nutrient and anti-nutrient contents), processing methods, age of birds and diet composition may all affect utilisation of peel meals by poultry. The following shows a summary of some recommendations from different studies:
Cassava peels
Inclusion of 200g of cassava peels/kg feed does not compromise growth in broilers. Dairo (2011) reported improved weight gain and feed efficiency in broilers fed 500g/kg dietary sun-dried cassava peel compared to control. In another study, Panigrahi (1996) suggested that low hydrocyanic acid (<4 mg kg) cassava cultivars can be included up to 500–600 g kg without affecting performance. more recently, dayal et al. (2018) observed that inclusion of sun-dried cassava peel meal at 154g kg diet adversely affected broiler performance but this was overcome by fat and enzyme supplementation.>
Yam peels
Broiler chick growth was not compromised when yam peel meal was included at 150g/kg diet. Ayodele (2011) observed that yam peel meal at 250g/kg diet was optimum for broiler growth and carcass traits. Diarra et al. (2012) recommended a yam-sweet potato peel mixture (1:1 wt/wt) at 68 and 224 g/kg diet for starter and finisher broilers, respectively. It was concluded that a yam-sweet potato peel mixture can replace maize up to 15 and 45% in broiler starter and finisher diets, respectively, without adverse effects on the growth, haematological profile and carcass measurements.
Sweet potato peels
Maphosa et al. (2003) advised that sweet potato peel meal should not be fed to broiler starter feeds but could be included up to 310g/kg diet in the finisher diets. More recently, 150g/kg diet was recommended by Abdel- Hafeez et al.
Sweet potato peel is high in energy, moderate in protein and low in crude fibre. Photo: Shutterstock
Sugar beet pulp
A 2015 study observed that 23g/kg was optimum for broiler growth and a more recent trial found that enzyme supplementation can allow the utilisation of the pulp up to 75g/kg diet in broilers.
Citrus pulp
Feeding 20g/kg citrus pulp meal diet was reported to improve the productivity and health of broiler chickens. Trials have shown that inclusion of 50g/kg citrus peel in diets of broiler chicks resulted in similar growth performance to the control group based on maize. Another trial reported that sweet orange peel can be included up to 79.2g/kg diet in broiler diet without adverse effects on performance.
Banana peel
Abel et al. (2015) recommended 100g/kg sun-dried banana peel meal in the diet for broilers. Additionally, Blandon et al. (2015) observed that enzyme supplementation allows the utilisation of air-dried banana peel meal up to 340g/kg. Furthermore, the effect of replacing 15, 30 or 45% of yellow corn with dried banana peels was not detrimental to growth performance, carcass characteristics and haematological parameters.
Papaya peel
Papaya peel meal at 120g/kg feed had no adverse effect on broiler growth. In terms of layer diets, several factors including the source of cassava peel, processing and age of birds may all affect the composition of cassava peel and its recommendations in the diet. Table 2 shows recommendations of selected peels in layer diets.
The future of peels
The huge world production of root/tuber and fruit crops to meet the increasing world demand for food and industrial uses indicates high availability of peels – if properly processed and stored. The utilisation of this waste in poultry feed would reduce feed cost and the potential environmental risks. Peels have moderate nutrient content, which makes them potential ingredients in poultry diets. This, coupled with the advances in processing technology to reduce anti-nutritional factors, would see an added value to peels for poultry feeding.
With the growing market and availability of feed additives (exogenous enzyme products, amino acids, antioxidants, anti-nutrients binding agents) and research interest into phytobiotics by the feed industry, the future use of peels is brighter. Less variable recommendations on inclusion rates would be better established. Besides the nutritive content, several functional properties (antioxidant, antimicrobial, cholesterolemic, etc.) are available in peels, this may further increase their use to produce consumer-friendly poultry products.