歐盟即將禁用高劑量氧化鋅
EU to end high-level zinc oxide use for piglets in 5 years
If they were using zinc oxide to control post-weaning diarrhoea, pig producers in the European Union will soon have to start looking for alternatives. The European Commission has voted to phase out zinc oxide as a veterinary instrument in the entire union within 5 years.
The outcome of the commission does not come as a surprise, as the advice of theCommittee for Medicinal Products for Veterinary Use (CVMP) to the commission had already been to ban the high-level use of zinc oxide.
Read also: David Burch’s latest Expert Opinion on zinc oxide
Zinc oxide’s mode of action
Zinc can be applied at low dosages (around 150 ppm) to weaners as a nutritional component. Usage in high levels as zinc oxide (around 2,500 ppm) has been shown to be an effective strategy to prevent and control e.g. post-weaning diarrhoeaproblems.
The strategy is therefore widely used in various countries, the UK, Spain and Denmark being a few of them. The European Commission zoomed in on the effects of usage of zinc oxide at the request of the Netherlands and France.
Read also: What alternatives are available for zinc oxide? John Gadd’s latest Expert Opinion
Effects of zinc oxide on the environment
The application of zinc oxide is considered a key alternative to the reduction of antibiotics usage. The European Commission, however, pointed to zinc oxide having a serious impact on the environment as much of the substance gets excreted and ends up in fields when the manure is applied on the lands. From the side of the UK, this environmental impact is heavily contested.
Zinc oxide will have to be phased out in pig production in 5 years. Photo: iStock
In some studies, the use of zinc oxide has been associated with the occurrence of methicillin-resistant Staphylococcus aureus (MRSA) as the resistant bacteria might carry zinc-resistance genes. In addition, certain antimicrobial effects are suspected, e.g. by the Netherlands Veterinary Medicines Institute (SDa). Again, these outcomes are also under debate.
Effect for the UK in the light of Brexit
Last week, the decision was made by the Standing Committee on Veterinary Medicinal Products (CVMP) of the European Commission in Brussels, to withdraw the marketing authorisation for all veterinary products containing zinc oxide within 5 years.
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For the United Kingdom, it is unclear what the outcome will be in practice, seeing that the country is in the process to secede from the European Union (Brexit). The 5-year period might be longer than it takes the country to step out of the union.
歐洲將在5年內(nèi)禁止使用高劑量氧化鋅
歐盟委員會(huì)已經(jīng)投票決定,在5年內(nèi)逐步淘汰高濃度氧化鋅作為獸醫(yī)治療手段。
歐盟委員會(huì)的投票結(jié)果并不令人驚訝,因?yàn)槲瘑T會(huì)獸醫(yī)用藥品委員會(huì)(CVMP)在早期就已經(jīng)是建議禁止使用高濃度的氧化鋅。
氧化鋅的作用方式
鋅元素是斷奶仔豬的必須營養(yǎng)元素之一,但是這僅僅限于低濃度的情況下(約150ppm)。而高濃度氧化鋅(約2500ppm)是目前預(yù)防和控制斷奶仔豬腹瀉較為有效的方法。目前使用高濃度氧化鋅的策略已經(jīng)廣泛應(yīng)用于不同國家,包括英國、西班牙、丹麥等。歐盟委員會(huì)應(yīng)當(dāng)初荷蘭和法國的申請(qǐng),擴(kuò)大的氧化鋅的使用范圍。
氧化鋅對(duì)環(huán)境的影響
氧化鋅的應(yīng)用被認(rèn)為是減少抗生素使用的關(guān)鍵替代方案。然而歐盟委員會(huì)指出,氧化鋅對(duì)環(huán)境造成的影響極為嚴(yán)重,動(dòng)物直接吸收的鋅元素極少,因而糞便中含有大量的重金屬鋅,在糞污處理還田的情況下會(huì)直接污染土壤。然而從英國方面的研究來看,這種環(huán)境的影響是非常有爭議的。
在另外一些研究中,使用氧化鋅與耐甲氧西林金黃色葡萄球菌(MRSA)的發(fā)生有關(guān),因?yàn)槟退幖?xì)菌可能攜帶抗鋅基因。同樣的,這些研究結(jié)果仍然存在一些爭議。
氧化鋅造成的危害
高劑量氧化鋅可以促進(jìn)仔豬生長,降低腹瀉率,斷奶仔豬料中應(yīng)用普遍。但同時(shí)氧化鋅自身存在許多缺陷,長時(shí)間使用不僅會(huì)對(duì)仔豬造成負(fù)面影響,也會(huì)對(duì)生態(tài)環(huán)境和食品安全造成危害。
1. 易造成肉品鎘超標(biāo)
氧化鋅的雜質(zhì)問題嚴(yán)重,因其來源于化工副產(chǎn)物,殘留許多有害物,產(chǎn)品質(zhì)量難以控制,尤其是重金屬鎘。鎘是器官毒素,它的半衰期較長,因此,如果組織在斷奶后被污染了,胴體屠宰時(shí),畜產(chǎn)品中鎘水平仍然會(huì)較高。
在泰國和中國,按照鋅的藥理劑量添加是允許的,而歐盟則禁止。泰國最近對(duì)214份豬肉腎臟進(jìn)行研究,結(jié)果表明25%多的豬肉腎臟鎘濃度均高于監(jiān)管值。分析表明,被污染的氧化鋅是日糧中鎘的主要來源,盡管中國未見相關(guān)報(bào)道,但這種風(fēng)險(xiǎn)可能存在。
2、影響仔豬對(duì)其他微量元素的吸收及皮毛外觀
氧化鋅的藥理用途會(huì)讓斷奶仔豬受益,但如果長時(shí)間使用,它可能會(huì)影響仔豬的健康。一方面,影響其它微量元素的吸收,導(dǎo)致銅、鐵吸收不平衡,降低其它營養(yǎng)素的效價(jià),生長性能欠佳;另一方面,斷奶仔豬后期常出現(xiàn)皮膚蒼白、被毛粗亂卷曲、貧血等現(xiàn)象,影響皮毛外觀。
3、 造成豬糞中鋅超標(biāo)
當(dāng)飼料中的鋅濃度不超過150ppm時(shí),土壤從糞便中獲得的鋅富集不超過3000微克/千克DM /年。在歐洲,斷奶后頭2周噸飼料添加3kg氧化鋅,豬生長周期中排泄出來的鋅將達(dá)到近30%。豬糞的工藝處理也突出了這個(gè)問題,因?yàn)殇\集中于固體部分,然后副產(chǎn)品中的鋅含量將會(huì)超過歐盟規(guī)定的有機(jī)肥料中鋅的最高水平。
4、使耐藥細(xì)菌普遍性增加
在動(dòng)物日糧中過度使用鋅可能有利于細(xì)菌耐藥性的發(fā)展。其機(jī)制被認(rèn)為是細(xì)菌使用外排泵系統(tǒng)調(diào)節(jié)細(xì)胞內(nèi)的鋅濃度。這些泵不僅特定于鋅,或許可以排泄其他分子,如抗生素。使用藥理學(xué)劑量的氧化鋅,產(chǎn)生的高濃度鋅往往會(huì)增加外排泵的合成,可能會(huì)減少細(xì)菌對(duì)抗生素的敏感性。