不只是挑嘴問題　寵物營養師警告 - 貓

: 大多數貓咪都比較喜愛半生熟，甚至是全生的蛋黃（其實是OK的，因貓咪腸胃內的酸性特
: 別高，所以牠們對沙門氏菌的抵抗力比人類強）。但切記一定要將蛋白煮熟，因蛋白中含
: 有抗生物素蛋白質（Avidin），若未經煮熟就進食，可能會破壞貓咪體內的生物素（
: Biotin，即維生素B群的一種）。

回應有人說ok，我實在很懶得去翻教科書…

以下內容節自：
《Canine and Feline Nutrition 3 edition： A Resource for Companion Animal
Professionals (2010)》

首先是p.33談biotin的部分：

"Eggs provide a very rich source of biotin,
but egg white contains a compound called avidin,
which binds biotin and makes it unavailable for absorption.
Thoroughly cooking eggs destroys avidin and
allows the biotin in the yolk to be used."

這裡明白說到avidin會造成biotin無法被吸收，
將蛋白煮熟則會破壞avidin，讓biotin可以被吸收。
(小弟註：因為avidin對biotin具高親和力，
蛋黃中的biotin會被生蛋白中的avidin綁住，造成蛋黃中的biotin無法被吸收。
而如果貓攝入的avidin可以綁住的biotin量大於蛋黃中含有的biotin量時會發生什麼事，
我想就不用我解釋了。
所以有人說什麼蛋黃中含有大量biotin可以一併吃就沒問題，聽聽就好)。

同時，在p.283中提到：
"Although egg is a high-quality food ingredient, the white of the egg
(albumen) contains several inhibitory substances that alter the metabolism
of specific nutrients.The two most important are avidin, an inhibitor of
biotin absorption, and a compound that interferes with the action of the
pancreatic protease, trypsin (trypsin inhibitor). The antitryptic activity
of egg white is a characteristic that is much less well documented in
current literature than avidin, yet one that has the potential for
causing severe nutritional imbalances."

這裡明白說明了雖然雞蛋是高營養價值食物，但蛋白(白蛋白)含有數種抑制物質，
可以改變特定營養素的代謝，其中最重要的兩個，一個就是avidin，
另一個就是trypsin(胰蛋白酶抑制蛋白)，而trypsin可能導致嚴重的營養失衡。

在p.283中，對avidin進一步做敘述：
"Avidin is a protein that is a secretory product of the hen’s oviduct
and is subsequently deposited in the albuminous portion of the egg.
When consumed, avidin combines with dietary biotin in the intestine
and prevents its absorption."

這裡是說明avidin會在腸道內阻礙biotin被吸收(因為被avidin綁走了)。

同時，在p.283中說明到：
"Practically speaking, potential risk for biotin deficiency will only
occur if an owner supplements the pet’s food with only the white of
the raw egg. As in other species, signs of biotin deficiency in dogs
and cats include dermatitis, loss of hair and poor growth rate."

這裡特別說明了「如果飼主『只有將』蛋白作為寵物食物的『補充』」，
才有可能出現biotin缺乏的問題，
但這裡有個重點是，因為這裡的「寵物食物」已經擁有足量的biotin了，
而生蛋白只是作為「補充」(蛋白質上的補充)，
但若飼主是在做自製生鮮食時，「同時加入了生蛋白和生蛋黃」呢？
換言之，若生蛋白不是作為補充，而是作為「主要提供蛋白質的材料之一」，
那麼仍然要擔心寵物可能出現biotin缺乏的問題。

p.283繼續談到蛋白中含有的trypsin(胰蛋白酶抑制蛋白)：

"EGG WHITE TRYPSIN INHIBITOR
The white of the egg also contains another potentially damaging
inhibitory substance. This substance is actually a group of proteins that
have antitryptic activity. The antitryptic effect of feeding raw egg white
has received less attention than avidin, yet its capacity for causing
nutritional problems in pets is potentially much greater."

這裡提到胰蛋白酶抑制蛋白通常比avidin少被關注，
但胰蛋白酶抑制蛋白可能會引起比avidin更嚴重的營養問題。

"Early studies reported that dogs fed as little as two raw egg whites
per day in their food exhibited loose stools, and when the amount was
increased further, chronic diarrhea and weight loss developed. Dried
(uncooked) egg white was found to be just as active in causing diarrhea
and weight loss as was fresh, raw egg white. The utilization
of raw egg white protein (as determined by apparent digestibility)
was reported to be only 58.6%."

這裡提到對狗的早期研究發現(沒有提到樣本體重與數量)，
每天餵狗吃兩顆生蛋白，就會開始出現排稀便的情況，
如果數量再增加，就會開始出現慢性腹瀉與體重減輕的情況，
即便是乾燥的生蛋白，也和新鮮生蛋白一樣具有導致體重減輕和腹瀉的作用。
而生蛋清蛋白質只有58.6%的利用率(小弟註：熟蛋白通常有88%以上的利用率)

"Subsequent feeding studies and in vitro tests of protein digestibility
confirmed that the factor responsible for these effects was a group of
trypsin inhibitor proteins found in the white of the egg. Egg white trypsin
inhibitor reduced a food’s protein digestibility when included at just 7% of
the diet, and a linear relationship was reported between the amount of egg
white trypsin inhibitor and loss of protein digestibility."

這裡提到隨後的研究證實了生蛋白中的一組胰蛋白酶抑制蛋白，
會降低食物中的蛋白質消化率。

同時，在p.284中繼續提到：

"Similar to avidin, heat treatment denatures the trypsin inhibitor of egg
white and allows utilization of the protein in the egg white and of other
protein sourcesin the food.

For example, the most recent study with dogs confirmed that the inclusion of
raw (dried) egg in the diets of growing puppies impaired diet digestibility
and caused chronic diarrhea and weight loss in all of the puppies during a
14-day feeding period.However, when the same amount of heat-treated dried egg
white was included in the food, stools were normal, the puppies showed
healthy growth rates, and diet digestibility coefficients were improved.
Laboratory analysis of each diet showed that trypsin inhibitor activity was
significantly reduced in the heat-treated egg white, when compared with raw
egg white."

這裡提到胰蛋白酶抑制蛋白和avidin一樣，會因為熱處理而變性，
而使得蛋白中的蛋白質和食物中的其他蛋白質可以被正常利用。

後續提到最近對狗的研究亦表明，在連續14天對狗餵食含有乾燥生蛋的食物時，
所有狗都出現慢性腹瀉以及體重減輕的情況，
但若是餵食煮熟的同等量乾燥生蛋白時，所有狗的排便都正常，
成長速率、消化速率也都獲得改善。
實驗室針對每一次飲食的分析也都呈現了，
經熱處理的蛋白在胰蛋白酶抑制蛋白比生蛋白具有胰蛋白酶抑制蛋白活性的顯著降低。

"Again, the practical relevance of this knowledge to the feeding of companion
animals is that if an owner insists on adding egg products to a pet’s food,
the eggs should always be cooked thoroughly before feeding.This is necessary
to denature both avidin and the trypsin inhibitors present in the egg white.

In addition, feeding raw eggs is not recommended due to the risk of bacterial
contamination. A general guideline is to limit eggs to just one or two cooked
eggs per week for a medium or large dog. This level should not result in a
dietary imbalance and will not affect energy consumption to the degree of
causing weight problems."

這裡提到，如果飼主堅持要將雞蛋加入寵物的飲食中，
雞蛋則應該得煮熟，這對avidin和胰蛋白酶抑制蛋白的變性是必須的。

同時也提到「對中型犬或大型犬的指導方針是，每週只提供1~2顆煮熟雞蛋。」
教科書上從來沒提到生蛋白和生蛋黃一起吃就沒關係，
而若對中型犬和大型犬來說，每週1~2顆的煮熟雞蛋才適量，
那麼對通常沒有中型犬體型的「貓」來說，
如果我們在每週(或每月)的自製生食中對應應加入的生蛋黃顆數，
加入同等量的生蛋白，會發生什麼事，應該大家心裡都明白了。

總結以上，生蛋白中對貓來說具有風險的不止是avidin，
還有胰蛋白酶抑制蛋白，無論如何，請不要餵貓咪吃生蛋白。


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