Abu Dawud

Benefits and Issues:
In other ahadith, there is also a prohibition on drinking the milk of such an animal and eating its meat.
See:
(Sunan Abi Dawud, Al-At'imah, Hadith: 3785)

Benefits and Issues:
Benefit: “Jallalah” refers to that animal which eats impurity (najasa).
Imam Ibn Hazm does not include a chicken that eats impurity among them.
However, according to the majority, all birds, including chickens, if they eat impurity, will also fall under the category of jallalah.
Abu Ishaq al-Marwazi, Imam al-Haramayn, al-Baghawi, and al-Ghazali have made an analogy between the egg of a chicken that eats impurity and the milk of a goat, cow, etc., that eats impurity.
In fact, they have included every animal in the ruling of jallalah whose upbringing is on impure food.
For example, a kid goat that is raised on the milk of a female dog.
See (Fath al-Bari, Book of Slaughtered Animals and Hunting, Chapter: The Meat of Chicken).
Nowadays, animal protein is also included in the feed of chickens.
Even blood, etc., is added to the feed in Muslim countries like Pakistan.
In non-Muslim countries, the meat components of forbidden animals are also used in the feed.
Will such a chicken be called jallalah? Yes, if the majority of its food consists of forbidden and impure ingredients, or if its meat, eggs, etc., develop a foul odor because of it,
then it will certainly be forbidden (haram).
These two points are important reasons for an animal not being halal.
Some jurists have said that if the majority of its food is impure, then it is jallalah.
However, according to Imam Layth, if the animal eats only impurity,
then it is jallalah.
Rafi’i and others are of the opinion that the quantity of food is not important;
the real importance is whether or not a foul odor develops in the meat, milk, etc.
If these items are free from odor, then they may be used, and if they are foul-smelling, then they are prohibited.
According to veterinarians, doctors, and feed manufacturers, the feed of chickens in Western countries contains a certain amount of mixed animal protein.
The general experience is that their meat does not have any unpleasant odor.
Therefore, these chickens will not be considered under the ruling of jallalah.
However, it is necessary that Muslims establish their own farms for their use and stop relying on the import of such items from disbelievers.
There is consensus among the jurists that if such an animal is confined and fed only fodder, etc.,
then after some time its meat, milk, etc., become purified from the effects of impurity.
Hafiz Ibn Hajar states that Ibn Abi Shaybah has transmitted with a sound chain the practice of Ibn Umar, that he used to confine a jallalah chicken for three days.
Regarding large animals like cows, camels, etc., Ata and other jurists permit eating their meat after confining them for forty days and feeding them fodder.
In this regard, the marfu’ hadith of ‘Amr radi Allahu anhu is also mentioned,
in which there is an order to confine the animal for forty days for the prohibition and permissibility of jallalah.
But this narration is weak in its chain.
However, in authentic ahadith, there is explicit mention that the prayer of a person who drinks wine is not accepted for forty days.
(Sunan al-Nasa’i, al-Ashriba, Chapter: Mention of the Sins Resulting from Drinking Wine, Hadith 5672, 5671; Jami’ al-Tirmidhi, al-Ashriba, Chapter: What Has Been Reported about the Drinker of Wine, Hadith: 1862)
From this, it can be deduced
that the effects of using impure things are removed from bodies after forty days.
Some jurists, such as Imam Nawawi, say that since the real reason for prohibition is the foul odor,
therefore, when this is removed, the meat, milk, etc., of the animal will be legally permissible for use.
See (Awn al-Ma’bud, al-At’imah, Chapter: The Prohibition of Eating Jallalah and Its Milk)
This ruling is probably similar to the ruling for purifying the water of a well contaminated with impurity: after removing the impurity, water should continue to be drawn until it becomes completely pure in color and taste.
Riding on a camel, etc., that eats impurity will also be permissible
when the impurity’s odor is completely removed from its body (such as sweat, etc.).
This high standard of purity and cleanliness is taught only by this religion.
Allah Himself has described this attribute: (wa yuhillu lahumu al-tayyibat wa yuharrimu ‘alayhimu al-khaba’ith) (al-A’raf: 157) — He makes lawful for them the pure things and forbids for them all filth.

Fiqh al-Hadith:
This hadith does not establish the absolute prohibition of jallalah; rather, its use is only prohibited until the foul odor from its filthy feed is removed, as:
It is authentically reported from Abdullah ibn Umar radi Allahu anhuma that: «إنه كان يحبس الدجاجة الجلالة ثلاثا»
"Abdullah ibn Umar radi Allahu anhuma would confine a jallalah chicken for three days (and then use it)." [رواه ابنِ ابي شيبه]
Allamah Nasir al-Din al-Albani has declared its chain of narration to be authentic. [ارواء الغليل ج8، ص151]
And the famous commentator of Sunan Abu Dawud, Allamah Shams al-Haqq Azimabadi, writes in the explanation of this hadith in 'Awn al-Ma'bud':
«قال الخطابي واختلف الناس فى أكل لحوم الجلالة وألبانها فكره ذلك أصحاب الرأي والشافعي وأحمد بن حنبل وقالوا لا يؤكل حتى تحبس أياما وتعلف علفا غيرها فإذا طاب لحمها فلا بأس بأكله وقد روي فى حديث أن البقر تعلف أربعين يوما ثم يؤكل لحمها وكان بن عمر تحبس الدجاجة ثلاثة أيام ثم تذبح»
"Imam Khattabi states that regarding the meat and milk of animals that eat filth, some of the people of opinion, as well as Shafi'i and Hanbali scholars, say it is disliked (makruh). However, if the animal is prevented from eating filth for a few days and is fed other pure food, and the effect of impurity is removed from its meat, then there is no harm in eating it. And it is narrated in a hadith that such a cow should be fed clean food for forty days, then its meat may be eaten. And Sayyiduna Ibn Umar would keep such a chicken away from filth for three days and then slaughter it."
He would do this only so that its stomach would be cleansed and the stench of filth would be removed from its meat.
If the prohibition of jallalah was due to the impurity of its meat, then the meat that has grown from the unlawful would never become pure under any circumstances.
As Ibn Qudamah has said, if jallalah were impure, then even confining it for two or three days would not purify it. [المغني ج9، ص41]
From this authentic narration of Abdullah ibn Umar radi Allahu anhuma, it is understood that the prohibition of jallalah is not due to its meat being impure and filthy, but rather the reason is the presence of the stench of filth, etc., in its meat. As:
Hafiz Ibn Hajar states:
«و المعتبر فى جواز اكل الجلالة زوال رائحة النجاسة عن تعلف بالشيى الطاهر على الصحيح» [فتح البارى ج9 , ص 565]
"In the permissibility of eating jallalah, the criterion is the removal of the odor of impurity, etc. That is, when the odor is gone, its consumption is permissible."
Allamah San'ani also states: «قيل بل الإعتبار بالرائحة و النتن»
"In the permissibility of jallalah, the removal of the odor is considered." [سبل السلام، ج3، ص77]
There is also no harm in knowing the statements of the linguists regarding jallalah. Most linguists have written:
«ألجلالة هى البقرة التى تتبع النجاسات»
"Jallalah is the cow that seeks out impurities." [لسان العرب ج2، ص336، الصحاح للجوهري ج4، ص1258، القاموس الميط ج1، ص591]
The famous Arabic lexicographer Ibn Manzur al-Ifriqi writes:
«و الجلالة من الحيوان التى تأكل الجلة العذرة»
"Jallalah is the animal that eats human excrement and the like." [لسان العرب، ج2، ص336]

Benefits and Issues:
➊ Jallalah refers to that animal which becomes so accustomed to filth that its meat and milk are affected by it.

➋ According to some scholars, if such an animal is confined and fed pure and clean food until the effect of the impurity disappears, then the animal is no longer considered jallalah. Therefore, eating its meat and drinking its milk becomes permissible.
For further details, see: (Sunan Abu Dawood, (Urdu edition Darussalam)
Hadith: 3787, Benefits)

Takhrij:
«أخرجه أبوداود، الأطعمة، باب النهي عن أكل الجلالة وألبانها، حديث:3785، والترمذي، الأطعمة، حديث:1824، وابن ماجه، الذبائح، حديث:3189، ابن أبي نجيح عنعن، وحديث أبي داود (2557، 2558) يغني عنه.»©

Explanation:
➊ The aforementioned narration has been declared weak in its chain of transmission by our esteemed researcher, and he has further written that the narration from Sunan Abi Dawud suffices in this regard. Moreover, he has considered the hadith mentioned in Sunan Ibn Majah to be hasan (good), from which it is understood that the aforementioned narration is also considered authoritative (hujjah) by our esteemed researcher.
Therefore, despite the aforementioned narration being weak in its chain, it is actionable and authoritative due to other supporting evidences.
And Allah knows best.

➋ This hadith is evidence for the prohibition of animals that eat filth.

➌ Imam Khattabi has said that in one narration it is reported that if a cow has eaten filth, it should be fed clean fodder for forty days; after that, its meat may be consumed.
The commentator of Tirmidhi has stated in Tuhfat al-Ahwadhi (5/464) that Ibn Ruslan, in Sharh al-Sunan, says there is no fixed or specified period for confining an animal that eats filth in order to provide it with clean food and protect it from filth.
And some are of the opinion that the period is forty days for camels and cows, seven days for goats, and three days for chickens.
This opinion has been preferred in al-Muhadhdhab and al-Tahrir.
And in Subul al-Salam it is mentioned that there appears to be no reason for the disagreement regarding the determination of the period.