Sacrificing a young and plump animal
Is it permissible to sacrifice young animals that are plump? Or must they meet the age requirement of sacrificial animals even though they may be lean?
Slaughtering a sacrificial animal is a confirmed sunna for those who are capable, following the actions of the Prophet [pbuh] who said, "There are three things which are obligatory for me and voluntary for you: observing witr prayer, animal sacrifice and observing the duha prayer [mid-morning prayer]" [Reported in Ahmed's Musnad].
In consideration of the interest of the poor and the destitute, Islam stipulated a certain age for sacrificial animals based on the expectation that they be fully grown and therefore have a lot of meat. If sacrificial animals meeting the age requirement prescribed in Islamic law are emaciated and there are other animals that do not meet the age requirement but have a lot of flesh (as is the case at present when animals are fed concentrated diets to increase their bulk but when they reach a certain age they start losing weight), Islam takes into consideration the needs of people, for this is one of the objectives of Islamic law.
If a plump animal meeting the age requirement is not available while a younger one with a lot of meat is, it is then permissible to offer the younger animal as a sacrifice due to the words of the Prophet [pbuh] who said, "Do not slaughter anything but a mussinah. But if this is difficult, slaughter a jadh'ah" [Muslim]. A musinnah is a two-year-old cow. A jadh'ah is a one-year-old male sheep.
By analogy, it is permissible to sacrifice a young and plump animal instead of an emaciated one meeting the age requirement when there is a need; and needs sometimes reach the status of necessities, be they public or individual. Bilal (may Allah be pleased with him) is reported to have said, "[For sacrifice], I consider nothing except a rooster."
Based on this and in reference to the question, it is permissible to offer a young sacrificial animal that is plump.