I have spoken to many collagen suppliers in several countries and each one of them has stated that it is not possible to verify what percentage of the cattle's feed was grass or how long they spent in pasture, if at all.
There are no specific laws governing these terms and no independent body that regulates or verifies these claims, so anyone can state pasture-raised/grass-fed on their labels, but they are pretty meaningless and just marketing hype.
There would be no extra benefit to pasture-raised/grass-fed collagen anyway as it consists of only pure protein and does not contain the macro-nutrients that are found in muscle meat, organs and glands.
The most important thing is that the bovine skins used to produce bovine collagen come from animals certified as fit for human consumption by ante and post-mortem veterinarian inspection and meet all EU regulations.
No collagen powder (bovine, porcine or marine) is eligible for organic status due to the processing it undergoes, so if you see it stated on any product know that it's just marketing hype.
What makes the collagen halal is not the method of cattle slaughter, but the principle of Istihalah: If a prohibited food undergoes a transformation that changes its properties or attributes to the point that it becomes a different product, it is no longer forbidden.
In Islam, a prophetic tradition (hadith) prescribes that generally things are divisible into three categories; the lawful (halal), the unlawful (haram) and the doubtful (mushtabihat).
The first Islamic principle that may change the status of something haram into halal, or filthy to pure, is known as istihalah. Literally, it means “switching over”, “substantial change”, or “transformation”.
Technically, it refers to a situation whereby “when a substance is converted into a new substance, the lawfulness of the new substance is not determined by the lawfulness of the original substance”.
Meaning, if an unlawful thing, or a prohibited food undergoes a transformation which changes its properties or attributes to the point that it becomes a different product, then it is no longer forbidden.
It has to be a substantial change, affecting properties like colour, taste and smell.
If the public can generally perceive gelatin and collagen as an entirely different substance than the animal bones or other bodily parts, then it is sufficient to conclude that istihalah has occurred.
Istihalah does not take place if the original substance is merely mixed with some other substances or if it is merely broken up into its constituents.
Basically, the original entity needs to be completely and entirely transformed to another entity and not simply mixed, broken up or changed in shape.