For the avoidance of doubt as to my own views, I do not accept that animals have rights, at least not in any human sense, but I do accept that wanton cruelty to animals is wrong.
That is not because animals have "rights" but because it is morally bad for humans to practice cruelty, even if only against animals.
For the further avoidance of doubt, I do not consider it cruel to kill and eat some animals.
That is, indeed, one of the reasons God put them on earth.
However, to derive enjoyment by inflicting pain upon them is a form of perversion. No hunter I have hunted with ever behaved like that and, if he did, he would be packed off by his fellow hunters as some sort of pervert to be shunned and avoided.
In heaven, there will be no killing or eating so the issue will not arise.
In heaven we shall be sustained by the love of God and shall be immortal beings like Him, without the need for physical growth and development and thus for food and drink, as we are here below. Our pleasure and contentment will be in loving and praising God which will be greater by far than any pleasure or contentment we could ever imagine, here below.
Moreover, the pleasure that we currently derive from animals will also be there in some mysterious but currently inexplicable way, whether the pleasure of the hunter in the chase or the pleasure of the grandmother stroking her favourite cat.
Yes, there is a sense in which the sacrifice of Christ can be likened to the cruel killing of a defenceless creature and we do well to contemplate upon Him in such fashion since Scripture and the Church themselves liken him to a lamb - nay, the very sacrificial lamb of the old Jewish sacrifice. In heaven we shall also continue to contemplate Him in such wise. Indeed, it the very dumbness of the lamb led to the slaughter that we see in the innocency and silence of the persecuted Christ. This is not a reflection upon the status of the lamb so much as an insight into the pure innocence of Christ and the horror we should have of sin which so caused innocence and holiness to be so persecuted.
It certainly does not mean that men and animals are in any way equal or should be accorded equal rights.
Neither does it mean that granny's little doggy Spot will go to heaven in some naive, anthropomorphic way but it does mean that granny will derive the same pleasure she currently gets from Spot, a millionfold in heaven and that, in some way, will be related to, and derive from, Christ our Lord and God.
There can be no happiness greater than that of the saints in heaven as they contemplate a God of infinite love, mercy and fathomless compassion. Simply to see Him will produce the greatest possible satisfaction, wonderment, love, pleasure and awe in the souls of the saints in heaven.