This is perhaps an uncommon dilemma to be presented here, but the recent threads on Kosher and Halal food, and Ramadan have caused to me to ponder this issue.

I raise sheep and goats, and work/am studying in the livestock industry, specifically small ruminant management and medicine.  Currently, it is very popular to raise specialty lambs (and kids) for the "ethnic" markets, typically for people of Bosnian, Chinese, Hispanic, Indian, Mediterranean, Middle Eastern, etc. descent, and usually, though not always, specifically for certain holidays- Id al-Fitr (breaking of the Ramadan fast), Easter, Mardi Gras, Passover, and so forth.

Producers are more than happy to supply for these markets, which typically pay very well, and the customers typically desire smaller and often uncastrated lambs.

Is there a moral issue in producing lambs specifically for these holidays, if they are against the Faith?  Obviously, Easter, Christmas, Independence Day, and others are acceptable, but what about Muslim and Jєωιѕн holidays?  What about Greek Orthodox holidays, especially their Easter?

What about advising shepherds on this issue?  Many are looking to practice accelerated lambing in order to meet these markets in an effort to stay afloat in this economy.  A good many of these people will not look into alternative markets- they want to practice standard commercial farming but bring in more income.  

Personally, I feel it's wrong to support or even appear to support the feast days of false religions even if it's only selling them a lamb.  I suppose one could argue that selling vegetables or other foods or products could also go to that use, and that not much can be done about it.  I really don't have a problem with selling lamb to anyone for day-to-day use, just the holidays bother me.  And I would never allow Halal slaughter on the farm, as Muslim customers typically wish to practice (and generally leave an atrocious mess).

I suppose I ask this question more from the morality standpoint of a Catholic  working with and advising non-Catholic producers on this issue.  

It is a very good question that you bring up.

Most sane and semi-sane theologians would likely assess something like this based upon proximity and type of cooperation.  

To the extent that you are selling sheep to people who for desire sheep, likely for false rites, you have to consider that we are A) in a highly pluralistic, non-Catholic society B) Church law is effectively non-existent at this point C) you are accidental to the process.

We will necessarily encounter these dilemmas in our lives; personally, I think your situation is well-within the safe harbor of remote and indirect cooperation.  Indeed to the degree that we choose not to run into caves or desert cells, we are going to interact with the world, which is an enemy.

But this is one (among many) reason why constant, structured and heartful prayer is necessary.  The more we are opening the gates of our souls to the Holy Ghost, in like proportion we will be led consciously and unconsciously away from evil.  We always have to meditate and allow the interior lights of Truth to illuminate our minds.  We can never permit ourselves to get caught in a web of formulas and legalisms in accessing a moral dilemma because, frankly, we are poor judges of our own cases naturally speaking.

I know of self-described traditionalists who do, for money, things that I would never consider (e.g., marketing for producers of abortifacients.)  

Returning to your case, if you were to say you had a business centered around Muslim religious festivals, this would be another case.  But for the reasons I presented, based on your description, it sounds to me that you are fine.  As always, a solid Priest's advice is generally better than Internet banter!