While your horse's reluctance to eat the new 'batch' may indeed be due to a poorer quality product than he is used to enjoying, it is also true that he could just be letting you know that he is not happy that you've switched hay type or source.
For example, if you have a yearling Thoroughbred colt that you have been feeding an alfalfa/grass blend 2nd cut hay, then you introduce a good quality 2nd cut hay but he ignores the new hay and instead paws through it and won't eat at all or at best picks through it, then he is certainly complaining.
A horse does have an innate ability to 'complain' but in truth he is probably just protecting himself from a significant change in diet and the dire results such as colic, that could result.
His actions do not necessarily mean there is anything wrong with the new hay, just that it is not as palatable as the hay he previously ingested.
When a hay dealer or hay farmer delivers hay to your farm, stacks it for you and then takes a check in payment, it is important that you don't rush to judgement on the hay he has provided just because your horse is taking a while to adjust to the new provisions and rashly stop pay the check. Especially if the hay previously fed was full of yummy alfalfa. Give your horse a few days to adjust and always blend the new hay in with the old over several days to give your horse a chance to acclimatize to the new menu. Believe me he will adjust!
Similarly a horse that has become used to soft 2nd cut hay will turn his nose up at 1st cut which will provide more 'chewing satisfaction' but is likely not as sweet or soft to eat.
Always restock your hay supplies before you finish the last few bales so that you can blend the different types/sources of hay together for a period. This may prevent not just an upset with your hay vendor but also may save your horse from a colic episode. The equine gut needs time to adjust to the new digestive requirements especially by production of certain bacteria in the gut, to digest the new hay.
