HI,I'm Dr Steve. Without knowing what species of beetle is contaminating your feed, it would not be wise or safe for me to advise feeding it. Most beetles are not an issue.
But there is a beetle called a Canthardin beetle that is very toxic and could cause problems if fed to cattle.
In my practice I have run across issues with feed quality and in my experience, it has always turned out better to return the feed to the feed store and tell them you are not comfortable with feeding contaminated grain. That you paid full price for the grain and don't want to feed it .
Even if there beetles are not toxic or poisonous, they can affect feed taste and palatability by their badyparts , fecal material and urine in the feed,
In some cases , the feed store hasbeen grateful enough that you came to them with the problem that they are typically willing to go the extra mile and even pick up the feed, deliver new feed and I have had them over compensate the producer.
The fact that there were beetles in the grain is itself concerning. I would wonder about how long the bags of feed sat around to get beetles in them. Ifthe feed is old, it may have lost taste just from being old. Any reduction in taste either from age or from beetle contamination can affect consumption which can affect the cattle's performance . Milk production and rate of gain can be educed and result in economic loss.
If your feed store will replace the feed, that would be the best option. Otherwise you are taking financial risks from something that you had no control over in the first place. I hope this has helped. I see you are offline. I will check throughout the evening tomorrow night to see if you have more questions. Thanks for the questions and have a nice night.