Neutered dog still ties

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I have this male dog, he was neutered but it was done when he was over 1 year old. I found him tied to my female dog who is not fixed (She isn't fixed due to not only cost (5 times the cost to spay than to neuter) but also because the veterinarians in the area don't do many fixing (backward country folk don't get it done for ridiculous reasons like they believe nature has to take it's course or thy will died if they don't breed (seriously, they believe this) so vets don't get the experience - but at least I KNOW a neuter is simple in comparison) AND she presents as sterile (her entrance is lower and she never has a regular heat cycle - both signs of sterility) Any of you have stories on mating dogs? Intentional breeding gone array? Your first tie experience sent you into a panic?