Is it known that the bitch was the terrier, or is that an assumption? Even if that was the mating, it would be unlikely that the bitch would produce pups which were too large for her at parturition, and considering the likely size of a Mastiff's penis, I'd have thought that the mating would have been near impossible. I've put one finger inside a terrier bitch at the point of birth, and it wasn't easy, I'd have thought that a conventional mating, considering the vast difference in vagina and penis size would have made it an impossibility. Just a thought!
I suppose that AI could have been a possibility, but even that sounds unlikely. AI for dogs is not that simple a process.
I was discussing various crosses that have gone into the breeding of lurchers with my old pal Nicky MacNicol, tod hunter and master of a great fox killing bobbery pack, and expressed surprise at some of the crosses he mentioned as being good for the job.
He said, "Damn it man! They'd do it through a chain link fence given half the chance!"
Yes, this was on a buying & selling group on fb and the seller said the mum was the platter, Im just waiting for them to say what bread this is to go on his platter, no mentioning of chipping either. Mastiffs have huge heads, even the day old pups do and this is why Pugs.French Bulldogs & Bulldogs struggle to give birth naturally and have to have a C.section.