Help I need advice - I have two dogs, both are a rare breed of Mastiff and I have had my male one for 7 years and the female for 2.5 years - both from puppies. My male is very laid back and only gets stroppy when he is threatened which is rare. My female has always been more lively, but is very loving and normally no problem. However, she has had punch ups a few times with my male dog and last night went for him (partly my fault as I gave him the chew bone she had left in the middle of the floor) - she would not let go of him and had to be hauled of my male by my husband and I and she had bitten his ear which was bleeding. Now tonight she went for him again, this time I saw a look on her face and managed to pull her off quickly.

I don't know why she is doing this and I am worried sick that she will get worse and don't know what to do.

Will having her spayed help? Would dog training be the answer?

She is on medication (Meloxidyl) for a joint problem - could it be that she is in pain or could this be a side effect of the medication?

As I said she is normally the most loving and affectionate dog and is usually fine with my male and will play quite happily together, but this has really shaken me and am scared that I won't be able to sort it out.

If anyone out there has some advice or experience of their dogs doing the same, I would really appreciate your input.