i have 3 bitches, 5 and 3 year old mini schnauze'sr and a 1 year old gsd. from the minute i came home with the gsd at 7wks old they all got on great but her and the 3 year old really hit it off, they slept together, cleaned each other, where one went the other would always follow. then 10 months later the gsd started to become aggressive  towards the 3 year old so much so that i have to keep them separated. now both of the 2 older ones came into season at this time so i am assuming that this combined with her going into adolescence has triggered this behavior but it has now been 3 months and things are still the same, would it help if i got all 3 dressed. any help would be great.

Spaying will generally be of no help in bitch to bitch aggression, other than if it is only when they are in season, and are fine at other times.

On the other hand it is generally more beneficial than not to spay bitches once mature, so not a bad idea to spay for their health, bearing in mind that there are occasional negatives, like weight gain, changed in coat,a nd occasionally urine incontinence. 

Bitches left entire can develop life threatening womb infections, and sub clinical ones that will affect their well being and health, as well as being at higher risk of mammary tumours..

it is now all the time, my husband say's its me as they are fine when i am not in the house.  when the gsd was only 6 months old i had her out for a walk and a staffy attacked her, i ended up on my back with this dog trying to jump over me to get to her so i can understand why she would be protective but her behavior didn't change until a few months later and why is she only like this towards the middle one (her best friend) and not the older dog. any suggestions on how i can sort this problem, as getting rid of her is not an option.

> why is she only like this towards the middle one (her best friend) and not the older dog.

because the middle one is lower ranking and she is wanting to climb the ladder socially.

Also she is resource guarding (you).  A separate issue, but one that may instigate her behaviour, she feels she has the right to monopolise you, because she thinks she deserves to be above the middle dog, but really she isn't mature enough for a higher position yet (she's about 18 months yes?).

Unfortunately you may need to reduce her status, no attention  at all when the others are about.

My 19 month old has been trying to climb up the ranks by going straight for the top, trying to force the oldest (now 12) into confrontations and succeeding, so I have had to take a firm hand with them both, and anything starts they both get told off, but the youngster the most.  I am lucky as none of mine actually go as far as wanting to damage each other, though spats can sound awful.

You need to become very aware of the subtle signs of a challenge and nip it before it gets that far, distraction and firmness.

For example young bitch is starting to stare out the other, or deliberately stand over her, block her path, come to you and not allow the other too, you must then stop this, distract, do some obedience exercises, and then send her away and give the others attention.

A behaviourist may need to be contacted so they can see the situation, but make sure it is Vet refereed.

If the situation has got beyond redemption (I doubt as she is only adolescent and not fully socially mature), then you may have to split them up permanently, especially considering the size difference.  I have only ever dealt with bitches of same breed, which makes a difference, because of size, and reactivity/attitudes being the same.

thank you for the advise, she is only 11 months so it gives me a bit of hope that we can over come this, as everyone has been saying that she will be like this all the time and to get rid of her. the thing is the middle one is quite happy to let the gsd move into her position but i am terrified to let them go through the process as eva (gsd) can fit morag's head in her mouth no problem. i did buy a muzzle as i thought if i were to put this on her and then let her with morag she would be able to do her thing, morag would go submissive and things would start to get better. long shot i know but it was just a thought, i haven't tried it yet as i am to nervous

> For example young bitch is starting to stare out the other, or deliberately stand over her, block her path, come to you and not allow the other too, you must then stop this, distract, do some obedience exercises, and then send her away and give the others attention.
>

Gosh Barbara - I wish someone had told me these signs when I had my troubles with 2 bitches fighting.  It's not so much that I didn't know these signs, just that seeing them listed so clearly gives a sort of check list  to keep an eye on before all hell lets loose.  All dogs will do these things I know but if they become consistent regular or lots of these together then it does signify trouble brewing.
In young dogs it may be that owners don't realise what they're seeing I certainly didn't at first.It : they're learning about theri pup and its behaviours/body language as an individual/youngster, and so things can escalate before the owner knows what's going on.  That certainly makes sense for my past situation and sad re-homing of our Cocker pup - she was also a resource guarder [humans as well as objects].
My 13 yr old does all the behaviours as above but not in too drastic a way - but I think that's because we have built up a bond over many years and that means I can read her and her me and also she knows her limits - with me - and she is not too determined to be 'top dog' - she is an opportunist rather than making a totally determined effort to get to top position.  She joined in beating up Heidi but soon backed off.  The Cocker, very closes in age to Heidi, really meant it