“My cow died last night, so I don’t need your bull”

“My cow died last night, so I don’t need your bull” is a phrase of uncertain origin. It’s so familiar in some parts that “My cow died last night” is all that needs to be said to a speaker. The phrase dates from at least the 1960s.
 
 
Texas Sayings
TEXAS SAYINGS
1. Well, butter my butt and call me a biscuit.
2. It’s been hotter’n a goat’s butt in a pepper patch.
3. He fell out of the ugly tree and hit every branch on the way down.
4. Have a cup of coffee, it’s already been saucered and blowed.
5. She’s so stuck up, she’d drown in a rainstorm.
6. It’s so dry, the trees are bribing the dogs.
7. My cow died last night so I don’t need your bull.
8. Don’t pee down my back and tell me it’s raining.
9. He’s as country as cornflakes.
10 This is gooder’n grits.
11. Busier than a cat covering crap on a marble floor.
12. If things were any better, I may have to hire someone to help me enjoy it.
   
22 October 1967, Appleton (WI) Post-Crecent, pg. A11, col. 3:
In a bar in Rifle, Colo., under a sign that proclaimed “Our Cow Died, We Don’t Need Your Bull,” there was spirited discussion about the malfunction of the M16 rifle in Vietnam and among a tableful of uranium miners, China’s new bomb.