One should do his "VARNA ASHRAMA DHARMA" by knowing the (Dharma) SHAASTRAM-Srimadh Bhagavath Gita

Shikodakam, vAsodaka tarpana mantras after taking bath to satisfy pithru devatas

Shika: (Niveethi, making shika in front & allowing water to flow in front thru the tip of shika )
LathA vruksheshu gulmeshu vartantae pitharo mama|
thaeshAm AppyAyanarthanthu idham asthu Shikodakam ||
Vastra:(Prachinaveeethi & by folding cloth 2 or 4 times)
uchishta bhAgino dAsA yae mruthA thvamantraka: |
thripyanthu tharuthAm prAptha mama sambandhino mruthA:||
Anga vastra:
YaekaechAsmath kulae jAthA aputra gotrajA mruthA: |
Thae grunanthu maya dhattham vastra nishpeedanodakam ||

Ahimsa: Impact of Buddhism on Hinduism?.NO!

Diet of hindus was mainly vegetarian since time immemorial. Consumption of beef is prohibited. But consumption of meat etc is accepted only as prasad (Yagya Shaesha) after ritulas that too in very small quantity during 'special occasions'. Non-veg is NOT advocated for daily diet. Saying Change of culture after advent of Jainism & budhhism is unacceptable.

Did brahmins eat beef in sacrifices ?

NO. They did not eat. They should not eat beef.

BUT, they have to consume a small quantity (mustard size) of goat meat as 'Prasad' of Devathas to make the sacrifice fruitful. IF they refuse, it is considered as humiliating Devathas & the sacrifice become futile. It is COMPULSORY to take meat of Goat as prasad after offering to devathas!.

So, understand that brahmins didn't eat heaps of beef after sacrifice.