Set off of losses

No... Lottery (& Gaming, Race Horse) income can't set off to losses. It's flat rated income...

if there is a loss in lottery and income in salary

whether eligible to set off

No... No way for set off.

In fact Lottery income is taxed at 30% flat maximum rate + cess .
No set off if negative income from Lottery gaming racing etc

According to me,
As per the basic principals of set off:
Any inter head or intra head set off can be possible from losses only of

"THE SAID LOSS HAVE NOT BEEN MADE FROM ANY CASUAL INCOMES OR EXEMPT INCOMES"

And my brother in your case LOTTERY INCOME is a CASUAL INCOME.

So,Acoording to me
"LOTTERY INCOME's LOSS SHALL NOT BE ALLOWED TO BE SET OFF AGAINST ANY HEAD OF INCOME".

Good Luck