Abstract
Background:
Factors before and after slaughter can influence carcass quality. A factor that can affect carcass quality before slaughter is feed that includes additives. One alternative is to administer probiotics.

Aim:
This study aimed to determine the effects of liquid probiotics Bacillus subtilis and Bacillus coagulans as feed additives on carcass percentage, consumption, feed conversion rate (FCR), and abdominal fat percentage in broilers.

Methods:
Twenty-four Lohmann broilers (Gallus gallus domesticus) aged 21 days. Birds were randomly divided into four treatment groups. The T0 control group was orally administered 2 ml of distilled water/head/day. T1 was orally administered 2 ml of bacterial isolate/head/day. Group T2 was orally administered with 4 ml of bacterial isolate/head/day. Group T3 was orally administered with 6 ml/head/day of bacterial isolates. Each treatment was conducted for 14 days until the age of 35 days. Broilers were physically weighed to obtain the data sample.

Results:
All liquid probiotic dosages (2, 4, and 6 ml) had significant differences (p < 0.05) in carcass percentage, intake, FCR, and fat percentage. The carcass percentage resulted from a 4 ml liquid probiotic treatment, which was higher than the 2 and 6 ml doses.

Conclusion:
Four milliliters of liquid probiotics (B. coagulans and B. subtilis) are recommended for optimal broiler rearing outcomes.

Key words: Abdominal fat; Bacillus spp.; Carcass percentage; Feed conversion; Food producers.