ABSTRACT NUCUM, ADRIAN D., PANGILINAN, LAURENCE JOHN C, MANDAP, FRANCIS PAUL D. July 2022. GROWTH RESPONSE OF TWO STRAINS OF BROILER CHICKEN AS AFFECTED BY LACTIC ACIID BACTERIA SERUM (LABS) IN DRINKING WATER, Pampanga Agricultural State University, PAC, Magalang, Pampanga. Adviser: PERRY D, PEDIONGCO, MSA The study was conducted for 45 days from June 11 to July 19, 2022, at Brgy San Pedro 2, Magalang, Pampanga. The objectíve of the study was to determine the growth performance of two strains of broilers as affected by lactie acid bacteria serum (LABS) in drinking water. Specifically, it aimed to find out the following: average initíal weight, average final weight, average gain in weight, average daily gain (ADG), average feed consumption (AFC), average feed conversion ratio (FCR), water consumption, cost, and return of the study. A total of 90 Cobb broilers and 90 Ross broilers chicks were used in this study. Two factorial with a Randomized Complete Block Design (RCBD) was used in the study. The birds were randomly divided into 6 treatments with 3 replicatíons, 10 birds per replication; and 30 birds per treatment. The experimental treatments were as follows: Factor A is the broiler strain (AI is Cobb broilers and A2 is Ross broilers) and Factor B is the Lactic Acid Bacteria Serum (BI is 100% drinking water, B2 is 20% Lactic Acid Bacteria Serum + 80% water, and B3 is 40% Lactic Acid Bacteria Serum + 60% water). In the results, highly significant differences were found in final weight, gain in weight, and ADG, in which the interaction between the Cobb 500 strain and 409% inclusion of LABS gave the highest gain. There is also a significant difference found in terms of feed consumption, wherein those who were in the control treatment consume the most, followed by the inclusion of 20%. While the least feed consumption was found in the 40% inclusion of LABS, More so, in terms of FCR, the best result was in the Cobb 500 strain, supplemented with 40% LABS.