Health and nutrition in sheep receiving Bacillus thuringiensis

Abstract

Performance, nutrient apparent digestibility, ruminal parameters, enteric methane (CH4) emission and blood parameters were studied in sheep receiving spores of Bacillus thuringiensis (Bt) in their diet. Twenty Santa Inês lambs (10 castrated males and 10 females) with 18.0 ± 3.50 kg initial bodyweight (BW) and 3 months of age were maintained in individual stalls in a completely randomised design. They were divided into two groups with five males and five females each (Bt 2036 group (n = 10) and control group (n = 10)). The animals of the Bt 2036 group received daily 2.5 × 106 spores of Bt 2036/kg BW and control animals received a placebo. The diet consisted of Tifton-85 (Cynodon spp.) hay ad libitum and 300 g/animal.day of concentrate mixture, which was adjusted according to growth requirements. During 53 days, animal performance was evaluated, with feed intake measured three times per week and lambs weighed fortnightly. Blood samples were taken every 15 days to evaluate hematological and biochemical parameters. Rumen fermentation was investigated in three stages (start, middle and end of the experimental period) using parameters such as pH, ammoniacal nitrogen, short chain fatty acids, and populations of Fibrobacter succinogenes, Ruminococcus flavefaciens, anaerobic fungi, methanogenic archaea and protozoa. At the end of the performance experiment, 18 lambs (Bt 2036 (n = 9), control (n = 9)) were selected for a digestibility trial, and placed in metabolic cages to estimate apparent nutrient digestibility, nitrogen balance and microbial protein synthesis. Ten male (Bt 2036 (n = 5), control (n = 5)) lambs were used to evaluate CH4 production using the hexafluoride tracer technique. There was no effect (P > 0.05) of Bt 2036 on any of the evaluated parameters. The daily addition of 2.5 × 106 spores/kg BW of Bt 2036 in the ruminant diet did not cause any negative effects on hematological traits or animal poisoning, nor did it interfere with fermentation by rumen microorganisms, apparent digestibility of nutrients or animal performance.