LAUSR

ABSTRACT Mixed mono‐ and tributyrate glycerides have been used for effective delivery of butyrate to the gut to benefit broilers. However, limited information is available on the efficacy of butyrate glycerides individually and in combination with different levels and feeding schedules. The present study has first investigated the effects of monobutyrin at inclusion levels of zero, 500, 1,000, 2,000, and 3,000 ppm on the performance of broilers, and second, the effects of its combination with tributyrin. In the monobutyrin trial, there were no overall significant differences in average daily gain or feed efficiency. However, 2,000 ppm birds had significantly decreased abdominal fat deposition compared to controls (P ≤ 0.05), and the breast muscle deposition increased in a dose‐response manner to the supplementation of monobutyrin (P ≤ 0.05). The combination trial tested 5 treatment groups: control, 500 ppm tributyrin + 500 ppm monobutyrin (5T5M), 500 ppm tributyrin + 500 ppm monobutyrin staggered (5T5Ms), 500 ppm tryibutyrin + 2,000 ppm monobutyrin (5T20M), or 500 ppm tributyrin + 2,000 ppm monobutyrin staggered (5T20Ms). In staggered groups, birds were fed tributyrin for one wk followed by 2 wk of monobutyrin, after which the feed was butyrate glyceride free. The non‐staggered groups had constant inclusions levels through the 5 weeks. There were no significant differences in average daily gain or feed efficiency among groups. At 5 wk of age, all treatment groups except for 5T5Ms had significantly lower relative abdominal fat weight compared to control birds (P ≤ 0.05), although 5T5Ms birds demonstrated a trend for a decrease (P = 0.095). Relative breast muscle weight was significantly increased only in 5T5M birds over control birds at 5 wk of age (P ≤ 0.05). Serum biochemistry revealed significant changes in factors relating to muscle growth and fat deposition (P ≤ 0.05). These results indicate a consistent shift in lipid metabolism with the addition of butyrate glycerides and that the deposition of breast muscle may be highest with the incorporation of butyrate glycerides at a moderate level for the duration of development.