Evaluation of a mixture of crude glycerol and molasses as an energy supplement for beef cattle consuming bermudagrass hay

Abstract Text: The objective of this study was to evaluate the effects of a crude glycerol:molasses supplement on forage digestibility and cattle performance.  Twenty-four Angus crossbred heifers (380 ± 31 kg) were used in the study.  On d 0, heifers were weighed after 16-h feed withdrawal, stratified, blocked by initial BW (2 blocks: lightest and heaviest), and randomly assigned to one of 4 treatments: 0.00, 0.45, 1.36, and 2.27 kg/d of a 50:50 liquid mixture of crude glycerol: molasses.  Heifers were housed in individual pens for 28 d and had ad libitum access to ground Tifton 85 bermudagrass hay (13.0% CP, 56% TDN, DM basis).  Individual intake of hay was monitored using a GrowSafe feed intake monitoring system.  The liquid supplement was weighed and offered daily to each individual animal.  Any unconsumed amount of supplement was weighed and recorded.  Feed (hay and liquid) and fecal samples were collected starting on d 22 and d 23, respectively, for 4 consecutive days to determine apparent total tract digestibility of DM, OM, CP, NDF, and ADF.  Fecal samples were collected twice daily at 0800 h and 1600 h from the ground, inside the pen, immediately after the animal defecated.  Feed and fecal samples were pooled within heifer and indigestible NDF (iNDF) was used as an internal indigestible marker.  Concentrations of iNDF in feed and feces were determined by in vitro incubations conducted for 288 h.  Data were analyzed as a generalized randomized block design using heifer as the experimental unit and the model included the fixed effects of treatment, and the random effect of block.  Orthogonal polynomial contrasts were conducted to determine the effects of supplementation level on animal performance or nutrient digestibility.  There was a linear effect (P ≤ 0.05) of liquid feed supplementation level on ADG, total DMI, and G:F measured using hay DMI only. No effect on G:F (P =  0.70) was observed using total DMI (hay plus supplement).  The ADG was 1.31, 1.37, 1.39, and 1.56 kg for 0, 0.45, 1.36, and 2.27 kg/d, respectively.  Apparent total tract digestibility of DM, OM, NDF, and ADF increased linearly (P ≤ 0.05), while that of CP decreased linearly (P = 0.01) as the level of supplementation increased.  The inclusion of up to 2.27 kg/d of a mixture of crude glycerol:molasses supplement may favor forage fiber digestion, improving performance of beef cattle.

Keywords: Crude glycerol, Molasses, Forage digestibility