The effects of feeding molasses on rumen fermentation, intake and milk production

The feeding of molasses to dairy cows was reviewed with emphasis on the effects on rumen fermentation, food intake and milk production. Three diary cow experiments and one fistulated wether sheep trial were conducted. Experiment 1 investigated the maximum feeding of molaferm 20 to mid-lactating dairy cows in a 3 X 3 Latin Square. The three complete diets each contained molaferm 20 at 156, 312 and 468 g/kg DM, respectively. Some cows suffered some scouring when they were fed 468 g/kg DM of molaferm 20, but recovered when they were fed lower levels. Blood concentrations of protein, urea, beta-hydroxybutyrate, Mg and K all were within normal range. Feed intake was increased with each increment of dietary molaferm 20 levels (p<0.01). Milk yield in the medium molaferm 20 treatment was higher than in the low treatment (p<0.01), but was similar between the high and medium treatments. Milk fat concentration was independent of diets, whereas protein was significantly higher with increment of dietary molaferm 20 levels. Experiment 2 determined the effects of dietary ERDP and DUP concentrations on the performance of early lactating dairy cows fed 310 g/kg DM of molaferm 20 in a 3 x 3 Latin Square. The three diets (L/L, H/L and H/H) each contained similar concentration of ME but differing levels in ERDP and DUP (93/17, 117/17 and 121/32 (g/kg DM)). No clinical symptoms of the ill health of the cattle were found during the experiment. Treatments showed little effects on blood concentrations of protein, urea, beta-hydroxybutyrate, Mg and K. Feed intake was significantly increased with each increment of CP levels. Milk yield was higher as ERDP increased (p < 0.05) and further higher as DUP increased (p<0.01). Milk fat concentrations was similar between treatments, whereas protein was higher as ERDP increased (P<0.05). Experiment 3 determined the responses of lactating dairy heifers to decreases in dietary FME concentrations produced by addition of unprotected tallow in a 3 x 3 Latin Square. Three complete diets (HFME, MFME and LFME) each contained 310 g/kg DM of molaferm 20 and similar levels of ERDP, DUP and ME but differing in levels of FME (9.4, 8.9 and 8.4 MJ/kg DM). No clinical symptoms of the ill health of the cattle were found during the experiment. Treatments showed little effects on blood concentrations of protein, urea, beta-hydroxybutyrate, Mg and K. Feed intake was slightly lower with decreases in dietary FME concentrations achieved by addition the unprotected tallow. Milk yield in the HFME treatment was significantly lower than in the MFME or LFME treatment (p<0.01), while milk concentrations of protein and fat were significantly higher in the HFME (p<0.05). Milk concentration of uric acid was lower as decreasing dietary FME, but yield was similar between treatments. Experiment 4 investigated the effects of dietary ERDP and DUP concentrations on the rumen fermentation of ruminal fistulated wether sheep in a 4 x 4 Latin Square design. Four complete diets (C, CU, CS and CSF) each contained 310 g/kg DM of molaferm 20 and similar ME and FME, but differing in levels of ERDP/DUP (84/17, 109/17, 116/38 and 119/54 g/kg DM). Whole tract digestibilities of DM and OM was similar between treatments, while NDF and hay degradability in the rumen were significantly higher in sheep fed the diets CS and CSF than those fed the diets C and CU. Average ammonia-N in the rumen was significantly higher with each increment of dietary protein levels. However, PD-N output in urine did not respond to the ammonia concentrations. Microbial N supply was similar between the 4 treatments. Total volume of VFAs in the rumen was independent of the diets. Molar percentages of propionic and butyric acids were lower, while acetic acid was higher as ERDP levels increased, but not as DUP increased. The effects on the microbial protein synthesis and the efficiencies of utilization of ME intake and MP supply were discussed and areas of further research suggested.