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

The effects of dietary crude protein level on ammonia emissions from slurry from lactating Holstein-Friesian cows as measured in open-circuit respiration chambers.

Publication history: Accepted - 10 May 2022; Published online - 12 May 2022The effect of dietary crude protein (CP) level on ammonia (NH3) emissions from slurry from lactating Holstein-Friesian cows was studied. Twenty-four-hour total collections of faeces and urine were made from 24 lactating Holstein-Friesian cows fed four total mixed rations containing 141, 151, 177, and 201 g CP/kg DM (6 cows/diet). The collected urine and faeces from each cow were combined to form 2 kg duplicate slurry samples (weight/weight; fresh basis) according to the proportions in which they were excreted. NH3 emissions from the slurry samples were measured, during 0–24 and 24–48 h intervals in six open-circuit respiration chambers maintained at two temperatures (8 or 18 °C). NH3 emissions for the 0–24 and 0–48 h intervals, as well as the average daily emissions, increased linearly with increasing dietary CP level. Increasing the temperature from 8 to 18 °C positively affected NH3 emissions, but only for the 0–24 h interval. In situations where direct measurements are impossible, NH3 emissions from slurry can be predicted accurately using equations based on dietary CP level supported by either urinary nitrogen, faeces nitrogen, or both. In summary, increasing dietary CP level linearly increased average daily NH3 emissions from slurry, with a 5.4 g increase for each 10 g increase in dietary CP.This research project was funded by the Department of Agriculture Environment and Rural Affairs (DAERA) in Northern Ireland

Effects of concentrate crude protein content on nutrient digestibility, energy utilization, and methane emissions in lactating dairy cows fed fresh-cut perennial grass

Although many studies have investigated mitigation strategies for methane (CH4) output from dairy cows fed a wide variety of diets, research on effects of concentrate crude protein (CP) content on CH4 emissions from dairy cows offered fresh grass is limited. The present study was therefore designed to evaluate effects of cow genotype and concentrate CP level on nutrient digestibility, energy utilization and CH4 emissions of dairy cows offered fresh grass based diets. Twelve multiparous lactating dairy cows (6 Holstein and 6 Holstein × Swedish Red) were blocked into 3 groups within each breed and assigned to low, medium or high CP concentrate diet (14.1, 16.1 and 18.1 % on dry matter (DM) basis), respectively, in a 3-period changeover study (25-d / period). Total diets contained (DM basis) 32.8 % concentrates and 67.2 % perennial ryegrass, which was harvested daily. All measurements were undertaken during the final 6-d of each period; digestibility measurements for 6-d and calorimetric measurements in respiration chambers for 3-d. Feed intake and milk production data were reported in a previous paper. No significant interaction between concentrate CP level and cow genotype on any parameter was observed. Concentrate CP level had no significant effect on any energy utilization parameter, except for urinary energy output which was positively related to concentrate CP level. Similarly concentrate CP content had no effect on CH4 emission (g/d), CH4 per kg feed intake or nutrient digestibility. The crossbreeding of Holstein cows significantly reduced gross energy, digestible energy and metabolizable energy intake, heat production and milk energy output. However, cow genotype had no significant effects on energy utilization efficiency or CH4 parameters. Furthermore, the present study yielded a value for gross energy lost as CH4 (5.6 %) on fresh grass-based diets that is lower than the widely accepted value of 6.5 %. The present findings indicate reducing concentrate CP content from 18.1 to 14.1 % may not be a successful approach to alleviate CH4 emissions from lactating dairy cows offered good quality fresh grass, however grazing cows could be offered a low CP concentrate without compromising energy utilization efficiency. Further research is needed to investigate whether larger differences in dietary CP content may yield positive results

Effect of Varying Dietary Crude Protein Level on Feed Intake, Nutrient Digestibility, Milk Production, and Nitrogen Use Efficiency by Lactating Holstein-Friesian Cows

Publication history: Accepted - 17 December 2020; Published online - 19 December 2020The effect of dietary crude protein (CP) level on intake, digestibility, milk production, and nitrogen (N) use efficiency was studied. Twenty-four Holstein-Friesian cows (17 multiparous and seven primiparous) were grouped by parity, days in milk, milk yield, and live weight into six blocks of four, and randomly assigned to four total mixed ration (TMR) treatments, containing 141, 151, 177, or 210 g CP/kg dry matter (DM), over 28 day experimental periods. Apparent total-tract DM and fiber digestibilities and milk fat composition were similar across treatments. Milk protein and urea-N compositions, and urinary and manure N excretion increased linearly, while milk N efficiency (MNE) decreased linearly with increasing CP. DM intake was highest with the 177 diet, while CP intake increased linearly with increasing CP, peaking at 200 g/kg DM. Milk yield increased with CP intake for the three lower CP levels, peaking at 176 g CP/kg DM. The further increase in CP level from 177 to 210 g/kg DM did not result in improved milk yield, but resulted in decreased milk N secretion and increased urinary N excretion. In summary, milk protein composition increased linearly with increasing CP, accompanied by a linear decrease in MNE, resulting in a bell-shaped relationship between milk yield and dietary CP level.This research project was funded by the Department of Agriculture Environment and Rural Affairs (DAERA) in Northern Ireland

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