Net flux of nutrients across the rumen wall of lactating dairy cows as influenced by dietary supplements of folic acid

Abstract

The objective of the present study was to determine whether a dietary supplementation of folic acid, at levels used in our previous studies, would affect ruminal fermentation and the net flux of nutrients across the rumen wall of lactating dairy cows. Approximately 4 wk after calving, 5 lactating multiparous cows were surgically equipped with a ruminal cannula, an ultrasonic flow probe around the right ruminal artery, and indwelling catheters in the right ruminal vein and the ileocolic artery. Cows were fed a total mixed ration served in 7 equal meals per d (i.e., every 3.4 h). The experimental design was an unbalanced crossover arrangement with 3 periods of 4 wk each. The vitamin supplement, incorporated in equal amounts into each meal, was supplied at 0, 3, or 6 mg of folic acid per kg of BW per d. During the last week of each experimental period, blood samples were taken simultaneously from the 2 catheters every 30 min and rumen fluid was collected every 60 min during 2 consecutive meal intervals. Dietary supplementation with folic acid had no effect on milk production (27.2 +/- 1.3 kg/d) or DMI (19.9 +/- 0.7 kg/d), but milk concentrations and yields of total solids, fat, and protein increased linearly with increasing doses of folic acid ingested. Concentrations of folates in rumen fluid and arterial plasma, averaged over time, increased linearly with the dose of folic acid ingested but the net flux of folates across the rumen wall was not different from zero. Concentrations of butyrate in ruminal fluid decreased quadratically with the daily supply in folic acid. Dietary supplements of folic acid had no effect on pH and osmolality of ruminal fluid, nor on ruminal concentrations of lactate, ammonia, acetate, or propionate, total VFA, or microbial counts. The uptake of urea-N by the rumen wall tended to increase quadratically with the dose ingested but net fluxes of other nutrients were not affected by treatments. These results suggest that the effects of folic acid supplements on lactational performance cannot be explained by effects on rumen metabolism.

Effects of rumen-protected folic acid on ruminal fermentation, microbial enzyme activity, cellulolytic bacteria and urinary excretion of purine derivatives in growing beef steers

“…The reason for the increased CP degradability failing to result in the increased ammonia N content was attributed to the increased synthesis of microbial protein demonstrated by the increased urinary PD excretion. The results were in agreement with the finding of Wejdemar (1996) where the addition of folic acid to clarified ruminal fluid promoted the growth of B. fibrisolvens TC33 and its utilization of ammonia N. Nevertheless, Girard et al (2009) reported that the uptake of urea N by the rumen wall tended to increase quadratically when lactating multiparous cows supplied folic acid daily at 0, 3, or 6 mg/kg BW.…”

“…Although in the current study the supplementary RPFA which contained 100 g/kg of folic acid and its ruminal degradability was 0.304, could provide 18.2, 36.4 and 54.6 mg/d of folic acid for ruminal microorganism in LRPFA, MRPFA and HRPFA group, respectively, the level of folic acid released into the rumen was lower than that of in Chiquette et al (1993), Girard et al (1994) and Girard et al (2009). The positive effects of supplementary RPFA on ruminal fermentation may have resulted from a combined action of the low CP and energy diets, lower passage rate through the rumen, ruminal degradable folic acid and its protection material.…”

“…In previous study, Hayes et al (1966) also found that folic acid was negatively correlated with pH in steers fed concentrate diets and this was attributed to an increased microbial activity. However, other studies reported limited effects of folic acid on ruminal fermentation (Chiquette et al, 1993;Girard et al, 1994Girard et al, , 2009. Ruminal ammonia N derives from ruminal CP degradation and in turn is used for microbial protein synthesis or enters into the rumen-liver nitrogen cycle (Reynolds and Kristensen, 2008).…”

“…The inconsistent results on rumen fermentation response to folic acid should be associated with the dietary composition, the mode of administration of folic acid (unprotected folic acid vs. protected folic acid) and supplemental dose of folic acid (Chiquette et al, 1993;Girard et al, 1994Girard et al, , 2009. Although in the current study the supplementary RPFA which contained 100 g/kg of folic acid and its ruminal degradability was 0.304, could provide 18.2, 36.4 and 54.6 mg/d of folic acid for ruminal microorganism in LRPFA, MRPFA and HRPFA group, respectively, the level of folic acid released into the rumen was lower than that of in Chiquette et al (1993), Girard et al (1994) and Girard et al (2009).…”

“…Supplementary folic acid promoted the growth of celluloytic bacteria (Wejdemar, 1996), increased cellulose digestion (Hall et al, 1953;Ragaller et al, 2010), improved ruminal fermentation (Hayes et al, 1966) and increased the utilization of ammonia N for microbial protein synthesis (Wejdemar, 1996;Lee et al, 2000). However, other researches found limited influence of folic acid on ruminal fermentation (Clifford et al, 1967;Chiquette et al, 1993;Girard et al, 1994Girard et al, , 2009 and the utilization of ammonia N (Girard et al, 1994(Girard et al, , 2009Ragaller et al, 2010). The inconsistent influences of supplementary folic acid on ruminal fermentation and ammonia N utilization could be associated with diets with different ingredient and chemical composition, dose, physical form and way of administration of folic acid.…”