Use of dicarboxylic acids and polyphenols to attenuate reticular pH drop and acute phase response in dairy heifers fed a high grain diet.

BACKGROUND: The aim of this study was to determine the ability of two feed additives, a fumarate-malate (FM) and a polyphenol-essential oil mixture (PM), in attenuating the drop of ruminal pH and the metabolic and immune response resulting from an excessively high grain diet. Six heifers were used in a 3 × 3 Latin square experiment and fed a low starch (LS) diet for 14 d, followed by a high starch (HS) diet for 8 d (NDF 33.6%, starch 30.0% DM). In the last 5 days of each period, barley meal was added to decrease rumen pH. During HS feeding all animals were randomly assigned to one of the following three dietary treatments: no supplement/control (CT), a daily dose of 60 g/d of FM, or 100 g/d of PM. Reticular pH was continuously recorded using wireless boluses. On d 21 of each period, rumen fluid was collected by rumenocentesis (1400 h), together with blood (0800 h) and fecal samples (0800, 1400, and 2100 h). RESULTS: The correlation coefficient of pH values obtained using the boluses and rumenocentesis was 0.83. Compared with CT and PM, the FM treatment led to a lower DMI. Nadir pH was lowest during CT (5.40, 5.69, and 5.62 for CT, FM and PM, respectively), confirming the effectiveness of both supplements in reducing the pH drop caused by high grain feeding. This result was confirmed by the highest average time spent daily below 5.6 pH (199, 16 and 18 min/d) and by the highest acetate to propionate ratio of the CT fed heifers. The PM decreased the concentrations of neutrophils (2.9, 3.2, and 2.8 10(9)/L) and acute phase proteins: SAA (37.1, 28.6 and 20.1 µg/mL), LBP (4.1, 3.8, and 2.9 µg/mL), and Hp (675, 695 and 601 µg/mL). Free lipopolysaccharides (LPS) were detected in blood and feces, but their concentrations were not affected by treatments, as the remaining blood variables. CONCLUSIONS: Data suggest that both additives could be useful in attenuating the effects of excessive grain feeding on rumen pH, but the PM supplement was more effective than FM in reducing the inflammatory response compared to CT.

Ergot alkaloids from endophyte-infected tall fescue decrease reticuloruminal epithelial blood flow and volatile fatty acid absorption from the washed reticulorumen.

An experiment was conducted to determine if ergot alkaloids affect blood flow to the absorptive surface of the rumen. Steers (n=8) were pair-fed alfalfa cubes and received ground endophyte-infected (Neotyphodium coenophialum) tall fescue (Lolium arundinaceum; E+) seed (0.015 mg ergovaline·kg BW(-1)·d(-1)) or endophyte-free tall fescue (E-) seed via the rumen cannula 2x daily for 7 d at thermoneutral (TN; 22°C) and heat stress (HS; 32°C) conditions. On d 8, the rumen was emptied and rinsed. A buffer containing VFA was incubated in the following sequence: control (CON), 15 µg ergovaline·kg BW(-1) (1×EXT) from a tall fescue seed extract, and 45 µg ergovaline·kg BW(-1) (3×EXT). For each buffer treatment there were two 30-min incubations: a 30-min incubation of a treatment buffer with no sampling followed by an incubation of an identical sampling buffer with the addition of Cr-EDTA and deuterium oxide (D2O). Epithelial blood flow was calculated as ruminal clearance of D2O corrected for influx of physiological water and liquid outflow. Feed intake decreased with dosing E+ seed at HS but not at thermoneutral conditions (TN; P<0.02). Dosing E+ seed decreased serum prolactin (P<0.005) at TN. At HS, prolactin decreased in both groups over the 8-d experiment (P<0.0001), but there was no difference in E+ and E- steers (P=0.33). There was a seed treatment×buffer treatment interaction at TN (P=0.038), indicating that E+ seed treatment decreased reticuloruminal epithelial blood flow at TN during the CON incubation, but the two groups of steers were not different during 1×EXT and 3×EXT (P>0.05). Inclusion of the extract in the buffer caused at least a 50% reduction in epithelial blood flow at TN (P=0.004), but there was no difference between 1×EXT and 3×EXT. There was a seed × buffer treatment interaction at HS (P=0.005), indicating that the reduction of blood flow induced by incubating the extract was larger for steers receiving E- seed than E+ seed. Volatile fatty acid flux was reduced during the 1×EXT and 3×EXT treatments (P<0.01). An additional experiment was conducted to determine the effect of time on blood flow and VFA flux because buffer sequence could not be randomized. Time either increased (P=0.05) or did not affect blood flow (P=0.18) or VFA flux (P>0.80), indicating that observed differences are due to the presence of ergot alkaloids in the rumen. A decrease in VFA absorption could contribute to the signs of fescue toxicosis including depressed growth and performance.

Kinetics of phosphate absorption in lactating dairy cows after enteral administration of sodium phosphate or calcium phosphate salts.

Hypophosphataemia is frequently encountered in dairy cows during early lactation. Although supplementation of P is generally recommended, controversy exists over the suitability of oral P supplementation in animals with decreased or absent rumen motility. Since the effects of transruminal P absorption and the reticular groove reflex on the absorption kinetics of P are not well understood, it is unclear in how far treatment efficacy of oral P supplementation is affected by decreased rumen motility. Phosphate absorption was studied in six phosphate-depleted dairy cows fitted with rumen cannulas and treated with test solutions containing either NaH2PO4 or CaHPO4 with acetaminophen. Each animal was treated orally, intraruminally and intra-abomasally in randomised order. Absorption kinetics of P were studied and compared with the absorption kinetics of acetaminophen, a marker substance only absorbed from the small intestine. Intra-abomasal treatment with NaH2PO4 resulted in the most rapid and highest peaks in plasma inorganic P (Pi) concentration. Oral and intraruminal administration of NaH2PO4 resulted in similar increases in plasma Pi concentration from 4 to 7 h in both groups. Treatment with NaH2PO4 caused more pronounced peaks in plasma Pi concentration compared with CaHPO4. Neither transruminal P absorption nor the reticular groove reflex affected P absorption kinetics as determined by comparing plasma concentration­time curves of P and acetaminophen after administration of 1M-phosphate salt solutions. It is concluded that oral treatment with NaH2PO4 but not CaHPO4 is effective in supplementing P in hypophosphataemic cows with adequate rumen motility. Decreased rumen motility is likely to hamper the efficacy of oral phosphate treatment.

Reaction cements as materials for the sustained release of trace elements into the digestive tract of cattle and sheep. II. Release of cobalt and selenium.

Acid-base reaction cements, containing salts of copper, cobalt and selenium, were placed in the reticulum of sheep and cattle, and the rate of release of cobalt and selenium from them was measured. The rate of release of cobalt decreased with time but was sufficient to provide adequate supplementation for at least 6 months. After an initial rate of release of 4 mg Se/day for 1-2 weeks, the mean subsequent rate of release of selenium over a period of 4 months was 0.1 mg Se/day (identical to 5 micrograms Se/day/cm2 surface area). Field trials in lambs and growing steers showed that the cement increased the selenium concentration of their blood throughout a summer grazing period.