The influence of dietary buffer value index and dietary ADF content on ruminal fluid pH, buffering capacity, and buffer value index was measured. Four lactating Holstein cows (two primiparous) averaging 72 +/- 60 DIM were used in a 4 x 4 Latin square with 3-wk experimental periods. Treatments were a 2 x 2 factorial arrangement of TMR containing two ADF concentrations (16 and 21% of DM) and two buffer value indexes (calculated from analysis of individual dietary ingredients to be -200 and 0). Milk fat content and milk fat yield tended to be increased by high ADF, and protein yield tended to increase with low buffer value index and low ADF. Although the high ADF diets increased ruminal fluid pH, they reduced buffering capacity; because the magnitude of the pH increase was greater than the reduction in buffering capacity, ruminal fluid buffer value index was increased by added ADF. The high buffer value index diets reduced ruminal fluid pH and increased ruminal fluid buffering capacity; effects on pH outweighed those on buffering capacity so that the ruminal fluid index paradoxically decreased as the dietary index increased. Ruminal fluid acetate increased and propionate decreased as ADF increased. We conclude that ruminal fluid buffer value index increases with dietary ADF, likely because of reduced ruminal concentrations of fermentation acids. Because diets with the highest index produced the lowest ruminal indexes, dietary buffer value index must be studied further before it can be included in any model purporting to predict the need for supplemental dietary buffers.
Our objective was to compare the influence of dietary NaHCO3 and a multielement buffer on ruminal acid-base status and lactation performance of dairy cows. Five ruminally fistulated, primiparous and multiparous lactating Holstein cows averaging 123 +/- 21 d postpartum were assigned randomly to treatments in a 5 x 5 Latin square with 3-wk experimental periods. Treatments were a basal diet without supplemental buffers, with 1.5% NaHCO3 or 1.5% multielement buffer, or with NaHCO3 or multielement buffer solutions poured into the rumen via cannula at 2 h postfeeding. Addition of either buffer to the diet reduced ruminal fluid hydrogen ion concentration from 0 to 6 h postfeeding; only NaHCO3 reduced ruminal fluid acidity when dosed via the cannula. Addition of buffers via ruminal cannula appeared to retard the reduction in ruminal fluid acidity that normally occurs from 6 to 12 h postfeeding; this may have been related to a feedback mechanism inhibiting salivary buffer secretion. Buffering capacity of ruminal fluid tended to increase with buffer addition; the increase was greatest during infusion of NaHCO3. The ruminal fluid buffer value index increased by 4 units for control cows from early (0 to 6 h) to late (6 to 12) postfeeding; smaller increases were noted for addition of multielement buffer. This index was not different for NaHCO3 during these two intervals. Milk yield and DMI were not affected by buffer addition. Although milk fat content tended to be higher with the multielement buffer than with NaHCO3, it was not accompanied by the expected alterations in ruminal acid-base status. Therefore, this increase may be related to systemic effects of specific minerals in the multielement buffer rather than to a more stable ruminal environment. Based on the ruminal fluid buffer value index, NaHCO3 tended to maintain the most stable ruminal acid-base status.
We describe a device that can display very high intensity (up to 400,000 cd/m 2 ), high-resolution visual stimuli. The device is inexpensive, is easily controlled by a conventional computer and video card, and can be calibrated for use in vision research or clinical applications. The display is capable of presenting highly saturated, near spectral colors. Unlike Maxwellian view optical systems, our display can be viewed binocularly and does not require exacting head restraint. We describe the construction, give a design example, and describe our calibration procedure. Furthermore, we report measurements of the color gamut, spatial resolution, temporal characteristics, and the dynamic range of light intensity.
No‐till agriculture involves the use of granular pesticide formulations, chemically treated seeds, and pelleted baits. Some of these may accidentally kill birds. We have tested whether methyl anthranilate (MA), a known bird repellent, would eliminate consumption of a pelleted bait. In two laboratory experiments and an outdoor aviary trial, cowbirds (Molothrus ater Bodd.) were presented with pellets containing pesticide and MA, pellets containing pesticide but no MA, and carrier pellets without pesticide or MA. Consumption of any formulation was low, but the addition of MA significantly decreased bait loss in the laboratory, and prevented the disappearance of bait in the outdoor trial.
The objective of this study was to evaluate the influence of dietary buffer value index on ruminal fluid pH, buffering capacity, and buffer value index in lactating cows. Three Holstein cows averaging 18 +/- 10 DIM were used in a 3 x 3 Latin square with 3-wk experimental periods. Diets contained grain:sorghum silage DM ratios of 50:50, 60:40, and 70:30. By analysis, these diets had buffer value indexes of -74, -41, and -7. The analyzed dietary buffer value index of the total diets was higher than the index that was calculated from the buffer value index of individual ingredients. Although milk fat content tended to be highest for milk from cows fed the 50:50 concentrate to forage diet and although milk protein production was highest for cows fed the 70:30 concentrate to forage diet, milk yield, 4% FCM, milk fat yield, protein content, and milk fat content were not significantly affected by dietary buffer value index. Dietary buffer equivalents were calculated to be 11% of total buffering equivalents available to the cow, and dietary acid equivalents were 15% of total acid production in the rumen. Compared with ruminal acid production and salivary buffering in the rumen, dietary acid and dietary buffer contributions to the acid-base balance of the cow are minor quantitatively. Ruminal fluid pH, hydrogen ion concentration, buffer value index, buffering capacity, and total VFA were not affected significantly by dietary buffer value index. Hence, dietary acid-base status alone is inadequate as a predictor of the need for buffers in the diet of lactating cows.
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