The effect of supplemental concentrate fed during the dry period on morphological and functional aspects of rumen adaptation in dairy cattle during the dry period and early lactation.

ABSTRACT

Ten rumen-cannulated Holstein-Friesian cows were used to examine the effect of feeding supplemental concentrate during the dry period on rumen papillae morphology and fractional absorption rate (ka) of volatile fatty acids (VFA) during the dry period and subsequent lactation. Treatment consisted of supplemental concentrate [3.0kg of dry matter (DM)/d] from 28d antepartum (ap) until the day of calving, whereas control did not receive supplemental concentrate. Cows were fed for ad libitum intake and had free access to the dry period ration (27% grass silage, 28% corn silage, 35% wheat straw, and 11% soybean meal on a DM basis) and, from calving onward, to a basal lactation ration (42% grass silage, 42% corn silage, and 16% soybean meal on a DM basis). From 1 to 3d postpartum (pp), all cows were fed 0.9kg DM/d of concentrate, which increased linearly thereafter to 8.9kg of DM/d on d 11 pp. At 28, 18, and 8d ap, and 3, 17, 31, and 45d pp, rumen papillae were collected and kaVFA was measured in all cows. On average, 13.8 (standard deviation 3.8) papillae were collected each from the ventral, caudodorsal, and caudoventral rumen sacs per cow per day. The kaVFA was measured by incubating a standardized buffer fluid (45 L), containing 120mM VFA (60% acetic, 25% propionic, and 15% butyric acid) and Co-EDTA as fluid passage marker, in the evacuated and washed rumen. Treatment did not affect ap or pp DM and energy intakes or milk yield and composition. Treatment increased papillae surface area, which was 19 and 29% larger at 18 and 8d ap compared with 28d ap, respectively. Surface area increased, mainly due to an increase in papillae width. However, treatment did not increase kaVFA at 18 and 8d ap compared with 28d ap. In the control group, no changes in papillae surface area or kaVFA were observed during the dry period. In the treatment group, papillae surface area decreased between 8d ap and 3d pp, whereas no decrease was observed for control. From 3 to 45d pp, papillae surface area and kaVFA increased for all cows by approximately 50%, but the ap concentrate treatment did not affect kaVFA pp. In conclusion, the efficacy of supplemental concentrate during the dry period to increase papillae surface area and kaVFA in preparation for subsequent lactation is not supported by the present study. Current observations underline the importance of functional measurements in lieu of morphological measurements to assess changes in the adapting rumen wall.