Abstract #T404

# T404
Effect of lactation stage and rate of increase of concentrate allowance on rumen adaptation in dairy cows.
Kasper Dieho*1, André Bannink2, Thomas J. Schonewille3, Jan Dijkstra1, 1Animal Nutrition Group, Wageningen University, Wageningen, the Netherlands, 2Animal Nutrition, Wageningen UR Livestock Research, Wageningen, the Netherlands, 3Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, Utrecht, the Netherlands.

We studied the effects of lactation stage and postpartum rate of increase of concentrate allowance on daily fermentable organic matter (FOM) intake, rumen papilla surface area, and fractional VFA absorption rate (kaVFA). The concentrate treatment aimed to create a transient difference in daily FOM intake. Twelve rumen-cannulated, Holstein-Friesian cows had free access to either a dry period ration or a basal lactation ration. Starting at 4 DIM, concentrate allowance increased at a high (1.0 kg DM/d; HIGH, n = 6) or a low rate (0.25 kg DM/d; LOW, n = 6) up to a maximum of 10.9 kg DM/d. On sampling days (−50, −30, −10, 3, 9, 16, 30, 44, 60, and 80 DIM), the rumen contents were evacuated and papilla biopsies taken. Thereafter, kaVFA was measured using the empty washed rumen technique with 46 L McDougall buffer (pH 6.0, 39°C), containing 120 mM VFA (60% acetic, 25% propionic, and 15% butyric acid) and a marker (Co-EDTA). From −50 to 3 DIM, FOM intake was 5.7 ± 0.3 kg/d (P = 0.29), papilla surface area decreased from 34.4 to 28.0 ± 2.0 mm2 (P = 0.02) and kaVFA decreased from 0.51 to 0.33 ± 0.03 /h (P < 0.01), with no differences between future treatment groups HIGH and LOW (P ≥ 0.33). From 3 to 80 DIM, FOM intake, papilla surface area, and kaVFA increased to 15.0 ± 0.3 kg/d, 63.4 ± 2.0 mm2, and 0.75 ± 0.03 /h respectively (all P < 0.01). A treatment by DIM interaction occurred for daily FOM intake (P < 0.01), which was greater in group HIGH at 16 DIM (12.3 vs. 10.1 ± 0.3 kg/d, P < 0.01), and for papilla surface area (P = 0.01), which was greater in group HIGH from 16 DIM (46.0 vs. 33.2 ± 2.0 mm2, P < 0.01) through to 44 DIM (60.5 vs. 49.7 ± 2.0 mm2, P = 0.01). However, a treatment by DIM interaction did not occur for kaVFA (P = 0.28), which was similar for group HIGH and LOW at 16 DIM (0.60 vs. 0.56 ± 0.03 /h, P = 0.53) and 44 DIM (0.69 vs. 0.69 ± 0.03 /h, P = 0.95). In conclusion, lactation stage but not concentrate treatment affected kaVFA. This suggests kaVFA increases with, but is not limited by, papilla surface area during the first weeks of lactation, which was affected by the rate of increase of concentrate allowance.

Key Words: VFA absorption, rumen papillae