Abstract #T248

# T248
Effects of limit-feeding forage to concentrate ratios on nutrients intake, rumination, ruminal fermentation, digestibility, and growth in Holstein heifers.
J. Zhang1, H. Shi1, Z. Cao1, S. Li1, S. Ji*1, Y. Wang1, 1State Key Laboratory of Animal Nutrition, Beijing Engineering Technology Research Center of Raw Milk Quality and Safety Control, College of Animal Science and Technology, China Agricultural University, Beijing, China.

Dairy heifers commonly receive diets in which the majority of nutrients come from forages instead of concentrates in China. The objective of this study was to evaluate the effects of limit-feeding of different levels of concentrate diets on nutrients intake, rumination, ruminal fermentation, digestibility, and animal growth in Holstein heifers. Twenty-four Holstein heifers (8–10 mo and 253 ± 29 kg of BW) were randomly allocated into 4 groups for a 28 d period fed with one of 4 diets containing different levels of concentrate (20%, 40%, 60%, and 80%, namely C20, C40, C60, and C80, respectively). Feed intakes were adjusted for heifers to obtain similar ADG at 0.8 kg/d. Individual rumination loggers were used to monitor rumination time. DMI was recorded daily, and BW, body measurements, and BCS were recorded weekly. Rumen liquid samples were taken at d 28 for detecting fermentation parameters. Data were analyzed using the PROC MIXED procedure of SAS. Contrast was used to test the linear and quadratic changes affected by increasing amount of dietary concentrate. DMI (5.32 vs. 4.97 vs. 4.69 vs, 4.42 for C20, C40, C60, and C80, respectively), intakes of OM, NDF and ADF, total rumination time, and ruminal pH were linearly decreased with increasing amount of concentrate in diets (P < 0.01). However, intakes of NFC and starch, rumination time per kg of NDF and ADF, and concentrations of NH3-N, propionate, and butyrate were linearly increased with increasing amount of concentrate in diets (P < 0.01). Digestibilities of DM, OM, and CP were significantly higher in C80 group than in C40 and C20 groups (P < 0.01). Dietary concentrate levels had no significant effects on BCS, feed efficiency (0.19 vs. 0.18 vs. 0.18 vs, 0.18 for C20, C40, C60, and C80, respectively; ADG/DMI; FE), and most of body measurements expect for paunch girth. What is worth mentioning, the results of ADG and FE might be eliminated or even reversed when gastrointestinal tract digesta was removed. In conclusion, limit-feeding of high concentrate diet gave heifers similar body growth as low concentrate diet feeding, and had the potential to be used as an effective feeding strategy in dairy heifers.

Key Words: heifer, high concentrate, limit-feeding