Abstract #T246

# T246
Metabolic responses in biofluid and feces of dairy cows fed different ratio of dietary neutral detergent fiber to starch.
L. Ma1, T. T. Li2, M. Zhao1, L. S. Zhao1, J. Q. Wang1, J. J. Wang2, Z. T. Yu3, D. P. Bu*1,4, 1State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, China, 2China Agricultural University, Beijing, China, 3Department of Animal Sciences, The Ohio State University, Columbus, OH, 4CAAS-ICRAF Joint Lab on Agroforestry and Sustainable Animal Husbandry, World Agroforestry Centre, East and Central Asia, Beijing, China, 5Hunan Co-Innovation Center of Animal Production Safety, CICAPS, Changsha, Hunan, China.

The objective of this study was to evaluate how the metabolic pathway of carbohydrates and milk composition are affected by ratios of dietary neutral detergent fiber (NDF): starch. Eight primiparous dairy cows were assigned to 4 total mixed rations (TMR) with NDF to starch ratios of 0.86, 1.18, 1.63, and 2.34 in a replicated 4 × 4 Latin square design. The duration of each period was 21 d including a 14 d for adaptation and 7 d for sampling. At the beginning of the study, milk production and days in milk were 35.1 ± 0.5 kg/day and 146 ± 21.6 d, respectively. The NDF to starch ratios were achieved by altering the proportions of forage (corn silage and oat hay) and concentrate (corn), with the same composition and inclusion proportion of other dietary ingredients. Plasma, urine, milk, rumen fluid, and feces were collected once daily on the last 3 d of each period. The metabolic profiles were analyzed using HPLC Q-TOF MS, and the identified metabolites were confirmed by both retention time and mass spectra. All data were processed using the Agilent MassHunter Qualitative Analysis and Mass Profiler Professional software. A student t-test was used to search for compounds with a fold change greater than 2 and a P-value less than 0.05. Metabolites were identified using the METLIN and Human metabolome database. 31 different metabolic profiles in feces, 5 in rumen fluid, 3 in plasma, and 6 in urine were detected, including leukotriene increased (P < 0.05) in rumen fluid, fatty acids increased (P < 0.05) in plasma, vitamin D3 increased (P < 0.05) in plasma, glucuronide decreased (P < 0.05) in urine, isovalerate decreased and then increased (P < 0.05) in urine and L-isoleucyl-L-proline increased (P < 0.05) in feces. All the different metabolic profiles were related to several metabolic pathways, including fatty acid biosynthesis, the metabolism of vitamin D3, amino acids, protein and alkaloids, bile secretion, and inflammatory mediator regulation. Taken together, different NDF: starch ratio in diets can affect metabolism inside and outside of the rumen of dairy cows, and some of these metabolic responses may be attributable to the observed effects of NDF: starch ratio on animal productivity and health.

Key Words: dairy cow, NDF:starch ratio, metabolic