| Choline is a crucial nutrient for animals. It can enhance the output of triglycerides from the liver and thus prevent the development of fatty liver. Peripartum, consisted of prepartum period(21 d) and postpartum period(21 d), was considered to be the most crucial period for dairy cows, which demand large amounts of energy during this period. Nevertheless, dairy cows in prepartum are usually under the state of Negative Energy Balance(NEB) attributed to decreasing Dry Matter Intake(DMI). NEB can cause metabolic disorders(such as fatty liver,ketosis) and limit the production performance of milking cows. Choline supplementation can reduce the formation of fatty liver and ameliorate the NEB status of dairy cows. Consequently,it’s necessary to develop efficient rumen-protected choline products as the choline is easy to degrade in rumen. This research was conducted to fabricate a new emulsion-based microencapsulation system for rumen-protected choline(W/O-RPC), and evaluate its release properties in vitro. In particular, the following series of experiments were performed:preparation of W/O-RPC(Expt 1), formula optimization of W/O-RPC(Expt 2), and the evaluation of W/O-RPC protective effect in vitro(Expt 3).Expt 1 was designed to investigate the effects of emulsifier concentration(wt%) and oil-to-water ratio on the protection rate of encapsulated choline chloride. The results showed that the protection rate was relatively stable(>90%) when the emulsifier concentration was above 4% and oil-to-water ratio was below 5:5.In Expt 2, the Central Composite Design(CCD) and Response Surface Methodology(RSM) were employed to investigate the influence of emulsifier concentration(wt%) and oil-to-water ratio on the release properties of choline chloride in W/O-RPC. Response surface and contour were graphed with the value of release property of choline chloride in W/O-RPC as response value. Results were as follows:(1) The order of 2 factors’ effects on response value was O:W ratio > emulsifier concentration(wt%).(2) The optimal emulsifier concentration and oil-to-water ratio were 11.01 wt% and 8:2,respectively. Under this condition, the theoretical release rate of choline chloride in W/O-RPC was 81.01%, and the actual value was 81.65±1.03%.In Expt 3, an in vitro model simulating the rumen digestion conditions were used to evaluate the rate and extent of lipid phase digestion, as well as the protective effect of W/O-RPC. The results are showed as follows:(1) After the treatment of artificial saliva(2 hours), the release rate of W/O-RPC was significantly higher(9.72%, P<0.05) than that of a commercial product(Reashure RPC).However, there was no significant difference(P>0.05) between W/O and Reashure RPC after a 24 h digestion of artificial saliva, the release rate was 13.67% and 13.18%, respectively.(2) The release rates between two different kinds of RPC were significantly different within the in vitro rumen digestion model(P<0.05): when the digestion duration was relatively short(2 h), the release rate of Reashure RPC and W/O-RPC was 5.09% and 44.00%,respectively; when the digestion duration was increased to 24 h, the digestion rate was also improved to 26.10% and 87.55%, respectively.(3) During the post-rumen period, the release rate of Reashure RPC was prominently lower(12.30%) than that of W/O-RPC(28.06%) within a shorter digestion duration(2 h)(P<0.05). Nonetheless, with longer treatment duration(24 h), the release rate of Reashure RPC was increased to 67.84%, which was significantly higher than that of W/O-RPC(52.11%). |
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