New insights into the regulation of cholesterol eft from the sperm membrane

Cholesterol is an essential component of the mammalian plasma membrane because it promotes membrane stability without comprising membrane fluidity. Given this important cellular role, cholesterol levels are tightly controlled at multiple levels. It has been clearly shown that cholesterol redistribution and depletion from the sperm membrane is a key part of the spermatozoon＇s preparation for fertilization. Some factors that regulate these events are described （e.g., bicarbonate, calcium） but the mechanisms underlying cholesterol export are poorly understood. How does a hydrophobic cholesterol molecule inserted in the sperm plasma membrane enter the energetically unfavorable aqueous surroundings？ This review will provide an overview of knowledge in this area and highlight our gaps in understanding. The overall aim is to better understand cholesterol redistribution in the sperm plasma membrane, its relation to the possible activation of a cholesterol transporter and the role of cholesterol acceptors. Armed with such knowledlze, sl）erm handlin~ techniques can be adapted to better prepare spermatozoa for in vitro and in vivo fertilization.

Sainfoin(Onobrychis viciifolia)silage in dairy cow rations reduces ruminal biohydrogenation and increases transfer efficiencies of unsaturated fatty acids from feed to milk

The effects of replacing grass silage by sainfoin silage in a total mixed ration(TMR)based diet on fatty acid(FA)reticular inflow and milk FA profile of dairy cows was investigated.The experiment followed a crossover design with 2 dietary treatments.The control diet consisted of grass silage,corn silage,concentrate and linseed.In the sainfoin diet,half of the grass silage was replaced by a sainfoin silage.Six rumen cannulated lactating multiparous dairy cows with a metabolic body weight of 132.5±3.6 kg BW^0.75,214±72 d in milk and an average milk production of 23.1±2.8 kg/d were used in the experiment.Cows were paired based on parity and milk production.Within pairs,cows were randomly assigned to either the control diet or the sainfoin diet for 2 experimental periods(29 d per period).In each period,the first 21 d,cows were housed individually in tie-stalls for adaptation,then next 4 d cows were housed individually in climate-controlled respiration chambers to measure CH4.During the last 4 d,cows were housed individually in tie stalls to measure milk FA profile and determine FA reticular inflow using the reticular sampling technique with Cr-ethylenediaminetetraacetic acid disodium salt dihydrate(EDTA)and Yb-acetate used as digesta flow markers.Although the dietary C18:3n-3 intake was lower(P=0.025)in the sainfoin diet group,the mono-unsaturated FA reticular inflow was greater(P=0.042)in cows fed the sainfoin diet.The reticular inflow of trans-9,trans-12-C18:2 and cis-12,trans-10 C18:2 was greater(P≤0.024)in the sainfoin diet group.The cows fed sainfoin diet had a lower(P≤0.038)apparent ruminal biohydrogenation of cis-9-C18:1 and C18:3n-3,compared to the cows fed the control diet.The sainfoin diet group had greater(P≤0.018)C18:3n-3 and cis-9,cis-12-C18:2 proportions in the milk FA profile compared to the control diet group.Transfer efficiencies from feed to milk of C18:2,C18:3n-3 and unsaturated FA were greater(P≤0.0179)for the sainfoin diet.Based on the results,it could be concluded that replacing grass silage by sainfoin silage in dairy cow rations reduces ruminal C18:3n-3 biohydrogenation and improves milk FA profile.