| This study evaluated the effects of sodium selenite(SS)and coated SS(CSS)addition on performance,nutrient digestibility,rumen fermentation,blood metabolites,hepatic lipid content and gene expression in Holstein cattles.The experiment is divided into two parts.Part 1: Thirty-six Holstein bulls with similar age and weight were randomly divided into one of three groups: without Se addition,with 0.3 mg kg/DM of Se from SS addition and with 0.3 mg kg/DM of Se from CSS addition,respectively.Part 2: Sixty multiparous Holstein dairy cows were fed the same basal diet containing 0.087 mg Se/kg dry matter(DM),blocked by parity,daily milk yield and days in milk and randomly assigned to one of five treatments: control,SS addition(0.3 mg Se/kg DM as SS addition)or CSS addition(0.1,0.2 and 0.3 mg Se/kg DM as CSS addition for LCSS,MCSS and HCSS,respectively).The results of part 1 showed that:(1)the overall DM intake was greater(P<0.05)for both Se supplements.During days of 31 to 60 and the overall,average daily gain(ADG)was greater(P<0.05)in CSS addition than in control and feed conversion ratio(FCR)was lower(P<0.05)in CSS addition than in control and SS addition.(2)Lower(P<0.05)ruminal p H and higher(P<0.05)total volatile fatty(VFA)concentration were observed for both Se treatments.The lower(P<0.05)acetate to propionate ratio was found in Se addition.(3)Total tract digestibility of DM,organic matter(OM)and crude protein(CP)was highest for CSS addition,followed by SS addition,and lowest for control.The greater(P<0.05)digestibility of ether extrac(EE),neutral detergent fibre(NDF)and acid detergent fibre(ADF)was found for SS and CSS addition than for control.(4)The higher(P<0.05)serum glucose,total protein,albumin,triglyceride,glutathione peroxidase(GSH-Px),total anti oxidizing capability(T-AOC)and Se concentration was observed for CSS addition than for control.Serum total cholesterol and insulin increased(P<0.05)with both SS and CSS addition.(5)Hepatic expression of peroxisome proliferators-activated receptors α(PPARα),sterol regulatory element-binding transcription factor 1(SREBP1),acetyl-Co A carboxylase(ACC),carnitine O-palmitoyltransferase 1(CPT1),stearoyl-Co A desaturase(SCD)and hydroxymethylglutaryl-Co A reductase(HMGCR)was higher(P<0.05)for CSS addition than for control.The results of part 2 showed that:(1)DM intake,yield of milk,fat corrected milk,milk fat and milk protein was higher(P<0.05)for MCSS and HCSS than for control.(2)Dietary SS or CSS addition increased(P<0.05)total tract digestibility of DM,OM,EE,NDF and ADF.Total tract digestibility of DM,CP and OM was higher(P<0.05)for MCSS and HCSS than for control,SS and LCSS.(3)Ruminal p H and ammonia N concentration were lower(P<0.05)but total VFA concentration was higher(P<0.05)for SS,MCSS and HCSS than for control and LCSS.(4)Blood glucose,total protein,albumin concentration and GSH-Px activity were greater(P<0.05)for SS,MCSS and HCSS than for control and LCSS.Blood T-AOC activity and Se content were greater(P<0.05)for SS or CSS addition than for control.The rusult indicated that supplement of CSS was more efficient in stimulating animal growth,total tract digestibility of DM,OM and CP as well as hepatic lipid metabolism gene expression compared with the SS,and 0.2 or 0.3 mg Se/kg DM as CSS addition was more efficient in improving performance,total tract nutrient digestibility and rumen fermentation compared to SS addition in dairy cows. |
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