Plane Of Prepartum Dietary Energy Density And Rumen-protected Lysine On Liver Functions,Antioxidant Status And Performance Of Dairy Cows During The Transition Period

The transition period is a key period in the lactation cycle which is characterized by physiological,metabolically and immunological change.During the transition period the nutrient demands of the dairy cows are dramatically increased and the cows unable to meet nutrient demands due to restricted feed intake which results in negative energy balance and subsequently leads to mobilization of adipose tissue.Manipulating of pre-calving dairy energy density and supplementing rumen-protected lysine is a critical factor to alleviate the harmful effect of negative energy balance and may improve overall performance.However,the combined effect of pre-partum energy density and rumen-protected lysine on biomarkers of blood metabolites of liver function and antioxidant in dairy cows during the transition period has been not explore well.The objectives of the present study were to evaluate performance,biomarkers of blood metabolites,liver function and antioxidant status in dairy cows fed pre-calving energy density and supplementing with rumen-protected lysine during the transition period.Sixty-eight third lactation Holstein dairy cows entering their 4^th lactations were randomly allocated into 4 treatments groups in a 2 x 2 factorial design with two dietary energy levels?High NE_L=1.53Mcal/kg DM vs Low NE_L=1.37Mcal/kg DM,HE vs LE?fed either with rumen-protected lysine 40 g/cows per day,bypass lysine?Blys?,or without rumen-protected lysine?control,CK?.Treatments were low energy diet with bypass lysine?LEByls?,low energy diet without bypass lysine?LECK?,high energy with bypass lysine?HEByls?and high energy without bypass lysine?HECK?.From-50 d to-21 d before expected to calving,all cows received the same diet?1.34 Mcal/kg DM?.From-21 d to calving,experimental cows were received low energy or high energy with or without bypass lysine.From calving to 21 DIM,cows were fed the same lactation diet?1.69 Mcal/kg DM?and continued supplementing with rumen-protected lysine.Rumen-protected lysine was top-dressed on the TMR once per day at a rate of 40 g lysine/cows per day by using 50 g of ground corn as a carrier from d-21 to d 21 after calving.Blood?d-21,-14,-7 and 0,3,7,14,21?and milk?d 7,14 and21?samples were collected for biomarkers analyses.The results revealed that feeding high diet to close-up cows decreased the concentrations of free fatty acid?P=0.03?and?-hydroxybutyrate levels?P<0.01?in pre-partum cows but did not affect FFA and BHBA levels in post-partum cows.Addition of rumen-protected lysine increased pre and post-partum dry matter intake,and decreased free fatty acid and?-hydroxybutyrate concentrations in postpartum cows?P<0.01?.Neither energy nor rumen-protected lysine supplementation nor their interaction impacted milk yield,fat nor lactose yields but their interaction increased prepartum DMI?P<0.01?and reduced milk urea nitrogen levels during the postpartum period?P=0.03?.Prepartum high energy diet increased insulin levels?P=0.003?and albumin concentrations?P=0.02?,decreased blood urea nitrogen levels?P<0.01?,total bilirubin concentrations?P<0.01?and IGF-1 concentrations in pre and postpartum cows?P<0.01?.The interaction between pre-calving high energy diet and RPL tended to increase prepartum albumin levels?P=0.08?,decreased AST levels?P=0.04?and tended to decrease IGF-1concentrations in postpartum cows?P=0.08?.Feeding high energy diet during close-up period significantly lowered blood serum MDA concentrations?P<0.01?,tended to increase serum GSH-Px activity?P=0.06?and SOD activities?P=0.09?in prepartum cows.Pre and postpartum RPL supplementation during the transition period reduced the concentrations of MDA in prepartum cows?P=0.03?and decreased MDA levels in postpartum cows?P<0.01?,increased T-AOC in postpartum cows?P=0.003?,and increased serum GSH-Px activity in prepartum cows?P=0.008?.Interaction of pre-calving high energy diet and rumen-protected lysine increased serum SOD activity in prepartum cows?P<0.01?,tended to increase serum GSH-Px activity in postpartum cows?P=0.07?.Collectively,pre-calving high energy diet decreased free fatty acids,?-hydroxybutyrate levels,milk urea nitrogen,blood urea nitrogen,total bilirubin,IGF-1,MDA concentrations,and increased insulin,albumin concentrations in dairy cows during the transition period.Supplementation of rumen-protected lysine increased dry matter intake,GSH-Px activity,T-AOC,and decreased free fatty acid,?-hydroxybutyrate,and MDA levels in transition cows.Interaction between high energy diet and rumen-protected lysine increased DMI,SOD activity,and decreased milk urea nitrogen levels,AST levels in dairy cows during the transition period.This implied that addition of rumen-protected lysine to prepartum high energy diet substantially decreased energy metabolites,improve the antioxidant status,reduce the susceptibility of transition cows to production diseases by favoring liver functions during the transition period.Further study is needed to explore the combined effect of rumen-protected lysine and prepartum energy density on immune response during the transition period.