Effects Of Rumen-protected Glucose On Reproductive Hormones Secretion And Performance During Transition Period In Dairy Cows

This experiment was conducted to investigate the effects of rumen-protected glucose?RPG?on dry matter intake?DMI?,milk yield,milk composition,rumen fermentation,blood biochemical parameters and reproductive performance of transition cows,and to provide a theoretical basis and reference for the better use of the production performance of dairy cows.Twelve?12?Chinese Holstein dairy cows in transition period with similar calving date,parity and average milk production were randomly divided into 2 groups,the control group and trial group,with 6 replicates per group and 1 cow in each replicate.The cows in the control group were fed 90g rumen-protected fat each day,and the cows in the trial group were fed 200g RPG?comprising 110g glucose+90g rumen-protected fat?.The experiment lasted for 35days?2 weeks before parturition to three weeks after?.During the experimental period,the cow's feed intake and milk yield were measured and recorded,blood samples,milk samples and rumen fluid samples were collected to analyze,calf birth weight,the rate of dystocia,incidence of retained placenta and organ indexes were also recorded.The results showed as follows:1.There was no significant effect of RPG on the DMI of dairy cows?P>0.05?.However,daily DMI of the control group was 50g/d,240g/d,and 50g/d higher than the trial group at the first,second,and third week of the experimental period respectively.The beginning of third week coincided with the parturition and in the fourth week,that is,two weeks postpartum,the DMI of trial group was higher than the control group by 490g/d.2.The RPG supplementation had no significant effect on the average daily milk yield and milk composition of dairy cows?P>0.05?.the average daily milk yield in the control group was 0.18kg higher than that in the trial group from parturition to postpartum 7th day?P>0.05?;the average daily milk yield in the trial group was1.28kg higher than that in the control group from postpartum 7th day to postpartum14th day?P>0.05?;the milk fat content in the control group was 0.29%higher than that in the trial group?P>0.05?;the milk DM,fat-free DM,protein and lactose contents in the trial group was 0.01%,0.19%,0.45%and 0.09%higher than that in the control group?P>0.05?respectively;but the milk urea nitrogen content in the control group was 0.96%higher than that in the trial group?P>0.05?;the somatic cell count in the milk of cows in trial groups was reduced by 1.95×10⁵/mL and1.22×10⁵/mL compared to the control group at 2^nd and 4^th day postpartum respectively?P<0.05?.3.The RPG supplementation in the diet significantly increase rumen fluid total volatile fatty acid?VFA?production?P<0.05?.RPG significantly increased butyrate and valerate concentration in the trial group but reduced the concentration of rumen fluid propionic?P<0.05?;RPG had no significant effects on the proportion of VFA and the acetic to propionic ration in the rumen fluid?P>0.05?.Furthermore,RPG had no significant effect on rumen fluid dissolved CH4?dCH4?and dissolved H2?dH2??P>0.05?.4.Adding RPG in the diet significantly decrease the serum?-hydroxybutyric acid?BHBA?level?P<0.05?;Serum Nonesterified fatty acids?NEFA?level was also reduced with RPG but no significantly different from control group?P=0.073?,and the RPG had no significant effects on serum glucose level?P>0.05?.5.Adding RPG in the diet could significant influence serum E₂?FSH?LH?P₄?IGF-I levels.the serum E_2,FSH,LH concentrations were significantly higher in the trial group than the control group at day 7 and 14 postpartum?P<0.05?.Also,the serum P₄ and IGF-I concentration in the trial group were significantly higher than in the control group on the 14 day postpartum?P<0.05?.6.Adding RPG in the diet of transition dairy cows had no significance on calf birth weight,the rate of dystocia,incidence of retained placenta,heart,liver,spleen,lung,and other organ indexes.According to the above results,it can be concluded that the RPG can alleviate the negative energy balance,improve secretion of reproductive hormones and performance of transition dairy cows.