| It has been reported that progesterone (P4) could regulate metabolite of environmental microorganisms. Progesterone will maintain high levels in blood serum when dairy cow become pregnant. However, information associated with about effect of P4on rumen microbes when it enter the reticulo-rumen through the wall of forestomach and saliva reproductive cycle are not well investigated. Thereby, the authors in the present study carried out following experiments:Firstly, a5×5Latin square experiment design was applied to investigate the effects of five total mixed rations (TMRs) which were formulated at same ratio of concentrate to forage (61:39) including different forage combinations on diurnal variation of P4, testosterone and ADD concentrations in rumen fluids of the lactating dairy cows. The whole experiment was completed in five periods and each period was carried out for18d, the cows were gradually adapted to the corresponding TMRs from d0to d15, and rumen fluids were intensively collected on d16, d17, and d18in each period. Over the24-h period, ruminal P4, testosterone and ADD concentration varied from5.21to6.61ng/mL,1.37to1.61ng/mL, and4.10to5.51ng/mL, respectively. The varyations were positively related to diurnal varyation in rumen total VFA concentration, with coefficiens of0.56(P<0.010),0.62(P<0.010), and0.66(P<0.001), respectively. The TMRs with different forage combinations hadt effect on ruminal concentrations of P4, testosterone and ADD (P<0.001). Compared with TMR including corn stover, the rumen P4concentration in TMR including corn stover plus ensiled corn stover; ensiled corn stover plus Chinese wild ryegrass hay; Chinese wild ryegrass(Leymus chinensis) hay plus whole corn silage; Chinese wild ryegrass hay plus whole corn silage plus alfalfa hay were increased by4.17%,5.44%,9.07%, and34.48%(P<0.001), respectively. Meanwhile, testosterone was increased by8.10%,33.33%,54.05%, and65.76%(P<0.001), respectively. ADD was increased by14.51%,49.84%,77.60%, and95.26%(P<0.001), respectively. The results indicate that increased of diary protein and energy leves may enhance ruminal P4, tstousterone and ADD concentration.Sencondly, A completely randomized design was applied to five runs of in vitro batch cultures with six P4dose rates of0(control),2,20,40,80and100ng/mL in culture fluids to investigate microbial transformation of P4. Within each run, five fermentations for each incubation interval of6,12,24,36,48and72h were arranged for each P4dosage treatment. Rumen microbes could translate1molar of P4into0.55to0.99molar testosterone, and the produced testosterone was further translated into0.39to0.82molar ADD. The transformation was related to intial P4concentration and incubation time, the high the initial P4concentration was, the quickly translated rate (P<0.001); and the longer incubated time, the more microbial transformation was (P<0.001). The results suggested that rumen should not be neglected as another important arena of P4metabolism.Thirdly, the effects of P4on microbial metabolism was investigated with high and low starch substrate in vitro batch culture.Rumen contents were collected from five lactating dairy cows. P4was added into culture fluids to achieve final concentration of0(control),2,20,40,80and100ng/mL. Compared with P4control, microbial crude protein was increased by15.43(P<0.001); dry matter degradation and rate were increased by6.57%(P=0.043) and19.91%(P<0.001), respectively. In addition, total VFA concentration was increased by11.03%(P<0.001). In the present study, molar proportion of milk and body fatty precursor were increased, whereas glucogentic VFA was decreased.The result in the present experiments showed that P4may be benefial for milk fatty synthesis.Fourthly, effects of P4on metabolite in methanogens was investigated. In this study, P4could inhibit growth of methanogens and decreased methano production (P<0.05). Meanwhile, fibrolytic enzymes were also decreased, which resulted in decrease in degradation of substrate (P<0.05) and production in total VFA (P<0.05), respectively. The result indicated that P4could inhibit metabolitic avtivity of methanogens, and the increase of P4in the rumen may be beneficial for reduce of energy loss.Fivthly, effects of P4on metabolite in pured fungi of Neocallimastix sp was investigated. In this study, P4could stimulate growth of Neocallimastix sp and increase fibrolytic enzymes activity, degradation of dry matter, NDF and ADF (P<0.05), which resulted in increases in total VFA concentration (P<0.05) and ratio of non-glucogentic to glucogentic acids, respectively. The enhanced Neocallimastix sp indicted that P4was benefial for degradation of feed and production of VFA.In brief, the results presented contribute important new knowledge about the P4transformation in rumen and effect of P4on metabolism of rumen microbes.The results showed that host may regulate microbial metabolite via its steroid hormone. |
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