EFFECTS OF THE SYNCHRONIZATION OF THE RATE OF CARBOHYDRATES AND NITROGEN RELEASE OF THE CONCENTRATE ON RUMEN FERMENTATION, PLASMA METABOLITES AND INSULIN, IN THE DRY PREGNANT GOAT

Ruminal fermentation, plasma metabolites and insulin concentrations ha ve been studied in eight dry pregnant goats, with sequential ruminal a nd blood samples taken during the 200 min after feeding, through rumin al cannulas with 400 g of four experimental concentrates + 100 ml of a rtificial saliva. The four concentrates used were isoenergetic and iso -nitrogenous, but they differed in the rate of degradation of the carb ohydrate and protein fractions: RS-RN (rapid degradation of starch (S) - rapid degradation of nitrogen (N)); RS-SN (rapid degradation of S sl ow degradation of N); SS-SN (slow degradation of S - slow degradation of N); and HDF-SN (highly digestible fibers - slow degradation of N). After 3 days of adaptation to the concentrate, the increase in total v olatile fatty acids (VFA) concentration and the decrease in pH in the rumen after feeding of the concentrate were greater in HDF-SN and lowe r for SS-SN than for the concentrates with rapidly degradable starch; the same tendencies were observed for acetate and propionate. Goats re ceiving HDF-SN concentrate had higher ruminal acetate molar proportion s and lower proportions for butyrate and other minor VFA than any othe r concentrates. Differences in the molar proportions of any VFA were n ot significant between starchy concentrates. Differences in plasma con centrations of glucose, lactate, and insulin were not significant. Rum inal ammonia concentrations were higher for RS-RN concentrate (for 180 min) and for SS-SN (for the first 45 min) than for the other concentr ates. Plasma urea concentrations reflected the ranking of ruminal ammo nia concentrations.