Progesterone metabolism in ovariectomised non-lactating Holstein-Friesian cows treated with progesterone with two levels of feed intake

The goal of this study was to measure the effects of level of feeding and t he form of progesterone (P4) administration on the concentrations and yield s of faecal P4 metabolites relative to differences in plasma P4 concentrati ons in non-lactating cows. Six non-lactating Holstein-Friesian cows were ov ariectomised (OVX) and allocated to two groups: (i) P4 by subcutaneous inje ction (P l -s.c., n = 3); and (ii) P4 administration per vaginum (P4-p.v,, n = 3), Each cow in the P4-s.c. group was injected subcutaneously once dail y with 200 mg P4, Each cow in the P4-p.v. group had a CIDR device inserted for 11 days when it was removed and replaced with a second device for furth er 11 days. Cows were fed a ration containing lucerne (33%) and oaten (66%) chaff at a maintenance level (M) in two portions in the first period of th e study, and at a half-maintenance (1/2M) level during the second period. C hromic oxide capsules (Cr2O3) were administered twice daily to allow faecal output (FO) to be estimated, Plasma P4 and faecal P4 metabolites (FP4M; 20 -oxo-pregnanes. 20 alpha- and 20 beta -OH-pregnanes) were measured during t he treatment period. Daily FO declined after reducing the M diet to 1/2M (4 .77 versus 2.61 kg; P < 0.01), whereas plasma P4 concentrations increased i n the P4-s.c. group (4.2 versus 6.2 ng/ml; P < 0.05), but not in the P4-p.v . group (0.9 versus 1.0 ng/ml, P < 0.2). The mass of P4 released from a CID R device during each 11-day period (M or 1/2M) was similar (0.66 versus 0.6 3 g), Faecal 20-oxo-pregnanes (20-oxo-) concentrations were not affected by day or level of feeding, whereas faecal 20 alpha -OH (20 alpha-) and 20 be ta -OH (20 beta-) concentrations were increased with the 1/2M diet in the P 4-s.c. group (4.3 Versus 5.6 mug/g DM; 2.2 versus 5.6 mug/g DM, respectivel y; P < 0.05), but not in the P4-p.v. group (2.3 versus 2.7 mug/g DM; 1.7 ve rsus 3.04 mug/g DM P > 0.05). These changes in concentration only partly co mpensated for the reduced FO with the 1/2M diets as daily yields of FP4M (2 0-oxo- and 20 alpha-) were greater during the M diet period (20-oxo-: 6.9 v ersus 4.1 mug/g DM; 2.7 versus 1.5 mug/g DM, for P4-s.c, and P4-p.v. groups , respectively; P < 0.05, 20 alpha-: 19.9 versus 13.6 mug/g DM; 10.9 versus 6.6 mug/g DM for P4-s.c. and P4-p.v. groups, respectively; P < 0.05). The level of feeding and the route of P4 administration had key roles in contro lling P4 concentrations in blood and daily FP4M yield. (C) 2001 Elsevier Sc ience B.V. All rights reserved.