48 P. Razdan et al. efﬁcient of variation for one control sample was 11% (2 nmol/l). The average detection limit of the assay was 0.2 nmol/l. I n s u l i n . Plasma samples were analysed by ra- dioimmunoassay for insulin determination (In- sulin RIA 100, Pharmacia Diagnostics AB, Uppsala, Sweden) (Mburu et al. 1998). Serial dilutions of porcine plasma with high insulin concentrations produced inhibition curves par- allel to the standard curve. Intra-assay coefﬁ- cients of variation were 7.4% (0.93 µU/ml), 4.9% (2.01 µU/ml) and 5.8% (5.80 µU/ml), for low, medium and high assay controls, respec- tively. The average detection limit of the assay was 1 µU/ml. Blood serum metabolite assays Tr i g ly c e r i d e s . Blood serum triglycerides were analysed with an enzymatic colorimetric method (GP/PAP method) with a Cobas MIRA analyzer (Roche, Basel, Switzerland) using re- agents from the same company (UNIMATE 5 TRIG). The intra-assay coefﬁcient of variation was 1.2% (1.4 mmol/l) and the inter-assay coef- ﬁcient of variation was 4% (1.4 mmol/l). F r e e f a t t y a c i d s . Blood serum free fatty ac- ids were analysed on Cobas FARA (Roche) with reagents from W (NEFA C, Wako chem- ichals GmbH, Neuss, Germany). The intra-as- say coefﬁcients of variation for 2 quality con- trol samples were 3% (0.4 mmol/l) and 2% (0.8 mmol/l) and the corresponding inter-assay co- efﬁcients were 5.7% and 6.4%, respectively. G l u c o s e . Serum levels of glucose were deter- mined on Cobas MIRA (Roche with an enzy- matic method (HK/G6P-DH method). Standar- dised reagent kits (Unimate 5 Gluk HK, Roche) were used. The intra-assay coefﬁcient of varia- tion was 1.3% (7.5 mmol/l) and the inter-assay coefﬁcient was 3.5% (5.5 mmol/l). Statistical analysis The statistical analyses were carried out using Acta vet. scand. vol. 42 no. 1, 2001 SAS- procedures (SAS Institute Inc. 1989). The t-test in the MEANS procedure was used to make comparisons between the groups of mean values for the ovulation rate, ova recovery rate, time elapsed from the time of ovulation to onset of fasting and time of slaughter. Fisher´s Exact test (2-tail) was used to compare the number of ova recovered in the upper part of the isthmus (segments 1 and 2) with the number of ova found in the lower part of the genital tract (seg- ment 3 and uterine horn) within each group. To make between-group comparisons with regard to degree of transit of ova at the time of slaugh- ter, the total number of ova detected in each segment (the sum total of both sides of the ovi- ducts in each sow) was multiplied with Factor 1-4, depending on which of the 4 segments con- tained the ova (proximal isthmus=1, middle isthmus=2, distal isthmus=3, uterus=4) (Hultén et al. 2000). The sum was divided by the total number of ova recovered for each sow giving average number of segments the ova had cov- ered at the time of slaughter within each sow. The data was analysed by the GLM procedure and the model included treatment and interval, from ovulation to slaughter. In the 2 groups, overall mean values for the period before and after start of treatment respectively, were calcu- lated for glucose, insulin, free fatty acids and triglycerides and between group comparison was performed using the t-test. Plasma was col- lected on 6 occasions for progesterone and prostaglandin F2α-metabolite analyses during ﬁve 12 hour periods, one period before and 4 periods after time 0. For progesterone, time 0 was set as the time of ovulation because of the physiological rise in P4, which is expected after ovulation, whereas for prostaglandin F2α-me- tabolite time 0 was the start of food deprivation. The observations at time 0 were included in the ﬁrst period (-11 to 0 h). Mean values were cal- culated for each 12 hour period and these val- ues were analyzed by the GLM-procedure in