57 DIETARY CLA SUPPLEMENTATION AFFECTS LUTEAL GENE EXPRESSION AND PERIPHERAL BLOOD PROGESTERONE CONCENTRATION IN CATTLE

Abstract

Shortly after parturition the metabolic situation of high-yielding dairy cows is often dominated by a negative energy balance. These effects affect the whole animal and may especially be detected in the reproductive tract, where they result in reduced fertility. An oral supplementation with dietary fats is often used to counteract by reducing milk fat content and, thus, supplying the individual animal with an increased amount of energy. The focus of the present study was to analyse the effects of an oral supplementation with conjugated linoleic acids (CLA) on corpus luteum (CL) function. Healthy Holstein-Friesian cows and heifers were randomly allocated to 2 treatment groups (Group 1: 50 g of CLA day^–1 per animal, 2 heifers, 6 cows; Group 2: 100 g of CLA day^–1 per animal, 2 heifers, 6 cows) and 1 control group (Ctl; 0 g of CLA day^–1 per animal, 3 heifers, 4 cows). Feeding of the supplement began shortly after calving. After calving, all animals were subjected to a standard synchronisation protocol and experienced AI on Day 59 ± 3. Following AI, transvaginal biopsies of the corpus luteum were obtained of pregnant (Group I: n = 4; Group II: n = 4; Ctl: n = 4) and nonpregnant (Group I: n = 4; Group II: n = 4; Ctl: n = 3) animals on Days 6, 13 and 20 post-AI. Animals deemed pregnant on Day 28 were again biopsied on Day 42. Additionally, blood samples were taken from the vena sacralis mediana at the time of each biopsy. The biopsies were analysed regarding the relative abundance of 8 gene transcripts (VEGF, ECE1, PLA2G4A, PTGS2, PTGFR, PPARG, STAR and HSD3B1) via RT-qPCR. Blood samples were analysed for their concentration of progesterone through a radioimmunoassay (RIA). Statistical analysis for both datasets was performed via a 3-way ANOVA with adjoining Tukey test. The expression of 7 of these genes was affected by 1, 2, or all 3 of the following factors: day of cycle (VEGF, ECE1, PLA2G4A, PTGFR, STAR and HSD3B1), pregnancy status (ECE1, PTGFR and HSD3B1) and CLA supplementation (ECE1, PTGS2, PTGFR, STAR and HSD3B1). The effects of the CLA supplementation could be seen as a down-regulation in the mentioned gene transcripts. Progesterone concentrations differed significantly in dependency of the pregnancy status (significantly higher in pregnant vs nonpregnant individuals) of the animals, as well as during the days of the oestrous cycle (physiological progesterone curve with highest values on Day 13 of these samples). An effect of the oral supplementation with CLA could be detected during the early luteal phase (Day 6) where animals that had received 100 g of CLA day^–1 had a significantly lower blood progesterone concentration than those receiving 50 g of CLA day^–1 or no CLA. In conclusion, dietary CLA supplementation has an effect on luteal gene expression and functionality.

The authors thank the DFG (German Research Foundation) for their financial support (PAK286/1; WR154/1-1).