Presentations

According to our working hypothesis based on literature data, in peri-parturient dairy cows conjugated linoleic acid (CLA) supplementation influences the degree of negative energy balance, the function of the GH-IGF1 axis, and perhaps also the degree of whole-body insulin sensitivity. Due to these positive effects CLA supplemented cows 1) can ovulate, and their cyclic ovarian activity can resume sooner after calving. 2) They may produce more competent oocyte, 3) show more intensive luteinisation, and therefore they may have better fertility at the first postpartum artificial insemination (AI). These positive effects may be more obvious, if the CLA supplementation is started 2 to 3 weeks before calving.

High producing, multiparous, healthy Holstein Friesian cows were allotted into 3 treatment groups (n=20 in each) with regard to similar distribution of age, parity, and milk production in the preceding lactation. Daily diet of CLA1 group was supplemented with 70g of Lutrell Pure (100 g/kg of cis-9 trans-11 + 100 g/kg of trans-10 cis-12 CLA isomers) from 21 days before calving until 10 days after AI. The CLA2 group was supplemented with 70g of Lutrell Pure only from calving until 10 days post AI. The diets of both CLA1 and CLA2 groups were changed to the diet of control group from d 10 after insemination until pregnancy check. Control group was not supplemented with any CLA however its diet was isocaloric, isonitrogenous and isolipidic with the experimental groups. Starting on day 49 to 63 postpartum animals were synchronised (Pre-Synch) than inseminated at fix time.

Dry matter intake, milk production, plasma metabolits (NEFA, BHB, urea-N, total cholesterol, glucose) and metabolic hormones (IGF-1, insulin, leptin, T3, T4) were measured to follow-up energy balance weekly before and after parturition until week 5 postpartum, furthermore on the day before AI. Ovarian activity was monitored by assaying milk progesterone (P4). Pregnancy was checked on day 33-35 after AI by transrectal ultrasonography completed with determination of pregnancy-specific protein B in blood. All cows returning to estrus following fix AI were inseminated again, and pregnancy was checked as usually in the herd.

The time of the first postpartum ovulation did not differ between groups. At the same time re-conception in both supplemented groups came forward compared to control (p = 0.04). P4 rise in CLA supplemented animals tended to be higher between days 3 to 6 following ovulation, however it was statistically non-significant. Unfortunately due to the low number of animals incidence of embryo mortality could not be evaluated.

Conclusion: CLA supplementation did not enhance the resumption of postpartum ovarian cyclicity. However in the periparturient period CLA had beneficial effect on the intensity of luteinisation which may increase the survival rate of the conceptus and thus shorten transition period.