The effect of diet on fatty acid composition of elongated bovine conceptuses

Abstract

Conceptus elongation is crucial for establishment of pregnancy in ruminants. During the elongation step, endometrium secreted lipids are required as a source of energy and for the remodeling and proliferation of cellular membranes (Ribeiro et al., Reprod 2016;152:R115-R126). The present study investigated the effects of diets designed to cause 15 % reduction in milk fat synthesis (milk fat depression) on fatty acid (FA) composition of elongated bovine conceptuses. The day-14 conceptuses were collected from 22 Nordic Red multiparous dairy cows during two sequential indoor housing periods. Treatments comprised a grass silage based basal diet (CO; 10 cows), basal diet supplemented with 12 g/d of rumen protected trans-10, cis-12 CLA (Lutrell Pure, BASF, Germany) (CLA; 8 cows), and grass silage based diet containing high-starch concentrate components and supplemented with 26.7 g/kg diet dry matter of sunflower oil and 13.3 g/kg diet dry matter of fish oil (MFD; 4 cows). CLA supplement was mixed in total mixed ration and administered in two equal proportions per day. Oil supplements replaced concentrate ingredients. Cows were randomly allocated to the treatments immediately after parturitions. The diets were total mixed rations with 55:45 forage:concentrate ratio on dry matter basis. In total of 45, 35 and 13 conceptuses having visible embryonic discs were used after recovery from the superovulated CO, CLA and MFD donors 130 days after parturitions, respectively. Lipids were extracted separately from each cryopreserved conceptus using a mixture of hexane and 2-propanol (3:2, vol/vol). FA were transesterified to methyl esters using methanolic sodium methoxide and analyzed with a gas chromatograph equipped with a flame ionization detector (Shingfield et al., Anim Sci 2003;77:165–179). Data were analyzed using linear mixed models with MIXED procedure in SAS 9.4. The proportions of the most abundant FA in conceptuses, cis-9 18:1 (30-32 g/100g FA, %), 16:0 (25-26 %), and 18:0 (12-14 %), did not differ between treatments (P > 0.10). In addition, total proportions of cis unsaturated FA (53-54 %) and saturated FA (43-45 %) and ratio of cis unsaturated FA to saturated FA was not different among treatments (P > 0.10). CLA had no effect on the conceptus’ FA composition compared with CO. However, MFD induced higher (P < 0.01) 22:6n-3, and lower (P < 0.05) 22:4n-6 and 22:5n-6 proportions compared with CLA and CO. The proportion of cis-12 18:1 and trans-9, cis-12 18:2, which are biohydrogenation products of 18:2n-6 found in rich amounts in sunflower oil, tended to be higher (P < 0.10) in MFD compared with other treatments. In conclusion, although CLA and MDF caused changes in lipogenesis in the mammary gland and milk fat depression, a substantial effect on the FA composition of conceptuses was not observed. However, unsaturated FA deriving from the MFD diet and metabolized in the rumen biohydrogenation processes had a specific impact on conceptus FA profiles during elongation stage.