Effect of supplementation with different fat sources on the mechanisms involved in reproductive performance in lactating dairy cattle

Abstract

Supplementary fat positively influences reproductive performance in dairy cattle, although the mechanisms involved are not clearly defined. Our objective was to determine the effects of four different fat supplements on follicle development, plasma steroid hormone concentrations and prostaglandin (PG) synthesis in lactating dairy cattle. Forty-eight early lactation Holstein-Friesian cows (21 primiparous, 27 multiparous) were used in a completely randomized block design. Cows were fed the same basal TMR diet and received one of four fat supplements: (i) palmitic acid (18:0 fatty acid; Control), (ii) flaxseed (rich in 18:3 n-3 fatty acid; Flax), (iii) conjugated linoleic acid (a mixture of cis-9, trans-11 and trans-10, cis-12 isomers; CLA), and (iv) fish oil (rich in 20:5 and 22:6 n-3 fatty acids; FO). All lipid supplements were formulated to be isolipidic; palmitic acid was added as necessary to provide a total lipid supplement intake of 500 g/day. Cows were synchronized to be in estrus on Day 15 of dietary treatment. All antral follicles were counted, and dominant follicles, subordinate follicles and corpora lutea were measured daily via transrectal ovarian ultrasonography for one complete estrous cycle. Blood samples were collected daily, and selected samples were analyzed for progesterone, estradiol, insulin-like growth factor-1, insulin, cholesterol and non-esterified fatty acids. Estrus was synchronized a second time, and liver and endometrial biopsies were collected on Day 7 of the estrous cycle. Gene expression was evaluated for a number of genes involved in prostaglandin synthesis (endometrium) and fatty acid uptake and utilization (liver). Fat supplementation had little effect on follicle development. Cows receiving supplementary n-3 fatty acids had lesser plasma progesterone (P4) and smaller corpora lutea than cows receiving the CLA or Control supplements. Effects of fat supplementation on the endometrial expression of genes involved in PG synthesis were minor. Hepatic expression of SREBF1, ASCL1 and FABP1 was reduced by FO supplementation. Reduced plasma P4 in n-3 supplemented cows may lead to a suboptimal uterine environment for embryo development and hence reduced fertility compared to cows receiving the control or CLA supplements.

Supplementation of dairy cows with docosahexaenoic acid did not affect ovarian activity

“…The size of CL on D11 of the oestrous cycle tended to be larger (on D32 of the experimental period significant difference, on D53 closely nonsignificant), this is in agreement with the study of Bilby et al (2006a) but not with others (Childs et al 2008a;Hutchinson et al 2012). The tendency for higher cholesterol concentrations determined in all terms in our study is in agreement with previous studies (Bilby et al 2006a;Childs et al 2008a;Hutchinson et al 2012), however, nonsignificant. It could be due to the total amount of fat supplement fed to the animals in our study.…”

“…The size of preovulatory follicles was not different between the groups, this is in agreement with the studies of Childs et al (2008a) and Hutchinson et al (2012), but not with that of Bilby et al (2006a). The size of CL on D11 of the oestrous cycle tended to be larger (on D32 of the experimental period significant difference, on D53 closely nonsignificant), this is in agreement with the study of Bilby et al (2006a) but not with others (Childs et al 2008a;Hutchinson et al 2012). The tendency for higher cholesterol concentrations determined in all terms in our study is in agreement with previous studies (Bilby et al 2006a;Childs et al 2008a;Hutchinson et al 2012), however, nonsignificant.…”

“…However, data from some studies describing biological action of PUFAs on reproduction in dairy cattle are not always consistent with earlier work (Hutchinson et al 2012).…”

“…In another study, feeding increasing doses of fish meal and FO containing EPA and DHA did not affect plasma progesterone concentrations in lactating dairy cows (Mattos et al 2002). In contrast to the study by Hutchinson et al (2012), the effect of diets enriched in unsaturated FA was shown to enhance early embryonic development in another study (Thangavelu et al 2007). Progesterone and oestradiol concentrations, as well as follicle growth rate and CL diameter were similar for a group fed FO or control (Childs et al 2008a).…”

“…Similarly, in a more recent study (Hutchinson et al 2012) diverse effects of the fat supplements on reproductive parameters were described. Peak plasma oestradiol concentrations were higher in cows receiving flaxseed in comparison to cows receiving FO.…”