Effect of supplementing algae to breeding and early gestation first calf heifers on growth and reproduction

Abstract Fat supplementation has potential to improve reproductive performance and increase pregnancy rates in cattle by increasing the energy density of the diet. However, some of the positive effects of fat seem to be influenced by the type of fatty acid fed. Docosahexaenoic acid (DHA, 22:6n-3) and eicosapentaenoic acid (EPA, 20:5n-3) are long-chain n-3 poly-unsaturated fatty acids (PUFA) that have important biological effects on reproduction through their involvement in hormone and series 3 prostaglandin synthesis. Ruminant tissues are naturally almost devoid of n-3 long-chain PUFA, specifically EPA and DHA. Algae biomass provides a consistent source of DHA and EPA that could be fed to alter hormonal profiles and improve reproduction of beef heifers. Eighty-eight Angus × Simmental heifers (427 ± 1.8 kg BW) were blocked by BW and allotted to 2 treatments (44/treatment, 4 pens/treatment, 11 heifers/pen). Control heifers were fed a diet that contained (DM basis) 52.8% mixed grass silage, 32% corn silage, and 15.2% concentrate. DHAgold™ (49% fat; 21.8% DHA; DSM Inc.) was included in the algae diet at 1.65% of DM, replacing equal parts of corn and DDGS. Diets were formulated to contain 12% CP and 0.85 Mcal/kg NEg. Heifers were fed treatment diets from 54 d prior to the breeding season through the first trimester. Follicular fluid was collected on day 47 for hormonal analysis. Artificial insemination (AI) was from d 54 to 77. Heifers that did not get pregnant to AI were removed from the study on d 109 and placed with a bull. The study ended on d 180. Data were analyzed using the MIXED procedure of SAS. During the pre-breeding period, algae heifers had lesser DMI (P=0.006) compared to control heifers. Heifers supplemented with algae had greater ADG (P=0.03) during the breeding period and BW tended (P=0.06) to be greater for algae compared to control heifers on d 98 and was greater on d 180 (P=0.03). Dominant follicle diameter and follicular estrogen concentration were unaffected by treatment (P≥0.12). Follicular insulin-like growth factor-1 was greater in algae compared to control heifers (P=0.03). First service conception rate did not differ between treatments (P=0.67); however, second service and overall conception were lesser (P≤0.03) in algae compared to control heifers. These data suggest supplementing DHA-rich algae improved growth but decreased conception rates of primiparous beef females.