75 Effect of mycobacterium cell wall fraction immunostimulant on conception rates in heifer recipients

Abstract

In cattle, the average pregnancy for IVF embryos around Days 45 to 90 is 35% (Ealy et al. 2019 J. Anim. Sci. 97, 2555–2568). Among other factors, uterine contamination with pathogens from the vagina during embryo transfer may affect pregnancy success. Prophylactic antibiotic treatment for this purpose in embryo recipients is considered malpractice. An alternative to antibiotics is the use of mycobacterium cell wall fraction (MCWF) immunostimulant (Amplimune, NovaVive Inc.) against these pathogens. Therefore, the objective was to determine the effect of MCWF on conception rates in heifer recipients. For this purpose, Holstein heifers were synchronized with 2 injections of prostaglandin F2α 14 days apart and randomly allocated to 2 groups: (1) MCWF (n=292), single intramuscular injection of 5mL of Amplimune on the day of pretransfer oestrus; (2) Control (n=296): no Amplimune treatment. Embryo transfers using quality 1 frozen IVF embryos were performed in all recipients 7 to 8 days after oestrus and with a corpus luteum ≥22mm, using a double sanitary sheath technique. Data were analysed using the generalized linear mixed model (GLMM). Results are shown in Table 1. In conclusion, treatment with MCWF increased the number of recipients to be used for embryo transfer and improved the conception rate at Day 60. Importantly, MCWF treatment was more efficient for getting a recipient pregnant by Day 60 per total of synchronized recipients. Table 1. Effect of mycobacterium cell wall fraction (MCWF) on pregnancy in heifer recipients transferred frozen embryos (quality 1) Variable MCWF Control Utilisation rate 227/292a 174/296b (No. of transferred recipients/no. of synchronized recipients) (78%) (59%) Pregnancy Day 30 144/227 94/174 (No. of pregnant recipients at Day 30/no. of transferred recipients) (63%) (54%) Pregnancy Day 60 131/227a 83/174b (No. of pregnant recipients at Day 60/no. of transferred recipients) (58%) (48%) Embryo mortality 13/144 11/94 (No. of embryo loss at Day 60/no. of pregnant recipients at Day 30) (9%) (12%) Pregnancy Day 60 per total of synchronized 131/292a 83/296b (No. of pregnant recipients/no. of synchronized recipients) (45%) (28%) a,bValues with different superscripts within a row are different (P ≤ 0.05).