In cattle, early embryonic loss during the first two to three weeks after fertilisation is recognised as the major cause of reproductive failure, with consequent significant impacts on business performance of beef and dairy farms. Inadequate endometrial receptivity is considered an important cause of early embryonic mortality in cattle. A pilot experiment was conducted to compare the outcome of performing different endometrial sampling procedures in tropically adapted (Bos indicus x Bos taurus) heifers, and to select the most suitable method to collect samples for investigation of endometrial gene expression. Endometrial biopsy (EB) using a biopsy device with a diameter similar to an artificial insemination gun (10366L Karl Storz®, Germany) was found to be the most reliable method of collecting endometrial samples in these heifers, with the samples recovered yielding a mean concentration of RNA of 72.9 ±39.3 ng/µl and mean RNA integrity number (RIN) of 7.3 ±1.1.To assess the likely safety of conducting EB in cattle a systematic review of published information assessing the impact of EB on subsequent pregnancy rates was conducted. Using the Preferred Reporting Items for Systematic reviews and Meta-Analysis (PRISMA) protocol, online searches identified 1164 possible studies. After applying the exclusion criteria, six studies allowed the comparison of pregnancy rates between sampled (n= 1,208) and non-sampled cows (n=2,393). The results showed that EB can be performed before breeding without adversely affecting the likelihood of cows becoming pregnant.A major objective of the research was to determine whether EB and evaluation of endometrial gene expression could be used to identify tropically adapted embryo transfer (ET) recipients more likely to become pregnant. Three potential EB scenarios were investigated, 1) EB on Day 7 of the oestrous cycle prior to the cycle when ET would be performed, 2) EB on Day 4 of the oestrous cycle in which ET would be performed i.e. EB 3 days before ET, and 3) EB on the same day when ET would be performed.The first study assessed the morphological and inflammatory changes induced by endometrial biopsy. Pre-synchronised heifers underwent EB from the horn ipsilateral to the corpus luteum (CL) either at Day 7 of the previous cycle (Group 1 n=10) followed by administration of a luteolytic dose of prostaglandin F2α or at Day 4 (Group 2, n=7) of the present cycle. All heifers were slaughtered on Day 7 of the present cycle. The site of EB was visually evident in 40% (4/10) of Group 1 and 42% (3/7) of Group 2 heifers. Histological assessment revealed no evidence of changes indicative of endometritis in either the biopsied or non-biopsied horns in both groups. The histological iii changes observed included mild mononuclear infiltration of the epithelium and mild vascular changes associated with haemorrhage and congestion.Initial investigation of the endometrial expression of the pro-inflammatory cytokine IL1β and wound healing cytokine TGFβ genes found no significant difference betwe...