J Anim Physiol Anim Nutr. 2020;00:1–10. wileyonlinelibrary.com/journal/jpn | 1 © 2020 Blackwell Verlag GmbH 1 | INTRODUCTION Male-factor infertility contributes significantly to the total infer- tility burden in both animals and man (Moore & Reijo-Pera, 2000; Zarei, Ashtiyani, & Vaezi, 2014). In humans, male-factor infertility is a well-known global public health problem affecting both developed and emerging societies, affecting about 10%–15% of the male pop- ulation (Polito, Conti, Tiroll, Capece, & Mouzzonigro, 2011). Studies by Eslamian, Amirjannati, Rashidkhani, Sadeghi, and Hekmatdoost (2012) and Ross et al. (2010) showed that more than 40% of global cases of infertility come from males. Several epidemiologic studies have shown that male reproductive failure has become more prev- alent during the last 4–5 decades (Moore & Reijo-Pera, 2000; Zarei et al., 2014). The prevalence varies between and within countries (Abarikwu, 2013; Nachtigall, 2006; Ombelet, Cooke, Dyer, Serour, & Devroey, 2008; Ugwuja, Ugwu, & Ejikeme, 2008). It is reported Received: 29 August 2019 | Revised: 20 February 2020 | Accepted: 8 April 2020 ORIGINAL ARTICLE A low protein maternal diet during gestation has negative effects on male fertility markers in rats – A Systematic Review and Meta-analysis Peter K. Ajuogu 1 | Mohammed A. K. Al-Aqbi 1,2 | Robert A. Hart 1 | James R. McFarlane 3 | Neil A. Smart 1 1 School of Science and Technology, University of New England, Armidale, NSW, Australia 2 College of Agriculture, Wasit University, Wasit, Iraq 3 Centre for Bioactive Discovery in Heath and Ageing, University of New England, Armidale, NSW, Australia Correspondence James R. McFarlane, School of Science & Technology, University of New England, Armidale, NSW 2351, Australia. Email: jmcfarla@une.edu.au Abstract Research indicates that some adult diseases including reproductive pathologies are programmed in utero during foetal development. In particular, maternal low dietary protein, during the most critical developmental periods of male foetal development, may have a detrimental impact on male fertility through direct and epigenetic mecha- nisms. The aim of our study was to evaluate the impact of a gestational low protein diet on fertility markers in male offspring in rats through a systematic review and meta-analysis. A systematic search using PubMed, and EMBASE databases was per- formed and two investigators independently screened the 1,703 prospective arti- cles. Eleven articles met the eligibility criteria. Outcome measures were pooled using random-effects models and expressed as mean differences (MDs) at 95% CIs for each study. The results reveal significant reduction in testis weight (MD (mean difference) -0.08 g; -0.12, -0.42; p = .0001), epididymal sperm count (MD -35.34 × 10 6 cells; -52.15, -18.53; p = .0001), number of Sertoli cells (MD -7.27 × 10 6 (-13.92, -0.62; p = .03), testosterone (T) concentration (MD -0.29 ng/ml; -0.48, -0.09; p = .004) and luteinising hormone (LH) concentration (MD of -0.24 ng/ml; -0.45, 0.04; p = .02) in comparison with controls. In contrast, follicle-stimulating hormone (FSH) concentration (MD of 0.07 ng/ml; -0.16, 0.29; p = .56) was not significantly differ- ent from controls. We conclude that low gestational dietary protein maternal intake potentially negatively impacts fertility in male progeny later in life. The mechanisms of action responsible for these phenomena remain unclear. KEYWORDS fertility, gestation, low protein diet, males, meta-analysis, rats, systematic review