95 Bulls fed a high-gain diet produce semen that results in fewer blastocysts following in vitro fertilisation and embryo culture
Z. K. Seekford A , M. J. Dickson A , D. B. Davis B , L. Gonçlaves C , S. Burato D , M. P. Holton B , J. Gordon E , K. G. Pohler F , G. C. Lamb F , T. D. Pringle B , R. L. Stewart B , M. S. Ferrer B , J. J. Bromfield A and P. L. P. Fontes BA University of Florida, Department of Animal Sciences, Gainesville, FL, USA
B The University of Georgia, Department of Animal and Dairy Science, Athens, GA, USA
C Federal University of Uberlandia, Uberlandia, Minas Gerais, Brazil
D Sao Paulo State University, Botucatu, Sao Paulo, Brazil
E The University of Georgia, College of Veterinary Medicine, Athens, GA, USA
F Department of Animal Science, Texas A&M University, College Station, TX, USA
Reproduction, Fertility and Development 34(2) 284-285 https://doi.org/10.1071/RDv34n2Ab95
Published: 7 December 2021
© 2022 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of the IETS
Increased paternal adiposity or nutrient supply reduces the physiological potency of spermatozoa and decreases embryonic competency in both humans and rodents. In parallel, bulls used for commercial breeding are commonly fed highly anabolic diets to increase their body weight (BW) before the breeding season. The objective of this study was to determine developmental potential of semen collected from bulls fed a high-gain diet. We hypothesised that semen collected from bulls fed a high-gain diet would have a reduced capacity to develop embryos following IVF and embryo culture. Eight mature beef bulls were blocked by their initial BW (948 ± 28 kg) and fed the same diet (net energy for maintenance (NEm) = 2.10, net energy for gain (NEg) = 1.44, crude protein (CP) = 14.1%, neutral detergent fiber (NDF) = 16.6%, dry matter basis) for 67 days at either a maintenance level (0.5% BW per day) or an elevated rate of gain (1.25% BW per day). Semen was collected by electroejaculation on Day 67 and subjected to computer-assisted sperm analysis and frozen using commercial extender and a programmable freezer. The semen from each bull was cryopreserved and used for IVF followed by embryo culture. Fertilisation and culture were performed with BO-IVF and BO-IVC media (IVF Bioscience) and utilised a final sperm concentration of 2.0 × 106 spermatozoa mL−1. A total of 2227 cumulus-oocyte complexes were used for IVF and embryo culture for 7 days in four replicates (average 100 ± oocytes/bull/replicate). Oocyte cleavage (Day 3) and blastocyst development (Day 7) were evaluated by individuals blinded to treatment. Data were analysed by generalised linear model using repeated measures, and embryo development was analysed using logistic regression binomial distribution. Data are presented as mean ± s.e.m. Bulls fed a high rate of gain increased BW by 142 ± 39.3 kg (P = 0.02) and rump fat thickness by 1.22 ± 0.447 cm (P = 0.01) compared with bulls fed a maintenance diet. Feeding bulls a high rate of gain reduced oocyte cleavage (69.9% ± 2.5 vs. 65.0% ± 2.7; P < 0.04), reduced the percentage of oocytes to reach blastocyst (16.7% ± 2.9 vs. 11.5% ± 2.1; P < 0.01), and reduced the percentage of cleaved oocytes to reach blastocyst (24.1% ± 3.8 vs. 11.5% ± 2.1; P < 0.01). In conclusion, feeding bulls a high rate of gain diet increased adiposity and reduced the fertilisation capacity of sperm and the ability of embryos to develop to the blastocyst stage. Mechanisms by which increased body fat impairs fertility remain to be elucidated in the bull but might involve altered epigenetic machinery or oxidative damage to sperm cells, endocrine disruptions during spermatogenesis, and thermal dysregulation of the testes.
