Effect of enhanced early life nutrition on testes miRNA transcriptome in bull calves

The aim of this study was to measure the impact of contrasting feeding regimes in the first 12 wk of life, known to impact age at puberty on the molecular control of the testes in bull calves. Holstein bull calves were designated to high (HI; n=15) or moderate (MOD; n=15) dietary groups, with diets designed to provoke growth rates of 1.0 and 0.5 kg/day, respectively. At 12 wk of age, all calves were euthanized, and testes parenchyma harvested. RNA was extracted from the testes and used for miRNAseq. Bioinformatic analysis identified 7 miRNA as differentially expressed between the HI and MOD treatment groups, with target mRNA genes invovled in pathways related to AMPK and IGF-1 signaling. In total 30 testes RNA samples were analyzed, 15 samples were derived from bull calves fed the High plane of nutrition (HI, n=15) and 15 samples were derived from the calves fed the Moderate plane of nutrition (MOD, n=15). From 2 weeks of age calves on the High-plane of nutrition received 1.5 kg of milk replacer (10 liters) per day and ad libitum concentrates, whilst the MOD group received 0.5 kg of milk replacer (4 litres) per day and 0.5 kg of concentrates. Tissue samples were collected from all calves at 12 weeks of age.