Early Postnatal Methionine Supplementation in Ewe Lambs: Long-Term Effects on Performance, Milk Fatty Acid Profile, Metabolism, Gut Microbiome, and Epigenetic Regulation
Nutritional strategies that supply methyl donors such as methionine in the early postnatal period of lambs could program feed efficiency and milk production during adult life due to persistent changes in epigenetic marks. To test this hypothesis, 26 newborn ewe lambs from the same flock were stratified and distributed into two groups with equal body weight distribution. The control group (F0-CTRL, n=13) was fed ad libitum with a milk replacer. In contrast, the second group (n=13) received the same milk replacer supplemented with 1 g methionine/kg DM based on a milk replacer. After weaning, all animals were raised the same way and fed ad libitum with a complete pelleted diet formulated according to nutrient requirements. At 45 days of age, blood was collected from the jugular vein for DNA isolation and DNA methylation was analyzed by Reduced Representation Bisulfite Sequencing (RRBS) in ten animals [5 ewe lambs (F0-MET) vs. 5 ewe lambs (F0-CTRL), corresponding to 5 twin births, of which one lamb was assigned to each group]. The main results show that CPT1B, a gene involved in fatty acid catabolism, was differentially methylated in F0-MET lambs. In addition, these animals presented increased insulin and non-esterified fatty acids levels, while cholesterol levels were reduced. No differences in feed efficiency were observed during the replacement or lactation phase. Still the fatty acid (FA) profile of the milk showed increased levels of long-chain fatty acids, n-3 and n-6 polyunsaturated fatty acids. All these results suggest that methionine supplementation in early life can modify ewes' milk fatty acid profile  without compromising feed efficiency. However, further studies need to clarify whether this effect is passed on to the offspring (F1) through permanent epigenetic marks in the germline.