Effect Of Rearing Systems On Growth Development And Hepatic Gene Expression In Lambs

This experiment was conducted to study the effects of different rearing systems on growth development and hepatic gene expression in twin lambs. Twenty-four pairs of newborn Hu male twin lambs were used and either lamb of a pair was randomly assigned to two treatments: artificially reared(AR) with a milk replacer or ewe reared(ER) as control. The trial lasted 90 days, live weights of lambs were recorded and blood samples were collected at birth and every other ten days thereafter. Two digestion trials were undertaken during days 45~55 and 75~85 with four pairs of lambs in each period. When the lambs reached 60 and 90 days old, three pairs at each time point were chosen for slaughter trial. Hepatic gene expression were analyzed via microarray and bioinformatics method.In experiment 1, effects on growth, nutrient utilization and serum indices, the results showed that the weights of AR lambs were significantly lower than that of ER lambs at day 20, 30 and 40(P<0.05), but the differences were narrowed down as aging and there were no significant differences after day 50. Average daily gain(ADG) of AR lambs was lower during day 10~20(P<0.05) and higher during day 40~50(P<0.05), while there was no differences in other time periods, nor was the overall ADG. On day 60, the relative weight of the rumen weight to total complex stomach weight(TCSW) in AR group was higher than that of ER group(P<0.05) whereas the relative weight of the omasum and abomasum were lower(P<0.05). On day 90, no significant differences were observed in the fresh or relative weight, only to find slightly higher of fresh weight of rumen in AR group(P>0.05). The relative weight of the small intestine to shrunk body weight(SBW) was higher in AR group than that in ER group(P<0.05). There was no differences in the fresh or relative weight to SBW for internal organs between groups(P>0.05), nor were the nutrient utilization(P>0.05) or the serum indices(P>0.05). Interestingly, the serum indices between groups manifested similar trend.In experiment 2, effects on hepatic gene expression, we found many differential expressed genes because of different rearing systems. They were OR1E2, S1PR3, KMO, APOA4, ORM2, HTR4, FADS1 in both 60 AR vs 60 ER and 90 AR vs 90 ER and ACO1, HBA1, MFSD2 A, CYSJ, LOC785954, FCN, GRB2, LOC100037663, ORM2, RXRG, LOC100602447, SQLE, HSD17B2, CYP4F2, INHBE, EAAT2 in both 60 AR vs 90 AR and 60 ER vs 90 ER, among which 4 unknown genes were identified with the probe ID 14780690, 14815720, 14845504, 14854080. ORM2 was differently expressed among all the comparisons. Those DEGs involved in the amino metabolism, small molecular metabolism, enzyme activities and immune response of GO processes and amino metabolism, lipid metabolism hormone biosynthesis and p53 signaling transductions of KEGG pathways.In summary, artificial rearing system of early weaned lambs fed with milk replacer could achieve the same feeding effects as lambs fed with mother milk. Different rearing systems altered hepatic gene expression. The pathways and functions those DEGs involved shed lights on the regulational role of nutrients on growth development of lambs. Our study lay the foundation for underlying the mechanisms of early cultivation of lambs.