PSIX-24 - Higher glucose transporter SLC2A1 expression in milk somatic cells as a compensatory milk production strategy in young prolific Pelibuey ewes

Abstract: The number of lambs per birth expressed as prolificacy is a key trait that determines productive efficiency in sheep. However, the optimal litter size depends on the production system, since the ewes' milk production impacts in the postnatal development of lambs. Milk yield in turn, is related to the expression of the SLC2A1 gene in mammary epithelial cells. This gene encodes the solute carrier/glucose transporter 1 and is upregulated in peak/mid lactation. In order to assess the productive efficiency of twinning ewes in regard to SLC2A1 expression, the objective of this study was to measure the mRNA levels of SLC2A1 in milk somatic cells (MSC) of Pelibuey ewes lambing twins. Eight healthy ewes, three primiparous and five multiparous, were selected to quantify and compare levels of SLC2A1 mRNA. Management was under feedlot conditions, and the milk samples were taken between 16 and 20 d post-lambing. Total RNA was purified from MSC and SLC2A1 mRNA levels were measured by RT-qPCR, relative to β-actin as reference gene. The total birth weight (TBW) and weaning weight of their lambs were recorded, calculating the total weight of lamb weaned (TWLW). TBW, TWLW and relative expression of SLC2A1 were analyzed with PROC GLM of SAS, whereas the Pearson correlation coefficient between TWLW and relative expression of SLC2A1 was calculated using PROC CORR of SAS. Although there was no statistical difference in TBW (p = 0.13) and TWLW (p = 0.38) between lambing groups, a numerical difference was observed both in TBW (5.7 ± 0.54 and 6.9 ± 0.42) and in TWLW (21.5 ± 3.94 and 26.2 ± 3.05) for primiparous and multiparous, respectively. The levels of SLC2A1 mRNA were 3.1-fold change (p = 0.0005) higher in MSC of primiparous ewes than in the multiparous ones. In multiparous ewes a positive correlation, r = 0.96 (p = 0.01) was found between TWLW and relative expression of SLC2A1. It is concluded that higher relative expression of SLC2A1 in young prolific ewes could be a compensatory mechanism to produce more milk to feed their lambs, even with a smaller udder volume. Such finding gives way for further research on the subject.