Relevance of antioxidant vitamin supplementation for improvement of milk production, milk quality and energy status of lactating ewes

Abstract

This study aimed to determine the potential benefits of vitamin A or C supplementation for lactating ewes in terms of milk production, milk quality and energy status. Late-stage pregnant Rahmani ewes received an oral dose of either 50.000 IU of vitamin A (n = 8) or 3 g of vitamin C daily (n = 8) and were compared with ewes that did not receive any vitamin dose (control, n = 7). The milk yield was determined, and milk samples were collected and analysed for milk compositions and fatty acid (FA) profiles. The energy status of the ewes was evaluated by estimating the milk energy value (MEV), net energy required for lactation (NEL) and energy balance calculated from milk components (EBM). The antioxidant activity of the milk was evaluated by determining the 1,1-diphenyl-2-picrylhydrazyl (DPPH)scavenging activity and the concentration of malondialdehyde (MDA, lipid peroxidation index). The quality of milk FAs was determined by estimating the atherogenicity index (AI) and the concentration of hypercholesterolaemic FAs (C12:0 + C14:0 + C16:0). The results revealed that vitamin A treatment resulted in the greatest milk yield (P = 0.073), energy-corrected milk yield (ECM, P ≤ 0.05), fat yield (P = 0.034) and NEL (P = 0.049); however, the MEV and EBM were not affected by the treatment. Both vitamins increased (P < 0.05) the concentrations of C13:0, C17:0, C18:1 and total mono-unsaturated fatty acids (MUFAs). The antioxidant activity of the milk produced by ewes that received either vitamin A or C was significantly greater than that of the milk produced by control ewes, as indicated by the increased DPPH scavenging activity and decreased MDA concentration. The FA quality was improved in both vitamin-treated ewes compared to the control ewes, as both the AI and hypercholesterolaemic FA levels decreased. In summary, administration of vitamin A or C to lactating ewes from late pregnancy to mid-lactation improved milk quality by increasing the concentrations of healthy FAs and the antioxidant capacity of the milk. In the context of animal productivity, vitamin A should be given priority due to the specific potential of this vitamin to improve milk yield and energy utilization compared to vitamin C.