Immunological effects of feeding macroalgae and various vitamin E supplements in Norwegian white sheep-ewes and their offspring

Abstract

It is assumed that ewes raised in areas with long indoor winter feeding periods need to be supplemented with vitamins or other substances that help to maintain the health status of the animals. Various supplements are available on the market, but the most widely used supplemental antioxidant and vitamin E source is synthetic all-rac-α-tocopheryl acteate. The objective of the present study was to compare potential vitamin E and immune stimulant sources with synthetic vitamin E regarding bioactivity associated with immunological parameters in order to identify alternatives to synthetic vitamin E for small ruminants. Sources tested were meal of the seaweed Ascophylum nodosum and natural RRR-α-tocopheryl acetate. Forty pregnant ewes were randomly allocated to four treatment group with two replicates (5 ewes in each replicate). The treatments were supplements containing seaweed (SW: 546g Ascophylum nodosum/kg), natural vitamin E (NatE: 562.5mg RRR-α-tocopheryl acetate/kg), synthetic vitamin E (SyntE: 1125mg all-rac-α-tocopheryl acetate/kg), or no extra seaweed or vitamin E (control). The supplements were fed at an isoenergetic daily rate, on average 144g DM/ewe for SW and 114g DM/ewe for the three other treatments, from mating until start grazing season (200 days). It was assumed that 0.5mg RRR- α-tocopheryl acetate was equal to 1IU=1mg all-rac-α-tocopheryl acetate. The planned supplementation in the SyntE and NatE treatments were 140IU vitamin E/ewe daily, and the daily supplemental rate was on average for the whole experimental period 20, 146, 121 and 4IU in SW, SyntE, NatE and C treatments, respectively. The ewes and their newborn lambs were monitored throughout the entire indoor feeding period. Supplementing pregnant ewes with natural vitamin E had a positive effect on immunity against Mycobacterium sp. in the lambs, whereas supplementing ewes with seaweed interfered with the passive immunity of the offspring resulting in a mortality rate of 35%, compared with 10% in C, 5.6% in NatE and 0% in SyntE. The adaptive immunity of the lambs was not affected by seaweed supplementation. In the ewes, it seemed that supplementation with either seaweed, natural vitamin E or synthetic vitamin E had no beneficial health effects, and serum IgG concentrations were reduced in the seaweed treatment group.