Effect of supplementation with n-3 polyunsaturated fatty acids and/or β-glucans on performance, feeding behaviour and immune status of Holstein Friesian bull calves during the pre- and post-weaning periods

Background: Previous research in both calves and other species has suggested n-3 polyunsaturated fatty acids (PUFA) and beta-glucans may have positive effects on immune function. This experiment measured performance, behaviour, metabolite and immunological responses to pre-weaning supplementation of dairy bull calves with n-3 PUFA in the form of fish oil and beta-glucans derived from seaweed extract. 44 Holstein Friesian bull calves, aged 13.7 +/- 2.5 d and weighing 48.0 +/- 5.8 kg were artificially reared using an electronic feeding system. Each calf was offered 5 L (120 g/L) per day of milk replacer (MR) and assigned to one of four treatments included in the MR, (1) Control (CON); (2) 40 g n-3 PUFA per day (FO); (3) 1 g beta-glucans per day (GL) and (4) 40 g n-3 PUFA per day & 1 g/d beta-glucans (FOGL) in a 2 x 2 factorial design. Milk replacer and concentrate was offered from d 0-62 (pre-weaning), while concentrate provision continued for a further 31 d post-weaning period. Individual daily feed intake and feeding behaviour was recorded throughout, while bodyweight and blood analyte data were collected at regular intervals. Results: Overall mean concentrate DMI from d 0-93 was 1.39, 1.27, 1.00 and 0.72 kg/d for CON, FO, GL and FOGL calves, respectively (SEM = 0.037; P < 0.0001). Calves supplemented with GL were significantly lighter (P < 0.0001) at both weaning (d 62) and turnout to pasture (d 93) than un-supplemented calves, with a similar effect (P < 0.0001) evident for calves receiving FO compared to un-supplemented contemporaries. Supplementation with GL reduced the number of unrewarded visits where milk was not consumed (P < 0.0001) while supplementation with FO increased mean drinking speed (P < 0.0001). Supplementation with GL resulted in greater concentrations of haptoglobin (P = 0.034), greater serum osmolality (P = 0.021) and lower lymphocyte levels (P = 0.027). In addition, cells from GL supplemented calves exhibited a lower response than un-supplemented contemporaries to both Phytohaemagglutinin A stimulated IFN-gamma (P = 0.019) and Concanavalin A stimulated IFN-gamma (P = 0.012) following in vitro challenges. Conclusions: Pre-weaning supplementation of bull calves with either n-3 PUFA or beta-glucan resulted in reduced voluntary feed intake of concentrate and consequently poorer pre-weaning calf performance. There was no evidence for any beneficial effect of either supplementation strategy on calves' immune responses.