Inclusion of Sub-Antarctic Macroalgae (Gigartina skosttsbergii) as Feed Ingredient for Grazing Sheep

Abstract

Two experiments were carried out to evaluate the inclusion impacts of macroalgae Gigartina skottsbergii (Gs) for grazing sheep. Experiment (Exp.) 1 studied the effect of Gs on in vitro gas production (IVGP), dry matter (DM) digestibility (IVDMD), and methane (CH4) emission using three fistulated sheep and 96 h incubation of samples. In Exp. 2, ten Dohne Merino ewes [5-year-old; 47 ± 0.14 kg body weight (BW)] were randomly assigned to dietary treatments supplemented with Gs at 0 or 450 g DM/d per animal. The study lasted 31 days and was preceded by an adaptation period of 9 days. The BW, body conditional score (BCS), and blood were sampled at the first and the last day of the trial. The results of Exp. 1 showed that Gs supplementation reduced (MCP, p = 0.026) gas production (A), lag time (p = 0.013), and IVDMD (p = 0.071), while it enhanced partition factor (PF96; p = 0.004) and microbial crude protein (MCP) (p = 0.054). The concentration of CH4 decreased after 3 h (p = 0.0002), 6 h (p = 0.013), and 12 h (p = 0.010) with a tendency at 9 h (p = 0.109) and 24 h (p = 0.068). In Exp. 2, there were no diet effects on the initial BW (IBW, p = 0.77), final BW (FBW, p = 0.91), and average daily gain (ADG, p = 0.24) of ewes; however, Gs supplementation decreased BCS (p = 0.004). Of all blood parameters, only the concentration of glucose (p = 0.021) and albumin (p = 0.011) decreased in the Gs group. Overall, our results revealed that the dietary inclusion of Gs (at 450 g DM/d) affected neither the BW nor ADG of ewes; however, Gs was accompanied by lesser IVGP and CH4 emission.