Replacement of fish oil for sunflower oil in growing goat diet induces shift of ruminal fermentation and fatty acid concentration without affecting intake and digestion

This study aimed to measure the effects of replacing sunflower oil (SO) with fish oil (FO) in growing goat diet on feed intake, nutrient digestibility, rumen characteristics and fatty acid concentration. Experiment 1 was conducted in four growing male goats aged 9 months and weighing 20.13 ± 0.25 kg by a 4 × 4 Latin square design. All goats were received a basal diet supplemented (DM basis) with 25 g/kg SO (0FO), or SO was replaced with FO at 5 g/kg (5FO), 10 g/kg (10FO) and 15 g/kg (15FO). Experiment 2 was carried out by a continuous in vitro incubation system including 12 fermenters. Each fermenter was added 40 ml rumen fluid, 160 ml pre-warm buffer, 2 g mixed substrates, and 50 mg FO plus SO blends. The treatments in this experiment were the same as those in the Experiment 1. Different oil blends had no effect on feed intake, nutrient digestibility as well as nitrogen retention. However, replacement of SO with FO caused shifts in ruminal fermentation patterns. Inclusion of FO linearly decreased (P < 0.05) concentrations of NH3-N and quadratically reduced (P = 0.002) total VFA as well as molar proportion of acetate and propionate. Ruminal protozoa population were markedly quadratically alleviated (P < 0.001) by adding FO. Replacing SO with FO linearly decreased (P < 0.001) concentrations of C18:0 and c-9,c-12 C18:2 but linearly increased (P < 0.001) concentrations of C20:5n-3 and C22:6n-3. Adding 5FO and 15FO decreased (P < 0.001) concentration of c-9,t-11 CLA, but 10FO did not. To improve ruminal concentrations of C20:5n-3, C22:6n-3, c-9,t-11 CLA and to reduce C18:0 concentration without or less affecting intake, digestibility and ruminal fermentation, an ideal replacement of SO with FO would be at 10 g/kg DM.