Document Type : Research Paper
M. Sc. Student, University College of Agriculture and Natural Resources, University of Tehran
Assistant Professor, University College of Agriculture and Natural Resources, University of Tehran
Associate Professor, University College of Agriculture and Natural Resources, University of Tehran
In this study 36 Holstein bulls (initial BW of 345±61 kg) were randomly assigned to 6 dietary treatments, following a 3×2 factorial arrangement, with 3 concentrate level of fish oil (0, 1 and 2.1% of DM) and 2 levels of alfalfa hay versus corn silage (10 and 20 % of alfalfa hay forage) to investigate the effects of fish oil supplementation and ratio of alfalfa hay and corn silage in diet on performance, carcass characteristics and fatty acids profile. There was no difference in average daily gain, dry matter intake and feed conversion ratio among dietary treatments. The highest level of fish oil had a negative effect on dry matter intake (P<0.01) regardless of alfalfa hay level. In addition, high portion of alfalfa hay forage in diet affected DMI detrimentally, regardless of fish oil levels (P<0.01). Fish oil supplementation increased TBARS value at 2 months of storage (P<0.01). Moreover dietary inclusion of fish oil increased the concentration of Eicosapentaenoic and docosahexaenoic (P<0.01) fatty acids (P<0.01) which subsequently reduced n-6: n-3 (P<0.01). The results of this study indicate that fish oil can be supplemented to feedlot diet to enrich ruminant products by introducing some peroxides production inhibitors in storage period. Furthermore, alfalfa hay can be replaced by corn silage to mitigate the detrimental effect of supplemented fat on dry matter intake.