Influence of flaxseed with rumen undegradable protein level on milk yield, milk fatty acids and blood metabolites in transition ewes

An experiment was conducted to determine the effects of two levels of rumen undegradable protein with whole or extruded flaxseed on milk yield, milk component, milk fatty acids (FAs) profile and plasma metabolites in transition ewes. Three weeks before and after lambing, 72 Baluchi ewes were grouped in six treatments based on a 3×2 factorial experiment with a completely randomized design. The treatments contained 1) no flaxseed + 20% RUP (NFLR); 2) no flaxseed + 40% RUP (NFHR); 3) 10% whole flaxseed + 20% RUP (WFLR); 4) 10% whole flaxseed + 40% RUP (WFHR); 5) 10% extruded flaxseed + 20% RUP (EFLR), and 6) 10% extruded flaxseed + 40% RUP (EFHR). Ewes fed 10% extruded flaxseed exhibited highest dry matter intake (DMI) compared to other treatments (p<0.001). Two flaxseed types and RUP levels had no significant effect on milk yield, but milk fat and protein contents respectively decreased and increased in diets containing 40% RUP. Supplementation of diets with extruded flaxseed resulted in further decrease of milk saturated fatty acids (SFA), but concentrations of C18:3n3, poly unsaturated fatty acids (PUFA) and mono unsaturated fatty acids (MUFA) increased compared to other groups (p<0.05). Also, 40% RUP lowered the concentrations of medium-chain FAs (MCFA) and SFA, while the concentrations of C18:3n3, long-chain FAs (LCFA), PUFA and MUFA increased. During the post-lambing, the ewes fed diet containing flaxseed exhibited higher concentration of serum non-esterified FAs (NEFA) compared to diets without flaxseed (p<0.01). The concentration of serum β-hydroxybutyric acid (BHBA) decreased in the diets containing flaxseed types at pre-lambing, but increased in diets containing extruded flaxseed at post-lambing (p<0.01). The serum glucose concentration of ewes (pre and post-lambing) which consumed diets containing extruded flaxseed or 40% RUP increased, but blood urea nitrogen (BUN) concentration was elevated following supplementation of diet with whole flaxseed or 40% RUP (p<0.001). In conclusion, extruded flaxseed along with 40% RUP in the diets of transition ewes had more positive effects on DMI and glucose concentration. They also changed BHBA, NEFA and BUN and improved milk FAs profile in terms of theirs impacts on animal health and subsequently human health.