Effects of different lipid sources and tannins on performances of high producing dairy cows

Is well known that the degree of saturation in dietary lipids could influence the ruminal metabolism and thus the performances in dairy cows. On the other hand, the addition of tannins is reported that could have positive effects on by-pass-proteins and modulation of ruminal fermentations. Aim of this experiment was to test two different lipid sources one saturated (hydrogenated fat – SF) and one unsaturated (extruded whole soybean – UF) and the addition of a tannins blend (T) on high producing dairy cows fed Parmigiano Reggiano type ration. 8 Italian Friesian cows were assigned to a latin square design (14d adaptation, 7d sampling). Diets were balanced using NDS software, (CNCPS 6.55) to be isoenergetic and isoproteic: SFT+; SFT-; UFT+ and UFT-. Dry matter intake (DMI), daily water intake (WI), body weight, body condition score, rumination time (RT), reticular pH (r-pH) and milk yield (MY) were recorded. Rumen fluid VFA and ammonia, and milk composition were determined. Energy corrected milk (ECM) was calculated. Mixed model procedure was used for data analysis; fat source and tannins presence and interactions were used as fixed effects, while animals and period as random effect. Multiple comparisons were then performed by Student's t-test. DMI (24.8 kg/d), WI (140 L/d), RT (521 min/d), BW (620 kg), BCS (2.25 pts) and total VFA production (98 mmol/L) resulted not strongly influenced by the treatments. r-pH resulted always safe excluding any risk of SARA (6.35 on average), however, the addition of T showed better pH stability, with fewer minutes below 5.8 (-20 min/d, P = 0.02). UF diets reported higher MY (+1.55 kg/d, P < 0.01) but lower milk components (-0.21 % milk fat, -0.04 % milk protein P < 0.01), so ECM resulted equal (37.87 vs 38.12kg in SF and UF respectively, P= 0.38). As expected, milk urea was positively modulated by T (-0.91 mg/dl, P < 0.01), even if rumen ammonia resulted with no variations (5.02 vs 4.71 mg/dl in T- and T+ respectively, P = 0.55). Obtained results showed that substitution of UF with SF produce an equalization of the production outputs with no risk of animal health and that tannins blend could improve nitrogen utilization and reticular pH.