Rumen protected lysine and diet energy density improved health status, milk production and nitrogen efficiency in dairy cows

A86. Rumen protected lysine and diet energy density improved health status, milk production and nitrogen efficiency in dairy cows D. Cavallini1 , A. Palmonari1 , L. Mammi1 , G. Visentin1 , G. Buonaiuto1 , A. Concolino1 , I. Fusaro2 , E. Valle3 , A. Formigoni1 . 1Department of Veterinary Sciences, University of Bologna, Italy. 2 Department of Veterinary Sciences, University of Teramo, Italy. 3 Department of Veterinary Sciences, University of Turin, Italy. e-mail: damiano.cavallini@unibo.it Introduction. The use of rumen-protected aminoacids helps to balance the dairy cows’ rations, reducing the nitrogen use and improving the efficiency and sustainability of milk production. Methionine (M) is well recognized as a first limiting aminoacid in dairy cows' rations while the effectiveness of lysine (L) is postulated for high milk production, low protein diets, or when proteins source are deficient. Besides, energy availability is a key factor to maximize the aminoacid use for the synthesis of body or milk proteins. Aim of this study was to evaluate the effects of diets with higher or lower energy (HE – 0.5kg/day/head of Megafat® vs LE - no addition) and the supplement (L+) or not (L-) of AjiPro-L ® (0.1kg/day/head) with constant addition of Smartamine® (22g/day/head). Animals, materials and methods. 8 Italian Friesian cows were assigned to a latin square design with different diet profiles (%DM): HEL+:15.8 CP, 72.1 ME, 3.30 L/ME, 1.16 M/ME; HPL-: 15.8 CP, 72.1 ME, 3.05 L/ME, 1.16 M/ME; LEL+: 16.0 CP, 69.5 ME, 3.50 L/ME, 1.22 M/ME; LEL-: 16.0 CP, 69.5 ME, 3.21 L/ME, 1.23 M/ME. Dry matter intake (DMI), daily water intake (WI), body weight (BW), rumination time (RT), reticular pH (r-pH), milk yield (MY) and its components were recorded after 14 d of adaptation. Nitrogen efficiency (NEf) was calculated as N milk yield/N intake. While, blood samples were taken after 21 d of diet adaptation and analysed for cell count, biochemistry and electrophoresis. Data were analysed with a Mixed model procedure. E and L levels and interactions were used as fixed effects, while animals and period as random effect, and each sampling as repeated measure. Results and discussion. DMI and BW were 26.5kg/d and 620kg on average respectively. RT (504min/d on average) and r-pH data were good excluding any risk of SARA. HE diets improved MY and components (p<.01), moreover, HEL+ gave the best results (MY: 37.5kg/d, fat: 1420g/d, protein: 1265g/d, p<.05) and the highest NEf (33%, p<.05). Serum urea did not change among diets (23mg/dl on average). All the analysed parameters were in the physiological ranges [1]. HEL+ diet showed a reduced neutrophils level (-7% compared to LEL+, p=0.05) indicating a lower inflammation status. HE diets improved serum cholesterol content (+55mg/dl, p<.01) and α2-globulins (+0.55%, p=0.02), on the other hand, reduced α1-globulins and β2globulins (-0.57%, p=0.04; -0.45%, p=0.05 respectively). The change in globulins proportions indicates modifications on serum lipoproteins and metal-carriers due to the diet E level. Moreover, L+ diets increased total serum proteins (+0.4g/dl, p<.01), especially albumin (+0.12g/dl, p=0.08) and γ-globulins (+1.2%, p=0.09). These findings could be interpreted as a L positive effect on serum protein synthesis. Conclusion. The use of hydrogenated fats combined with rumen-protected Lysine were effective to improve indicators of cow health status, performances and NEf. References. [1] https://www.vet.cornell.edu/animal-health-diagnostic-center/laboratories/clinicalpathology/reference-intervals/chemistry (2021).