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The effect of a low protein diet, with and without amino acid supplementation, on the performance of lactating dairy Holstein cows.

L. Vandaele

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06-24-2020

Abstract:

318
The effect of a low protein diet, with and without amino acid supplementation, on the performance of lactating dairy Holstein cows.
L. Vandaele*, E. Vandekerckhove, D. Van Wesemael, J. De Boever, B. Ampe, S. De Campeneere. Flanders Research Institute for Agriculture, Fisheries and Food (ILVO) Melle, Belgium.

Limiting the dietary crude protein (CP) intake in cattle to reduce N excretion is gaining interest, but can negatively affect milk production and the farmers' income (1). This research investigates the supplementation of digestible Methionine (dMET) and Lysine (dLYS) in a low CP diet on milk production of lactating cows in comparison with a control diet and a non-supplemented low CP diet. After an adaptation period of 3 weeks, 36 lactating Holstein cows were randomly divided in 6 homogeneous groups in a balanced crossover design with 3 treatments and 3 consecutive periods of 4 weeks each. The 3 treatments were a control diet (CTRL) with 16.9% CP and a rumen degradable protein balance (RDPB) of around 350g/d; a low protein diet (LOW) with 15.1% CP and a RDPB of around 130g/d; and a low protein diet with similar CP (15,2%) and RDPB level (around 150g/d) but supplemented with 14.7g/d dLYS (55g AjiPro-L) and 4.4g/d dMET (14g Excential Rumenpass MET) (LOW+AA) to reach the same levels as in the CTRL diet. The partially mixed ration of grass, maize and pressed beet pulp was fed ad libitum and supplemented with a fixed amount of concentrates to meet individual needs of 105% of net energy (all treatments) and 105% of digestible protein at the intestines (DPI) for CTRL, whereas only 100% of DPI was met for LOW and LOW+AA. The data were analyzed using a linear mixed model (period*treatment+DIM+(1|cow)). Daily total dry matter intake (DMI) was higher (P < 0.05) for CTRL (22.2 � 0.35kg) than for LOW (21.4 � 0.35kg), whereas LOW+AA had an intermediate DMI (21.8 � 0.35kg). Milk yield in the CTRL group (29.3 � 0.7kg) was higher (P < 0.05) than in LOW (28.3 � 0.7kg), whereas LOW+AA performed intermediate (28.8 � 0.7kg); similar effects were observed for fat-protein-corrected milk (FPCM). Both LOW diets reduced milk urea excretion and increased N efficiency (P < 0.05). Adding extra dLYS and dMET, regarded as the most limiting amino acids (2) to the LOW protein diet showed intermediate milk production results, whereas no supplementation resulted in less (P < 0.05) milk in comparison with the CTRL. (1) Schwab & Br�derick, 2017 (2) Bahrami-Yekdangi et al., 2016.

Keywords: amino acids, N excretion, milk production.