Effect of dietary protein content on animal production and blood metabolites of dairy cows during lactation

• Published in: Journal of dairy science Vol. 92; no. 3; pp. 1001 - 1012
• Main Authors: Law, R.A., Young, F.J., Patterson, D.C., Kilpatrick, D.J., Wylie, A.R.G., Mayne, C.S.
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.03.2009; American Dairy Science Association; Am Dairy Sci Assoc; Elsevier
• Subjects: Animal Feed; animal performance; animal production; Animal productions; Animals; Biological and medical sciences; Blood Chemical Analysis; blood chemistry; blood metabolites; body condition; Body Constitution - physiology; body weight; Body Weight - physiology; Cattle - blood; Cattle - metabolism; Cattle - physiology; cow feeding; dairy cows; Dairying; Diet - veterinary; dietary protein; Dietary Proteins - metabolism; dry matter intake; Eating - physiology; energy balance; experimental diets; Female; Food industries; Fundamental and applied biological sciences. Psychology; high protein diet; lactation; Lactation - physiology; metabolites; Milk - secretion; Milk and cheese industries. Ice creams; milk production; Nitrogen - metabolism; Pregnancy; protein content; protein intake; Terrestrial animal productions; Vertebrates; milk production; energy balance; dietary protein; dry matter intake; Farming animal; Lactation; Metabolite; Dairy cattle; Dry matter; Milk production; Protein; Blood; Energy balance; Vertebrata; Mammalia; Dairy industry; Artiodactyla; Animal production; Ungulata; Protein content
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.2008-1155

Ninety autumn-calving Holstein dairy cows [45 primiparous and 45 multiparous (mean parity, 3.1)] were allocated to 1 of 3 dietary crude protein (CP) concentrations: 173, 144, or 114g of CP/kg of DM, from calving until d 150 of lactation. On d 151, half of the animals in each treatment were allocated an alternative dietary protein concentration. Half of the animals receiving 114g of CP/kg of DM went onto 144g of CP/kg of DM; half of the animals receiving 144g of CP/kg of DM went onto 173g of CP/kg of DM; and half of the animals receiving 173g of CP/kg of DM went onto 144g of CP/kg of DM, with the remaining animals staying on their original treatment. This resulted in 6 treatments in the mid to late lactation period: 114/114, 144/144, 173/173, 114/144, 144/173, and 173/144g of CP/kg of DM. An increase in dietary CP concentration significantly increased milk, fat, and protein yield in early lactation (d 1 to 150). Dry matter intake was also increased with increased dietary protein concentration; however, this was not significant between 144 and 173g of CP/kg of DM. Increased dietary CP significantly increased plasma urea, albumin, and total protein concentrations but had no significant effect on NEFA, leptin, or IGF-1 concentrations. Decreasing the dietary CP concentration in mid-late lactation (d 151 to 305) from 173 to 144 g/kg of DM had no significant effect on milk yield, dry matter intake, or milk fat and protein yield, compared with animals that remained on 173g of CP/kg of DM throughout lactation. Increasing dietary CP concentration from 144 to 173 g/kg of DM significantly increased dry matter intake compared with animals that remained on the 144g of CP/kg of DM throughout lactation. There were no significant dietary treatment effects on live weight or body condition score change throughout the experiment. Results of this study indicate that high protein diets (up to 173g of CP/kg of DM) improved feed intake and animal performance in early lactation (up to d 150), but thereafter, protein concentration can be reduced to 144g of CP/kg of DM with no detrimental effects on animal performance.