Kidney function, but not nitrogen excretion, differs between Brown Swiss and Holstein dairy cows

Area of Science:

• Animal Science
• Veterinary Medicine
• Dairy Cattle Physiology

Background:

• Brown Swiss (BS) cows naturally have higher milk and blood urea concentrations compared to Holstein (HO) cows.
• Understanding the physiological basis for these differences is crucial for dairy herd management and nitrogen metabolism studies.

Purpose of the Study:

• To test the hypothesis that Brown Swiss and Holstein cows differ in kidney function and nitrogen excretion.
• To compare glomerular filtration rate (GFR) and urea excretion markers between BS and HO breeds.

Main Methods:

• Blood, saliva, urine, and feces were collected from 31 multiparous BS and 46 HO cows under identical conditions.
• Concentrations of urea, creatinine, and symmetric dimethylarginine (SDMA) were measured in serum, urine, and saliva.
• Fecal dry matter (DM) and nitrogen content were analyzed; milk urea, protein, and yield data were obtained from DHIA records.

Main Results:

• BS cows had significantly greater serum concentrations of urea, creatinine, and SDMA compared to HO cows.
• Milk urea concentration and protein content were higher in BS cows, but milk yield, fecal DM, and fecal nitrogen did not differ.
• Urea and creatinine concentrations in urine and saliva were similar between the two breeds.

Conclusions:

• Results indicate a lower renal glomerular filtration rate (GFR) in Brown Swiss cows compared to Holstein cows.
• The reduced GFR in BS cows contributes to their higher plasma urea concentrations.
• Nitrogen excretion estimated via milk, urine, and feces may not fully represent the overall nitrogen turnover in dairy cows.