Factors affecting urinary creatinine in heifers and cows

Area of Science:

• Animal Science
• Nutritional Physiology
• Biochemistry

Background:

• Urinary creatinine (UC) and purine derivative (PD) excretion are key indicators of nitrogen metabolism and energy status in cattle.
• Understanding factors influencing UC and PD excretion is crucial for optimizing animal nutrition and health management.
• Previous research has explored various physiological and dietary factors, but comprehensive evaluation in heifers and cows is needed.

Purpose of the Study:

• To investigate the effects of age, diet, gestation, and body condition score (BCS) on urinary creatinine (UC) and purine derivative (PD) excretion in cattle.
• To assess the diurnal and daily variations in UC excretion.
• To establish optimal collection periods for accurate UC estimation.

Main Methods:

• Total urine collections were performed over 5-day periods in heifers and cows under controlled feeding conditions.
• Animals were fed either forage-based diets supplemented with dried distillers grains (DDG) or finishing diets (90% concentrate).
• UC and PD concentrations were analyzed, and diurnal urine sampling was conducted at 2-hour intervals.

Main Results:

• Dietary composition significantly affected UC and PD:creatinine (PD:C) ratios, with higher excretion observed on forage-based diets.
• Age, gestation, 12th rib fat thickness, and BCS did not show significant correlations with UC or PD:C.
• At least 3 days of urine collection are required for reliable UC estimation, with significant diurnal and daily variations observed.

Conclusions:

• Dietary type is a primary determinant of UC and PD excretion in cattle, highlighting the importance of diet formulation.
• While age, gestation, and BCS are not direct predictors of UC and PD excretion, diurnal variations necessitate careful sampling strategies.
• Accurate assessment of urinary metabolites requires consideration of dietary influences and extended collection periods to account for diurnal fluctuations.