Dry matter intake from parturition to midlactation

Area of Science:

• Animal Science
• Dairy Nutrition
• Ruminant Physiology

Background:

• Dry matter intake (DMI) is a critical factor influencing dairy cow productivity and health.
• Existing models for predicting DMI may not accurately reflect the dynamic changes in cows throughout lactation.

Purpose of the Study:

• To quantitate the relationships among DMI, days in milk (DIM), body weight (BW), and fat-corrected milk (FCM) yield.
• To develop and validate improved equations for predicting DMI in dairy cows.

Main Methods:

• Utilized six years of individual feeding data from the Purina Research Center.
• Developed predictive equations for DMI based on BW, 4% FCM, and DIM, with adjustments for different lactation periods.

Main Results:

• The best overall DMI prediction equation was established: kg DMI = .008037 x kg BW + .3134 x kg 4% FCM + .2286 x DIM - .002176 x (DIM)^2 + .00000705 x (DIM)^3 (R^2 = .64).
• Separate equations were most accurate when developed for specific weeks postpartum (up to 6 wk) and lactation periods (6-8, 9-13, 14-20 wk).
• Commonly used equations and NRC estimates showed discrepancies, often over- or underestimating DMI compared to the developed model, particularly beyond 8 weeks postpartum.

Conclusions:

• The developed DMI prediction equation offers improved accuracy across different stages of lactation compared to existing models.
• Energy balance calculations indicated a more pronounced and extended energy deficit in later-lactation cows versus first-lactation cows.
• Body weight loss alone is an insufficient indicator of energy status in early lactation dairy cows.