Management-related factors in dry cows and their associations with colostrum quantity and quality on a large commercial dairy farm

The objective of this observational study was to evaluate the association of management-related factors in dry cows and colostrum quantity and quality in Holstein cows on a large commercial dairy farm. This study was conducted from January 2018 to December 2020 on a commercial dairy farm in Germany, milking approximately 2,500 Holstein cows. Dairy personnel recorded colostrum quantity (n = 7,567) and evaluated colostrum quality in a subsample of animals (n = 2,600) using a digital Brix refractometer. Generalized linear mixed models were constructed to evaluate the association of management-related factors and colostrum quantity and quality. Models were run separately for primiparous or multiparous cows. The outcome variable was either colostrum quantity (kg) or quality (% Brix). Average colostrum quantity was 4.0 �� 2.5 kg, 5.1 �� 3.4 kg, and 5.5 �� 3.5 kg for cows in lactation 1, 2, and ���3, respectively. In primiparous cows (n = 2,351), colostrum quantity was affected by month of calving (greatest in April = 4.1 kg, and lowest in November = 3.2 kg), sex of the calf (female singleton = 3.50 �� 0.26 kg; male singleton = 3.76 �� 0.27 kg; twins = 2.97 �� 0.66 kg), stillbirth (stillbirth = 3.14 �� 0.39 kg; no stillbirth = 3.68 �� 0.31 kg). In multiparous cows (n = 5,216), colostrum quantity was affected by month of calving (greatest in May = 5.5 kg, and lowest in October = 3.8 kg), calving ease (calving ease 0 = 4.23 �� 0.26 kg; score 1 = 4.77 �� 0.21 kg; score 2 = 4.98 �� 0.22 kg; score 3 = 5.30 �� 0.22 kg), sex of the calf (female singleton = 4.42 �� 0.21 kg; male singleton = 5.00 �� 0.21 kg; twins = 5.03 �� 0.30 kg), stillbirth (stillbirth = 4.24 �� 0.38 kg; no stillbirth = 5.39 �� 0.11 kg), milk yield in previous lactation (+0.1 kg increase for 1,000 kg more milk yield in previous lactation), days spent in the far-off group (0.05 �� 0.003 kg for every day), and days in the close-up pen (0.06 �� 0.010 kg for every day). Average colostrum quality was 25.1 �� 3.4% Brix, 24.7 �� 3.3% Brix, and 27.6 �� 4.4% Brix for cows in lactation 1, 2, and ���3, respectively. In primiparous cows (n = 817), colostrum quality was affected only by month of calving. Colostrum quality in primiparous cows was greatest in December (26.8% Brix) and lowest in August (23.9% Brix). In multiparous cows (n = 1,783), colostrum quality was affected by parity (lactation 2 = 25.2 �� 2.7% Brix; lactation 3+ = 27.9 �� 2.7% Brix), month of calving (greatest in February = 27.5% Brix, and lowest in August = 25.7% Brix), milk yield in previous lactation, and colostrum quantity. We observed a seasonal pattern for colostrum quantity and quality. Future intervention studies using multiple farms need to elucidate whether management of the photoperiod or length of exposure to close-up diets, or both, can help to optimize colostrum production.