Rapeseed meal in complete feeds for dairy cows

Area of Science:

• Animal Science
• Dairy Nutrition
• Agricultural Chemistry

Background:

• Rapeseed meal is a valuable protein supplement for dairy cows.
• Evaluating different rapeseed meal cultivars is crucial for optimizing animal nutrition.
• Understanding the impact of glucosinolate and erucic acid content is key.

Purpose of the Study:

• To compare the efficacy of low glucosinolate rapeseed meal (Cultivar "1788"), high glucosinolate rapeseed meal (Cultivar "Span"), and soybean meal as protein supplements for lactating Holstein cows.
• To assess the effects of these diets on lactation performance, metabolic parameters, and milk composition.

Main Methods:

• A double 3x3 Latin square design was employed with three complete feeds.
• Lactating Holstein cows were fed diets supplemented with Cultivar "1788" rapeseed meal, Cultivar "Span" rapeseed meal, or soybean meal.
• Measurements included lactation performance, hematology, blood chemistry, serum-free amino acids, volatile fatty acids, and milk fatty acid composition.

Main Results:

• Cultivar "1788" rapeseed meal tended to increase milk and total solids yield.
• No significant differences were observed in nitrogen utilization, volatile fatty acid concentrations, or milk fat erucic acid content.
• High glucosinolate Span ration did not reduce feed intake, but suggested potential hypothyroidism.

Conclusions:

• Rapeseed meals (Cultivar "1788" and "Span") and soybean meal are nutritionally equivalent protein supplements for lactating dairy cows.
• Low glucosinolate rapeseed meal (Cultivar "1788") may offer advantages in milk production.
• Further investigation into the potential metabolic effects of high glucosinolate rapeseed meal is warranted.