Location: Dairy Forage Research
Project Number: 5090-31000-027-008-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Jan 1, 2019
End Date: Mar 31, 2023
Objective:
The overall objective of this research will be to investigate and determine how canola meal affects metabolism and productivity of early-lactation dairy cows.
Approach:
In the first study, 72 cows will be assigned to either a canola meal-based diet or a soybean meal-based diet (36 cows for each treatment) during the dry-cow period (a minimum of 3 weeks prior to calving) After calving, half of each group (18 cows) will be switched to the opposite diet so that overall, cows will be assigned to 1 of 4 diets regimens: 1) canola meal/canola meal (pre•fresh/post-fresh), 2) canola meal/soybean meal, 3) soybean meal/soybean meal and 4) soybean meal/canola meal. The experimental design will be a randomized complete block design, and the experiment will continue for 12 weeks postpartum. In the second study, 48 multiparous cows will be identified as either high efficiency (HE) or low efficiency (LE) in converting feed to milk within the ARS dairy herd. Genomic information and previous lactation information will be used to identify HE and LE dairy cows. Within each group, half of the cows will be fed a canola meal-based diet; whereas, the other half will be fed a soybean-based diet. Cows will be fed a common diet for 4 weeks, followed by 9 weeks of treatment assignments. In the 9th week of study 2, cows will be placed in environmental chambers to measure gas emissions. The effects of these diets on the following will be determined: a) Lactation performance, including intake, milk production, milk composition, feed efficiency, and nutrient digestibility, b) The uptake of amino acids by the mammary gland and their effect on milk protein synthesis, and c) The changes in gene and microRNA expression, when this occurs, and how this contributes to nutrient utilization and milk protein synthesis. For both studies 1 and study 2, a subset of 8 cows per treatment will be biopsied for liver and mammary tissue for enzyme and gene expression analysis.
