Submitted to: Joint Abstracts of the American Dairy Science and Society of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: February 25, 2009
Publication Date: June 1, 2009
Citation: Connor, E.E., Hutchison, J.L., Norman, H.D., Baldwin, R.L. 2009. Estimates of residual feed intake in Holstein dairy cattle using an automated, continuous feed intake monitoring system. [abstract]. Journal of Dairy Science. 92(E-Suppl. 1):123. Abstract 33. Technical Abstract: Improving feed efficiency of cattle is a primary goal in livestock production to reduce feed costs and production impacts on the environment. In dairy cattle, studies to estimate efficiency of feed conversion to milk production based on residual feed intake (RFI) are limited primarily due to a lack of individual feed intake measures available for lactating cows. The goal of this study was to apply state-of-the-art radio-frequency identification equipment to measure feed intake in Holstein cows during the first 90 days of lactation (DIM) and characterize the RFI trait in dairy cattle. A total of 107 animals (55 first-lactation heifers [L1]; 32 second-lactation cows [L2]; twenty '3 lactation cows [L3+]) were evaluated between Oct 2007 and Nov 2008. Animals were housed in a free-stall barn and individual daily feed consumption was monitored continuously using the GrowSafe 4000 System (GrowSafe Systems, Airdrie, Canada; 33 nodes), at a maximal density of < 2 cows per node. Cows were fed a total mixed ration 3× daily, milked 2× per day, and weighed every 10 to 14 d. Milk yield was measured at each milking. Feed %DM was measured daily and nutrient composition was analyzed from a weekly composite. Milk composition was analyzed weekly, alternating AM and PM milking periods. Estimates of RFI were determined as the difference between actual intake and predicted feed and energy intake based on the equation b0 + b1* BW0.75 + b2 * gain + b3* energy-corrected milk. A subset of 11 L1 heifers was evaluated for a 305-d lactation to determine the relationship between RFI during the first 90 DIM and the full lactation. Using this system, RFI ranged from -2.2 to 3.6 kg/d for L1, -3.0 to 2.6 kg/d for L2 and -2.9 to 3.2 kg/d for L3+, meaning a difference of 6.6 kg/d between the most efficient and least efficient animals across all lactational groups. Regression analysis indicated RFI of L1 during the first 90 DIM was predictive of RFI during the full lactation (r2 = 0.48; P = 0.02). Based on our small sample size, heritability of the RFI trait was estimated to be very low (h2 = 0.05).