EFFICIENCY OF NUTRIENT USE IN CATTLE:IDENTIFICATION OF CRITICAL PHYSIOLOGIC AND GENOMIC REGULATORY PATHWAYS
Title: Opportunities for improving milk production efficiency in dairy cattle
Submitted to: Journal of Animal Science
Publication Type: Review Article
Publication Acceptance Date: October 23, 2011
Publication Date: October 28, 2011
Citation: Connor, E.E., Hutchison, J.L., Olson, K.M., Norman, H.D. 2011. Opportunities for improving milk production efficiency in dairy cattle. Journal of Animal Science. 90:1687–1694.
Interpretive Summary: Multiple approaches have been used to assess and improve efficiency of milk production in dairy cattle, each with its own limitations. One measure of feed efficiency, known as residual feed intake (RFI), has been used successfully to identify and select beef cattle that are superior for feed conversion to growth. This review discusses the application of RFI for improving milk production efficiency and its potential benefits to the dairy cattle industry for reducing production costs and negative impacts of dairy production on the environment. Recent data on the characterization of RFI in lactating Holstein cows are also discussed.
Increasing feed costs and the desire to improve environmental stewardship have stimulated renewed interest in improving feed efficiency of livestock, including that of U.S. dairy herds. For instance, USDA cost projections for corn and soybean meal suggest a 20% increase over 2010 pricing for a 16% protein mixed dairy cow ration in 2011, which may lead to a reduction in cow numbers to maintain profitability of dairy production. Furthermore, an October 2010 study by The Innovation Center for U.S. Dairy to assess the carbon footprint of fluid milk found that the efficiency of feed conversion is the single greatest factor contributing to variation in the carbon footprint, due to its effects on methane release during enteric fermentation and from manure. Thus, we are conducting research to identify the most efficient dairy cattle at conversion of feed to milk using residual feed intake (RFI), a measure used successfully to identify the most efficient beef cattle at conversion of feed to gain. Residual feed intake is calculated as the difference between predicted and actual feed intake to support maintenance and production (e.g., growth in beef cattle, or milk in dairy cattle). Selection for a lower RFI phenotype can reduce feed intake, methane production, nutrient losses in manure, and visceral organ weights substantially in beef cattle. We have evaluated RFI measures during the first 90 d of lactation for the USDA-Beltsville Holstein herd and found the heritability of RFI to be 0.16 (n = 254 lactations from 193 cows), which is within the range of heritabilities of 0.01 to 0.38 reported in the literature. Our RFI estimates indicated standard deviations for net feed intake of 1.4 and 1.5 kg/d DM, and 3.9 and 4.3 Mcal ME/d for net energy intake, for heifers and cows, respectively. Mean actual DMI differed by 3.7 kg/d (P < 0.0001) between the efficient and inefficient groups (± 0.5 SD from the mean RFI of 0), with no differences (P > 0.20) in mean BW, ADG, or ECM exhibited between the 2 groups. These results suggest promise for using RFI in dairy cattle to improve feed conversion to milk. Previous and current research on the use of RFI in lactating dairy cattle are discussed, as well as opportunities to improve production efficiency of dairy cattle using RFI for milk production.