Examining pasture-based dairy systems to optimize profitability environmental impact, animal health and milk quality

Examining pasture-based dairy systems to optimize profitability environmental impact, animal health and milk quality

Summary

Summary: This report covers progress through the first full year of a 3-year study. Optimal grazing strategies require an appropriate balance between stocking rate and per cow performance in pasture-based dairy systems. This project was established to focus on questions that limit current grazing systems such as: forage species and quality, stocking rates, nutrient supplementation strategies, and use of crossbreeding. At the Center for Environmental Farming Systems in Goldsboro NC, two 40-cow herds were established with cows calving from late September through December, 2003. Based on soil maps to ensure comparable percentages of similar soil types, paddock areas were carefully defined to allow one herd access to 40 acres (1 cow/acre) and the other herd access to 27 acres (1.5 cows/acre) of pasture. Cows in each group included Holsteins, Jerseys, and crosses of those breeds. Cows at the higher stocking rate have less pasture forage available and are provided supplemental concentrates at a higher rate than the herd at the lower stocking rate. Pasture types for the grazing paddocks were set to include 50% summer and winter annuals, 30% fescue clover mix, and 20% Bermudagrass over-seeded with ryegrass in winter. Paddock areas were arranged to allow multiple rotational subdivisions so that cows would have access to fresh pasture allowances after each milking. Areas for each group were designated as a winter sacrifice area for feeding supplemental forage when pastures were limiting. Shade paddock areas were also designated for summer. Preliminary information from year 1 revealed that cows at the higher stocking rate with more supplemental concentrate yielded an average of 5,833 kg milk (6,646 kg mature equivalent) compared to 5,405 kg (5,985 kg mature equivalent) for cows at the lower stocking rate. Respective percentages of fat (3.4 vs. 3.5 %) and protein (3.1 vs. 3.3 %) were not markedly different. However, multiple years of data and careful statistical and economic analyses will be required to ascertain if there are economically significant differences in production variables. Breed differences were as expected with Holsteins > crossbreds > Jerseys. Cow fertility was similar across stocking rates but crossbred cows had higher conception rates than either Holsteins or Jerseys in the first breeding season. Cows at the low stocking rate appeared to have greater protection against oxidative stress based on lower lipid hydroperoxide production and higher antioxidant activities in blood. Data from the second year are currently being collected and will include observations of grazing behavior across breed groups.

Objectives/Performance Targets

1. 1). Examine and quantify factors affecting economic and production efficiency of environmentally sound pasture-based dairy systems in the region;
   2). Characterize potentially beneficial differences in the composition of milk produced under pasture-based production systems;
   3). Characterize the antioxidant components of forages and their impact on cow immunocompetence and health;
   4). Provide interactive educational programs for dairy producers and industry leaders to enable them to make informed production and management decisions.

Accomplishments/Milestones

Preliminary discussion of some aspects of the project were presented at part of the American Forage and Grassland Council/Mid-Atlantic Dairy Grazing Conference in Roanoke, VA in June 2004.

Information about the project has also been shared with many visitors to the dairy unit at the Center for Environmental Farming Systems (CEFS) in 2004. These have included a faculty group from Auburn, Alabama A&M, and Tuskegee Universities, the NC Board of Agriculture, an external review team evaluating dairy research programs in NC, a group of NCSU veterinary students, an NRCS group studying Pastureland Ecology, 12 CEFS student interns, representatives of the NC Environmental Defense, a faculty group from University of Louisiana- Lafayette, a group of agents and livestock producers from Northeastern NC, a group of 12 agricultural workers from Turkey as part of a short course, 10 Dairy Science Club students from NCSU, CEFS external stakeholders, along with several individual visitors. The CEFS dairy project was one of four dairy articles featured on August 17 in the on-line magazine, New Farm: http://www.newfarm , published by the Rodale Institute.

Also, project updates have been included in the CEFS quarterly electronic newsletter and Dairy Extension News, the quarterly dairy newsletter of the Department of Animal Science.

Arrangements were made to host an animal science student intern from Peru during the breeding season for cows calving in the second year of the project.

An abstract has been submitted and accepted for presentation at the 2005 joint meeting of the American Dairy Science Association and the American Society of Animal Science:

Saker, K. E., J.H. Fike, S.P. Washburn, and A. Meier. 2005. Immune function and oxidative stress vary by management and lactation stage for dairy cows in a pasture-based production system. J. Dairy Sci. (Suppl 1): in press.

The Clemson experiment to evaluate different starch sources for grazing cows is underway. That experiment is designed to evaluate if starch sources (barley, molasses, citrus pulp) that degrade at different rates from corn will promote microbial growth and fermentation by increasing the free ammonia capture from pasture.

Electronic grazing monitors have been received to allow studies to be conducted on grazing behavior for various breed groups at CEFS.

Data on fertility of cows of the various breed groups used in this project were reported in October, 2004 as part of a national cooperative research project: “Genetic Selection and Crossbreeding to Enhance Reproduction and Survival of Dairy Cattle.”

Impacts and Contributions/Outcomes

This SARE project is expected to be of interest to many dairy graziers throughout the United States. It has served and will continue to serve as a training site for farmers, student interns, and graduate students with interests in sustainable agricultural systems.

Collaborators: