Location: Dairy Forage Research
2024 Annual Report
Objectives
Objective 1: Develop and evaluate dietary feed formulation strategies that increase the utilization of conventional feeds/forages and alternative feeds/forages that reduce competition with human food consumption, increase milk production, enhance nutrient use efficiency, and reduce greenhouse gas emissions in dairy production systems.
Sub-objective 1.A: Evaluate effects of forage type, amount, and quality on animal performance, nutrient digestibility, and feed conversion efficiency.
Sub-objective 1.B: Evaluate effects of alternative/byproducts feeds that replace or reduce traditional concentrate feeds in the diet on animal performance, nutrient digestibility, feed conversion efficiency, and gas emissions.
Sub-objective 1.C: Evaluate the inclusion of feed additives to forage-based diets on animal performance, nutrient digestibility, feed conversion efficiency, and gas emissions.
Objective 2: Develop and evaluate dietary feed formulation strategies using partial mixed rations (PMR), based on forage base, nutrient composition and feed physical form, to enhance individual animal feed efficiency and reduce environmental impact of dairy farms.
Sub-objective 2.A: Evaluate individual animal energetic usage and efficiency based on plane of nutrition and management that can impact feeding in a Partial Mixed Ration (PMR) system.
Sub-objective 2.B: Evaluate effects of one versus two feeds, nutrient composition, and feed forms on feed efficiency, precision data collected, environmental impacts and measurements within and between individual or small groups of cows using a PMR.
Objective 3: Evaluate the effects of forage/feed type and soil health management interventions on farm carbon balance, nutrient losses, and milk productivity and quality in dairy production systems.
Sub-objective 3.A: Evaluate soil health factors for their effects on forage productivity and nutritive value, to inform management practices and forage selection that will improve milk yield and quality.
Approach
Objective 1. A series of dairy cattle studies will be conducted to evaluate the effect of forage type, forage amount, and forage quality on animal performance, nutrient digestibility, and feed conversion efficiency. In addition, alternative forages and byproduct feedstuffs will be evaluated as replacements for traditional feedstuffs used in dairy cattle diets. Inclusion of feed additives to forage-based diets will be evaluated for animal performance, nutrient digestibility, feed conversion efficiency, and gas emissions. We will collect production measurements, rumen samples, feces, urine and gaseous emissions to determine the effects of altering fiber digestibility on ruminal fermentation, lactation performance, and environmental output.
Objective 2. A series of dairy cattle studies will be conducted to evaluate dietary feed formulation strategies using partial mixed rations (PMR), based on forage base, nutrient composition and feed physical form, to enhance individual animal feed efficiency and reduce environmental impact of dairy farms. In the first study, calves born to either nutrient-restricted dams and nutrient-sufficient dams will be followed through to adulthood to determine whether nutrient-restricted heifers with emit be less productive and have greater environmental impact due to reduced productive efficiency relative to their herdmates. In a second study, cows will be evaluated on how milking permissions in automatic milking systems impact animal metabolism. In a third study, the effects on a one or two feed system, nutrient composition and feed forms of cows fed a partial mixed rations will be evaluated for production measures, feed efficiency, and environmental impacts.
Objective 3. Two exploratory field investigations and a greenhouse trial are planned to evaluate the effects of forage/feed type and soil health management interventions on farm carbon balance, nutrient losses, and milk productivity and quality in dairy production systems. Field investigations will investigate fields with different management and land cover differences to determine whether specific soil health indicators are positively correlated with forage nutritive quality or digestibility. A greenhouse trial will be conducted implementing a factorial arrangement of treatments with the following factors: soil source, crop type (corn silage, alfalfa) and water availability (optimal vs 50% optimal water availability). 4 x 2 x 2 factorial design with the following factors: soil source, crop type (corn silage, alfalfa) and water availability (optimal vs 50% optimal water availability). Optimal water availability will be determined based on the field capacity of soils, with 50% of field capacity for the drought treatment. This trial will 1) determine the effects of soil health indicators on forage quality and productivity; 2) Compare input costs for soil source x crop type for an assessment of production efficiency; and 3) Compare carbon assimilation and water use efficiency of crops under varied soil conditions.
Progress Report
For Objective 1, a study was conducted to evaluate the inclusion of feed additives to forage-based diets on animal performance, nutrient digestibility, feed conversion efficiency, and gas emissions (Objective 1.C). Inclusion of macroalgal species may be effective in improving nutrient digestibility in forage-based dairy cow diets and reduce enteric methane emissions. Over 20 different macroalgal species were evaluated by in vitro methods, and one species was chosen for the feeding study. Because of limited availability of the seaweed at the time of the experiment, one inclusion level was evaluated in the feeding study (0.75% of the diet). The feeding portion of the study has been completed and laboratory analysis is currently underway. Additional analysis will be completed before a manuscript will be written.
A study was conducted to evaluate the effect of processing on two different types of forage (corn silage and alfalfa silage) on lactation performance, nutrient digestibility, feed conversion efficiency, and gas emissions (Objective 1.A). Extreme mechanical processing of alfalfa silage has previously been demonstrated to improve fiber digestion in lactating dairy cows. This study will evaluate the inclusion of both processed and unprocessed corn silage and alfalfa silage to determine if the combination of both processed forages enhances fiber digestion and productivity. The feeding study was just completed, and laboratory analysis has not yet started. Once sample analysis and statistical analysis has been completed, a journal manuscript will be written.
Objective 2: An on-going study is being conducted to accomplish Sub-objective 2.A. Hypothesis 2.A.1. Evaluate individual animal energetic usage and efficiency based on plane of nutrition and management that can impact feeding, where dairy animals born to nutrient-restricted dams are being evaluated through their first lactation. A manuscript is in preparation to report the pre-weaning impacts of maternal diets. Currently, experimental animals are entering their first lactation and will be followed through their entire lactation to measure growth, blood metabolites, and enteric gas production. Sample chemical composition and statistical analysis is on-going for the data collected thus far, representing the prepubertal, pubertal, and post-pubertal differences in animals based on maternal diets.
Two experiments were completed in collaboration with Clemson University and University of Wisconsin-Platteville to meet Hypothesis 2.A.2. Laboratory analysis has been completed, one manuscript has been published, and two more are in preparation. Experiments were designed to compare production, metabolic, and behavioral differences based on milking frequency in automatic milking systems at different stages of lactation. At Clemson, animal visit behavior, time allocations, milk production and composition, and heart rate variables were compared between cows in their first lactation and those in their second and greater. At University of Wisconsin-Platteville, milking frequencies were set to three or six times per day from four days after calving to 28 days in milk. Blood metabolites, rumen fluid composition, and milk production and composition were analyzed over this time. Animals were evaluated for carryover effects until 90 days in milk for milk yield and composition.
Objective 3: The two exploratory field investigations and a subsequent greenhouse trial have been conducted and lab analyses are underway. Funding was awarded in 2024 through a grant with Dairy Management, Inc. to explore the greenhouse gas and carbon accumulation dynamics in forages along a gradient of perenniality and diversity. This work will be complementary to the research described in Objective 3.A.
Accomplishments
1. Identified the importance of grouping lactating cows based on age on automatic milking systems with guided traffic. ARS researchers at Madison, Wisconsin, identified that cows in their first lactation spent significantly more time waiting to be milked than cows that were in their second lactation and had previously been milked on an automatic milking system (AMS) and were less likely to approach the automatic milking system. Cows previously milked on AMS tended to displace more cows inside the commitment area near the AMS while primiparous cows demonstrated lower heart-rate variability and higher low-frequency to high- frequency measurements indicating they were in greater states of stress. Also, multiparous cows were identified to spend more time lying at night than primiparous, with longer lying bouts for multiparous cows overall. Multiparous cows also had greater stepping frequency in the AMS, suggesting greater stress inside the milking robot. When comparing the same groups of cows before and after decreasing the number of visits to the AMS from six to four times per day, short-term stress indicators in older cows increased. These indicators include visits to the entrance gate of the AMS pen, displacement of animals around the AMS, stepping, and heart rate. First lactation cows demonstrated greater stress signs when co-housed with older cows. Results emphasize the importance of grouping primiparous and multiparous cows to decrease social competition in automatic milking systems particularly if primiparous animals cannot be pre-trained. Additionally, results identify key differences to evaluate AMS animal behavior based on parity to inform dairy management decisions to improve animal health and productivity.
Review Publications
Davis, L., French, E.A., Aguerre, M.J., Ali, A. 2023. Impact of parity on cow stress, behavior, and production at a farm with guided traffic automatic milking systems. Frontiers in Animal Science . https://doi.org/10.3389/fanim.2023.1258935.
Salazar, R., Alegre, J., Pizarro, D., Duff, A., Garcia, C., Gomez, C. 2024. Soil carbon stock potential in pastoral and silvopastoral systems in the Peruvian Amazon. Agroforestry Systems. https://doi.org/10.1007/s10457-024-00969-w.