Improvements in feed efficiency, milk yield, and components by delineating the rumen microbiome

Improvements in feed efficiency, milk yield, and components by delineating the rumen microbiome

Summary

In the Northeast, early spring, mid-late summer, and late-fall are periods when pasture mass is decreased. The purpose of this study was to determine if the addition of alternative forage crops (AFC) (i.e., small grains and warm season grasses) could alter rumen microbes, feed efficiency, and milk production of 16 lactating Jersey dairy cows during periods of low pasture mass. Two experiments were performed in May (spring) and July (summer) 2015 at the University of New Hampshire Organic Dairy Research Farm (Lee, NH). The cows were divided into two groups based on parity, days in milk, and milk yield. The fall experiment was not carried out because of poor pasture growth. In spring and summer, cows consumed either a control (CON; legume/grass mixture), or a treatment (TRT) pasture supplemented with AFC for a 21d period. The spring TRT pasture contained 5.95% AFC grains (wheat, cereal rye, triticale, and wheat) and <1% hairy vetch per dry matter(DM)-basis. The neutral detergent fiber (NDF) was higher in the CON pasture (61.0%) than in the TRT (53.5%), while the crude protein content was lower in the CON pasture (12.3%) than in the TRT (13.4%). No differences between groups were observed in milk production, rumen microbial numbers, or rumen pH.

            In the summer experiment, although oat, teff, sorghum, millet, buckwheat, and chickling vetch were planted, teff, sorghum, and millet did not grow. The TRT pasture was supplemented with 21.7% buckwheat + chickling vetch and 3.0% oats per DM-basis. The TRT pasture had a lower NDF (47.1%) and higher starch (2.7%) content than the CON pasture (52.4%, 1.5%, respectively). No differences were observed in milk yield, rumen bacteria and protozoa (i.e., microbes that digest feed) numbers, or rumen pH. Rumen methanogens (i.e., microbes that produce methane) numbers were higher in the CON pasture (P=0.045). All milk components, energy-corrected milk, and fat-corrected milk were higher in the treatment group (P<0.05). Milk fat yield was 0.92 kg/d in the TRT group and 0.74 kg/d in the CON group (P=0.02). Milk protein yield was 0.70 kg/d in the TRT group and 0.59 kg/d in the CON group (P=0.02). In conclusion, the summer AFC had a greater impact on milk production and rumen microbes than the spring AFC. Further work will be performed to determine if on-farm costs (e.g. milk check, seed) were affected during each period.

Objectives/Performance Targets

1. 1. Compare the feed efficiencies between the treatment and control groups.

1. 1. Identify and quantify the rumen microbes (i.e., bacteria, methanogens, and protozoa).

1. 1. Measure the rumen fermentation products (i.e. volatile fatty acids).

1. 1. Determine if the incorporation of AFC into the cows’ diet will benefit dairy farmers.

Accomplishments/Milestones

Although the first two experiments went according to plan, the third experiment (fall) did not. We planned to start the third experiment in late September/early October, however, the pasture growth was too poor for both the treatment and control groups as a result of drought and cooler nights than normal. Since the pasture biomass was not enough, the animals needed to be taken off the pasture, thus ending the project.

The information provided below will discuss the fulfillment of objectives from the spring and summer experiments.

Objective 1. Quantify feed efficiencies of each animal. The specific aim was to compare the feed efficiencies of the experimental group (25% AFC, 25% legume-pasture, and 50% TMR) to a control group (50% legume-pasture and 50% TMR) during early spring, mid-summer, and late fall.

Objective 1 will be completed in January/February 2016. The analyses of dry matter intakes using chromium oxide need to be completed at the University of New Hampshire before feed efficiency calculations can be performed.

Objective 2. Identify and quantify the rumen bacteria, methanogens, and protozoa.?We collected whole rumen digesta samples to delineate what microbes (diversity) and how many are present (density).

The specific aims of this objective are to a) determine the species of each type of rumen microbes with DNA sequencing,?b) estimate the rumen microbial densities via real-time polymerase chain reaction (PCR), and c) determine if certain microbial taxa relate to feed efficiency.

Objective 2b has been completed. Objective 2a and 2c are in the process of being completed. PCR and sequencing were completed for all rumen microbes (bacteria, methanogens, and protozoa) from both experiments.

Objective 3. Measure the rumen fermentation products. We are studying the rumen fermentation products because they contribute to the environment of the microbes and are key to their growth, maintenance, and survival. For example, some microbes prefer a higher pH optimum than other microbes or produce a different volatile fatty acid profile. Therefore, if we know what environment the rumen microbes are living in, we can better understand why they thrive over other microbes.

The specific aims of this objective are to ?a) measure the chemical (nutrient) composition of the experimental diets, ?b) quantify the VFA profile (rumen microbial fermentation by-products) via gas-liquid chromatography (GLC), ?and c) measure rumen pH.

Objectives 3a and 3c were completed. Objective 3b is in the process of being completed. Rumen fluid samples were sent to the West Virginia University Rumen Fermentation Profiling Laboratory for VFA analyses.

Objective 4. Determine if the incorporation of AFC will benefit dairy farmers.?The specific aims of this objective are to a) compare feed costs, dry matter intake (DMI), and cow performance (milk yield, butterfat, and protein) between the legume-based pasture (control) and AFC-based feeding groups, and b) determine if the milk check is affected by the different diets and time periods.

Objective 4 will be completed in 2016. DMI estimates will be determined from the chromium oxide measurements. Milk, protein, and fat yields have all been analyzed by Lancaster Dairy Herd Improvement Association (Manheim, PA).

Impacts and Contributions/Outcomes

During both experimental periods, cows consuming legume and grass pastures supplemented with AFC, showed similar or higher milk quality measures. In spring, milk quality measures did not differ between groups. In the summer, milk protein and fat yields were higher in the AFC group, which could potentially impact the milk check a farmer receives. We will determine the cost to buy and grow the AFC versus the control pasture to establish whether summer AFC would be profitable to the farmer. By demonstrating the positive production impacts of AFC, our study has the potential to influence current on-farm practices and increase agricultural sustainability by producing a higher quality dairy product. This project enables us to determine if AFC increase feed efficiency, while decreasing the amount of feed required by the cow. Although no outreach to the farmer has yet occurred, we plan to host an eOrganic webinar about this study and present our research results in the Northeast Organic Dairy Producer’s Alliance newsletter in early Spring 2016 and at the Vermont Organic Conference in February 2016.

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