Grass-birdsfoot trefoil mixtures to improve the economic and environmental sustainability of pasture-based organic dairies in the western U.S.

2020 Annual Report

Objective 1

• Completed analyses of all data from Objective 1 and published (in press) results in peer-reviewed journal. Reprint attached and results outlined in Research Conclusions section.  
• ABSTRACT. Low dietary energy and decreased intake of herbage have been attributed to the reduced performance of grazing dairy cattle. We hypothesized that grasses with inherently greater energy would interact in a complementary way with condensed tannins (CT) in birdsfoot trefoil to increase herbage intake by grazing dairy heifers. Eight pasture treatments comprised of high-sugar perennial ryegrass (Lolium perenne L.; PR), orchardgrass (Dactylis glomerata L.; OG), meadow bromegrass (Bromus riparius Rehmann; MB), and tall fescue (Schendonorus arundinaceus [Schreb.] Dumort; TF) were established in Lewiston, Utah, USA as monocultures and binary mixtures with birdsfoot trefoil (Lotus corniculatus L; BFT). Pasture treatments were rotationally stocked by Jersey heifers for 105 days in 2017 and 2018, and herbage samples were collected pre- and post-grazing each 7-day grazing period and analyzed for herbage mass, nutritive value, and apparent herbage intake. We observed differences among pasture treatments in herbage quantity and nutritive value, as well as differences in herbage intake by grazing Jersey heifers. On average, grass-BFT mixtures had greater herbage intake than grass monocultures, and individually every grass-BFT treatment had greater herbage intake than their respective grass monocultures. Using multivariate analyses, we determined that approximately 50% of the variation in herbage intake was due to nutritive and physical herbage characteristics, with the most explanatory being characteristics related to fiber and energy, followed by those related to the percent of BFT in the herbage. Grass monocultures exhibited a range of inherent dietary energy, but there was indication that an energy to crude protein imbalance (e.g., protein deficient) reduced intake of grass monocultures. Moreover, there was some evidence of a complementary effect between increased dietary energy and CT, however, low CT levels made it impossible to determine the effect of CT on herbage intake per se. This study confirmed that chemical and physical characteristics inherent to different pasture species have a large effect on herbage intake by grazing cattle. Pastures planted to binary mixtures of nutritious grasses and birdsfoot trefoil increase herbage intake of temperate pastures by grazing Jersey heifers.

Objective 2

• Completed all analyses of data from Objective 2 and published (in review following revision) results in peer-reviewed journal. Heifer gains and economic tables attached, and results outlined in Research Conclusions section.  
• ABSTRACT. Dairy heifers developed in certified organic programs, especially those utilizing pasture-based management schemes, have lower rates of gain than heifers raised in non-organic confinement production systems in temperate climates, such as in the Intermountain West region of the US. This study investigates the effects that different forages in a rotational grazing system have on development of organically raised Jersey heifers. Over three years, 210 yearling Jersey heifers were randomly assigned to one of nine treatments, including a conventional confinement control where animals were fed a total mixed ration or one of eight pasture treatments: Cache Meadow bromegrass (Brumus riparius Rehmann), QuickDraw orchard grass (Dactylis glomerata L.), Amazon perennial ryegrass (Lolium perenne L.), or Fawn tall fescue (Schendonorus arundinaceus [Schreb.] Dumort) and each individual grass interseeded with birdsfoot trefoil (Lotus corniculatus L., BFT). Each treatment had three blocks per year over the three year period with each block having a 0.4 ha pasture of each treatment. Every 35 d, over a 105 d period, heifers were weighed, measured for hip height, and blood samples were collected to determine serum insulin-like growth factor-1 and blood urea nitrogen concentrations. Fecal egg counts were also assessed. Heifer body weights (BW), blood urea nitrogen, and insulin-like growth factor-1 concentrations were affected by treatment when analyzed over time. Heifers on grass-BFT pastures had increased BW compared to heifers on monoculture grass pastures. Heifers receiving a total mixed ration or perennial ryegrass+BFT had increased BW gain over the 105 d period compared to heifers grazing tall fescue+BFT, orchard grass, perennial ryegrass, meadow bromegrass, or tall fescue. Whereas, individually for all grass species, heifers grazing +BFT pastures had greater ending BW and weight gain than heifers grazing the respective grass monocultures. Furthermore, weight gain for heifers on perennial ryegrass+BFT, meadow bromegrass+BFT, and orchard grass+BFT were not different from those on a total mixed ration. Heifers grazing grass-BFT pastures had increased blood urea nitrogen compared to heifers grazing monoculture grass pastures. Heifer hip-height and fecal egg counts were not affected by treatment. These results show that the addition of BFT to organic pasture improves growth of grazing replacement heifers. Economic analyses also demonstrate that interseeding grass pastures with BFT results in an increased economic return compared to grazing monoculture grass pastures. Grass pastures interseeded with BFT may be a sustainable option to achieve adequate growth of Jersey heifers raised in an organic pasture scenario in a temperate climate.

Objective 3

• All soil sample, leachate, urine, and fecal samples have been analyzed for nitrate, urea, ammonia, and/or total nitrogen. Statistical analyses and manuscript preparation are ongoing.

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2019 Annual Report

Objective 1

• Grazing and herbage measurement portions of study at the USU pasture research facility were previously completed in 2018. The forage treatments included Amazon perennial ryegrass (PR), Quickdraw orchardgrass (OG), Cache meadow bromegrass (MB), and Fawn tall fescue (TF), in monoculture and mixed with birdsfoot trefoil (BFT). In 2019, the herbage data was analyzed and reported as part of the requirements for a USU M.S. thesis (Marcus Rose).  The main results of the thesis are summarized as follows:
  • Herbage intake was measured by sampling herbage before and after each seven-day grazing period. Overall, grass-BFT mixtures had greater herbage intake than grass monoculture pastures (Table 1), and greatest to least intake for pasture treatments was as follows: MB+BFT, OG+BFT, OG, MB, PR+BFT, TF+BFT, PR, TF (Table 1).
  • Multivariate analyses indicated that physical characteristics of pasture bulk density, herbage height, herbage allowance, leaf pubescence, leaf softness, and birdsfoot trefoil content as well as nutritive value properties of fat, non-fibrous carbohydrates, fiber, and energy resulted in nearly 100% discrimination (identification) among the pasture treatments; and were moderately associated with the differences in herbage intake.
  • While PR+BFT did not have the greatest overall herbage intake by heifers, it was the only treatment that consistently had greater intake than its respective grass monoculture (PR). Since it had more energy and tannins than all other grasses, a complimentary effect between energy and tannins to increase herbage intake was likely.
  • The fact that both physical and chemical herbage characteristics were associated with intake shows the importance of planting the right species in pasture as well as making proper management decisions to maximize nutritive value and herbage intake.
  • Annual Report 2019_Table 1
• On-farm trials – Completed two years of evaluation on the Bingham dairy in Weston, ID. Objective was to determine which grass and/or grass-birdsfoot trefoil mixture had the greatest nutritive value, predicted intake and predicted milk production in a rotationally grazed dairy operation. Pasture treatments were as described above.  Animals in the study consisted of lactating, crossbred Holstein, Montbeliard, Swedish red dairy cows in an organic dairy operation in Weston, Idaho. Rotational stocking was used with a typical stocking period of 24 hours, followed by a rest period ranging from 21 to 45 days depending on herbage growth and climatic conditions. Herbage from strips of the treatments inside two randomly placed 0.25 m² hoops was clipped before grazing in 2017 and 2018 at a height of 7.6 cm. Samples were dried, weighed, and ground and analyzed with NIRS to determine herbage nutritive value of the feed on offer. Milk production was predicted from nutritive value via MILK equation and serves as a relative comparison among treatments. In 2019, the herbage data was analyzed and reported as part of the requirements for a USU M.S. thesis (Marcus Rose).  The main results are summarized as follows:
  • The perennial ryegrass treatments generally had the most favorable nutritive characteristics in many respects (Table 3), but they did not persist well and were largely overtaken by weeds by the end of 2018.
  • The tall fescue treatments were considered the benchmark in this study based on previous research. While they were not as readily consumed as the other treatments, likely due to course leaves, it consistently produced large amounts of herbage and had more predicted milk/acre than any other treatment (Table 3).
  • The meadow brome and orchardgrass were comparable in many respects. They often had intermediate nutritive values, with meadow brome treatments being slightly greater than the orchardgrass treatments (Table 3). However, since the orchardgrass treatments had the second highest herbage production, they were usually like the meadow brome treatments in milk production per acre (Table 3).
  • Annual Report 2019_Table 3
• On-farm trials – Completed one year of evaluation on the Wangsgard dairy in Young Ward, UT. Objective was to determine if herbage mass and nutritive value be increased by applying Chilean nitrate, elemental sulfur, and/or high sulfur gypsum to organic dairy grazing pastures. Soil amendments were applied in April 2018. Treatments consisted of high sulfur gypsum (G), elemental sulfur (S), high sulfur gypsum+sulfur (Gyp+Sulf), nitrate (Nit), nitrate+high sulfur gypsum (Nit+Gyp), and no amendment. Gypsum was applied at a rate of 300 lb./acre, sulfur was applied at a rate of 125 lb./ acre, and nitrate was applied at a rate of 100 lb./ acre, resulting in a nitrogen rate of 15 lb./acre. Mixed amendment treatments were applied separately at the same rates as single amendment applications. Grazing and sampling took place on existing mixed pastures of meadow bromegrass, garrison creeping foxtail, and clover. Livestock consisted of lactating Holstein dairy cows in an organic dairy operation. Rotational stocking was used with a typical stocking period of approximately 24 hours, followed by a rest period ranging from 21 to 45 days depending on herbage growth and climatic conditions. Cows were on pasture for at least 120 days per growing season which consisted of three rotations. Herbage within four randomly placed 0.25 m2 hoops was clipped to a height of 3.8 cm before grazing and harvesting. Samples were dried, weighed, and ground and analyzed with NIRS to determine herbage nutritive value of the feed on offer. Milk production was predicted from nutritive value via MILK equation and serves as a relative comparison among treatments. In 2019, the herbage data was analyzed and reported as part of the requirements for a USU M.S. thesis (Marcus Rose).  The main results are summarized as follows:
  • Although only 15 lb N/acre was applied to the nitrate treatments, a slight nitrogen response was evident, showing the importance of nitrogen in pasture grass production (Table 4).
  • The Nit+Gyp treatment herbage production was significantly greater than the untreated pasture and the sulfur treatments and not significant from the others (Table 4). The nitrate treatment was only greater than the sulfur treatment (Table 4). The nitrate treatments also had the greatest predicted milk production/acre (Table 4).
  • While the pasture treated with sulfur had low herbage mass, it seemed to play a role in many of the nutritive value parameters and was usually among those treatments with the greatest nutritive value and milk production/day (Table 4). Many of the other treatments were not significant from one another and more replication would be necessary to effectively distinguish one from the other.
  • Annual Report 2019_Table 4

 Objective 2

• Data relative to growth, health and reproductive capacity of the heifers when grazing grass-BFT versus grass monoculture pastures was collected in 2017 and 2018. These measurements include, weight, hip height, serum concentrations of blood urea nitrogen (BUN) and insulin-like growth factor-1 (IGF-1), conception rates, and fecal parasite load (FEC). In 2019, the heifer data was analyzed and reported as part of the requirements for a USU M.S. thesis (Jacob Hadfield).  The main results from the thesis are summarized as follows:
  • Heifer weight, overall weight gain and BUN concentrations were affected by pasture treatment (Table 2), whereas heifer hip-height, IGF-1, conception rate, and FEC were not affected by treatment.
  • Heifers receiving grass-BFT mixture pastures had increases in weight and BUN compared to heifers receiving grass monoculture pastures (Table 2).
  • Heifers receiving total mixed ration (TMR) or PR+BFT had higher weight gains over the 105-d period than heifers grazing TF+BFT, OG, PR, MB, or TF.
  • These results show that the addition of BFT to pasture increases growth and development of replacement heifers. Mixed pastures with BFT may be a sustainable alternative to feeding a TMR in a confined setting in order to achieve adequate growth of dairy heifers.
  • Annual Report 2019_Table 2

Objective 3

• All field data have been collected and sample analyses are ongoing. Field data collected included the following: 1) plant samples were collected before and after each grazing event and dried for later analysis; 2) soil samples were collected in the fall at the beginning of the study for a baseline reading, and in the spring, prior to grazing, and in the fall after the growing season using a Giddings® soil extraction instrument to a depth of 1.524 meters. Soil samples were also collected in the spring of the third year to monitor nutrient movement; 3) soil water (leachate) nitrogen was monitored by lysimeters and leachate collected every two weeks during the growing seasons, and as close as possible to every two weeks during the winter months; and 4) urine and feces were collected from heifers at weigh-ins.
• The 2016 soil samples have been analyzed for nitrate, but still need to be analyzed from 2017 and 2018. Nearly completed all three years of soil samples for ammonia, but still need to run all three years of soil samples for phosphorus.
• All leachate samples have been analyzed from 2016, 2017 and 2018 for nitrate.
• Urine samples have been analyzed for urea for all three years. Fecal samples have been run for total nitrogen and total carbon for all three years, but still need to be analyzed for ammonia.

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2018 Annual Report

Objective 1

• The grazing portion of study completed for 2016, 2017, and 2018. The forage treatments included Amazon perennial ryegrass (PR), Quickdraw orchardgrass (OG), Cache meadow bromegrass (MB), and Fawn tall fescue (TF), in monoculture and mixed with birdsfoot trefoil (BFT). Data analysis is ongoing and preliminarily summarized as follows:
• Grass-Birdsfoot trefoil mixtures had greater herbage mass, crude protein (CP), digestibility (IVTD48), and energy (NEgain) than their respective grass monocultures (Table 1 and 2).
• All grass-BFT mixtures had greater apparent dry-matter intake (disappearance) than their respective monocultures, except for OG+BFT (Table 3).
• Alternating versus mixed rows (Figure 3-2, 3-3): The grazing preference of heifers in mixed pastures of birdsfoot trefoil with tall fescue, perennial ryegrass, orchardgrass and meadow bromegrass was tested. When compared to tall fescue, birdsfoot trefoil was always utilized more, with an average of 23 percentage points difference. In most observations, birdsfoot trefoil utilization was higher than orchardgrass utilization, with an average difference of 14 percentage points. In contrast, there was no difference in utilization in all comparisons with meadow bromegrass. During early growth, perennial ryegrass utilization was higher than birdsfoot trefoil utilization, but no difference in utilization was detected in later observations, though, perennial ryegrass averaged 9 percentage points higher utilization than birdsfoot trefoil.
• In depth data analysis is being undertaken to look at and explain differences and trends.
• Annual-Report-2018_Tables-from-M.Rose-thesis
• Annual-Report-2018_Figures-from-J.Briscoe-thesis

Objective 2

• Data relative to growth, health and reproductive capacity of the heifers was collected in 2017 and 2018. These measurements include, weight, hip height, serum concentrations of blood urea nitrogen (BUN) and insulin-like growth factor-1 (IGF-1), conception rates, and fecal parasite load. Data analysis is ongoing and preliminarily summarized as follows:
• At d-105 heifers receiving TMR, PR+BFT, OG+BFT, or MB+BFT had higher (P<0.05) weights than heifers receiving TF (Table 4). Heifer hip-height (P = 0.13), conception rate (P = 0.67), and FEC (2017: P = 0.26; 2018: P = 0.62) were not affected by treatment when analyzed over time.
• Heifers receiving MIX pastures had increases in weight (P < 0.01) (Figure 1) and BUN (P < 0.01) compared to heifers receiving MONO pastures. Heifer IGF-1, FEC, and conception rates were not influenced (P = 0.63, P > 0.05, P = 0.56, respectively) by pasture type when analyzed over time. Heifers on MIX pasture had a tendency (P = 0.06) to have increased hip-heights.
• These results show that the addition of BFT to pasture increases growth and development of replacement heifers. Mixed pastures with BFT may be a sustainable alternative to feeding a TMR in a confined setting in order to achieve adequate growth of dairy heifers.
• In depth data analysis is being undertaken to look at and explain differences and trends.
• Annual-Report-2018_Figures-and-table-from-J.Hadfield-thesis

Objective 3

• Plant samples were collected before and after each grazing event and dried for later analysis. Soil samples were collected in the fall at the beginning of the study for a baseline reading. Soil samples were collected in the spring, prior to grazing, and in the fall after the growing season using a Giddings® soil extraction instrument to a depth of 1.524 meters. Soil samples will also be collected in the spring of the third year to monitor nutrient movement. Four soil cores are taken in each plot and divided into three subsamples; 0-30.48 cm, 30.48-60.96 cm, 60.96-152.40 cm. Composite soil subsamples are analyzed for available nitrogen (ammonia and nitrate) and for total N.
• Soil water (leachate) nitrogen is monitored by means of zero-tension lysimeters that were previously installed at this location. Leachate is collected every two weeks during the growing season, and as close as possible to every two weeks during the winter months from zero-tension lysimeters. Suction cup lysimeters (60 cm deep) were installed in each plot, with samples being collected weekly by suction cup lysimeters. All leachate samples will be analyzed for nitrate-nitrite. 
• Data analysis is ongoing.

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2017 Annual Report

Objective 1

• The grazing portion of study completed for 2016 and 2017. The forage treatments included Amazon perennial ryegrass (PR), Quickdraw orchardgrass (OG), Cache meadow bromegrass (MB), and Fawn tall fescue (TF), in monoculture and mixed with birdsfoot trefoil(BFT). Data from 2016 has been analyzed and is summarized as follows:
• All grass-BFT mixtures had higher protein content than their respective monocultures. Protein content ranged from 9.3% (TF, PR) to 18.4% (MB+BFT, PR+BFT). OG, MB, and PR mixes and monocultures all had higher TDN (56.7-57.5%) than TF+BFT mixes and monocultures (53.2-54.8%). The TF+BFT had a statistically higher TDN percentage than the TF monoculture.
• OG and OG+BFT had the highest predicted dry matter intake (2.5%, 2.4% BW) while TF and MB+BFT had the lowest (2.2%, 2.15%). The other treatments fell between those two margins.The overall average rate of gain for all of the heifers was around 1.47 lb/day. The BFT mixtures and OG and PR monocultures resulted in the highest rates of gain (1.44-1.62 lb/day). The TF and MB monocultures had the lowest rate of gain(1.08, 1.34 lb/day), but the TF+BFT and MB+BFT rates of gain were statistically equivalent to many of the higher energy grasses.
• Alternating versus mixed rows: Birdsfoot trefoil is preferred over tall fescue, and alternating rows may accelerate dominance of tall fescue. In late spring and early summer perennial ryegrass is preferred over birdsfoot trefoil, resulting in possible dominance of birdsfoot trefoil. Birdsfoot trefoil is preferred in mixtures with orchardgrass. The meadow bromegrass-birdsfoot trefoil mixtures show the least preferential grazing.
• The mixed row utilization was generally in between the alternating rows. This suggests a more stable mixture over time.

Objective 2

• Data relative to growth, health and reproductive capacity of the heifers was collected in 2017. These measurements include, weight, hip height, serum concentrations of blood urea nitrogen (BUN) and insulin-like growth factor-1 (IGF-1), conception rates, gene expression in oocytes and embryos, fecal parasite load.
• Preliminary statistics indicate that pasture had a significant effect (P < 0.01) on growth over time, indicating that different pastures have the capability to impact growth rates of developing heifers. There were no significant difference between pastures relative to change in hip height over time in preliminary analyses. However, additional years of data are needed in order to validate the effects of specific pastures on growth.
• Significant differences (P < 0.01) in BUN were noted between the different treatments over time. Specifically, heifers that consumed pasture that included birdsfoot trefoil (BFT) had a higher (P < 0.07) BUN at all time points, indicating an increased intake of protein/nitrogen in those animals.
• No differences in fecal parasite loads were detected between the different pasture treatments. Additionally, when comparing grass monocultures and pastures with BFT, there was no significant difference in fecal egg count, although the data at some time points was tending towards showing a difference. We anticipate that we might be able to further elucidate this difference with additional years of animals added to our data set.
• Furthermore, no differences in conception rates were noted in the heifers between the different pasture treatments. Currently, we are still completing analyses relative to serum IGF-1 concentrations and gene expression in oocytes and embryos.

Objective 3

• Plant samples were collected before and after each grazing event and dried for later analysis. Soil samples were collected in the fall at the beginning of the study for a baseline reading. Soil samples were collected in the spring, prior to grazing, and in the fall after the growing season using a Giddings® soil extraction instrument to a depth of 1.524 meters. Soil samples will also be collected in the spring of the third year to monitor nutrient movement. Four soil cores are taken in each plot and divided into three subsamples; 0-30.48 cm, 30.48-60.96 cm, 60.96-152.40 cm. Composite soil subsamples are analyzed for available nitrogen (ammonia and nitrate) and for total N.

• Soil water (leachate) nitrogen is monitored by means of zero-tension lysimeters that were previously installed at this location. Leachate is collected every two weeks during the growing season, and as close as possible to every two weeks during the winter months from zero-tension lysimeters. Suction cup lysimeters (60 cm deep) were installed in each plot, with samples being collected weekly by suction cup lysimeters. All leachate samples will be analyzed for nitrate-nitrite.