Final report for GNE17-153
Supplemental grain is the greatest operational costs in organic dairy farms in the Northeast. However, one of the major limitations of feeding high-forage rations is the reduction in milk production and increased output of nitrogen (N) and enteric methane (CH4) to the environment. Therefore, forage-based diets must be designed to increase dietary energy intake (i.e., sugars and starch) relative to N as this approach has potential to increase the supply of essential amino acids (AA) for production of milk and milk components, while reducing urinary N excretion and enteric CH4 emissions to the environment. A balanced supply of dietary energy to N may also elicit change in the ruminal microbial community, thus providing further insights regarding nutrient use efficiency in dairy cows fed high-forage diets. To address these knowledge gaps, a feeding trial using different legume-grass mixtures was conducted to improve the economic and environmental sustainability of dairy farms in the Northeast.
Specifically, the feeding trial was conducted at the University of New Hampshire Organic Dairy Research Farm to investigate the effects of different legume-grass mixtures on ruminal microbial diversity and fermentation profile, feed intake, milk yield and composition, milk fatty acids (FA) profile, plasma concentration of amino acids, and enteric CH4 emissions. Two fields were planted with alfalfa (ALF)- or red clover (RC)-grass mixture with a 79:14:7 legume:meadow fescue:timothy seeding rate (% total). Forages were harvested as baleage, with second- and third-cut legume-grass mixtures used in the study. The botanical composition (dry matter basis) of second-cut ALF- or RC-grass swards averaged 65 vs. 80% legume, 17 vs. 15% grasses, and 18 vs. 5% weeds, while that of third-cut ALF- or RC-grass mixture averaged 84 vs. 96.5% legume, 3 vs. 2.3% grasses, and 13 vs. 1.2% weeds, respectively. Diets were formulated to contain (dry matter basis) 65% second- and third-cut ALF or RC-grass (32.5% of each cut) and 35% concentrate. Twenty lactating Jersey cows (n = 10/diet) was used in the study, which lasted 9 wk (2-wk baseline) with sample collection done at wk 4 and 7. Data were analyzed with repeated measures over time in SAS. Diets averaged 18.8 vs. 18.1% CP and 30.5 vs. 31% NDF for ALF- vs. RC-grass, respectively. In general, ruminal microbial diversity was minimally affected by diets. However, the ruminal proportion of acetate increased and that of propionate and butyrate decreased with feeding ALF- vs. RC-grass, respectively. No dietary differences were observed for feed intake, yields of milk and milk protein, and concentrations of milk fat and protein. In contrast, milk fat yield increased with feeding ALF-grass. Significant diet by wk interactions were observed for milk urea N (MUN) and milk proportion of total ꙍ-3 FA, with ALF-grass showing elevated MUN relative to RC-grass in wk 4 than wk 7, while ꙍ-3 FA increased more noticeably in cows fed RC- vs. ALF-grass in wk 7 than wk 4. Moreover, cows fed RC-grass had lower urinary N excretion than those offered ALF-grass.
A significant diet by wk interaction was observed for CH4 production, with cows fed RC-grass showing lower CH4 (378 vs. 424 g/d) in wk 4 but no change in wk 7 (mean = 416 g/d). The plasma concentration of the essential AA leucine increased with feeding RC-grass. Significant diet by wk interactions were found for the plasma concentrations of arginine, histidine, phenylalanine, tryptophan, valine, and total essential AA. Feeding RC-grass increased plasma arginine, phenylalanine, valine, and total essential AA in wk 7 but not in wk 4. Further, RC-grass enhanced plasma histidine more noticeably in wk 7 (+62%) than wk 4 (+38%). Compared with ALF-grass, plasma tryptophan decreased in cows fed RC-grass in wk 4 and increased in wk 7.
It can be concluded that ALF-grass improved milk fat production, while RC-grass decreased MUN and elevated milk FA (i.e., total ꙍ-3 FA) with potential human-health benefits. Lowered MUN can be linked to improve N utilization in lactating dairy cows. Further, the impact of forage sources on ruminal microbial diversity and CH4 emissions was small, but RC-grass appeared to be more effective than ALF-grass to elevate plasma concentrations of essential AA. The immediate impact of this research is that farmers should relay more on ALF-grass than RC-grass mixture to improve farm profitability due to increased milk fat production in cows fed ALF-grass. Red clover-grass mixtures are recommenced to reduce N excretion to environment due to reduced MUN and urinary N excretion to the environment.
This proposal is part of a recently funded USDA-NIFA-ORG project (award #2016-51106-25713) entitled “Developing advanced perennial legume-grass mixtures harvested as stored feeds to improve herd productivity and mitigate greenhouse gas emissions in organic dairies in the Northeast”. The scope of this larger USDA-NIFA-ORG project includes integrated research and educational approaches to mitigate greenhouse gas emissions through dairy cattle nutrition and agronomic trials in synchrony with outreach activities such as workshops and eOrganic webinars. In the current project, we are proposing 2 complementary research objectives and we will capitalize on the established outreach platform to deliver our Legume-Grass Mixture Feeding Guide, which is the direct educational product of the present submission to Northeast SARE. Our proposal addresses the Northeast SARE priorities: “reduction of environmental and health risks in agriculture” and “improved productivity, the reduction of costs, and the increase of net farm income”.
Specific objectives of this proposal include:
Objective 1: IDENTIFY AND QUANTIFY RUMINAL MICROOBIOTA
Identify and quantify ruminal microorganisms (i.e., bacteria, protozoa, and methanogens) in cows fed baleage harvested from different legume-grass mixtures designed to yield high energy:N ratio.
Objective 2: MEASURE BLOOD AMINO ACIDS
Measure the concentration of amino acids in blood plasma in cows fed baleage harvested from different legume-grass mixtures designed to yield high energy:N ratio.
We hypothesize that: (1) baleage harvested from red clover-grass or alfalfa-grass mixture may result in different organic matter digestibility ultimately affecting methane emissions in lactating dairy cows; (2) Compared with red clover, cows fed alfalfa-grass baleage would have more proteolysis in the rumen resulting in less amino acids available for milk production and milk protein synthesis as alfalfa lacks polyphenol oxidase.
The goal of this project was to provide scientific-based information regarding the trade-offs between milk production, nutrient utilization, and output of N and enteric CH4 to the environment in forage-based dairy systems. Our goal was accomplished by shedding light on the ruminal microbiota diversity and amino acids nutritional factors that modulate the relationship between efficiency of nutrient utilization and milk production in cows fed alfalfa- vs. red clover-grass baleage designed to yield a balanced energy to N ratio. Note that this research has immediate application on organic dairy farms currently feeding or interested in using legume-grass mixtures to improve production of milk and milk components while reducing their environmental impact.
Two fields were planted with alfalfa (ALF)- or red clover (RC)-grass mixture with a 79:14:7 legume:meadow fescue:timothy seeding rate (% total). Cultivar selection was based on recommendations from forage evaluation programs at Cornell University and the University of Wisconsin, as well as from commercial plant breeders. Forages were harvested as baleage, with second- and third-cut legume-grass mixtures used in the study. Twenty mid-lactation Jersey cows housed at the University of New Hampshire Burley-Demeritt Organic Dairy Research Farm were assigned to 1 of 2 treatments: 1) alfalfa-meadow fescue-timothy mixture (ALF-grass diet) or 2) red clover-meadow fescue-timothy mixture (RC-grass diet) in a randomized complete block design (n = 10 cows/diet). The botanical composition (dry matter basis) of second-cut ALF- or RC-grass swards averaged 65 vs. 80% legume, 17 vs. 15% grasses, and 18 vs. 5% weeds, while that of third-cut ALF- or RC-grass mixture averaged 84 vs. 96.5% legume, 3 vs. 2.3% grasses, and 13 vs. 1.2% weeds, respectively (Table 1). The nutritional composition of the baleages and concentrate used are presented in Tables 2 and 3, respectively. Diets contained (dry matter basis) 65% second- and third-cut ALF or RC-grass (32.5% of each cut) and 35% concentrate (Table 4). The study lasted 9 wk (2-wk covariate) with sample collection done at wk 4 and 7, and it was conducted from February to April, 2019. Cows were blocked based on parity and days in milk and fed individually twice daily using the electronic recognition Calan doors system. Animals were milked 2 times daily with milk production recorded at every milking event. Diets were fed as total mixed rations consisting (dry matter basis) of 65% baleage and 35% concentrate (14% crude protein).
Feed and refusal samples were collected weekly, pooled by period (i.e., wk 4 or 7), freeze-dried, ground (1-mm screen), and analyzed for dry matter, crude protein, soluble crude protein, neutral detergent fiber, acid detergent fiber, lignin, crude fat, starch, sugars, and net energy of lactation using wet chemistry by a commercial laboratory (Dairy One, Ithaca, NY). Milk samples with preservatives were collected during 4 consecutive milkings and analyzed for fat, protein, lactose, and milk urea-N (MUN) using mid-infrared reflectance spectroscopy (Dairy One). Milk samples without preservative were collected during 2 consecutive milkings and stored at -80°C until fatty acids analysis. Samples were extracted and analyzed for milk fatty acids using gas liquid chromatography at the Pennsylvania State University. Blood samples were collected from the tail vein using vacutainer tubes for 2 consecutive days approximately 4 hours after the morning feeding, pooled, and analyzed for amino acids (University of Missouri). After blood collection, samples were centrifuged (1,200 × g, 20 min, 4°C) and 4-mL aliquot of plasma were placed in test tubes containing 1.0 mL of 15% of sulfosalicylic acid followed by a second centrifugation at the same conditions. An aliquot of 1.8 mL of deproteinized plasma was removed and analyzed for amino acids by high performance liquid chromatography.
Fecal grab samples (~200 g) were collected once daily for 5 consecutive days at 6 am, 9 am, noon, 3 pm, and 6 pm by stimulating defecation or collected directly from the rectum. Samples were pooled by cow based on fresh weight over the 5 days to obtain a single composite and stored at -20°C. At the end of each sampling week, composited fecal samples were thawed, oven-dried at 55°C, ground (1-mm screen), and sent to a commercial laboratory (Dairy One) to be analyzed for crude protein, ash, and neutral and acid detergent fiber. Approximately 0.5-g of total mixed ration, individual feed ingredients, and feces were placed in 100-cm2 bags (n = 3 replicates/sample) and incubated in the rumen of a ruminally-fistulated lactating dairy cow for 12 days to determine the concentration of indigestible acid detergent fiber. Indigestible acid detergent fiber was used as an intrinsic marker to estimate fecal output of N and nutrient digestibility. However, this procedure will be repeated because the digestibility results came too low and we are not confident that the data are reliable.
Spot urine samples were collected once daily for 5 consecutive days concurrently with the fecal samples by massaging the pudendal nerve located below the vulva. Samples (~200 mL) were diluted with 0.072 N sulfuric acid to prevent N losses, pooled over the 5 days by cow, and stored at -20°C until analyzed for creatinine, allantoin, uric acid, urea, and total N using colorimetric methods. Daily urinary volume was estimated based on the concentration of creatinine assuming a constant creatinine excretion rate of 29 mg/kg of body weight. Urinary excretion of total N and total purine derivatives (allantoin plus uric acid) were calculated based on their concentration in the urine multiplied by the urinary volume. Total purine derivatives were used as intrinsic microbial markers to estimate microbial protein synthesis.
Methane emissions were measured using the GreenFeed system (C-Lock Inc., Rapid City, SD) throughout the 2-week covariate and 6-week sampling collection periods. The GreenFeed operates by releasing a bait feed up to 5 times per feeding event with a minimum of 45 s apart triggered by a radio frequency ear tag and the cow’s head located inside the feed manger resulting in accurate breath sampling and near real-time analysis of methane emissions using built-in non-dispersive infrared gas sensors. Gaseous measurements were done during voluntary visits of the cows to the GreenFeed unit, usually 4 to 5 times daily.
Samples of ruminal fluid (~250 mL) were collected once during the covariate period and weeks 4 and 7 from all cows via stomach tubing approximately 4 hours after the morning feeding. At each sampling, cows were restrained using a squeeze chute to minimize movement. After collection, samples were squeezed through 4 layers of cheesecloth with pH immediately measured using a portable pH meter. A 10-mL aliquot of strained ruminal fluid was added to 0.2 mL of 50% sulfuric acid and stored at -20°C for later analysis of volatile fatty acids by gas liquid chromatography (Dairy One; results not yet available). A second aliquot of rumen fluid samples (2 mL) was stored at -80°C in cryovial tubes until sent to the University of New Hampshire Hubbard Center for Genome Studies for DNA extraction, quantitative real-time polymerase chain reaction (qPCR), and PCR amplification and sequence analysis. Microbial DNA was extracted using the PowerSoil DNA isolation method (kit #12888-100; MO BIO Laboratories Inc., Carlsbad, CA) following the manufacturer’s guideline. DNA was eluted in 100 µL C6 solution and quantified using a NanoDrop 2000 UV-VIS spectrophotometer, and qPCR conducted in 1 µL of template DNA using the TaqMan 2x Universal PCR Master Mix Kit (Thermo Fischer Scientific, Waltham, MA) in a StepOnePlus Real-Time PCR System. Amplification of V4 variable region of the bacterial and methanogen 16S rRNA gene will be conducted using the primer pair 515F (5’GTGCCAGCMGCCGCCCTA-3’) and 806R (5’ GGACTACHVGGGTWTCTAAT-3’). The PCR amplifications were performed using the HotStarTaq Plus Master Mix DNA polymerase kit (QIAGEN, Germantown, MD). All PCR products were checked in 2% agarose gel to determine the success of amplification and the relative intensity of bands. Multiple samples were pooled in equal proportions based on their molecular weight and DNA concentrations and then purified using calibrated Ampure XP beads (Beckman Coulter, Brea, MA). The purified PCR products were used to prepare DNA libraries following Illumina TruSeq (Illumina Inc., San Diego, CA) DNA library preparation protocol. Sequencing was performed on a MiSeq (Illumina Inc.) following the manufacturer’s guideline. Sequence data was processed using Molecular Research DNA laboratory analysis pipeline. Operational taxonomic unit (OTU) was defined by clustering at 3% divergence (97% similarity). Final OTU was taxonomically classified using BLASTn against curated databases. After sequencing, bioinformatics was performed using the software MOTHUR. The microbiome (Objective 1) data are not completely available to date.
Data were analyzed using the MIXED procedure of SAS according to a randomized complete block design with repeated measures over time. The statistical model included treatments, block, week, interactions, and the covariate period (i.e., baseline). Block and block × treatment effects were considered random, whereas all other model terms were considered fixed terms
Legume-grass mixtures establishment:
We were able to establish 3 legume-grass cropping systems as originally proposed: 1) alfalfa-meadow fescue-timothy grass mixture, 2) red clover-meadow fescue-timothy grass mixture, and birdsfoot trefoil-meadow fescue-timothy grass mixture. All 3 fields were harvested as baleage and yielded 197 bales in 3 cuttings distributed as follows: 68 ALF-grass bales, 75 RC-grass bales, and 54 birdsfoot trefoil-grass bales. The botanical composition of the ALF-grass and RC-grass baleages was as expected with a greater proportion of legumes than grasses (Table 1). However, the birdsfoot trefoil-grass baleage botanical composition was not was a expected and resulted in much less proportion of legume than grass. In addition, the field was "spotty" with some parts where birdsfoot trefoil were partially established and other areas where birdsfoot was not present at all. Therefore, we decided not to use the birdsfoot trefoil-grass baleage in the feeding trial. Note that the proportion of legumes increased substantially at expense of grasses from cutting 2 to 3 for both ALF- and RC-grass mixtures (Table 1).
Objective 1: IDENTIFY AND QUANTIFY RUMINAL MICROBIOTA
The effect of ALF- or RC-grass diets on the diversity of the relative frequency of ruminal bacteria phylum is presented in Table 5. Overall, diets did not affect the relative frequency of several ruminal bacteria phyla. The most abundant bacteria phyla were bacteroidetes, firmicutes, and proteobacteria, which agree with the literature. The relative frequency of methanogenic archaea is presented in Table 6. Feeding ALF- or RC-grass did not significantly affect the relative abundance of different methanogenic archaea in the rumen. The impact of diets on CH4 production was not consistent between treatments, with fed RC-grass showing lower CH4 on wk 4 but no treatment differences were observed in wk 7 (see Table 12). Therefore, the lack of dietary effects on ruminal methanogens partially agrees with the inconsistent response in CH4 production when cows were offered ALF- vs. RC-grass mix. In fact, diets did not impact the ruminal diversity frequency of different methanogenic/archaea genus as shown in Table 6.
The effect of ALF- or RC-grass diets on ruminal fermentation profile is presented in Table 7. No significant differences between treatments were observed for the ruminal concentration of total volatile fatty acids. However, the ruminal molar proportion of acetate was greater (P < 0.001) with feeding RC-grass than ALF-grass likely in response to increased fiber intake. In contrast, the ruminal molar proportions of propionate (P = 0.05) and butyrate (P = 0.02). Elevated acetate and reduced propionate led to increased acetate:propionate ratio in cows fed RC-grass. The ruminal molar proportion of isovalerate decreased with feeding RC- vs. ALF-grass. In addition, significant treatment by wk interactions were found for the ruminal molar proportions of isobutyrate and valerate, with cows fed RC-grass showing a greater reduction in isobutyrate and valerate in wk 4 than wk 7. Reduced ruminal molar proportions of isobutyrate, valerate, and isovalerate in cows offered RC-grass is possibly explained by the presence of the enzyme polyphenol oxidase in RC tissues, which reduces proteolysis in the rumen.
Objective 2: MEASURE BLOOD AMINO ACIDS
Results regarding the the impact of ALF- or RC-grass diets on dry matter (DMI), feed efficiency, and milk yield and milk composition are presented in Table 8. No treatment effects were observed for DMI, milk yield, feed efficiency, concentrations of milk fat, protein, and lactose, and yield of milk protein and lactose. In contrast, cows fed ALF-grass had greater 4% fat-corrected yield (P = 0.05), energy-corrected milk yield (P = 0.06), and milk fat yield (P = 0.05) than cows offered RC-grass. These results suggest that ALF-grass improved dietary energy partition towards milk fat production compared with RC-grass. A significant treatment by week interaction was observed for MUN, with cows fed RC-grass showing a more pronounced decrease in MUN during wk 4 than wk 7. Note that red clover contains the enzyme polyphenol oxidase known to bind proteins and reduce proteolysis in the rumen. Less ammonia formation in the rumen results in decreased urea synthesis in the liver ultimately reducing urea circulation in the blood and reduced MUN concentration.
The effect of ALF- or RC-grass diets on plasma concentration of essential amino acids (EAA) is presented in Table 9. Treatment effects were observed for the plasma concentrations of histidine and leucine, with cows fed RC-grass showing increased concentration of these 2 EAA compared with cows offered ALF-grass. A treatment by week interaction was also observed for the plasma concentration of histidine, with a greater difference between treatments in wk 7 than wk 4. The plasma concentrations of phenylalanine (P = 0.08), valine (P = 0.06), and total branched-chain amino acids (P = 0.07) tended to be greater with feeding the RC-grass versus the ALF-grass diet. Further, significant treatment by wk interactions were observed for the plasma concentrations of arginine, phenylalanine, tryptophan, valine, and total EAA. Specifically, the plasma concentrations of arginine, phenylalanine, valine, and total EAA were greater in cows fed RC-grass in week 7, but no differences between diets were observed in wk 4. It is conceivable that RC polyphenol oxidase decreased ruminal degradation of protein in the RC-grass diet, thereby increasing the amount of AA to be absorbed post-rumen.
The effect of ALF- or RC-grass diets on plasma concentration of nonessential amino acids (NEAA) is presented in Table 10. Except for the plasma concentration of citrulline, which was greater (P = 0.01) in cows fed the RC-grass rather than the ALF-grass diet, no other changes in the plasma concentrations of individual NEAA were observed. Trends for increased plasma concentrations of ornithine (P = 0.07) and proline (P = 0.10) in cows fed RC- versus ALF-grass were detected as well. Significant treatment by week interactions were observed for the plasma concentrations of citrulline, hydroxyproline, and tyrosine. For concentrations of both hydroxyproline and tyrosine in plasma, cows fed ALF-grass in wk 4 had greater hydroxyproline and tyrosine while the opposite was found in wk 7. Further, the plasma concentration of citrulline did not differ between treatments in wk 4, but increased with feeding RC-grass in week 7.
The impact of ALF- or RC-grass diets on the proportion of selected milk fatty acids (FA) is presented in Table 11. Significant treatment effects were observed for the milk proportions of individual FA like 16:0, 18:0, trans-10 18:1, cis-9, cis-12 18:2 (linoleic acid), and cis-9, cis-12, cis-15 18:3 (α-linolenic acid). Specifically, the milk proportion of 16:0 decreased while that of 18:0 increased with feeding ALF- versus RC-grass, which may be explained by intake differences in 16:0 and 18:0 and reduced ruminal biohydrogenation of unsaturated FA leading to increased 18:0 due to activity of the enzyme polyphenol oxidase present in RC. It is well known that ruminal biohydrogenation of unsaturated FA is reduced by polyphenol oxidase. In fact, cows fed the RC-grass diet had greater proportions of linoleic (P = 0.03) acid and α-linolenic acid (P < 0.001) in the milk fat likely in response to reduced biohydrogenation of these unsaturated FA. The milk proportion of trans-10 18:1 was greater (P = 0.01) in cows fed RC-grass than those offered ALF-grass. Trans-10 18:1 is involved in milk fat depression and reduced milk fat yield in cows fed the RC-grass diet (Table 8) may be associated with elevated trans-10 18:1 in milk fat. Total milk branched-chain FA, ω-6 FA, and ω-3 FA all significantly increased in cows fed RC- versus ALF-grass, which may be related, at least partially, with less ruminal biohydrogentation of unsaturated FA with the RC-grass diet. The ω-6:ω-3 ratio decreased when cows were fed RC-grass, which together with the increased proportion of ω-3 FA suggest that the RC-grass mixture was better than the ALF-grass mixture to change the milk FA profile towards FA that may be more beneficial to human health. While the sum of 16-carbon FA increased in the milk fat of cows fed ALF-grass, that of 18-carbon increased with feeding RC-grass. Increased 16-carbon FA indicates that the origin of FA in milk fat was a mix between de novo synthesis in the mammary gland and blood extraction (dietary supply and/or mobilization from adipose tissues), whereas increased 18-carbon FA indicates that FA originated from blood extraction only. Significant treatment by week interactions were observed for the milk proportions of 16:0 and α-linolenic acid, as well as total ω-3 FA, ω-6:ω-3 ratio, and total 16-carbon FA.
The impact of ALF- or RC-grass diets on CH4 production, CH4 yield, CH4 intensity, and urinary N excetion is shown in Table 12. No treatment effects were observed for CH4 yield (mean = 19.9 g/kg of DMI) and CH4 intensity (mean = 15 g/kg of energy-corrected milk). However, a significant treatment by wk interaction was detected for CH4 production with cows fed ALF-grass producing more CH4 in wk 4, but no difference was found in wk 7. Note that reduced CH4 production in wk 4 with cows fed RC-grass was not related to DMI, which did not change significantly between treatments. A significant treatment by wk interaction was also observed for the urinary excretion of N; cows fed RC-grass had decreases urinary N excretion in wk 4 despite no difference between treatments in wk 7.
Overall, cows fed the ALF-grass diet showed increased production of 4% fat-corrected milk, energy-corrected milk, and milk fat suggesting better dietary energy partition towards milk fat synthesis compared with the RC-grass diet. However, cows fed RC-grass had lower MUN concentration and urinary N excretion than those fed ALF-grass indicating reduced ruminal proteolysis of dietary protein and improved N utilization. Moreover, RC-grass significantly elevated the plasma concentrations of the EAA histidine and leucine, and tended to increase phenylalanine and valine also suggesting reduced ruminal proteolysis and increased passage of dietary protein to the small intestine. While inclusion of RC in the diet improved the proportion of ω-3 FA in milk and reduced the ω-6:ω-3 ratio, it also increased the proportion of trans-10 18:1, which is known to be involved in milk fat depression. Based on the results of the current research, dairy farmers should feed baleage harvested from ALF-grass mixture than that from RC-grass mixture to maximize milk fat production, which can improve farm profitability. Interestingly, feeding baleage harvested from RC-grass mixture appears to be more environmentally-friendly due to improved N utilization assessed via decreased MUN concentration and urinary N excretion. Red clover-grass mixture also improved ω-3 FA and this is in line with milk FA profile that better match human health. Further research is needed to better understand energy partition in cows fed RC-grass, as well as the impact of RC on milk trans-10 18:1 FA.
Education & Outreach Activities and Participation Summary
Dr. André F. Brito supervised and mentored Mohammad Ghelich Khan to successfully complete this project. Specifically, Dr. Brito assisted Mohammad to write scientific abstracts for conferences and Northeast SARE reports. Mohammad attended the NOFA-NY Winter Conference and presented results of the project together with Dr. Brito. In this meeting in Syracuse-NY, Mohammad had the opportunity to meet farmers and extension educators to share project results and his experience conducting the project. Mohammad will also attend the 2020 American Dairy Science Annual Meeting in West Palm Beach, FL this upcoming June to share his project results during 2 oral presentations. Note that the UNH feeding trial was delayed a year because of issues to establish the forage crops used in the study. Therefore, Mohammad was not not able to present project results earlier. Mohammad also helped Dr. Brito to prepare the power-point slides for the Dairy Grazing Webinar Series hosted by the Pennsylvania State University Extension (https://psu.mediaspace.kaltura.com/media/Dairy+Grazing+Webinar+on+2.12.2020/1_21omj8bf) this February. An additional educational product of this project is the “The Legume-Grass Mixture Feeding Guide”, which was put together to provide scientific-based information to guide dairy farmers and extension educators to make decisions on how to incorporate legumes and legume-grass mixtures in dairy diets (see attachment).
The Legume-Grass Mixture Feeding Guide
We showed that cows fed alfalfa-grass mixture had increased production of butterfat and this can improve farm profitability because milk processors are currently paying more for milk fat than milk protein. Increased profitability can improve the economic and social sustainability of dairy farmers in the Northeast and beyond. It should be also noted that red clover-grass mixture improved N use efficiency in lactating dairy cows, resulting is less N excretion to the environment. In addition, red clover-grass mixture improve the proportion of ω-3 fatty acids in milk. It is well established that consumption of ω-3 fatty acids has been associated with improved human health. Note that project results were shared in several venues (i.e., workshops, conferences, field days), so that extension educators and farmers can adopt management strategies to improve the proportion of legumes in pasture and hayfields. Our previous research showed that most pastures and hayfields in the Northeast are predominately composed by grasses and the lack of legumes may result in less production of milk and milk components. We also put together "The Legume-Grass Mixture Feeding Guide" to provide scientific-based information to guide dairy farmers and extension educators to make decisions on how to incorporate legumes and legume-grass mixtures in dairy diets.
This project allowed our team to better understand how different legume-grass mixtures impacts milk production and composition and nutrient use efficiency in lactating dairy cows. Specifically, we observed that milk fat production increased in cows fed alfalfa- versus red clover-grass baleage, which can help dairy farmers improve farm profitability particularly because butterfat is currently paying more than milk protein. Our team also learned that feeding red clover-grass baleage improved N utilization, thus resulting less output of N to the environment Overall, our results reveald that organic dairy farms in the Northeast can be more profitable and environmentally-friendly.
As a Ph.D. student I have plans to work in academic jobs at university or government level. I am also open to industry and extension jobs so I can help dairy farmers improve the economic sustainability of their family enterprises.
Dr. Brito's lab will build up on the current project by conducting followed-up research grass-legume mixture feeding trials and applying for additional federal grants.
The establishment of the legume-grass fields were challenging particularly the birdsfoot trefoil-grass mixture that did not establish well and this treatment was not used in the feeding trial. We think that further research on varieties of birdsfoot trefoil that best adapt to the conditions of the Northeast is needed. Research is also needed to investigate the impact of red clover on ruminal biohydrogenation of unsaturated fatty acids and the consequent increase in the proportion of trans-10 18:1 in milk fat, which is a fatty acid known to cause milk fat depression in dairy cows. Further research is need to investigate why red clover is better than grasses to improve milk production and components but usually lag behind other legumes like alfalfa or birdsfoot trefoil. It is possible that differences in dietary energy partition may explain the discrepant results in milk production between legume sources. Finally, the role of phytoestrogens present in most legume sources, especially red clover warrants additional research because of the knowledge gaps regarding the impact of phytoestrogens on animal and human health.