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PubMed2002

Effect of exogenous fibrolytic enzyme on ruminal fermentation and digestibility of alfalfa and rye-grass hay fed to lambs.

This experiment was carried out to study the effect of a directly fed exogenous fibrolytic enzyme on intake and digestion of DM, OM, protein, NDF, ADF, and hemicellulose of alfalfa and ryegrass hay by sheep. Four diets were randomly assigned to four ruminally cannulated lambs using a 4 x 4 Latin square design, repeated in time, with a factorial arrangement (2 x 2) of diets: 1) alfalfa hay; 2) alfalfa hay + exogenous fibrolytic enzymes (enzyme); 3) ryegrass hay; and 4) ryegrass hay + enzyme. Lambs consumed more DM and OM from alfalfa than from ryegrass hay (P < 0.001). The ADF intake was not different between the hays, but NDF intake was lower for alfalfa (P < 0.001). For both hays, the enzyme increased intake of DM (P < 0.01), as well as OM and CP (P < 0.05); however, NDF and ADF intake were not changed. Alfalfa hay had higher apparent digestibility of DM, OM, and CP (P < 0.001), but lower digestibility for NDF, ADF, and hemicellulose. The enzyme increased apparent digestibility of CP, hemicellulose (P < 0.05), and NDF (P < 0.10) for alfalfa. Also, for both hays, the enzyme improved N balance because lambs retained more N (P < 0.05). The enzyme increased (P < 0.05) total VFA concentration (3 and 6 h) for both hays. Results from this trial indicate that directly fed exogenous fibrolytic enzymes may change ruminal fermentation, intake, and digestibility of forages with different nutritive value.

Animals↗

PubMed2005

Behavior, preference for, and use of alfalfa, tall fescue, white clover, and buffalograss by pregnant gilts in an outdoor production system.

Sustainable outdoor pig production requires vegetation that can maintain ground cover, assimilate manure nutrients, and prevent soil erosion. Two experiments were conducted to evaluate the suitability of four forages: alfalfa (Medicago sativa), tall fescue (Festuca arundinacea), white clover (Trifolium repens), and buffalograss (Buchloe dactyloides) for grazing or ground cover in pastures for pigs. Each forage plot covered 7.5 m2, with nine replicates in a randomized block design. In Exp. 1, eight pregnant gilts had free access to all forages during a 2-d adjustment period. Immediately thereafter, pairs of gilts were assigned randomly to one of each of four blocks of the four forages during a 2-d measurement period. The percentage of ground cover for each forage was visually estimated at 0, 24, and 48 h of study. Behavioral data, including walking, eating, grazing, rooting, drinking, standing, lying, and time spent in hut were video-monitored continuously for 48 h. Initial percentage of ground cover was 100% for all species. By 48 h, percentage of ground cover decreased (P < 0.001) for white clover (11.3 +/- 0.88%) and alfalfa (36.3 +/- 0.88%), but not for tall fescue (98.0 +/- 0.88%) or buffalograss (98.0 +/- 0.88%). Gilts spent more (P < 0.01) time grazing white clover (16.3 +/- 1.97 min/d) and alfalfa (11.2 +/- 1.97) than tall fescue (0.8 +/- 1.97) or buffalograss (0.3 +/- 1.97), and rooted more (P < 0.04) white clover than other forages. In Exp. 2, six gilts from the initial group were put on six blocks of the four forages. Each gilt was assigned randomly to three replicates of each forage, including alfalfa, tall fescue, or buffalograss (white clover was excluded because of damage by gilts during Exp. 1), and gilts grazed single forages for 2 d. After this grazing period, the percentage of ground cover was less (P < 0.01) for alfalfa than for buffalograss or tall fescue (37.5 +/- 0.38, 96.7 +/- 0.39, 96.3 +/- 0.39%, respectively). With access to a single forage, pregnant gilts spent more (P < 0.01) time grazing alfalfa (15.8 +/- 2.36 min/d) than buffalograss (1.5 +/- 2.36) or tall fescue (0.7 +/- 2.37). These gilts clearly preferred grazing white clover and alfalfa, and rooting and eating white clover compared with buffalograss or tall fescue. Rates of ground cover loss were less (P < 0.01) for tall fescue and buffalograss than for the more preferred forages. Less preferred forages could have potential as pasture for swine when the primary objective is ground cover maintenance rather than nutrient supply.

Animal Husbandry↗

PubMed2000

Effects of pea, barley, and alfalfa silage on ruminal nutrient degradability and performance of dairy cows.

Six Holstein cows in early lactation were used in a double 3 x 3 Latin square design to determine the effects of feeding diets with pea silage, relative to barley silage, or alfalfa silage. Cows were fed rations formulated to contain 50:50 forage:concentrate ratio. Two ruminally fistulated cows were used in a randomized complete block design to determine ruminal nutrient degradability for pea silage relative to barley and alfalfa silages. Pea silage contained lower neutral detergent fiber (NDF), acid detergent fiber, and starch concentrations but higher crude protein than barley silage. Compared with alfalfa silage, pea silage had higher starch and NDF but lower crude protein content. Pea and alfalfa silage had similar effective ruminal degradability of dry matter, which was higher than that of barley silage. The rate of degradation and effective ruminal degradability of NDF was highest for alfalfa silage, intermediate for pea silage and lowest for barley silage. Results of the lactation trial showed that dry matter intake and milk yield were not affected by forage source. Milk composition was similar for cows fed pea or barley silage; however, cows fed pea silage produced milk with a higher fat and a lower protein percentage than those fed the alfalfa silage. Pea silage can replace barley or alfalfa silage as a forage source for dairy cows in early lactation.

Animal Nutritional Physiological Phenomena↗

PubMed2002

Effect of supplemental tallow on performance of dairy cows fed diets with different corn silage:alfalfa silage ratios.

A study was conducted to investigate the response to supplemental tallow of lactating cows fed basal diets with different alfalfa silage:corn silage ratios. We postulated that supplemental tallow will have decreasing negative effects on rumen fermentation, dry matter intake (DMI), and milk fat percentage as the dietary ratio of alfalfa silage:corn silage is increased. Eighteen Holstein cows averaging 134 +/- 14 d in milk were used in a replicated 6 x 6 Latin square design with 21-d periods. Treatments were arranged as a 2 x 3 factorial with 0 or 2% tallow (DM basis) and three forage treatments: 1) 50% of diet DM as corn silage, 2) 37.5% corn silage and 12.5% alfalfa silage, and 3) 25% corn silage and 25% alfalfa silage. Cows were allowed ad libitum consumption of a total mixed ration. Diets were formulated to contain 18% crude protein and 32% neutral detergent fiber. No fat x forage treatment interactions were observed. Fat supplemented cows had lower DMI and produced more milk with less milk fat content relative to non-supplemented cows. Concentration of trans-octadecenoic acids was higher in milk fat of tallow-supplemented cows. Tallow supplementation had no effect on ruminal pH and acetate:propionate ratio, but tended to decrease total volatile fatty acid (VFA) concentration in the rumen. Increasing the proportion of alfalfa silage increased DMI, milk fat percentage, and milk fat yield regardless of the fat content of the diet. Total VFA concentration and acetate:propionate ratio in the rumen were increased in response to higher levels of alfalfa in the diets. These results suggest that replacing corn silage with alfalfa silage did not alleviate the negative response of dairy cows to tallow supplementation at 2% of diet DM.

Animal Feed↗

PubMed2003

The effect of treating alfalfa with Lactobacillus buchneri 40788 on silage fermentation, aerobic stability, and nutritive value for lactating dairy cows.

Lactobacillus buchneri 40788 and enzymes (beta-glucanase, alpha-amylase, xylanase, and galactomannase) were applied to chopped alfalfa (39% DM) to study their effects on the fermentation and nutritive value of the silage. Alfalfa was treated with nothing, or L. buchneri 40788, for a final application rate of 1 x 10(5), 5 x 10(5), or 1 x 10(6) cfu/g of fresh forage and ensiled in laboratory silos for 2, 4, 8, and 56 d. Treatment with L. buchneri 40788 had few effects on the end products of fermentation through 8 d of ensiling. However, after 56 d of ensiling, treated silages had a higher pH (4.55 vs. 4.38) and higher concentrations of acetic acid (6.40 vs. 4.24%), propionic acid (0.18 vs. 0.06%), and ammonia-N (0.35 vs. 0.29%) when compared to untreated silage. Lactic acid was also numerically lower in treated (3.51%) than untreated (4.12%). Silages treated with the moderate and highest dose of L. buchneri 40788 also resulted in greater recoveries of DM than did untreated silage. Alfalfa (43% DM) was also untreated or treated with a commercial application of L. buchneri 40788 (4 x 10(5) cfu/g, a commercial dose) in farm-scale bag silo. Holstein cows were fed a diet comprised of 32% untreated or treated alfalfa silage, 11% corn silage, 5% chopped alfalfa hay, and 52% of concentrate (DMB) for a 6-wk treatment period. Dry matter intake and milk composition were unaffected by treatment, but cows fed silage treated with L. buchneri 40788 produced 0.8 kg more milk than did cows fed untreated silage. Treated silage had a higher concentration of acetic acid (5.67 vs. 3.35%) but lower lactic acid (3.50 vs. 4.39%) than untreated silage. When exposed to air, the total mixed ration containing treated alfalfa silage remained stable for 100 h, whereas the ration containing untreated silage spoiled after 68 h. Treating alfalfa silage with L. buchneri 40788 increased the concentration of acetic acid, and when the silage was combined into a total mixed ration and fed to lactating cows, it improved the aerobic stability of the ration and increased milk production.

Acetic Acid↗

PubMed2003

Effects of particle size of alfalfa-based dairy cow diets on chewing activity, ruminal fermentation, and milk production.

Effects offorage particle size measured as physically effective NDF and ratio of alfalfa silage to alfalfa hay of diets on feed intake, chewing activity, particle size reduction, salivary secretion, ruminal fermentation, and milk production of dairy cows were evaluated using a 4 x 4 Latin square design with a 2 x 2 factorial arrangement of treatments. The diets consisted of 60% barley-based concentrate and 40% forage, comprised either of 50:50 or 25:75 of alfalfa silage:alfalfa hay, and alfalfa hay was either chopped or ground. Various methods were used to determine physically effective NDF content of the diets. Cows surgically fitted with ruminal and duodenal cannulas were offered ad libitum access to these total mixed diets. The physically effective NDF content of the diets was significantly lower when measured using the Penn State Particle Separator than when measured based on particles retained on 1.18-mm screen. Intake of DM was increased by increasing the ratio of silage to hay but was not affected by physically effective NDF content of diets. Eating time (hours per day) was not affected by the physically effective NDF content of diets, although cows spent more time eating per unit of DM or NDF when consuming high versus low alfalfa hay diets. Ruminating time (hours per day) was increased with increased physically effective NDF content of the diets. Rumen pH was affected more by changing dietary particle size than altering the ratio of silage to hay. Feeding chopped hay instead of ground hay improved ruminal pH status: time during which ruminal pH was above 6.2 increased and time during which ruminal pH was below 5.8 decreased. Milk production was increased by feeding higher concentrations of alfalfa silage due to increased DM intake, but was not affected by dietary particle size. Feed particle size, expressed as mean particle length or physically effective NDF was moderately correlated with ruminating time but not with eating time. Although physically effective NDF and chewing time were not correlated to mean rumen pH, they were negatively correlated to the area between the curve and pH 5.8, indicating a positive effect on reducing the risk of acidosis. Milk fat content was correlated to rumen pH but not to physically effective NDF or chewing activity. These results indicate that increasing physically effective NDF content of the diets increased chewing activity and improved rumen pH status but had limited effect on milk production and milk fat content.

Animal Nutritional Physiological Phenomena↗

PubMed2004

Effects of alfalfa particle size and specific gravity on chewing activity, digestibility, and performance of Holstein dairy cows.

Two experiments were carried out to test the effects of alfalfa particle size and functional specific gravity (FSG) on chewing activity, digestibility, rumen kinetics, and production of lactating dairy cows fed corn silage based rations. In experiment 1, water-holding capacity (WHC), insoluble dry matter, hydration rate, and FSG changes were determined in alfalfa hay (varying in particle size) and corn silage. Reduction of particle size increased bulk density, FSG, and the rate of hydration, and decreased WHC of alfalfa. In experiment 2, 9 midlactation Holstein dairy cows fed total mixed rations containing 3 sizes of alfalfa hay (with geometric mean 7.83, 4.04, and 1.14 mm) were used in a replicated 3 x 3 Latin square design. The diets contained 20, 20, 35, 7, 7.5, 10, 0.3, 0.1, and 0.1% of DM alfalfa, corn silage, barley, soybean meal, beet pulp, wheat bran, dicalcium phosphate, vitamin premix, and salt, respectively. The geometric means (GM) of rations were 3.34, 2.47, and 1.66 mm in long, medium, and fine alfalfa treatments, respectively. Reduction of particle size increased daily NDF intake (kg), but decreased the proportion of physically effective factor (pef) and physically effective NDF (peNDF) in the ingested rations. Reduction of particle size increased the FSG of rations and intake of DM but reduced digestibility of NDF and ash. Reduction of particle size decreased ruminal mean retention time (RMRT), but increased the ruminal particulate passage rate. Milk and FCM yield were not affected by treatments. The rumen pH, total chewing activity, rumination, eating time, and milk fat were reduced as particle size decreased, but milk protein increased. This study showed that reduction of forage particle size increased bulk density, FSG, and hydration rate of alfalfa and was the most influential factor affecting DMI, milk composition, and chewing behavior. Reduction of forage particle size had minimal impact on digestibility and milk production.

Animal Feed↗

PubMed1985

Milk production, nutrient digestion, and rate of digesta passage in dairy cows fed long or chopped alfalfa hay supplemented with sodium bicarbonate.

Effects of forage particle size and sodium bicarbonate on milk production, ruminal fermentation, ruminal fluid dilution rate, dry matter passage from the rumen, and nutrient digestion were measured in four Holstein cows in a 4 X 4 Latin-square experiment. Cows were fed ad libitum amounts of a diet of approximately 46% concentrate and 54% alfalfa hay. The 2 X 2 factorial arrangement of treatments were: 1) long stem alfalfa hay, 2) long stem alfalfa hay + 1.4% sodium bicarbonate (3.0% of concentrate), 3) chopped alfalfa hay (1.3 cm), and 4) chopped alfalfa hay + 1.4% sodium bicarbonate. Feed intake, milk yield, and milk composition were similar among treatments. Ruminal pH and concentration and molar percentages of volatile fatty acids were not altered. Decreasing feed particle size reduced ruminal fluid outflow as estimated by polyethylene glycol and chromium ethylenediamine tetraacetic acid dilution rates. Digestion of nutrients was decreased with chopped alfalfa hay but was not related to faster rate of passage of smaller size feed particles as determined by rare earth markers. Sodium bicarbonate increased water intake and tended to improve nutrient digestion. Absence of a significant effect of sodium bicarbonate upon rate of passage of chopped hay indicates that feed particles of this size are not significantly affected by small increases of dilution rate of ruminal fluid. Addition of sodium bicarbonate to an alfalfa hay (forage)-based diet did not improve production responses but did increase nutrient digestion.

Animal Feed↗

PubMed1985

Utilization of chopped and long alfalfa by dairy heifers.

Two physical forms of alfalfa hay, chopped and long, were fed at maintenance and for ad libitum consumption to dairy heifers to determine effects upon digestibility and energy utilization. Ad libitum intake was associated with lower digestibility of dry matter (56 versus 58%), neutral detergent fiber (45 versus 58%), and acid detergent fiber (45 versus 52%). Energy balance was 1.77 Mcal/day at ad libitum versus .08 Mcal/day at maintenance. Dry matter intake was similar for chopped (5.4 kg/day) versus long alfalfa (5.5 kg/day). Digestibilities of dry matter, neutral detergent fiber, acid detergent fiber, and cellulose were 7 to 10 percentage units lower when heifers were fed the chopped alfalfa. Metabolizable energy intake generally reflected digestible energy intake, which was about 2 Mcal/day less for heifers consuming chopped alfalfa. Heat production was similar for the two physical forms. Consequently, heifers consuming chopped alfalfa had lower energy balance. Reducing particle size of the alfalfa resulted in lower dry matter and energy digestibility, presumably because of increased rate of passage. Increased intake to compensate for depressed energy utilization of the chopped alfalfa did not occur; effects upon animal gain could not be assessed.

Animal Feed↗

PubMed1988

Particle size reduction of alfalfa silage did not alter nutritional quality of high forage diets for dairy cattle.

Twelve multiparous, lactating Holsteins were fed an energy adequate diet (50% wilted alfalfa silage) and two isonitrogenous diets containing 80% of the same silage. The two 80% alfalfa diets were identical in all respects except that for one diet 38% of the alfalfa silage was rechopped after fermentation to reduce the particle length from 5.63 to 3.12 mm. Feeding the 80% alfalfa diets decreased milk production due to limitation of digestible energy intake. Under conditions of energy restriction, reduction of particle size of alfalfa silage after fermentation did not result in any changes in feed intake, feed digestibility, or milk production. The results do not preclude the possibility of some changes for intake or digestibility with more extensive reductions in particle length of alfalfa silage. However, because the extent of forage particle size reduction is limited by nutritional and economic constraints, the results of this study indicate that there is no practical advantage to reducing the particle size of fermented alfalfa beyond that required for adequate fermentation.

Animal Feed↗

PubMed1988

Site and extent of nutrient digestion in lactating dairy cows fed alfalfa protein concentrate or soybean meal.

In vivo and in situ trials were conducted to investigate the utilization of alfalfa protein concentrate as a protein supplement for lactating dairy cows. In the in vivo trial, four Holstein cows fitted with ruminal, duodenal, and ileal cannulae were used in a crossover experiment to measure site and extent of nutrient digestion. Isonitrogenous and isoenergetic diets containing alfalfa protein concentrate or soybean meal were fed four times daily. Sixty percent of dietary total N was provided by the test proteins. Ruminal ammonia and total VFA concentrations were lower in cows fed alfalfa protein concentrate. Fractional digestion coefficient of organic matter (52 vs. 43%) and degradation of dietary protein (57 vs. 47%) in the rumen were slightly lower in cows fed alfalfa protein concentrate. The ratio of amino acid flow to the small intestine to dietary intake of amino acid was higher in cows fed alfalfa protein concentrate. In the in situ trial, rate of N disappearance (2.4 vs. 9.5%.h-1) and potential protein degradability (35 vs. 68%) were lower for alfalfa protein concentrate. Results suggest that alfalfa protein concentrate may be more resistant to ruminal degradation than soybean meal and could be utilized as a relatively undegradable protein source for milk production.

Animal Feed↗

PubMed1993

Chewing activity and digestive responses of cows fed alfalfa forages.

Nonlactating Guernsey cows were fed alfalfa silage or coarsely chopped, coarsely chopped and reconstituted, or long alfalfa hays. A computer system was developed to monitor chewing activity. Effects of diets upon chewing activity, digestibility, and ruminal parameters were determined. Digestibilities of DM and N were lower for silage than for hays. Cows fed silage had lower ruminal ammonia concentrations that were caused, at least in part, by greater bound N. Digestibilities of DM, N, and fiber were not different among the hays. The computer system recorded 98% of chews; visual measurements of chewing activity agreed well with computer-logged data. Cows spent more time (463 vs. 348 min/d) eating long alfalfa hay than silage; time spent ruminating, total chewing time, and chewing rates were not different among diets. During eating, cows fed hay had more chews per unit of DM or NDF than when eating silage; during rumination, diets had no effect. Eating time of cows fed alfalfa silage was less than for those fed alfalfa hay. Coarsely chopped alfalfa hay was as effective as long alfalfa hay in eliciting chewing activity.

Animal Feed↗

PubMed1994

Effects of forage particle size and long hay for cows fed total mixed rations based on alfalfa and corn.

A 2 x 2 factorial arrangement of treatments, in which particle length of alfalfa silage in the TMR and supplementary long alfalfa-grass hay were the factors, was used to determine whether hay benefits lactating cows and whether its effects depend on fibrosity of the main forage source. Without supplementary hay, TMR contained 45% forage, including corn silage, and 26 to 27.5% NDF. When hay was fed, the amount of alfalfa silage in the corresponding TMR was reduced. In the production trial, 40 cows (20 multiparous) were fed the diets for 8 wk in early lactation. No interactions of silage length and hay occurred on any production variables except lactose concentration in the milk of multiparous cows. Addition of hay to the diet enhanced DMI, without effect on production, so efficiency of milk production was reduced. Shorter alfalfa silage enhanced DMI by multiparous cows, reduced SCM and FCM in primiparous cows, and depressed fat test in both groups. Milk composition and component production generally were unaffected. Five rumen-fistulated cows in early to midlactation each were given the four treatments during four 3-wk periods. Hay enhanced rumination when short alfalfa silage was fed but tended to reduce it on long alfalfa silage. Hay also depressed rumen pH and enhanced VFA concentrations. Alfalfa silage length had minimal effects on rumination and no effect on fermentation, and neither hay nor silage length affected digestion of silage DM or NDF in the rumen. Addition of hay to the diet may not be beneficial for cows fed TMR, but longer term feeding studies are needed.

Ammonia↗

PubMed1997

Yield response of dairy cows fed different proportions of alfalfa silage and corn silage.

Forty-five multiparous and 29 primiparous cows were used in a complete lactation study to determine milk yield and the potential for improving N utilization by cows fed diets containing different proportions of alfalfa and corn silages. Cows were fed diets with a 50:50 forage to grain ratio. The forage portion of the diet was either all alfalfa silage, two-thirds alfalfa silage and one-third corn silage, or one-third alfalfa silage and two-thirds corn silage (dry matter basis). Treatment diets were fed to 6 ruminally cannulated cows to study dietary effects on ruminal fermentation. Diets were fed as a total mixed ration. Dry matter intake as a percentage of body weight was higher for cows fed the diet containing one-third corn silage. Mean 3.5% fat-corrected milk yield from wk 1 to 36 of lactation was 31.0, 32.9, and 31.8 kg/d for cows fed the alfalfa, one-third corn silage, and two-thirds corn silage treatment diets, respectively. For 305 d of lactation, milk yield for multiparous cows was 9593, 10,170, and 10,024 kg and for primiparous cows was 8124, 8412, and 8168 kg for cows consuming the alfalfa, one-third corn silage, and two-thirds corn silage treatment diets, respectively. Diets containing two-thirds corn silage decreased milk fat content of multiparous cows during early lactation. Ruminal NH3 concentration was lower and N excretion in the environment was reduced by 6 to 15% with the diets containing corn silage. Results suggested that corn silage should constitute one-third to two-thirds of dietary forage dry matter when fed with alfalfa silage to derive maximal benefit.

Ammonia↗

PubMed1999

Behavior of enterohemorrhagic Escherichia coli O157:H7 on alfalfa sprouts during the sprouting process as influenced by treatments with various chemicals.

The behavior of Escherichia coli O157:H7 on alfalfa seeds subjected to conditions similar to those used commercially to grow and market sprouts as it is affected by applications of NaOCl, Ca(OCl)2, acidified NaClO2, acidified ClO2, Na3PO4, Vegi-Clean, Tsunami, Vortexx, or H2O2 at various stages of the sprouting process was determined. Application of 2,000 ppm of NaOCl, 200 and 2,000 ppm of Ca(OCl)2, 500 ppm of acidified ClO2, 10,000 ppm of Vegi-Clean, 80 ppm of Tsunami, or 40 and 80 ppm of Vortexx to germinated seeds significantly reduced the population of E. coli O157:H7. With the exception of acidified NaOCl2 at 1,200 ppm, spray applications of these chemicals did not significantly reduce populations or control the growth of E. coli O157:H7 on alfalfa sprouts during the sprouting process. Populations of E. coli on alfalfa sprouts peaked at 6 to 7 log10 CFU/g 48 h after initiation of the sprouting process and remained stable despite further spraying with chemicals. The population of E. coli O157:H7 on sprouts as they entered cold storage at 9 +/- 2 degrees C remained essentially unchanged for up to 6 days. None of the chemical treatments evaluated was able to eliminate or satisfactorily reduce E. coli O157:H7 on alfalfa seeds and sprouts. Observations on the ability of E. coli O157:H7 to grow during production of alfalfa sprouts not subjected to chemical treatments are similar to those from a previous study in our laboratory on the behavior of Salmonella Stanley. Our results do not reveal a chemical treatment method to eliminate the pathogen from alfalfa sprouts. We have demonstrated that currently recommended procedures for sanitizing alfalfa seeds fail to eliminate E. coli O157:H7 and that the pathogen can grow to populations exceeding 7 1og10 CFU/g of sprouts produced using techniques not dissimilar to those used in the sprout industry.

Colony Count, Microbial↗

PubMed2005

The effect of predators and hymenopterous parasites on population fluctuations of alfalfa aphids.

Among alfalfa pests in Iran three aphid species, green alfalfa aphid Acyrthosiphon pisum Harris spotted alfalfa aphid Therioaphis trifolii forma maculata Buckton and blue alfalfa aphid, Acyrthosiphon kondoi Shinji are important pests. The green alfalfa aphid can be observed all along the growing season particularly from late May to mid June at Karaj climate conditions. During this period, the mean monthly maximum temperature and relative humidity were about 28 degrees C and 60-65% respectively. This aphid overwinters as nymph and viviparous female. Sexual forms and eggs could not be seen under field conditions. Spotted alfalfa aphid, Therioaphis trifolii fonna maculata is the most prevalent aphid in summer time, when the mean monthly maximum temperature and relative humidity are about 33-34 degrees C and 44-58% respectively. Sexual individuals have been observed in the laboratory but not in the field. Among predators (Coccinella septempunctata, Adonia variegata, Syrphus cinctus, S. corolae, S. grassulariae, Chrysoperla carnea and Nabis capsiformis) one coccinellid species, C. septempunctata, had greatest impact on fluctuations of population. Among hymenopterous parasitoids two species have been collected from alfalfa field they were Aphidius ervi and Praon palitans. These parasitoids destroyed a good percent of aphids and statistically proved to lower aphid populations significantly.

Animals↗

PubMedDate not supplied

15N estimates of dinitrogen fixation in alfalfa-weeping lovegrass swards under field conditions.

Information on the amount and proportion of alfalfa (Medicago sativa L.) N derived from symbiotic N2 fixation is required in order to exploit this source of N in alfalfa-weeping lovegrass (Eragrostis curvula Schrad Nees) pastures in semiarid Argentina. A field experiment was conducted to determine N2 fixation by a legume grown alone or in two different associations with weeping lovegrass, using pure or associated lovegrass as the reference crop. On average, alfalfa derived over 80% of its N from fixation during the seeding year, equivalent to about 140 kg N ha-1. Compared to N2 fixation in the pure alfalfa sward, the percentage of N derived from atmospheric N2 in alfalfa increased significantly in the associated pastures and even more so by increasing the seeding ratio of both crops sown in the same row. The atom % 15N excess in associated grass was sometimes slightly lower than that in pure lovegrass, suggesting any possible release of N from alfalfa and subsequent uptake by grass to have been small. The highest proportion of grass N that could have derived from the legume was estimated to be 23% in the second harvest, equivalent to only 6 kg N ha-1. Differences in atom % 15N excess of pure and associated grass reference plants did not significantly affect the estimated percentage of N derived from atmospheric N2 in alfalfa.

Argentina↗

PubMed2026

The dirigent protein MsDIR6 functions in drought tolerance and modulates reactive oxygen species scavenging and secondary metabolite biosynthesis in alfalfa.

Alfalfa (Medicago sativa L.) is a globally significant forage crop essential for ensuring global food security. However, soil water deficit leads to a substantial decline in its yield, posing a severe threat to sustainable forage production. Dirigent (DIR) proteins play important roles in lignan biosynthesis and plant stress responses. Here, we identified 52 MsDIR genes in alfalfa through a genome-wide analysis, and screened MsDIR6 as a key candidate gene associated with drought tolerance. The results of qRT-PCR showed that MsDIR6 transcription was significantly induced by drought stress in alfalfa. MsDIR6 was preferentially expressed in roots and leaves, and its protein was localized in the nucleus and plasma membrane. Heterologous expression of MsDIR6 in yeast improved tolerance to mannitol-triggered osmotic stress. Heterologous overexpression of MsDIR6 in Arabidopsis significantly increased seed germination rate, seedling survival rate, and antioxidant capacity under drought stress, while improving leaf water-holding capacity by regulating stomatal movement. In transgenic alfalfa hairy roots, MsDIR6 alleviated drought-induced growth inhibition and enhanced reactive oxygen species (ROS) scavenging mediated by the antioxidant defense system under drought stress. Transcriptomic analysis revealed that MsDIR6 activated key genes in the phenylpropanoid and flavonoid biosynthesis pathways, which are crucial for ROS scavenging during drought adaptation. Additionally, we observed elevated flavonoid and lignin contents in MsDIR6-overexpressing alfalfa. Collectively, our findings offer novel insights into alfalfa's drought tolerance mechanisms and identify MsDIR6 as a promising genetic resource for molecular breeding strategies to improve this vital forage crop.

Alfalfa↗