This study investigated the effect of the method of applying a fibrolytic enzyme (Promote (R); Cargill; Minnetonka, MN) on the performance of lactating dairy cows. A diet consisting of Tifton 85 bermudagrass silage, corn silage, and concentrate (35, 10 and 55% of dietary DM respectively) was fed ad libitum as a total mixed ration (TMR) twice daily. Cows were assigned randomly to the following five treatments: 1) control (no enzyme added), enzyme applied 2) at ensiling to bermudagrass (ES), 3) at mixing to the concentrate (EC), 4) at feeding to the TMR (ETMR), or 5) the bemmdagrass silage (EF). In Experiment 1, thirty Holstein cows (129 days in milk, DIM) were used in a completely randomized, cross-over design consisting of two 28-d periods, with 14 d for adaptation and 14 d for sample collection. Voluntary DMI, total tract apparent digestibility of DM, NDF and CP, milk production and component yields were not affected by enzyme supplementation. Cows fed ETMR had lower blood beta-hydroxybutyrate concentration, tended to have greater milk fat and protein concentrations and lower blood urea-N concentration than cows fed the control diet. In Experiment 2, five ruminally-cannulated cows were fed the same five diets for three consecutive 15-d periods to measure rumen fermentation (d 12) and in situ degradation (d 14 and 15). Compared to cows fed the control diet, ruminal pH tended to be lower in cows fed EC and ruminal NH3-N concentration was lower in cows fed the ETMR diet. The molar proportion of acetic acid was lower in cows fed ETMR and EF diets vs. the control diet. Total volatile fatty acid concentration and acetate: propionate ratio were lower in cows fed ETMR vs the control diet. Enzyme application did not affect in situ degradability except that the ES diet tended to degrade at a faster rate than the control diet. Enzyme application to the TMR gave the most desirable responses (tended to increase milk fat and protein concentrations and improved the efficiency of ruminal energy utilization and decreased ruminal protein degradation). However, enzyme addition did not affect intake, digestibility or milk yield.

This study was conducted to determine the stage of maturity at which the dry matter (DM) yield and nutritive value of velvet bean (Mucuna pruriens) is optimized. Mucuna was harvested at 77, 110 and 123 days after planting (DAP) from quadruplicate 5m×1m plots within each of 6 blocks. At each DAP, DM yield, chemical composition, botanical composition, in vitro rumen fluid-pepsin DM digestibility (IVDMD) and concentrations of total polyphenols, l-dopa and tannins were determined on the whole plant and botanical fractions. Whole-plant Mucuna DM yield increased (P<0.01) linearly with maturity; proportions of leaves and stems decreased linearly (P<0.01), whereas proportion of pods increased (P<0.01). Concentrations of neutral-detergent fiber (aNDF) in whole plant, leaf, and stem increased (P<0.05), or tended (P<0.10) to increase linearly with maturity, as did the acid-detergent fiber concentration of leaves and stems. Maturity decreased (P<0.05) ether extract concentrations of leaves linearly, and stems quadratically, but increased (P<0.05) whole-plant and pod starch concentrations. Pods contained relatively high concentrations of lysine, histidine, phenylalanine, aspartate, glutamate, leucine, isoleucine, and valine, but low concentrations of methionine and cystine. The essential amino acid index did not vary with maturity. Most minerals in Mucuna are concentrated in the leaves and the whole plant contains sufficient Ca, P, K, Mg, Fe, Cu, Na, Mo, Mn, and Zn for growing sheep, although their bioavailability of these minerals is unknown. Total polyphenol concentration quadratically (P<0.01) increased with maturity in the whole plant, tended to increase (P<0.10) in pods, linearly (P<0.01) decreased in stems and fluctuated in leaves. Maturity quadratically increased l-dopa concentration of the whole plant (P<0.05) and stems (P<0.01), but did not affect those of leaves and pods. Maturity quadratically increased (P<0.05) total tannin concentration in the whole plant, but decreased (P<0.10) that of pods. The l-dopa was concentrated in the seeds and pods of mature (110–123DAP) plants, but tannins were concentrated in leaves and stems. Whole-plant IVDMD was not affected by maturity, but digestible DM yield linearly (P<0.01) increased with increasing DM yield. There was a 2-week harvest window (110–123DAP) during which whole-plant crude protein and IVDMD remained unchanged. Nevertheless, harvesting at 123DAP gave the best combination of biomass yield and nutritive value.

In the first of two experiments, effects of applying NH3 or a fibrolytic enzyme (Promote®, Pr) on the fiber concentration, and dry matter (DM) and fiber digestibility of two tropical grass hays was measured. In Experiment 2, effects of applying NH3 or 3 fibrolytic enzymes, Biocellulase X-20® (X-20), CA® (CA), and Biocellulase A-20® (A-20) on the same variables as in the previous experiment were measured. In situ rumen degradability responses were also measured in Experiment 2. The forages were 12-week regrowths of Coastal bermudagrass hay (Cynodon dactylon; BE) and Pensacola bahiagrass hay (Paspalum notatum; BA). The NH3 was applied at 40 g/kg DM and the enzymes were applied at 0 (Control) 0.5, 1, and 2 times the rates recommended by the respective manufacturers. In vitro DM (IVDMD), neutral detergent fiber (NDF, IVNDFD) and acid detergent fiber (ADF, IVADFD) digestibilities were calculated after digesting the hays in buffered-rumen fluid for 6 or 48 h in 2 ANKOMII Daisy Incubators. In Experiment 1, Pr and NH3 application to BA resulted in hydrolysis of NDF into water-soluble carbohydrates (WSC). Whereas, application of both additives to BE resulted in less ADF and higher 6 h IVDMD. Ammoniated hays consistently had more CP than Pr-treated or Control hays, and only NH3 treatment increased 6 and 48 h IVNDFD and IVADFD of both hays. In Experiment 2, all additive treatments decreased the NDF concentration and increased 6 h IVDMD of BE. Enzyme X-20 increased the 48 h IVDMD of both hays and CA and A-20 had similar tendencies. Ammonia treatment increased the 6 h IVDMD of BA, the CP concentration of both hays, the 6 and 48 h IVNDFD of BE, and the 48 h IVNDFD of BA. The 6 h IVADFD of BE hay was improved by X-20, A-20, and NH3 treatment. Treatment with X-20 and NH3 increased the washing loss (‘a’) fraction of BE, but only NH3 treatment increased that of BA. Only ammoniation increased the insoluble, but potentially degradable (‘b’) fraction, the total degradable fraction (a + b) and potential degradability (P) of both forages. Therefore, these fibrolytic enzymes had negligible effects on the extent of fiber digestion and in situ DM degradation of the hays, but X-20 and A-20 treatment increased the initial and later phases of DM digestion. Ammoniation was more effective than any enzyme treatment at improving DM and fiber digestibility, and in situ degradability.

Mucuna pruriens seeds have relatively high crude protein (CP) concentrations, but little is known about their potential to replace commonly used CP supplements in ruminant rations. The aim of this experiment was to determine effects of replacing soybean meal (SB) with Mucuna on the performance of lambs. Forty Rambouillet lambs (33.2±5.73kg) fed a basal diet of maize grain, cottonseed hulls and urea were randomly assigned to one of four supplements formulated by substituting 0 (SB), 330 (Lo), 670 (Med) or 1000g/kg (Hi) of soybean meal with rolled Mucuna seeds. Lambs were housed individually in metabolic crates and allowed ad libitum access to isocaloric (metabolizable energy=11.7MJ/kg dry matter, DM) and isonitrogenous (CP=146g/kg, DM) diets for 14d of adaptation and 7d of total fecal collection. Fecal egg counts and coccidian oocyst scores were determined on d 14. Dry matter intake (1.7kg/d versus 1.5kg/d; P<0.05), CP digestibility (774g/kg versus 714g/kg DM; P<0.05) and N retention (28.0g/d versus 20.4g/d; P<0.01) were higher and amylase-pretreated neutral detergent fiber digestibility (617g/kg versus 686g/kg DM) was lower (P<0.05) in sheep fed SB versus Mucuna diets. However, supplementary protein source did not affect rumen pH, blood urea N or glucose concentration, or fecal egg counts. Increasing the level of Mucuna supplementation increased (P<0.05) level and efficiency of microbial protein synthesis, ruminal fluid acidity, total volatile fatty acid concentration, decreased (P<0.05) coccidian oocyst scores, and tended (P<0.10) to increase N retention. Therefore, SB is a better supplement than Mucuna to support performance of lambs. Nevertheless, Mucuna seeds are a promising CP supplement for situations where cost or availability precludes use of SB in ruminant rations.

This study examined effects of an enzyme preparation (Depol 740L, Biocatalyst, Pontypridd, UK) containing high esterase (32U/ml) activity on in vitro digestibility and ruminal in situ degradability of three tropical grass hays. The enzyme was applied at 0, 0.5, 1, 2 and 3g/100g dry matter (DM) to ground (1mm), 12-week regrowths of Pensacola bahiagrass (BAH), Coastal bermudagrass (C-B), and Tifton 85 bermudagrass (T-85) hays in a 3×5 factorial experiment replicated thrice. Twenty-four hours later, samples were incubated in triplicate for 6, 24 and 48h in buffered ruminal fluid in two ANKOM Daisy II incubators The enzyme was also applied at similar rates to ground (4mm) samples of hays and incubated in duplicate in each of two cows for 0, 3, 6, 9, 12, 24, 48, 72, 96 and 120h. Enzyme application enhanced (P<0.05) release of WSC from the hays. The 6 and 24h in vitro dry matter digestibility (IVDMD) of the hays increased linearly (P<0.05) as the enzyme application rate increased. Incremental enzyme addition increased (P<0.05) release of free ester and ether-linked ferulic acid from BAH and T-85, respectively, as well as ester-linked p-coumaric acid from T-85 and BAH. The 48-h IVDMD of C-B increased linearly (P=0.05) as enzyme application increased (487, 484, 489, 506, 510g/kg) but that of T-85 and BAH did not. The 6-h neutral detergent fiber (NDF) digestibility (IVNDFD) of T-85 increased linearly (P<0.05) with increasing enzyme addition (41, 34, 29, 61, 72g/kg), whereas that of C-B or BAH did not. In vitro 24-h IVNDFD of hays increased linearly (P<0.01) as enzyme application increased. Incremental enzyme addition increased (P<0.05) the in situ washout fraction of all hays, and the potentially degradable fraction, the extent of degradability, and the effective degradability of C-B. Enzyme application increased (P<0.05) the degradation rate of T-85 and decreased (P<0.01) the lag phase of C-B. This enzyme enhanced in vitro digestion and ruminal in situ degradation of hays, but the pattern and extent of improvement was forage specific.

The effects of addition of bacitracin methylene disalicylate (BMD) or virginiamycin (VM) to a corn-soybean meal diet on broiler performance and gastrointestinal tract (GIT) growth parameters and morphology were studied at various ages during growth and finishing. Male and female birds were killed at 1, 3, 5, or 7 wk of age for gross and histologic examination of the duodenum and ileum. Feeding either antibiotic increased BW and decreased intestinal length and weight at all times compared with control birds. However, intestinal length and weight decreases were greater in birds fed VM than BMD at 1 and 3 wk of age. The only change found in the duodenum resulting from dietary treatment was an increase in the number of villi per unit length in birds given VM but not BMD or control. In the ileum, the muscularis mucosa was thinner in birds given VM than in those fed the control diet. Chicks supplemented with VM had a smaller total villus area and shorter villus height and crypt depth in the ileum than birds fed the control diet or BMD. Physical changes in the intestine of birds given either antibiotic growth promoter, although not the same, resulted in improved performance.

Increased atmospheric CO2 and temperature typically lead to greater DM (dry matter) production of grassland plants; however, limited plant N may reduce this response. A 2‐yr study (1998–1999) was conducted to evaluate the effects and interactions among atmospheric CO2, temperature, and N fertilization rate on yield and nutritive value of ‘Pensacola’ bahiagrass (Paspalum notatum Flügge). Bahiagrass was field grown in Millhopper fine sand (loamy, siliceous Grossarenic Paleudult) under greenhouses with controlled atmospheric CO2 and temperature. Atmospheric CO2 levels were 360 and 700 μmol mol−1, and temperatures were B (baseline, corresponding to ambient in the greenhouse), B + 1.5°C, B + 3.0°C, and B + 4.5°C. Bahiagrass was fertilized at 80 kg N ha−1 (BG‐80) or 320 kg N ha−1 (BG‐320). Dry matter yield for BG‐80 remained the same regardless of CO2 level (7.5 and 6.3 Mg ha−1 in Years 1 and 2), but BG‐320 DM yield increased with increasing CO2 concentration in three of four harvests in Year 1 and from 14.8 to 17.3 Mg ha−1 in Year 2. Total N harvested response followed a similar trend as DM yield. Increasing temperature from B to B + 4.5°C had a positive effect on DM yield of BG‐80 (23%) and a lesser positive effect on BG‐320 (9% increase). Bahiagrass nutritive value increased due to greater N fertilization, but elevated CO2 concentration and temperature had no effect. Nitrogen fertilization affected bahiagrass DM yield response to CO2, but not the nutritive value response to elevated atmospheric CO2 or temperature.

Two sources of methionine (Met) activity are frequently used in commercial feed formulation: (DL)-2-hydroxy-4-(methylthio) butanoic acid (HMTBA), most commonly available as an 88% solution with 12% water; and (DL)-methionine (DLM, 99% powder). Despite the fact that both compounds have been in commercial use for over 50 yr, controversy and confusion remain with respect to their relative bioefficacy (RBE). This paper presents a review of the use of a nonlinear common plateau asymptotic regression technique (NLCPAR) that has been used to compare the 2 Met sources with particular emphasis on the validity of the basic assumptions of that model. The thesis of this paper is that the controversy is due, at least in part, to the misapplication of this regression technique to estimate the RBE of HMTBA and DLM. The NLCPAR model is a bioassay with the key dependent assumptions that HMTBA is a dilution of DLM, and that each follows dose-response curves of the same form and approach a common plateau. Because both provide Met activity, it may be considered reasonable to accept these assumptions; however, specifically testing them demonstrated that the assumption of a common dose-response is not supported by data. The common plateau assumption was tested with an alternative approach of fitting nonlinear separate plateaus asymptotic regression (NLSPAR) to a set of 13 published broiler studies in which the NLCPAR model had been used to estimate RBE of HMTBA and DLM. The hypothesis of a common plateau was rejected (P < 0.01), meaning that the conclusion that HMTBA had lower bioefficacy than DLM based on the NLCPAR methodology was not valid. An example using published data demonstrated that the NLSPAR model was a significantly better fit than the NLCPAR model, and showed that HMTBA and DLM followed different dose responses. Consequently, there was no single value for RBE for the entire dose range; rather, the RBE of the 2 compounds varied with use level. The evidence presented here indicates that separate plateau models should be used when comparing these 2 products. These more valid models can then be used for predictions of differences between HMTBA and DLM at levels of expected use.

Kratzer and Ash(1996) presented Experimentation Science as a process to accomplish the Scientific Method with a complete protocol including relevant statistical design and analyses The first principal to sound Experimentation Science is the principle of Relevance. This is a case study primarily of Relevance in Experimentation Science. In our consulting work we found a so called “performance” design as not relevant because of the use of null hypothesis testing to promote a concept of equivalence. The best alternative involves equivalence testing, more replication and representative-ness. Secondly we found a dose response design for two products where non-linear asymptotic regression is misused in applying Bioassay techniques to estimate a single relative biological efficacy (RBV) because the basic assumption of sameness of mathematical form does not hold. We offer a relevant model which involves predicted differences in the relevant zone of commercial use (Vazquez- Añón, M et al, 2006b, Gonzales-Esquerra et al, 2007).

OBJECTIVE:To determine the effect of a controlled-release monensin capsule administered at cessation of lactation on incidence of calving-related disorders, fertility, and milk yield in dairy cows.ANIMALS:290 dairy cows treated with monensin and 290 untreated control cows.PROCEDURE:Treated cows received a capsule that released monensin at 335 mg/d for 95 days. Incidence of calving-related disorders; daily milk yield up to 20 days postpartum; test-day milk yield, fat, protein, and mature-equivalent 305-day milk production; and body condition score at calving were determined. Reproductive variables were conception rate at first service, pregnancy rate, and calving-to-conception interval.RESULTS:Cows treated with monensin were 2.1 times as likely to develop dystocia and 0.8 times as likely to develop metritis as control cows. For milk yield, there was an interaction of treatment X time X parity. In multiparous cows, monensin significantly improved milk yield at test days 4 and 7. In addition, monensin increased body condition score at calving.CONCLUSIONS AND CLINICAL RELEVANCE:Despite increasing the likelihood of developing dystocia and metritis, administration of monensin improved the lactational performance of multiparous cows and may be a promising additive for use at the time of cessation of lactation.

Aging patterns of nine muscles from the chuck and round from two quality classifications of beef: USDA Select and upper 2/3 of USDA Choice grade were determined. The following muscles were evaluated: infraspinatus, triceps brachii – lateral head, triceps brachii – long head, serratus ventralis, complexus, splenius, rhomboideus, vastus lateralis and rectus femoris. Muscles were divided into four portions, progressing from anterior to posterior or dorsal to ventral orientation to the carcass depending on muscle fiber orientation. One steak was removed from each portion and aged for 7, 14, 21, or 28 d postmortem, then Warner–Bratzler shear force (WBSF) analysis was conducted. Consistent aging recommendations can be given for all muscles studied, as there was no aging by muscle interaction. An aging by USDA grade interaction was noted (P < 0.05). The upper 2/3 of USDA Choice need not be aged beyond 7 d. USDA Select should be aged at least 14 d. Steak location within muscle had an effect (P < 0.05) on WBSF values in four muscles. These data indicate that fabrication and merchandizing decisions should be made on an individual muscle basis.

The aim of this study was to determine if the nutritive value and aerobic stability of bermudagrass (Cynodon dactylon) silage could be improved by addition of proprietary, exogenous cellulase/hemicellulase enzyme preparations at ensiling. A 5-wk regrowth of Tifton 85 bermudagrass was conserved without treatment (control) or after treatment with exogenous fibrolytic enzymes including Promote NET (Pr), Biocellulase X-20 (X20), Biocellulase A-20 (A20), and Enzyme CT. The respective enzymes were applied at half the recommended rate, the recommended rate, or twice the recommended rate corresponding to 0.65, 1.3, and 2.6 g/kg of DM, 7.3, 14.5, and 29 mg/kg of DM, at 7.3, 14.4, and 29 mg/kg of DM, and 89, 178, and 356 mg/kg of DM, for Pr, X20, A20, and CT, respectively. The enzymes were sprayed on the bermudagrass at ensiling (not added at feeding as suggested by the manufacturers) to test the objectives of the study. Six 1-kg replicates of chopped (5 cm) forage were ensiled for 145 d in 2.8-L mini silos. Three silos per treatment were used for chemical analysis and 3 for aerobic stability monitoring. The silage juice was analyzed for organic acids, pH, water-soluble carbohydrates (WSC), ammonia-N, and soluble N. Freeze-dried samples were analyzed for crude protein (CP), neutral detergent fiber (NDF), and acid detergent fiber (ADF). In vitro digestibility of DM (IVDMD), NDF (IVNDFD), and ADF (IVADFD) were determined after digesting the silages in buffered rumen fluid for 6 or 48 h in 2 ANKOM(II) Daisy Incubators. Compared with the other silages, those treated with Pr had lower DM losses, and lower pH and ammonia-N concentration than control silages. Residual WSC concentration was greater in Pr- and CT-treated silages than in control silages and greater in Pr-treated silages than CT-treated silages. Compared with control silages, NDF concentration was lower in silages treated with Pr, X20, and CT, and ADF concentration was lower in silages treated with Pr, X20, and A20. Nevertheless, Pr-treated silages contained lower ADF and NDF concentrations than silages treated with the other enzymes. Enzyme-treated silages contained less acetic acid than control silages, and Pr-treated silages had the lowest concentrations of acetic acid. Aerobic stability was increased by enzyme treatment but microbial counts were not affected. The 6-h IVDMD was increased by treatment with Pr and A20, however only Pr increased the IVDMD and IVNDFD at 48 h. The 48-h IVADFD was also increased by treatment with Pr, CT, and A20. These results show that when applied at ensiling, certain fibrolytic enzymes (particularly Promote) can improve the digestibility, fermentation, and aerobic stability of bermudagrass silage.

The objective was to compare productive and metabolic responses of lactating dairy cows managed on 2 pasture-based systems using a concentrate supplement (n = 16) with those of a freestall housing system (n = 24). In a 259-d experiment, 3 multiparous Holstein cows were assigned at calving to each of 4 replicates of 2 pasture systems. For system 1, winter pastures were a mixture of rye, ryegrass, and crimson and red clover; summer pastures were pearl millet. Pasture system 2 included a rye-ryegrass mixture during winter and bermudagrass during summer. Pregraze herbage mass averaged 2.3 and 3.6 Mg/ha for winter and summer pastures, respectively; however, during August through September, pearl millet pregraze mass was reduced to about 1 Mg/ha. Daily dry matter intake by cows on pasture averaged 24.7 kg/d in winter and 19.0 kg/d in summer, of which 55% was from pasture; that of cows in confined-housing averaged 23.6 kg/d. Cows in confinement produced 19% more milk (29.8 vs. 25.1 kg/d) than those on pasture systems. Differences in concentration of milk fat, protein, or urea N were not detected among treatment groups. Grazing cows lost more body weight than confined cows (113 vs. 58 kg) and had lower concentrations of plasma glucose in the early weeks postpartum. Despite greater milk yield by cows housed in freestalls, milk income minus feed costs including that of pasture was similar for the 3 management systems. Although these pasture systems might be a viable management system in the southeastern US, extensive loss of body weight immediately postpartum for pasture-based cows are a potential concern.

Biogenic amines, total volatile base-nitrogen (TVB-N), and sensory evaluation are some of the indicators used for fish quality determination. Our objective was to evaluate the relationship among histamine, cadaverine, putrescine, TVB-N, and sensory evaluation as quality assessment tools. Two groups of six mahi-mahi fillets were refrigerated at 7 degreesC and sampled on days 0, 2, 4, 6, 8, and 10. On day 3, histamine, cadaverine, and putrescine levels reached 5, 3, and 0.5 mg/100 g, respectively, whereas TVB-N reached 30 mg/100 g. Sensory scores were 6 to 6.5 (10 very fresh and 1 very spoiled) for odor, appearance, texture, and color. Correlations were 0.78 and 0.72 between histamine and cadaverine and histamine and putrescine, 0.74 and 0.80 between TVB-N and cadaverine and TVB-N and putrescine, and 0.75 and 0.78 between odor and putrescine and odor and cadaverine. AromaMaps showed distinct trends for deteriorating mahi-mahi (Coryphaena hippurus) quality.

Local influence diagnostics can be used to assess the influence of predictor values in multiple linear regression. For n observations and k regressors, an eigenanalysis of an nk x nk matrix is required to assess the influence on the estimated coefficients. We provide the analytic expressions for the eigenvectors and show that they are easily computed, describe influence on the parameter estimates of a principal components regression, and are related to leverage, outliers, and added-variables plots. The results indicate that multicollinearity and overfitting contribute to a fitted model's sensitivity, leading to strategies for model assessment and selection.

Sources of variation in juice quality of `Valencia'sweet orange [Citrus sinensis(L.) Osb.] were quantified and their relative contributions to variability in juice quality were determined, from which sample sizes were estimated. Commercial orchards of `Valencia' sweet orange trees on Carrizo citrange [C. sinensis × Poncirus trifoliata (L.) Raf.] rootstock were selected at four geographic locations representing the major citrus-producing regions in Florida. Within- and between-tree variation in soluble solids concentration (SSC) and titratable acidity (TA) were estimated in two experiments over two or three seasons, respectively. Variance components for all treatment effects were estimated to partition total variation into all possible component sources of variation. Seasonal variation in SSC and TA was relatively small, but larger for TA than SSC. Variation in SSC among blocks within a location was intermediate to low, and was less than variation among locations. In contrast, tree-to-tree variation in SSC and TA was large, in spite of sampling from trees of similar vigor and crop load, and variation in SSC and TA among fruit was relatively large. Based on results of this study, samples consisting of 35 fruit are required to detect differences (P ≤ 0.05) of 0.3% SSC and 0.06% TA, whereas 20-fruit samples can be used to detect differences of 0.4% SSC and 0.08% TA. Seven replications are required to detect differences of 0.5% SSC and 0.1% TA, with small gains in precision when tree numbers exceed 10.

Despite interest in mucuna (Mucuna pruriens) as a green manure/cover crop, biomass production of its accessions has been poorly quantified, including in the Los Tuxtlas region of Veracruz, Mexico where smallholders have used maize (Zea mays)-mucuna systems increasingly since 1991. This on-farm research compared the biomass production of three mucuna varieties (white-, mottled-, and black seeded) in a rotational maize-mucuna system. Mucuna was sole-cropped during the first season (on eleven and five fields in 1996 and 1997 respectively), and its impact on the second-season maize yield was measured (on seven fields in 1996). White and mottled varieties produced equal biomass (7.92 and 6.74 t ha−1 in 1996 and 1997 respectively), and more than the black variety (6.85 and 4.90 t ha−1 in 1996 and 1997 respectively). Mucuna increased 1996/97 second-season maize grain yields by 50 % (from 0.97 to 1.46 t ha−1). Plots previously cropped with white and mottled varieties produced greater maize yield (1.55 t ha−1) than did black-variety plots (1.29 t ha−1). The research confirmed the higher productivity of the white and mottled varieties and the potential of the rotational system. Allocating the more desirable first-season growth period to mucuna and the riskier second season to maize is problematic, but the system may have potential in the region as a short-term fallow that permits second-season maize production.