Digestible Organic Matter Content Research Articles

PSI-17 Use of Sunn Hemp as Forage for Early-Weaned Beef Calves

Abstract Sunn hemp (Crotalaria juncea) has been widely used as cover crop in the USA and due to superior biomass accumulation and nutritive value, there is interest from producers to use sunn hemp as forage for livestock. However, sunn hemp has pyrrolizidine alkaloids, which can affect animal performance. The objective of this study was to evaluate the effects of feeding sunn hemp hay to early-weaned beef calves in a dry lot in Florida. The experiment was conducted at the UF/IFAS Range Cattle Research and Education Center, Ona, FL from April to May 2021 (42 d). Treatments were calves receiving sunn hemp or stargrass (Cynodon nlemfuensis) hay distributed in a randomized complete block design with 12 replicates. Calves were supplemented with concentrate at 1.3% BW daily (18% CP and 78% TDN). Twenty-four Angus crossbred calves were weaned with 90 ± 14 kg BW and grazed annual ryegrass (Lolium multiflorum) with 1% BW concentrate supplementation for approximately 60 d. Subsequently, calves were randomly distributed and assigned to experimental units (pen) on 14 April 2021 with initial BW of 184 ± 10 kg. ‘Ubon’ sunn hemp hay was harvested approximately 49 d after seeding when 75% of the plants were initially flowering. Ground hay was fed daily targeting 10% refusals, and the initial CP and in vitro digestible organic matter concentrations of sunn hemp and stargrass hay were 9 and 48%, and 9 and 47%, respectively. The average concentration of pyrrolizidine alkaloids from sunn hemp hay was 58 μg/g DM. Early-weaned calves receiving stargrass had a tendency to have greater ADG than sunn hemp (0.5 vs. 0.4 kg/d, P = 0.09), and had greater forage DM intake (1.2 vs. 1.0% BW, P < 0.01) and total DM intake (2.5 vs. 2.3% BW, P < 0.01). Conversely, diets with sunn hemp had greater in vivo DM digestibility than stargrass (68 vs. 62%, P = 0.04). There was no difference between treatments on parasite egg count (mean = 45 eggs/3 g feces, P = 0.25) and coccidia egg count (log10 eggs/g feces, P = 0.35). Early-weaned calves receiving sunn hemp consumed 0.25 g pyrrolizidine alkaloids/d; however, there was no detectable amount (< 0.05 μg/g DM) of pyrrolizidine alkaloids in the feces. The presence of pyrrolizidine alkaloids in sunn hemp may be the potential cause of decreased early-weaned calves forage intake and animal performance.

Grazing intensity effects on sward responses of UF Riata Bahiagrass

AbstractBahiagrass (Paspalum notatum Flüggé) is a rhizomatous, perennial, warm‐season forage widely grown in the southeastern United States "UF Riata" bahiagrass is more upright growing with greater herbage production when days are shorter compared with most other cultivars. Lesser daylength sensitivity extends the grazing season, but in combination with more upright growth may negatively affect persistence under grazing, especially if out‐of‐season herbage production interferes with normal reserve storage. This 3‐year study investigated above and belowground sward responses of UF Riata bahiagrass to three levels of post‐grazing herbage mass (HM) (500 [heavy grazing, HG], 1500 [moderate grazing], or 2500 [light grazing, LG] kg DM ha−1, where DM is dry matter) imposed by mob stocking every 14 days. Total herbage accumulation (HA) and HA rate were not affected by treatment. Crude protein (CP) was affected by treatment × grazing cycle × year, whereas in vitro digestible organic matter concentrations were affected by treatment × year and grazing cycle × year. Root–rhizome biomass (12,940–9230 kg OM ha−1, where OM is organic matter) and soil cover percentage (97%–93%) decreased linearly as grazing intensity increased from LG to HG. Proportion of non‐planted grasses was 34% and 17% in HG and LG swards, respectively. Proportion of non‐grass weeds increased across treatments from 2% to 22% over the years. Moderate grazing could maintain similar CP to HG, and similar root–rhizome biomass to LG. Thus, considering both sward persistence and forage nutritive value, a target post‐grazing HM of ≈1500 kg DM ha−1 is recommended when UF Riata pastures are grazed every 2 weeks.

Potential of Tunisian carob pulp as feed for ruminants: chemical composition and in vitro assessment.

The nutritive value of the carob fruits harvested from ten different geographic regions of the North and the Center of Tunisia was assessed on the basis of chemical composition and in vitro rumen fermentation kinetic. Results showed that the chemical composition (ash, crude protein, fat, and sugar) of carob pods was highly influenced by geographic origin. Neutral detergent fiber varied from 24.37 to 35.58g/100g DM, acid detergent fiber from 13.24 to 25.15g/100g DM, and acid detergent lignin from 4.72 to 11.09g/100g DM. Total phenol, flavonoids, and condensed tannin contents varied from 2.55 to 6.84g gallic acid equivalents (GAE)/100g DM, from 74.89 to 276.51, and from 0.23 to 1.63mg catechin equivalents (CE)/100g DM, respectively. The samples varied widely in asymptotic gas production (66.6-86.34ml/300mg DM). The calculated metabolizable energy and digestible organic matter contents of carob pods ranged from 65.09 to 84.65% and 9.84 to 12.82MJ/kg DM, respectively.

The Quality, Intake, and Digestibility of Virginia Fanpetals (Sidahermaphrodita L. Rusby) Silage Produced under Different Technologies and Its Effect on the Performance of Young Cattle.

Simple SummaryCompetition for high-quality arable land has prompted a search for alternative forage crops. For example, Virginia fanpetals is a high-yielding perennial plant with low soil requirements. Due to its chemical composition, it can be a valuable component of ruminant diets. Previous research has shown that it cannot be used for hay production, and the natural moisture content of silage was unsatisfactory. Laboratory analyses suggest that the quality and feed value of Virginia fanpetals silage may be affected by harvesting and preservation methods. However, to date, most studies have focused on the nutritional value of Virginia fanpetals silage and its inclusion in animal diets. Therefore, the present study investigated different harvesting and preservation methods, such as direct-cut harvesting with a forage harvester, and harvesting after field wilting with a forage harvester or a round baler. The quality parameters, intake and digestibility of silage, and the performance of growing bulls, fed the experimental silage, as the sole forage was evaluated. It was discovered that the highest-quality silage was produced when herbage was harvested with a forage harvester after field wilting.Different harvesting and preservation methods of Virginia fanpetals herbage were evaluated, based on the chemical composition and digestible organic matter (OM) content (D-value) of silage fed to adult sheep, the intake and digestibility of silage, and the performance of young cattle. The following harvesting methods were compared: direct-cut harvesting with a precision-cut forage harvester (DC), harvesting after field wilting with a precision-cut forage harvester (WC) or a round baler (WRB). The silage was fed for 81 days to 24 Polish Holstein Friesian (HF) bulls, as the sole forage supplemented with 3.0 kg of concentrate/head/day. Harvesting methods affected the density (p < 0.001) and water-soluble carbohydrate (WSC) content (p = 0.047). Differences were found among the groups in the digestibility coefficients of OM (DC-73.7, WC-78.9, WRB-79.9%) (p = 0.007), and crude protein (CP) (69.8%, 77.1%, 78.5%, respectively) (p < 0.001). Dry matter intake (DMI) reached 8.38 kg (DC), 8.74 kg (WC) and 7.21 kg (WRB). Live weight gain (LWG) differed (p < 0.001) among groups (0.939, 1.033, 0.813 kg/day, respectively). The feed conversion ratio (FCR) tended to improve in WC (8.66 kg DMI/kg LWG) (p = 0.08). The highest-quality silage was produced in group WC, and it could be successfully fed to growing bulls as the sole forage.

Effect of ammoniation and harvest method on waste and consumption of corn residue bales fed to cows in a round bale feeder.

To determine the effects of harvest method and ammoniation (3.7% of dry matter) on consumption and waste of baled corn residue, a 6 × 6 Latin square with a 3 × 2 factorial treatment structure was conducted. Six treatments consisted of either nonammoniated or ammoniated residue, harvested one of three ways: conventional rake and bale (CONV), New Holland Cornrower with two rows of stem chopped into the windrow with tailings (2ROW), or EZBale system (EZB) with a disengaged combine spreader and tailings dropped in a windrow. Open cows were grouped by body weight to produce a light block of two pens (448 kg ± 49.6) and a heavy block of four pens (649 kg ± 65.9). One bale was fed to each pen during each of six 7-d periods using round bale ring feeders with closed bottom panels. Residue falling around (waste) and remaining in (refusals) the feeder was collected. The daily nutrient intake was estimated as the difference between what was offered and what remained (waste plus refusals). Crude protein (CP) of residue offered did not differ (P = 0.58) among harvest methods. The digestible organic matter (DOM) content of residue offered in 2ROW and EZB bales did not differ (P = 0.86) and was greater (P < 0.01) than CONV. Ammoniation increased (P < 0.01) CP and DOM content of the residue offered. Total wasted and refused residue did not differ (P = 0.12) between 2ROW (29%) and EZB (37%), while CONV (42%) was greater (P = 0.02) than 2ROW but did not differ (P = 0.34) from EZB. Ammoniation reduced (P = 0.03) total waste and refusals from 41% to 32%. The nutrient content of both waste and refusals did not differ (P ≥ 0.34) among harvest methods and, with the exception of CP, was not affected (P ≥ 0.15) by ammoniation. The CP content of the waste was greater (P = 0.02) and refusals tended to be greater (P = 0.08) from ammoniated bales. The CP intake of 2ROW was greater (P ≤ 0.02) than both EZB and CONV, while EZB tended (P = 0.06) to be greater than CONV. The CP intake of all ammoniated residues was greater (P < 0.01) than the nonammoniated residue. The DOM intake of nonammoniated 2ROW and EZB did not differ (P = 0.61) but was greater than nonammoniated CONV (P < 0.01). Ammoniation increased (P < 0.01) DOM intake. Overall, ammoniation had much larger effects than harvest method, resulting in reduced waste and refusals and greater intake of DOM and CP. However, the combination of both ammoniation and selective harvest (2ROW or EZB) was needed to result in energy and protein intakes that would meet the needs of a mature cow in mid-gestation.

Enhancing performance of berseem clover genotypes with better harvesting management through farmers\u2019 participatory research at smallholder farms in Punjab

A field study was conducted on smallholder farmer fields between 2012 to 2014 to evaluate the performance of cv. Agaitti Berseem-2002, against local landraces exchanged between farmers (LBF1) or available from local markets (LBM1). The effects of genotype and harvesting regimen on forage production, quality and seed production were evaluated. Significant differences (P < 0.05) among genotypes and cutting treatments were recorded for forage and seed yields, and forage quality across all research sites in both years. Maximum cumulative fresh forage (89.7 t/ha) and dry matter (DM; 13.4 t/ha) yields were obtained with Agaitti Berseem-2002 when harvesting occurred five times over the season. However, maximum seed yield (1048 kg/ha) with higher 1000-seed weight (3.63 g) were obtained if forage was only harvested three times and the crop then left for seed set. Agaitti Berseem-2002 also produced forage with the higher crude protein content (27%), DM digestibility (69%), digestible organic matter (DM basis; 65%) and metabolizable energy content (10%) compared to the local landraces (LBF1 and LBM1). Therefore, the harvesting regimen for greatest economic return which produced optimum fresh and DM forage yields of highest nutritive values and maximum seed yield, were comprised of taking three forage cuts (at 65, 110 and 150 days after sowing) prior to seed harvest.

Feeding and digestion of the marine isopod Idotea emarginata challenged by poor food quality and microplastics

Ingestion of microplastics can impair nutrition of marine invertebrates. In a laboratory study, we tested whether microplastics affect ingestion rates and gastrointestinal enzyme activities in the marine isopod Idotea emarginata. Isopods were fed for eight days with one out of four different food formulations: natural food (the brown alga Fucus vesiculosus) or synthetic diet consisting of freeze-dried algal powder embedded in agarose, both, with or without microplastic particles (fluorescent polymethyl methacrylate, 10–100 μm) at a concentration of 40 items per mg of food. The isopods accepted both types of food but consumed significantly more (average 3.1-fold) of the agar based synthetic food. I. emarginata responded to the reduced content of digestible organic matter in the synthetic food by a compensatory adjustment of the ingestion rates. Addition of microplastics had no effect on ingestion rates in natural food whereas the feeding rates for synthetic food varied in response to microplastics. Similarly, activity patterns of digestive enzymes, particularly those of esterases, changed significantly in the treatment with synthetic food. Isopods fed with synthetic food alone showed elevated esterase activities in the gut while those isopods fed with synthetic food and microplastics showed elevated esterase activities in the midgut gland but not in the gut. Apparently, not the exposure to microplastic alone, but the combined effects of reduced nutrient availability and microplastic ingestion caused considerable biochemical reactions in the digestive organs of the isopods.

Comparison of methods to estimate crude protein and digestible organic matter content of diets ingested by free-ranging sheep

Nutritional assessment of grazing ruminants, particularly on natural heterogeneous rangelands, remains a challenge for researchers and technicians. The aims of this study were: i) to compare methodologies of herbage sampling to determine crude protein (CP) and digestible organic matter (DOM) contents of ingested herbage and, ii) to evaluate the use of faecal near-infrared reflectance spectroscopy (fNIRS) to estimate those herbage attributes using either sampling procedure. Herbage samples were collected through hand-clipping (HC) or directly from rumen extrusa at the beginning (ExBM) and at the end (ExEM) of the longest daily sheep meal. In addition, DOM content of ingested herbage was also calculated from the amount of N excreted in faeces (FN). The study was conducted throughout thirteen consecutive months with six rumen-cannulated male sheep kept free on a rangeland plot in southern Brazil. Monthly, data on diet CP and DOM contents were collected by either method and related to near-infrared spectra of faeces collected from each respective sheep using the partial least squares method. Crude protein content in herbage ingested by sheep ranged from 108 to 172 g/kg DM and was, on average, lower (P < 0.05) in ExEM than in either ExBM or HC samples. Digestible organic matter content of ingested herbage, estimated through rumen in situ incubations, ranged from 546 to 717 g/kg DM and was, on average, similar for ExBM, ExEM, and HC samples. However, when this variable was estimated through the FN approach, values ranged from 446 to 601 g/kg DM and were, on average, lower (P < 0.05) than those found through other methods. The fNIRS models based on data obtained through extrusa (EX) and HC procedures produced similar and reliable results for estimating CP of herbage ingested by sheep, whereas the FN approach yielded the best fNIRS model for estimating DOM content of herbage.

Evaluating rumen fermentation kinetics and nutritive value of sunflower seed meal supplemented with acetonic extract of pomegranate peel using &lt;i&gt;in vitro&lt;/i&gt; gas production technique

This study was conducted to investigate effects of supplementing different levels (0.0, 0.5 and 1.0% of buffered rumen fluid) of acetonic extract of pomegranate peel on rumen fermentation kinetics of sunflower seed meal (SFM), using in vitro gas production technique. The samples were incubated in syringes containing rumen liquor obtained from three cannulated Iranian Ghezel rams for 2, 4, 6, 8, 12, 24 and 36h. Results indicated that, addition of acetonic extract of pomegranate peel resulted in increase in gas production volume in all of incubation times (p &lt; 0.0001). Amount of gas production, also increased by increasing dose of the extract. Amounts of a (the gas production from the immediately soluble fraction), b (the gas production from the insoluble fraction) and a + b (the potential gas production) for pomegranate peel extract supplemented sunflower seed meal were higher (p &lt; 0.05) than that of control meal. Adding pomegranate peel extract resulted in increase estimated short chain fatty acids (SCFA) production as well as digestible organic matter (DOM), metabolizable energy (ME) and net energy for lactation (NEL) content of SFM. Production of SCFA as well as DOM, ME and NEL content of SFM increased (p &lt; 0.05) by enhancing the level of the extract supplementation. In conclusion, it can be suggest that, supplementing acetonic extract of pomegranate peel may be lead to higher ruminal fermentation and better nutritive value of SFM in ruminants.

Effects of offering grass silage alone or in combination with lupin/triticale, lupin/wheat or pea/oat whole-crop silages on animal performance, meat quality and fatty acid composition of beef from cattle offered two levels of concentrate

AbstractAn experiment was carried out to examine the effects of offering beef cattle five silage diets. These were perennial ryegrass silage (PRGS) as the sole forage, tall fescue/perennial ryegrass silage (FGS) as the sole forage, PRGS in a 50:50 ratio on a dry matter (DM) basis with lupin/triticale silage (LTS), lupin/wheat silage (LWS) and pea/oat silage (POS). Each of the five silage diets was supplemented with 4 and 7 kg of concentrates/head/day in a five silages × two concentrate intakes factorial design. A total of 90 cattle were used in the 121-day experiment. The grass silages were of medium digestibility and were well preserved. The legume/cereal silages had high ammonia N, high acetic acid, low lactic acid, low butyric acid and low digestible organic matter concentrations (542, 562 and 502 g/kg DM for LTS, LWS and POS, respectively). Silage treatment did not significantly affect liveweight gain, carcass gain, carcass characteristics, the instrumental assessment of meat quality or fatty acid composition of theM. longissimus dorsimuscle. In view of the low yields of the legume/cereal crops, it is concluded that the inclusion of spring-sown legume/cereal silages in the diets of beef cattle is unlikely to be advantageous.

Annual and Perennial Peanut Mixed with ‘Pensacola’ Bahiagrass in North Florida

Fertilization of perennial grass pastures is a major expense in beef cattle operations, and grass pastures may degrade in the absence of N fertilization. Grass–legume mixtures can reduce the demand for N fertilizer use while increasing productivity of the system. Arachis spp. have shown potential for use in association with grasses in the southeastern United States. During 2014, 2015, and 2016, we evaluated one annual peanut species (Arachis hypogaea L. TUFRunner ‘727’) and two perennial peanut species, pintoi peanut (A. pintoi Krap. &amp; W.C. Greg ‘Amarillo’) and rhizoma peanut (A. glabrata Benth. ‘Florigraze’ and germplasm Ecoturf), when planted into previously established ‘Pensacola’ bahiagrass (Paspalum notatum Flügge) sod. Responses measured included herbage accumulation (HA), botanical composition, nutritive value, biological N2 fixation, and belowground root‐rhizome responses. TUFRunner 727 showed reseeding ability, illustrating potential for use as a short‐term forage, but by 2016, its contribution was negligible. In 2016, Ecoturf–bahiagrass had greater HA than unfertilized bahiagrass (4160 and 2710 kg ha−1, respectively), and the Ecoturf contribution to HA was ∼30% in 2016. Average N concentrations for Ecoturf and Florigraze were 25 and 22 g kg−1, respectively, and in vitro digestible organic matter concentration was 700 g kg−1 for both. Pintoi peanut contributed little to mixture HA in the first 2 yr, but it persisted and increased in proportion with time. Over the course of 3 yr, Ecoturf rhizoma peanut performed better than all other entries, exhibiting increasing participation in mixtures each year and the greatest total HA in 2016.

Chemical composition and in vitro digestibility of whole-crop maize fertilized with synthetic fertilizer or digestate and harvested at two maturity stages in Boreal growing conditions

Maize cultivation for silage could be a sustainable option in Boreal conditions, especially when combined with nutrient recycling. Effects of digestate (sludge from biogas of domestic origin) application in comparison with synthetic fertilizer and two maturity stages on chemical composition and in vitro digestibility of whole-crop maize were investigated. Starch, neutral detergent fiber, water soluble carbohydrate (WSC) and digestible organic matter (DOM) contents of maize did not differ in response to the two fertilizer treatments. However, starch, DOM and metabolizable energy of maize increased, while ash, crude protein and WSC contents decreased with increasing maize maturity. Heavy metals in maize fertilized with digestate remained low. The results indicate that whole-crop maize fertilized with digestate and harvested at 150 days after sowing is a promising feed and has good nutritive value, even in Boreal conditions.

Equations to predict methane emissions from cows fed at maintenance energy level in pasture-based systems

Ruminant production is a vital part of food industry but it raises environmental concerns, partly due to the associated methane outputs. Efficient methane mitigation and estimation of emissions from ruminants requires accurate prediction tools. Equations recommended by international organizations or scientific studies have been developed with animals fed conserved forages and concentrates and may be used with caution for grazing cattle. The aim of the current study was to develop prediction equations with animals fed fresh grass in order to be more suitable to pasture-based systems and for animals at lower feeding levels. A study with 25 nonpregnant nonlactating cows fed solely fresh-cut grass at maintenance energy level was performed over two consecutive grazing seasons. Grass of broad feeding quality, due to contrasting harvest dates, maturity, fertilisation and grass varieties, from eight swards was offered. Cows were offered the experimental diets for at least 2 weeks before housed in calorimetric chambers over 3 consecutive days with feed intake measurements and total urine and faeces collections performed daily. Methane emissions were measured over the last 2 days. Prediction models were developed from 100 3-day averaged records. Internal validation of these equations, and those recommended in literature, was performed. The existing in greenhouse gas inventories models under-estimated methane emissions from animals fed fresh-cut grass at maintenance while the new models, using the same predictors, improved prediction accuracy. Error in methane outputs prediction was decreased when grass nutrient, metabolisable energy and digestible organic matter concentrations were added as predictors to equations already containing dry matter or energy intakes, possibly because they explain feed digestibility and the type of energy-supplying nutrients more efficiently. Predictions based on readily available farm-level data, such as liveweight and grass nutrient concentrations were also generated and performed satisfactorily. New models may be recommended for predictions of methane emissions from grazing cattle at maintenance or low feeding levels.

An evaluation of the performance and efficiency of nitrogen utilization in cattle fed tropical grass pastures with supplementation

The objective of this study was to evaluate the efficiency of nitrogen utilisation (ENU) and animal performance in cattle fed tropical grass pastures and receiving nitrogen supplementation, using a meta-analytical approach. The dataset used to evaluate the ENU was compiled from 10 experiments carried out in Brazil, which were published between 2009 and 2012, totalling 47 treatment means. To compose the dataset for animal performance evaluation, mean treatment values were collected from 44 experiments involving grazing beef cattle, which were published in Brazil from 2001 to 2012, totalling 182 treatment means. The relationships between variables were evaluated using linear or non-linear mixed models, taking into account the random variations among experiments. There was no association between ENU and the balance of nitrogen in the rumen and the efficiency of microbial synthesis in the rumen (P>0.05). The ENU was linearly associated with the dietary content of digestible organic matter in the diet (DOM) and relative production of microbial nitrogen in the rumen (NMICR), which was positive with DOM (P<0.04) and negative with NMICR (P<0.03). The relationships between ENU and dietary crude protein (CP) and the concentration of rumen ammonia nitrogen (RAN) were described using hyperbolic models (P<0.05). The estimated values that correspond to the apparent equilibrium point (i.e., ENU=0) were 108g CP/kg of dry matter and 6.30mg RAN/dL of rumen fluid. There was a positive response on weight gain as the amount of supplement increased (P<0.01). However, this relationship was interactively affected by CP content in the supplement (P<0.02) and in the forage (P<0.01). Through this way, the response of weight gain to supplement is improved by increasing the CP content of the supplement, but decreased as the CP in the forage increases. From this it can be conclude that there is a positive response to nitrogen supplementation with regards to ENU and animal performance. The main benefit of supplementation is the improvement of the nitrogen status in the animal׳s metabolism.

Evaluation of the nutritive values of quail litter for ruminants after pelleting

The aim of this work was to study the nutritional value of pelleted meat quail litter (PMQL) and pelleted layer quail litter (PLQL). Both types of litter were pelleted, and the nutritive values were analyzed. The results showed that the total ash (TA), crude protein and acid detergent fiber (ADF) contents for the PMQL were much lower than those for the PLQL (P 0.05) different between the PMQL and PLQL. Estimations of the metabolizable energy (ME) were predicted from rumen fluid-pepsin in vitro digestible organic matter content of the DM (MEIV) and organic matter loss during a 72-h rumen incubation (ME-RI). The ME contents were closely correlated with the sum of the TA and ADF, and the correlation coefficient for the ME-IV was -0.881 and 0.913 for the ME-RI. Useful estimations of the ME from the TA and ADF values of the litter samples could be made utilizing regression equations for either ME-IV or ME-RI, with the ME-RI being preferred for its slightly greater correlation coefficient, ME-RI (MJ/kg DM) = 12.7 ‐ 0.0104 (TA + ADF) (g/kg DM).

Agro-ecological nitrogen management in soils vulnerable to nitrate leaching: a case study in the Lower Suwannee Watershed

Environmental benefits associated with reduced rates of nitrogen (N) application, while maintaining economically optimum yields have economic and social benefits. Although N is an indispensable plant nutrient, residual soil N could leach out to contaminate groundwater and surface water resources, particularly in sandy soils. A 2-year field study was conducted in an established bermudagrass (Cynodon dactylon) pasture in the Lower Suwannee Watershed, Florida, to evaluate N application rates on forage yield, forage quality, and nitrate (NO3-N) leaching in rapidly permeable upland sandy soils. Four N application rates (30, 50, 70, and 90 kg N ha−1 harvest−1) corresponding to 0.33, 0.55, 0.77 and IX, respectively, of recommended N rate (90 kg N ha−1 harvest−1) for bermudagrass hay production in Florida were evaluated vis-a-vis an unfertilized (0 N) control. Suction cups were installed near the center of each plot at two depths (30 and 100 cm) to monitor NO3-N leaching. The grass was harvested at 28 days intervals to determine dry matter yield, N uptake, and herbage nutritive value. Nitrogen application at the recommended rate produced the greatest total dry matter yield (~18.4 Mg ha−1 year−1), but a modeled economically optimum N rate of ~57 kg N ha−1 harvest−1 (~60% of the recommended N rate) projected an average dry matter yield of ~17.3 Mg ha−1 year−1, which represents >90% of the observed maximum yield. Nitrogen application increased nutritive quality of the grass, but increases in N application rate above 30 kg N ha−1 did not result in significant increases in in vitro digestible organic matter concentration, and tissue crude protein was not significant above 50 kg N ha−1. Across the sampling period, treatments with N rates ≤50 kg N ha−1 harvest−1 had leachate NO3-N concentration below the maximum contaminant limit of <10 mg l−1. Conversely, applying N at rates ≥70 kg N ha−1 harvest−1 resulted in leachate N concentration that exceeded the maximum contaminant limit, and suggest high risk of impacting groundwater quality, if such rates are applied to soils with coarse (sand) textures. The study demonstrates that recommendation of a single N application rate may not be appropriate under all agro-climatic conditions and, thus, a site-specific evaluation of best N management strategy is critical.

Pepsin-Cellulase Digestibility of Pasture Silages: Effects of Pasture Type, Maturity Stage, and Variations in the Enzymatic Method

Enzymatic in vitro digestibility has been studied as a method to predict energy values of forages for ruminants, although results have been affected by type of forage and methodological details of the technique. This work was performed to evaluate the effects of cellulase concentration (0.75, 1.0 and 6.25 g L -1 ), incubation time (24 or 48 h) and type of final washing of the residue (water or acetone) on the in vitro digestibility of the dry matter (DMD), organic matter (OMD) and content of digestible organic matter in the DM (D value) of silages made at three maturity stages from three types of pastures: a) permanent pasture (Dactylis glomerata, Lolium perenne, Bromus catharticus Vahl var. catharticus, Trifolium repens and Holcus lanatus); b) Italian ryegrass ley (Lolium multiflorum Lam. cv. Tama); c) oats (Avena sativa L.) and d) mixed pasture (L. perenne-T. repens). Regression equations among cellulase results and in vitro values obtained with rumen fluid were also developed. Higher enzyme concentration, longer incubation time and final washing with acetone, resulted in a significant (P < 0.05) increase in DMD, OMD and D value. A strong interaction (P < 0.001) among forage type, maturity stage and incubation time was observed. Interactions between stage and enzyme concentration were also apparent (P < 0.05) for D value, DMD and OMD. Type of pasture and maturity affected the performance of the enzymatic method to predict in vitro digestibility obtained with rumen fluid. Therefore, different prediction equations should be developed for any combination of the above mentioned factors. Adjusting this methodology with in vivo data is encouraged to improve prediction of digestibility values.

Forage Species and Stocking Rate Effects on Animal Performance and Herbage Responses of ‘Mulato’ and Bahiagrass Pastures

Bahiagrass (Paspalum notatum Flügge) is the most used forage for beef cattle (Bos sp.) in Florida; however, damage to bahiagrass pastures by mole cricket (Scapteriscus spp.) stimulated a search for other adapted grasses. The objective of this study was to test the effect of different stocking rates (SRs) on animal performance and herbage characteristics of ‘Mulato’ (Brachiaria sp.) and bahiagrass pastures. The experiment was conducted in Ona, FL, from May to September, 2007 and 2008. Treatments were three SRs (4, 8, and 12 heifers ha−1) and two forage species (Mulato and ‘Pensacola’ bahiagrass). There was a linear decrease in herbage mass (from 5.9 to 3.2 Mg ha−1) and herbage allowance (from 2.8 to 0.6 kg dry matter kg−1 liveweight)with increasing SR. Mulato had greater in vitro digestible organic matter concentration than bahiagrass (675 vs. 534 g kg−1) but similar crude protein concentration (130 g kg−1). There was a linear decrease in average daily gain (from 0.49 to 0.22 kg d−1) and a quadratic response of liveweight gain ha−1 as SR increased (190, 353, and 217 kg ha−1 for SRs of 4, 8, and 12 heifers ha−1, respectively). Mulato has potential to be an alternative forage to bahiagrass for beef cattle producers in Florida.

Evaluation of tomato crop by-products as feed for goats

The potential nutritive value of tomato by-products, both fruits and vegetative parts, was assessed by chemical analyses as well as by organic matter (OM) and crude protein (CP) in sacco degradability and in vitro organic matter digestibility. Tomato fruits contained 69 g dry matter (DM) per kg fresh fruit and the average composition, per kg DM, was 923 g OM, 28 g ether extract (EE), 170 g CP and 260 g ash-free neutral detergent fibre (NDFom). Whole tomato plants contained 177 g DM per kg fresh plant and their average composition, per kg DM, was 819 g OM, 12 g EE, 74 g CP and 457 g NDFom. Effective ruminal degradable and in vitro digestible OM content of tomato fruits were 534 and 583 g/kg DM, respectively, and those of tomato plants were 274 and 474 g/kg DM. Effective degradable CP content of tomato fruits and plants was, respectively, 33 and 20 g/kg DM. Daily ingestion of fresh tomato fruits more than 1.5 kg (about 100 g DM) caused soft faeces in goats.

Whole crop cereals: 1. Effect of method of harvest and preservation on chemical composition, apparent digestibility and energy value

A total of 133 samples (53 fermented unprocessed, 18 fermented processed, 62 urea-treated processed) of whole crop wheat (WCW) and 16 samples (five fermented unprocessed, six fermented processed, five urea-treated processed) of whole crop barley (WCB) were collected from commercial farms over two consecutive years (2003/2004 and 2004/2005). Disruption of the maize grains to increase starch availability was achieved at the point of harvest by processors fitted to the forage harvesters. All samples were subjected to laboratory analysis whilst 50 of the samples (24 from Year 1, 26 from Year 2; all WCW except four WCB in Year 2) were subjected to in vivo digestibility and energy value measurements using mature wether sheep. Urea-treated WCW had higher (P<0.05) pH, and dry matter (DM) and crude protein contents and lower concentrations of fermentation products than fermented WCW. Starch was generally lower in fermented, unprocessed WCW and no effect of crop maturity at harvest (as indicated by DM content) on starch concentrations was seen. Urea-treated WCW had higher (P<0.05) in vivo digestible organic matter contents in the DM (DOMD) in Year 1 although this was not recorded in Year 2. There was a close relationship between the digestibility values of organic matter and gross energy thus aiding the use of DOMD to predict metabolisable energy (ME) content. A wide range of ME values was observed (WCW, 8.7–11.8 MJ/kg DM; WCB 7.9–11.2 MJ/kg DM) with the overall ME/DOMD ratio (ME = 0.0156 DOMD) in line with studies in other forages. There was no evidence that a separate ME/DOMD relationship was needed for WCB which is helpful for practical application. This ratio and other parameters were affected by year of harvest (P<0.05) highlighting the influence of environmental and other undefined factors. The variability in the composition and nutritive value of WCW and WCB highlights the need for reliable and accurate evaluation methods to be available to assess the value of these forages before they are included in diets for dairy cows.