Stover Silage Research Articles

Yield, quality and ensilage characteristics of whole‐crop maize and of the cob and stover components: harvest date and hybrid effects

AbstractThe objective of the study was to determine the effects of maize hybrid and harvest date on the yield, quality and subsequent conservation characteristics of whole‐crop, cob and stover silages. The experiment had a split‐plot design, with three main plots (date of harvest) and six subplots (hybrid) in each of three replicate blocks. Four maize hybrids (Tassilo, Beethoven, Andante and Nescio) were conventional hybrids used in commercial livestock production in Ireland, and two were categorized as high‐biomass hybrids (Atletico and KXA 7211). The three harvest dates – 16 September, 7 October and 28 October – represented early, normal and late harvests respectively. Averaged across hybrids, harvesting on 16 September reduced the DM yield (P < 0·05) and starch concentration (P < 0·01) of whole‐crop and cob, and decreased the neutral detergent fibre (P < 0·05) and acid detergent fibre (P < 0·01) contents of stover. Later harvesting date generally resulted in a more restricted, heterolactic fermentation that was associated with increased dry‐matter (DM) content at ensiling. Whole‐crop and stover from Atletico and KXA 7211 generally had higher DM yields (P < 0·05) and a more extensive fermentation compared to Tassilo, Andante and Nescio. Despite the high‐biomass hybrids having a higher DM yield than conventional hybrids, the high‐biomass hybrids had a lower (P < 0·05) content of cob and a corresponding higher (P < 0·05) content of stover. The changes in proportions of cob and stover in whole‐crop maize with later harvesting significantly influenced its silage digestibility and conservation characteristics.

Yield, nutritive value and ensilage characteristics of whole-crop maize, and of the separated cob and stover components – nitrogen, harvest date and cultivar effects

SUMMARYThe objectives of the present study were to determine the effects of nitrogen (N) application rate, harvest date and maize cultivar on the yield, quality and the subsequent conservation characteristics of whole-crop, cob and stover silages. The experiment was organized in a spilt-plot design, with harvest date (15 September, 6 October and 27 October) as the main plot, and a three (maize cultivars: Tassilo, Andante and KXA 7211)×two (N application rate: 33 and 168 kg N/ha) factorial arrangement of treatments as the sub-plot, within three replicate blocks, and was conducted at Grange, Dunsany, Co. Meath, Ireland in 2009. The three harvest dates represented early, normal and late harvests, respectively, for a midland site in Ireland. Of the three maize cultivars selected, cvars Tassilo and Andante represent conventional cultivars sown by commercial livestock farmers in Ireland, while cvar KXA 7211 is categorized as a high biomass cultivar. No effect of N application rate was observed on the dry matter (DM) yield, nutritive value or ensiling characteristics of maize whole-crop or cob. Whole-crop and stover harvested on the later date had a lower digestible DM (DDM) content and the silages underwent a more restricted fermentation, compared to silages produced from herbage harvested on earlier dates. Cob silages produced from crops harvested on 15 September had lower DDM content and higher DM loss during ensiling than later harvest dates. Despite higher whole-crop DM yields, the later maturing cultivar KXA 7211 did not improve the DM yields of cob and also resulted in increased DM losses from the ensilage of cob, when compared with the other cultivars. In addition to the DM yield and nutritive value of forage maize at harvest, the subsequent fermentation profile during ensilage influences the optimum choice of cultivar and date for crop harvest in a maize silage production system.

Conservation characteristics of corn ears and stover ensiled with the addition of Lactobacillus plantarum MTD-1, Lactobacillus plantarum 30114, or Lactobacillus buchneri 11A44

The aim of this study was to investigate the effects of inoculating 3 contrasting lactic acid bacteria on the fermentation profile, estimated nutritive value, and aerobic stability of corn ears and stover produced under marginal growing conditions. Ears and stover were separated from whole-crop corn plants obtained from 3 replicate field blocks. Representative subsamples were precision chopped and allocated to 1 of the following treatments: an uninoculated control, Lactobacillus plantarum MTD-1 (LP1), L. plantarum 30114 (LP2), or Lactobacillus buchneri 11A44 (LB). Each bacterial additive was applied at a rate of 1 × 106 cfu/g of fresh herbage. Triplicate samples of each treatment were ensiled in laboratory silos at 15°C for 3, 10, 35, or 130 d. No difference was observed between the dry matter recoveries of uninoculated ear or stover silages and silages made with LP1, and the aerobic stability of uninoculated ear and stover silages did not differ from silages made with LB. Stover silages made with LP2 and ensiled for 35 d had a lower proportion of lactic acid in total fermentation products compared with LP1. The aerobic stability and dry matter recovery of ear and stover silages in this study were not improved when made with LB, LP1, or LP2, due to the indigenous highly heterolactic fermentation that prevailed in the uninoculated ear and stover during 130-d ensilage.

Rumen degradability characteristics of normal maize stover and silage, and quality protein maize silage-based diets offered to cows

Rumen degradability characteristics of dry matter (DM), organic matter (OM) and crude protein (CP) of normal maize (NM) stover (T1)-, NM silage (T2)- and quality protein maize (QPM) silage (T3)-based diets were studied using three rumen-fistulated Boran × Friesian non-lactating cows (371 ± 32.00 kg) in 3 × 3 Latin Square Design. Cows were supplemented with a similar concentrate mix. In sacco degradability of DM and OM indicated that the (a) values of DM (128) and OM (114) for NM stover were lower (P < 0.001) than that for NM silage (268 and 253) and for QPM silage (323 and 303), respectively. The (a) value for CP was lower (P < 0.05) for QPM silage (286) than for NM stover (404) and NM silage (326). The (b) values of DM in NM stover (597) and NM silage (535) were higher (P < 0.05) than in QPM silage (499). The (b) value of CP in NM stover (372) was lower (P < 0.05) than in NM silage (655) and in QPM silage (608). Rate of degradation of OM in NM stover and NM silage, each with 0.03, was faster (P < 0.01) than in QPM silage (0.02). Moreover, QPM silage had higher potentially degradable fraction for DM (821) (P < 0.05) and OM (840) (P < 0.01) than DM (725) and OM (712) in NM stover. The mean rumen ammonia concentration (209 mg/l) of QPM silage was higher (P < 0.05) than that of NM stover (179 mg/l) and NM silage (170 mg/l). The average rumen pH (6.1) in cows fed QPM silage was lowest (P < 0.05) compared to pH (6.3) in cows fed either NM stover or silage. The concentration of total volatile fatty acids (116 mmol/l) in the rumen of cows incubated with QPM silage was higher (P < 0.001) than in those incubated with NM stover (113 mmol/l) and NM silage (110 mmol/l). It was concluded that QPM silage-based diet was superior in DM and OM degradability, and had higher ammonia and VFA concentration than NM stover-based diet. No differences have been observed in all parameters measured between QPM and NM silages.

Pretreatment of Corn Stover Silage with Fe(NO3)3 for Fermentable Sugar Production

Corn stover silage is an attractive raw material for the production of biofuels and chemicals due to its high content of carbohydrates and easy degradability. The effects of Fe(NO(3))(3) pretreatment conditions on sugar yields were investigated for corn stover silage. In addition, a combined severity factor was used to evaluate the effect of pretreatment conditions on the concentration of total sugars and inhibitors. Optimum pretreatment condition was obtained at 150°C for 10min with 0.05M Fe(NO(3))(3), at which the yields of soluble xylose and glucose in liquid achieved 91.80% of initial xylose, 96.74% of initial arabinose and 19.09% of initial glucose, respectively, meanwhile, 91.84% of initial xylose, 98.24% of initial arabinose, and 19.91% of initial glucose were removed. In addition, a severity analysis showed that the maximum sugar concentration of 33.48g/l was achieved at combined severity parameter value of 0.62, while the inhibitor concentration was only 0.03g/l. Fe(NO(3))(3) is an effective catalyst to enhance hemicellulose hydrolysis in corn stover silage, the yields of monomeric xylose in the liquid fraction reached as high as 91.06% of initial xylose and 96.22% of initial arabinose, respectively.

Kinetic study for Fe(NO3)3 catalyzed hemicellulose hydrolysis of different corn stover silages

Five inorganic salts, ZnCl(2), FeSO(4), Fe(2)(SO(4))(3), FeCl(3) and Fe(NO(3))(3) were chosen as catalysts to determine their effects on hemicellulose hydrolysis in control silage (no silage additive), and the results indicated that Fe(NO(3))(3) was the most efficient catalyst for hemicellulose hydrolysis. The kinetics of Fe(NO(3))(3) catalyzed hydrolysis for control silage and acid silage (treatment with HNO(3)) were investigated at various pretreatment conditions. The results demonstrated that Saeman model was well consistent with Fe(NO(3))(3) catalyzed hydrolysis reaction for corn stover silage, and kinetic parameters for this model were developed by the Arrhenius equation. Optimum pretreatment conditions were 0.05 M Fe(NO(3))(3) at 150°C for 21.2 min for control silage and 12.7 min for acid silage, which obtained the maximum xylose yields 81.66% and 93.36% of initial xylan, respectively. The activation energies for hemicellulose hydrolysis in control and acid silage ranged from 44.35 to 86.14 kJ/mol and from 3.11 to 34.11 kJ/mol, respectively.

Effects of yeast culture and fibrolytic enzyme supplementation on in vitro fermentation characteristics of low-quality cereal straws1

The effects of yeast culture and fibrolytic enzyme preparation (containing cellulase and xylanase) on in vitro fermentation characteristics of rice straw, wheat straw, maize stover, and maize stover silage were examined using an in vitro gas production technique. Four levels of yeast culture and fibrolytic enzyme supplements (0, 2.5, 5.0, and 7.5 g/kg of straw DM, respectively) were tested in a 4 x 4 factorial arrangement. Supplementation of yeast culture increased the cumulative gas production, theoretical maximum of gas production, rate of gas production, IVDMD, and in vitro OM disappearance (IVOMD), and decreased the lag time for each type of straw. Fibrolytic enzyme supplementation tended to increase cumulative gas production, theoretical maximum of gas production, and rate of gas production; prolonged lag time of gas production; and enhanced IVDMD and IVOMD for 4 types of cereal straws, with the significance of this effect being dependent on the level of supplemented enzymes. There were significant interactions between fibrolytic enzymes and yeast on all in vitro gas production parameters, IVDMD, and IVOMD of each type of straw. The outcome of this research indicated that the application of fibrolytic enzyme preparation and yeast culture could improve in vitro gas production fermentation of cereal straws.

Effect of Non-Conventional and Conventional Fodder on Growth Performance of Goats in Farmers Field Condition

The present experiment was carried out on farmers’ goats in their sheds in Rayale village of Kavre district for 150 days. Eighteen khari goats (both male and female), 8-12 months old and having similar body weight were randomly divided into three groups comprising of six individuals in each group. Three types of rations were formulated for the experimental goats. Feed intake by experimental goats in terms of green and dry matter was significantly different (P&amp;lt;0.05) between the treatment groups. Growth rate of the goats fed with top dressed maize stover (treatment 2) was higher than the treatment 3 (seasonal fodder adlib + 200 g concentrate mixture) and treatment 1 (1/2 maize stover silage + seasonal fodder adlib + 200 g concentrate mixture). The lowest average daily gain (ADG) was found in treatment 3 where goats were fed conventional fodder and grasses supplemented with concentrate (18.4 g) followed by treatment 1 (24.6 g). &lt;i&gt; Nepal Journal of Science and Technology &lt;/i&gt; Vol. 7 2006

Fermentation quality and nutritive value of green soybean stover silage

AbstractThe aim of this study was to examine the effect of fermented juice of epiphytic lactic acid bacteria (FJLB) on fermentation quality and nutritive value of green soybean stover silage. Green soybean stover was cut and packed in drum silos without or with 5% (volume/weight) FJLB. Four sheep were fed a basal diet of 40% reed canarygrass hay and 60% commercial concentrate (dry matter basis) and assigned to two treatments: green soybean stover silage preserved without FJLB or with FJLB. Crude protein and neutral detergent fiber contents of green soybean stover silage (dry matter basis) were 16.4% and 45.2% for the silage without FJLB, and 15.8% and 47.1% for the silage with FJLB, respectively. Lactic acid content of the fresh green soybean stover silage was 1.41% for the silage without FJLB and 1.63% for the silage with FJLB. The butyric acid content of the fresh green soybean stover silage with FJLB was substantially lower than that of the silage without FJLB. There was no effect of FJLB added for silage making on the nutrient content, nitrogen retention or ruminal fermentation of the diets. It was estimated that total digestible nutrients content and digestible crude protein content of green soybean stover silage were 64.2% and 11.2% of dry matter, respectively.

A comparison of buffered propionic acid and &lt;i&gt;Propionibacterium acidipropionici&lt;/i&gt; as additives for high oil maize stover silage

A comparison of buffered propionic acid and &lt;i&gt;Propionibacterium acidipropionici&lt;/i&gt; as additives for high oil maize stover silage

Stage of maturity, processing, and hybrid effects on ruminal in situ disappearance of whole-plant corn silage

Five in situ trials with whole-plant corn silage (WPCS) were conducted in two ruminally-cannulated Holstein cows to determine 24-h ruminal disappearance of dry matter (DM), starch, and neutral detergent fiber (NDF). In Trial 1, the effect of maturity of WPCS on ruminal nutrient disappearance was evaluated. Treatments were early dent (ED), 1/4 milk-line (1/4 ML), 2/3 milk-line (2/3 ML), and black-layer (BL) stage of maturity. Ruminal disappearance of DM was lower (p<0.01) for BL (474g/kg) than ED (547g/kg), 1/4 ML (579g/kg), or 2/3 ML (530g/kg). Ruminal starch disappearance was lower (p<0.01) for BL (862g/kg) than ED, 1/4 ML, or 2/3 ML which averaged 950g/kg. In Trial 2, the effect of mechanical processing of mature and immature WPCS and stover silage at harvest was evaluated. Processing increased (p<0.01) ruminal starch disappearance for both immature (844 vs. 664g/kg) and mature (790 vs. 525g/kg) WPCS. In Trial 3, two WPCS hybrids (grain vs. leafy) at two plant populations (low=59,000 or high=79,000 plants/ha) were evaluated. Type of hybrid or plant population did not affect DM or NDF disappearance. However, starch disappearance was higher (p<0.01) for the leafy hybrid (872 vs. 731g/kg). In Trial 4, brown-midrib (BMR) corn harvested as WPCS was evaluated for ruminal nutrient disappearance versus a conventional grain hybrid. Ruminal DM (602 vs. 561g/kg) and NDF (326 vs. 220g/kg) disappearance were higher (p<0.01) for BMR. In Trial 5, ruminal nutrient disappearance of high- and low-NDF corn silage hybrids were compared. Ruminal DM (662 vs. 620g/kg) and starch (987 vs. 950g/kg) disappearance were higher, but NDF disappearance was lower (176 vs. 225g/kg) for the low-NDF hybrid (p<0.001). In summary, delaying silage harvest to BL reduced ruminal nutrient disappearance. Mechanical processing increased ruminal disappearance of WPCS, primarily through greater ruminal starch disappearance. Ruminal starch and NDF disappearance were higher for leafy and BMR hybrids, respectively, relative to a conventional grain hybrid. Ruminal DM disappearance was increased for a low-NDF hybrid, but effects were positive for starch and negative for NDF disappearance.

Development of an Economic Injury Level for European Corn Borer (Lepidoptera: Pyralidae) on Corn Grown for Silage

Studies were conducted in 1996 and 1997 at 2 locations in Wisconsin to assess the impact of European corn borer, Ostrinia nubilalis (Hubner), on corn grown for silage. Relationships between silage yield losses and control costs were used to develop economic injury levels specific to corn grown for silage in Wisconsin. Treatments were established as the percentage of plants infested with European corn borers. Treatment levels of 0, 12, 24, 40, and 84% of plants infested were used to separately examine simulations of 1st- and 2nd-generation European corn borer infestations. Experiments were performed using Pioneer dual purpose hybrids 3394 and 3751. Results from experiments showed that overall whole plant dry matter yields for 3394 were 8.5% > 3751 across the 3 experiments. Increasing European corn borer infestation proved to be highly correlated with a decrease in both whole plant and stover silage yields throughout experiments, hybrids, and simulated European corn borer generations. Differences in the rates of yield reduction were not seen between the 2 hybrids, however simulations of 1st-generation European corn borer infestation caused greater reductions than did simulations of 2nd-generation European corn borers. Linear regression models proved to best fit the yield loss relationships and were developed to describe silage yield losses resulting from European corn borer infestations. Economic injury levels were determined by comparing silage yield reductions and associated monetary losses with control costs. Economic injury levels were calculated separately for both 1st- and 2nd-generation European corn borers.

Digestibility and fermentative characteristics of mango, lemon and corn stover silages with or without addition of molasses and urea

Silages made from mango fruit (M), lemon (L) and corn stover (CS), with or without molasses (m) and urea (u), were evaluated to determine their fermentative characteristics, in situ disappearance and in vitro digestibility. Four silage treatments were carried out: (1) 80% M + 20% CS; (2) 60% M + 20% L + 20% CS; (3) 76.5% M + 19% CS + 2% m + 2.5% u; (4) 57.5% M + 19% L + 19% CS + 2% m + 2.5% u. Material was ensiled in 1-kg lots in flasks. The results were analysed by analysis of variance from a completely randomized design with 2 × 2 factorial arrangement (factor A: with or without lemon; factor B: with or without molasses and urea). A sample of each silage was taken out at 0, 15, 30 and 45 days. Protein and NDF content increased slightly ( P < 0.05) with respect to the control. During fermentation, ammonia concentration was constant. Silage in situ DM disappearance in sheep decreased for 0–15 days of silage ( P < 0.05), remaining constant after 15 days. The IVDMD was not different ( P < 0.05) among silages. Silage pH declined with time of fermentation and was constant at 30 days. Acetate and lactate were present in all silages, but lactate was detected in greater concentration, and was stabilized, at 30 days. In conclusion, silages containing molasses and urea have good-quality properties and the optimum fermentation time was 30 days.

Nutritional evaluation of cattle manure, molasses and corn stover silage for lambs

Two experiments were conducted to evaluate the nutritional quality of cattle manure silage for lambs. In experiment 1, qualitative characteristics, pH and lactic acid were determined in ensiled corn stover (35%) with four combinations (treatments, T) of fresh cattle manure:cane molasses-urea mixture (T 1, 55:10; T 2, 45:20; T 3, 35:30; T 4, 25:40). Lactate concentration (% of DM) was greater for the first two combinations (T 1, 4.6 a; T 2, 4.1 a; T 3, 3.4 b; T 4, 2.7 c; different superscripts indicate difference at P < 0.05). Experiment 2 was conducted to evaluate apparent digestibility and nitrogen balance of 20 lambs (29.0 ± 5.5 kg initial BW) fed silage with 50% cattle manure, 8% cane molasses, 12% water and 30% corn stover. For this silage, molasses and urea ratio was 20:1. Different silage levels (T 1, 0%; T 2, 16.4%; T 3, 32.7%; T 4, 49.1%; T 5, 65.5%; DM basis) were used in a completely randomized design with four lambs per treatment. Diets included sorghum grain (18.4%) and soybean meal (16.50, 13.20, 9.90, 6.60 and 3.30%). In T 5 a lower ( P < 0.05) apparent digestibility was found for OM (T 1, 57.6% a; T 2, 59.1% a; T 3, 55.3% a; T 4, 53.4% a; T 5, 51.7% b); but ADF, hemicellulose and energy digestibility did not change ( P > 0.05). Nitrogen balance (g day −1) was lower ( P < 0.05) for T 5 (T 1, 6.4 a; T 2, 5.5 a; T 3, 6.8 a; T 4, 5.8 a; T 5, −0.1 b). According to these results, cattle manure can be ensiled when molasses and urea proportions are adequate (20:1), and DM digestibility is not affected negatively if cattle manure silage is included up to 49% (DM basis) in lambs diets.

Effect of freezing on the nutritive value of untreated or enzyme-treated maize stover silages

Preferably, a crop for silage should be immediately ensiled after harvesting. However, this is not always possible in research situations when a large number of laboratory-scale silos have to be prepared. Thus, in many cases the chopped material is frozen and ensiled at a later date after defrosting. Richard and Allen (1992) and Nelson and Bozich (1996) have shown that freezing vegetative material may increase cell-wall contents, which in turn, may affect nutritive value. The current study was conducted to determine changes in the composition of fresh and frozen stover, ensiled with and without a cell-wall degrading enzyme solution.

Effects of the nature of roughage and concentrate and their proportion on ruminal characteristics of non lactating goats, consequences on digestive interactions

The effects on ruminal characteristics of 14 diets differing in nature and level of roughage and concentrate have been studied. The roughages were alfalfa hay (AH) or maize stover silage (MS) distributed alone or in a mixed diet containing 30 or 60% concentrate on a dry matter basis. Three types of concentrate were formulated to be either rich in rapidly degradable starch (RS), slowly degradable starch (SS) or digestible fibre (DF). The post feeding evolutions of pH, volatile fatty acids (VFA) and ammonia (NH 3) concentrations in ruminal fluid were measured. Microbial protein synthesis has been estimated. Ruminal pH was consistently high (pH > 6.3) and VFA concentrations in the rumen were 88.4 mmol L −1. VFA concentrations were higher after AH compared with MS, whereas differences between concentrates were not significant. The proportion of acetate decreased with the concentrate level while that of propionate increased. The NH 3 concentration was always over 50 mg L −1 and varied significantly with the tested diets. The efficiency of microbial nitrogen synthesis (EMS) was 32.7 g per kg of organic matter apparently digested in the rumen without significant differences between roughages or concentrates. No difference ( P < 0.05) was observed between the depressive effect of concentrates on the cellulolysis in the rumen.

Influence of the nature of forage and concentrate on the digestive interactions measured in sacco and in vivo

Reticulo-ruminal digestive interactions in complete mixed diets were studied in goats using various approaches. The nylon bag technique was used and the results were compared with stomach digestion estimated by duodenal flow from the same goats. Basal diets were composed of maize stover silage (MS) or alfalfa hay (AH) combined with 0, 30, or 60% of three types of concentrate, rich in rapidly (RS) or slowly (SS) degradable starch, or in digestible fibre (DF). Effective degradation (ED) of dry matter, structural carbohydrate (SC), neutral detergent soluble (NDS) and starch of roughage and concentrate were estimated. Significant decreases in ED of SC from roughage and concentrate were seen when the level of concentrate was increased in the basal diet. Compared with the duodenal flow technique, the in sacco measure overestimated the decrease in the SC degradation rate. Degradation of SC after 48 h of incubation in nylon bags was a better predictor than ED for SC duodenal digestibility. The in sacco method underestimated starch degradation of SS. Effective degradation of starch in SS has confirmed higher amilolytic activity after the (AH + SS) vs. (MS + SS) diets which had already been observed from in vivo duodenal digestion data.

Digestive interactions in the ruminant: relationships between whole tract and stomach evaluation

Two forages, maize stover silage (MS) and alfalfa hay (AH) were combined with 0, 30 and 60% of three types of concentrate either rich in rapidly degradable starch (RS), slowly degradable starch (SS), or rich in digestible fibre (DF). Treatment effects and interactions were compared in terms of organic matter (OM), holocellulose (SC), non-structural carbohydrate (NSC) and starch digestibility in the stomach and the whole tract. Mean intakes of OM, SC, NSC and starch were 925, 472, 270 and 224 g day −1, respectively. Mean digestibilities were 47.8, 59.0, 43.5 and 78.7%, respectively, in the stomach and 68.1, 63.9, 78.5 and 96.1%, respectively, in the whole tract. The precision of the estimates of stomach digestibility was lower than that of the whole tract. Significant treatment interactions were observed at the whole tract level except for the combination AH/DF. The influences of the level of concentrate on stomach and whole tract digestibility were parallel only when diets included RS and DF. In the case of SC digestion, large interactions were observed with MS-mixed rations contrary to AH-mixed ones. For the MS diet, there was good agreement between stomach and whole tract estimations. There was no influence of concentrate level on whole tract NSC digestibility, and no general relationship between stomach and whole tract NSC digestibilities. The use of whole tract digestibility to evaluate or quantify ruminal digestive interactions could be an inaccurate criterion. A specific feed effect must be taken into account when linking stomach and whole tract digestion of OM and SC.

Nutritive value and ensiling characteristics of maize stover as influenced by hybrid maturity and generation, plant density and harvest date

Because genotype, hybrid generation (F 1 vs. F 2), plant density and harvest date of maize ( Zea mays L.) may influence grain-to-stover ratio of the forage, the effects of these variables on composition and ensiling characteristics of maize stover were investigated. In each of two years, three maize hybrids (A632 × LH38, early-maturing; B73 × Mo17, medium-maturing; B73 × Pa91, late-maturing) were grown in three replications at plant densities of 4.9, 6.9 or 8.9 plants m −2. In Year 2, the F 2 generation of the hybrids was grown under conditions similar to those for the F 1 generation. Plants were harvested at physiological maturity and 28 days after physiological maturity. Grain and stover were separated for determination of the grain-to-stover ratio and stover yield. Stover was analyzed as either forage or silage prepared in polyethylene bags. The early-maturing hybrid had a higher grain-to-stover ratio, higher stover in vitro digestible dry matter (IVDDM) concentration and lower stover concentrations of acid detergent fiber (ADF) and acid detergent lignin (ADL) than the other hybrids. Plant density did not affect either grain-to-stover ratio or stover IVDDM concentration. Maize harvested 28 days post-physiological maturity had a higher grain-to-stover ratio, higher stover concentrations of neutral detergent fiber (NDF), ADF and ADL, and lower stover concentrations of IVDDM, crude protein and total nonstructural carbohydrates than maize harvested at physiological maturity. Silage produced from stover harvested at physiological maturity had a higher lactic acid concentration than when harvested 28 days after physiological maturity. F 2 generation maize had a lower grain-to-stover ratio, lower stover ADF concentration and higher stover crude protein concentration than F 1 generation maize. Stover IVDDM concentration from the F 2 generation was higher than that from the F 1 generation in unensiled forage, but lower than that from the F 1 in silage. Although there were no differences in the proportions of ADF and ADL in the NDF of stover forages or silages from F 1 generation maize, proportions of ADF and ADL in the NDF were greater in stover silages than in stover forages from F 2 generation maize. Concentrations of ADF and ADL in stover forage and the concentrations of ADF, ADL and NDF in stover silage were significant ( P < 0.10) variables in stepwise regressions predicting IVDDM concentration. These results imply that stover IVDDM concentration is primarily affected by differences in cell-wall concentration and composition that are unrelated to grain-to-stover ratio.

Effects of added dietary urea on the utilization of maize stover silage by growing beef cattle

The effects of varying the ruminal ammonia-nitrogen (NH 3-N) concentration with urea on the utilization of maize stover silage were studied. In a 4 × 4 Latin Square digestion experiment, 4 Holstein steers (mean weight 250 kg), fitted with ruminal and duodenal cannulae, were fed on maize stover silage as 700 g kg −1 of the dry matter (DM) with one of four protein supplements at 4-h intervals. Supplements contained a maize and formaldehyde-treated soya-bean meal base [109 g metabolizable protein (MP) kg −1 DM; 0 g urea fermentation potential (UFP) kg −1 DM] and 14.3, 24.7, 34.7 or 44.7 g urea kg −1 DM. Increasing the dietary urea concentration increased (linear effect, P < 0.05) ruminal NH 3-N and total volatile fatty acid concentrations. Increasing the concentration of urea in the diet increased (linear effect, P < 0.05) intake and total tract digestibility of DM. Increasing the urea concentration did not affect the amount and efficiency of bacterial protein synthesis. In an 84-day growth experiment, 60 Charolais×Angus heifers (mean weight 212 kg) were group-fed, once daily, on a diet containing maize stover silage as 700 g kg −1 of the DM with one of six supplements. These included the four supplements used in the digestion experiment, a negative control supplement (109 g MP kg −1 DM; 0 g UFP kg −1 DM) containing formaldehyde-treated soya-bean meal, and a positive control supplement (106 g MP kg −1 DM; −25 g UFP kg −1 DM) containing non-treated soya-bean meal. Increasing the concentration of urea in the diet increased ruminal NH 3-N concentrations (linear effect, P < 0.05), DM intake (quadratic effect, P < 0.05) and average daily gains (quadratic effect, P < 0.01), and decreased (quadratic effect, P < 0.01) feed-to-gain ratios of the heifers.