Corn silage management II: effects of hybrid, maturity, and mechanical processing on digestion and energy content

Effect of Spring Maize Genotypes on Fermentation and Nutritional Value of Whole Plant Maize Silage in Northern Pakistan

In the current study, we evaluated the growth, biomass yield, ensiling, and nutritional characteristics of spring maize genotypes grown under the climatic conditions of Northern Pakistan. Six promising spring maize genotypes were grown under uniform standard agronomic conditions in 72 plots (8 m × 10 m), blocked within three replicate fields. Maize crops were harvested at targeted dry matter (DM) content (33 g/100 g DM). Data were collected on plant phonological characteristics and biomass yield, and then the harvested crop of each plot was chopped, and subsamples were ensiled in three replicate 1.5 L laboratory silos (n = 12/genotype). After 90 days of ensiling, subsamples were analyzed for fermentation quality, nutrient composition, Cornell Net Carbohydrate and Protein System (CNCPS) carbohydrate subfractions, digestible nutrients, metabolizable energy (ME), and in vitro dry matter digestibility (DMD). Results revealed large differences (p < 0.001) among maize genotypes in the yields (tons/ha) of DM (13.0 to 17.9), crude protein (CP; 0.83 to 1.24), and starch (4.16 to 6.67). Except for total carbohydrates (CHO) and NH3-N, the contents of all measured chemical components varied (p < 0.001) among the spring maize genotypes. Similarly, all reported CNCPS subfractions varied (p < 0.01) among the genotypes, except for the non-digestible (CC) subfraction. Among the genotypes, there were large variations in the contents (g/100 g DM) of CP (6.60 to 8.05), starch (32.0 to 37.3), non-fiber carbohydrates (40.3 to 43.8), in vitro DMD (61.5 to 67.9), total digestible nutrients (68.1 to 70.6), digestible energy (2.80 to 3.07 Mcal/kg), and metabolizable energy (2.28 to 2.44 Mcal/kg), with genotype QPM300 having the highest values and genotype Azam having the lowest values. It was concluded that QPM300 is the most suitable spring maize genotype for silage production in terms of yields and silage nutritional and fermentation quality under the environmental condition of Northern Pakistan.

Temperature and microbial changes of corn silage during aerobic exposure

Objective

This study was conducted to estimate the temperature and microbial changes of corn silages during aerobic exposure.

Methods

Kwangpyeongok (KW) and Pioneer 1543 (PI) corn hybrids were harvested at 29.7% of dry matter and chopped to 3 to 5 cm lengths. Homo (Lactobacillus plantarum; LP) or hetero (Lactobacillus buchneri; LB) fermentative inoculants at 1.2×10⁵ colony forming unit/g of fresh forage was applied to the chopped corn forage which was then ensiled in quadruplicate with a 2×2 (hybrid×inoculant) treatment arrangement for 100 days. After the silo was opened, silage was sub-sampled for analysis of chemical compositions, in vitro digestibility, and fermentation indices. The fresh silage was continued to determine aerobic exposure qualities by recorded temperature and microbial changes.

Results

The KW silages had higher (p<0.01) in vitro digestibilities of dry matter and neutral detergent fiber than those of PI silages. Silages applied with LB had higher (p<0.001) acetate concentration, but lower (p<0.01) lactate concentration and lactate to acetate ratio than those of LP silages. The interaction effect among hybrid and inoculant was detected in acetate production (p = 0.008), aerobic stability (p = 0.006), and lactic acid bacteria count (p = 0.048). The yeast was lower (p = 0.018) in LB silages than that in LP silages. During the aerobic exposure, PI silages showed higher (p<0.05) temperature and mold than KW silages, while LP silages had higher (p<0.05) lactic acid bacteria and yeast than LB silages.

Conclusion

The results indicated that the changes of silage temperature during aerobic exposure seems mainly affected by mold growth, while applied LB only enhanced aerobic stability of PI silages.

Effect of ensiling time and exogenous protease addition to whole-plant corn silage of various hybrids, maturities, and chop lengths on nitrogen fractions and ruminal in vitro starch digestibility

The objective of this study was to evaluate the effects of ensiling time and exogenous protease addition on soluble CP (% of CP), ammonia-N (% of N), and ruminal in vitro starch digestibility (ivSD) of whole-plant corn silage (WPCS) from 3 hybrids, 2 maturities, and 2 chop lengths. Samples from 3 nonisogenic hybrids [brown midrib containing the bm3 gene mutation (BM3), dual-purpose (DP), or floury-leafy (LFY)] at 2 harvest maturities [2/3 kernel milk line (early) or 7d later (late)] with 2 theoretical lengths of cut settings (0.64 or 1.95cm) on a forage harvester were collected at harvest, treated with or without exogenous protease, and ensiled in triplicate in vacuum heat-sealed plastic bags for 0, 30, 60, 120, and 240d. Thus, the experiment consisted of 120 treatments (3 hybrids × 2 maturities × 2 chop lengths × 2 protease treatments × 5 time points) and 360 mini-silos (3 replications per treatment). Vitreousness, measured by dissection on unfermented kernels on the day of harvest, averaged 66.8, 65.0, and 59.0% for BM3, DP, and LFY, respectively. A protease × maturity interaction was observed with protease increasing ivSD in late but not early maturity. Ensiling time × hybrid interactions were observed for ammonia-N and soluble CP concentrations with greater values for FLY than other hybrids only after 120d of ensiling. Ensiling time × hybrid or protease × hybrid interactions were not observed for ivSD. Measurements of ivSD were greatest for FLY and lowest for BM3. Length of the ensiling period did not attenuate negative effects of kernel vitreousness or maturity on ivSD in WPCS. Results suggest that the dosage of exogenous protease addition used in the present study may reduce but not overcome the negative effects of maturity on ivSD in WPCS. No interactions between chop length and ensiling time or exogenous protease addition were observed for ivSD.

Nutritive value of maize silage in relation to dairy cow performance and milk quality

Maize silage has become the major forage component in the ration of dairy cows over the last few decades. This review provides information on the mean content and variability in chemical composition, fatty acid (FA) profile and ensiling quality of maize silages, and discusses the major factors which cause these variations. In addition, the effect of the broad range in chemical composition of maize silages on the total tract digestibility of dietary nutrients, milk production and milk composition of dairy cows is quantified and discussed. Finally, the optimum inclusion level of maize silage in the ration of dairy cows for milk production and composition is reviewed. The data showed that the nutritive value of maize silages is highly variable and that most of this variation is caused by large differences in maturity at harvest. Maize silages ensiled at a very early stage (dry matter (DM) < 250 g kg(-1)) were particularly low in starch content and starch/neutral detergent fibre (NDF) ratio, and resulted in a lower DM intake (DMI), milk yield and milk protein content. The DMI, milk yield and milk protein content increased with advancing maturity, reaching an optimum level for maize silages ensiled at DM contents of 300-350 g kg(-1), and then declined slightly at further maturity beyond 350 g kg(-1). The increases in milk (R(2) = 0.599) and protein (R(2) = 0.605) yields with maturity of maize silages were positively related to the increase in starch/NDF ratio of the maize silages. On average, the inclusion of maize silage in grass silage-based diets improved the forage DMI by 2 kg d(-1), milk yield by 1.9 kg d(-1) and milk protein content by 1.2 g kg(-1). Further comparisons showed that, in terms of milk and milk constituent yields, the optimum grass/maize silage ratio depends on the quality of both the grass and maize silages. Replacement of grass silage with maize silage in the ration, as well as an increasing maturity of the maize silages, altered the milk FA profile of the dairy cows, notably, the concentration of the cis-unsaturated FAs, C18:3n-3 and n-3/n-6 ratio decreased in milk fat. Despite variation in nutritive value, maize silage is rich in metabolizable energy and supports higher DMI and milk yield. Harvesting maize silages at a DM content between 300 and 350 g kg(-1) and feeding in combination with grass silage results in a higher milk yield of dairy cows.

Evaluation of the response of ruminal fermentation and activities of nonstarch polysaccharide-degrading enzymes to particle length of corn silage in dairy cows

The main objective of this study was to evaluate effects of particle length (PL) of corn silage (CS) on distribution of dietary particle fractions, contents of physically effective neutral detergent fiber (peNDF), cows' intake patterns and sorting activity, fermentation pro-file, and activities of nonstarch polysaccharide-degrading enzymes as well as degradation in the rumen and total tract in lactating dairy cows. Four ruminally cannulated Holstein cows, weighing 624 +/- 50 kg and 60 +/- 8 d in milk, were fed ad libitum 3 total mixed rations [about 16% crude protein, 34% neutral detergent fiber (NDF), and 7 MJ of net energy of lactation/kg of dry matter (DM)] containing on DM basis 50% concentrate, 10% grass hay, and 40% CS with 3 different theoretical PL at harvesting (14, 8.1, and 5.5 mm for long, medium, and short, respectively). Results showed that the amount of DM retained on sieves with 19- and 8-mm screens of Penn State Particle Separator decreased linearly with decreasing PL of CS. The latter was reflected in a significant decrease in the content of dietary peNDF including both the DM (peNDF(>8)) and the NDF (peNDF(>8-NDF)) retained on 19- and 8-mm screens. In contrast, the fraction of particles retained between the 1.18- and 8-mm screens was increased, such that no differences among the diets were observed regarding the content of peNDF that includes DM of particles >1.18 mm (peNDF(>1.18)). The intake of particles retained between the 1.18- and 8-mm screens increased linearly, whereas the intake of peNDF(>1.18) increased quadratically with decreasing PL of CS. Sorting consumption was reduced by feeding the short CS, which was reflected in a reduced proportion of propionate and increased acetate-to-propionate ratio and butyrate pro-portion in the rumen. In contrast, no effects of PL of CS were observed on the concentration of total volatile fatty acids and pH in the rumen. In general, decreasing the PL of CS significantly increased the activities of nonstarch polysaccharide-degrading enzymes. However, greater ruminal and total tract degradation of fiber and nonfiber carbohydrates were observed only by medium CS. Results of the present study suggest that in addition to fractions of long particles (i.e., >8 mm), the particle fraction retained between 1.18- and 8-mm should also be considered to better predict rumen conditions and digestion. In conclusion, a moderate reduction of PL of CS has beneficial effects on nutrient digestion, and may maximize feed efficiency and energy supply in high-yielding dairy cows.

Effects of mechanical processing on the nutritive value of barley silage for lactating dairy cows

Mechanical processing of whole crop barley before ensiling may be useful for improving nutrient use by dairy cattle. The objective of this study was to assess the effects of feeding mechanically processed barley silage as the main forage source on lactational performance. Twenty-four Holstein cows, 16 primiparous (187 +/- 52 days in milk) and 8 multiparous (87 +/- 69 days in milk) cows, were used in a completely randomized design with a 2-wk covariate period and a 6-wk treatment period. The 2 treatments were: 1) total mixed ration (TMR) containing regular barley silage (RBS-TMR), and 2) TMR containing mechanically processed barley silage (MPBS-TMR). Barley silage and alfalfa hay supplied 41 and 5% of the dietary dry matter (DM), respectively. Intake, body weight, and milk production were measured during the covariate and treatment periods. In addition, 2 multiparous cows were used for in situ measurements of the ruminal DM and fiber degradation kinetics of the barley silages and TMR. Data were analyzed with repeated measurements using a mixed model that included the covariate adjustment. Feeding MPBS-TMR had no significant effects on DM intake (DMI; 21.7 kg/d), milk yield (33.9 kg/d), or milk composition, with only 4% FCM (fat-corrected milk) yield (29.7 vs. 31.7 kg/d) and milk fat concentration (3.30 vs. 3.57%) showing a numerical improvement. Apparent digestibilities of DM and nutrients were not affected by feeding MPBS-TMR, with the exception of starch digestibility, which tended to increase. Dairy efficiencies calculated as milk yield/DMI or FCM/DMI were not different between treatments. Body weight and body condition score were not affected by treatments. Effective ruminal degradability of DM was similar for both barley silages, indicating that when the silages were ground to remove the effects of mechanical processing, the potential digestion was similar. Mechanical processing of barley silage harvested at a mid-dough stage of maturity resulted in small improvements in its nutritive value for lactating dairy cows and had minor impact on digestibility and milk production.

Effect of Length of Cut and Kernel Processing on Use of Corn Silage by Lactating Dairy Cows

Forty Holstein cows were used in an 8-wk randomized block design trial to determine the effects of theoretical length of cut (TLC) and kernel processing (KP) of whole plant corn silage on nutrient intake and digestibility, milk yield, and milk composition. Corn was harvested at three-quarters milk line stage of maturity at TLC of 1.90 or 2.54 cm. At each TLC, corn was KP at either 2 or 8 mm roll clearance. The control was harvested at 1.90 cm without KP. Corn silage provided 38% of the dietary dry matter (DM) in the experimental diets. Intake of DM and nutrients was similar among treatments. Apparent digestibility of DM and acid detergent fiber (ADF) increased with increasing TLC. Fiber digestibility was improved by KP compared with unprocessed corn silage. Starch digestibility was greater for corn silage KP at 2 vs. 8 mm. Apparent digestibility of DM, crude protein, and ADF was lowest for the diet containing silage harvested at 2.54 cm TLC and KP at 8 mm, resulting in an interaction of TLC and KP. No differences were observed in DM intake (DMI) among treatments. An interaction of TLC and KP was observed, however, for yield of milk protein and energy-corrected milk (ECM) and efficiency of converting DMI to ECM because of lower yield for diets containing silage harvested at 2.54 cm TLC and KP at 8 mm. Results of this trial indicate that as TLC increases, aggressive KP is necessary to maintain nutrient digestibility and performance of lactating dairy cows.

Effects of Corn Silage Processing and Amino Acid Supplementation on the Performance of Lactating Dairy Cows

This experiment was conducted to determine the effect of crop processing and amino acid supplementation on dairy cow performance. Corn silage processed (PCS) or unprocessed (UCS) was used as the main forage (45% of dry matter, DM) in a total mixed ration (TMR). Each TMR was either supplemented (AA) or not (AAO) with ruminally protected amino acids (lysine, 3 g/d and methionine, 14 g/d). Thirty-two (551 kg) Holstein cows were randomly assigned to four treatments: PCS-AA, PCS-AA0, UCS-AA, and UCS-AA0 in a 2 x 2 factorial structure. Between wk 7 and 17 of lactation, cows were fed ad libitum TMR comprising 45% of corn silage plus 1 kg of grass hay once a day. The UCS presented better fermentation characteristics than PCS. Dry matter intake (DMI) of the TMR was not affected by treatment and averaged 22.7 kg/d. Energy-corrected milk (ECM) production was 9% higher with UCS than with PCS (33.1 vs. 30.1 kg/d). Milk efficiency was therefore 6% higher with UCS than with PCS (1.43 vs. 1.35 kg ECM/kg of DMI). The concentration of major milk constituents (fat, protein, lactose, urea) was not affected by treatments. Apparent digestibility of DM, organic matter, N, starch, acid detergent fiber, and neutral detergent fiber were similar among treatments. The effective ruminal degradability of DM, starch, and protein, however, was greater with PCS than with UCS. Amino acid supplementation had no effect on milk production nor on milk constituents, whether it was used with processed corn silage or with unprocessed corn silage. These data indicate that feeding UCS resulted in a greater milk production compared with PCS. The numerically higher DMI, a potentially greater intestinal digestion of starch or the better conservation of UCS could have contributed to the greater milk production.

Corn silage management: effects of hybrid, chop length, and mechanical processing on digestion and energy content

Two experiments were conducted to evaluate the effects of chop length and mechanical processing of two hybrids of whole plant corn on digestion and energy content of the total mixed ration (TMR). The experimental designs in experiments 1 and 2 were 6 x 6 and 4 x 4 Latin squares, respectively. In the first experiment, Pioneer hybrid 3845 was harvested at three theoretical lengths of cut: 11.1, 27.8, and 39.7 mm. At each chop length, corn was harvested with and without mechanical processing using a John Deere 5830 harvester with an onboard kernel processor. In the second experiment, Pioneer hybrid Quanta was harvested at two theoretical lengths of cut: 27.8 and 39.7 mm, with and without mechanical processing. In both experiments, the increase in the theoretical length of cut of corn silage increased the average length of cut and tended to increase the percentage of particles greater than 19 mm and lower the percentage of particles between 8 and 19 mm. In experiment 1, apparent total tract dry matter, organic matter, and neutral detergent fiber (NDF) digestibilities were lower for cows fed diets containing corn silage harvested at a short chop length (11.1 mm) than for corn silage harvested at a long chop length (39.7 mm). The lower total tract digestibility of nutrients may have contributed to the lower TDN, metabolizable energy (percentage of digestible energy), and NEL concentration of diets containing the short chop length corn silage (experiment 1). In experiment 2, total tract starch digestibility was greater for cows fed medium chop (27.8 mm) corn silage diets, and total tract NDF digestibility was greater for cows fed long chop (39.7 mm) corn silage diets. The opposing effect of total tract starch and fiber digestibilities between chop lengths may have contributed to the lack of difference in energy content of the diets in experiment 2. The TDN and NEL concentrations of the processed corn silage diets were greater than the unprocessed corn silage diets in experiment 1. The increase in energy concentration for the processed corn silage diet was due to greater total tract digestibility of organic matter and ether extract. Total tract starch digestibility was greater, and total tract NDF digestibility was lower for cows fed processed corn silage diets than unprocessed corn silage diets in experiment 2. The opposing effect of total tract starch and fiber digestibilities between processed and unprocessed corn silage may have contributed to the lack of difference in energy content of the diets.

Corn silage management III: effects of hybrid, maturity, and processing on nitrogen metabolism and ruminal fermentation

Two experiments were conducted to evaluate the effects of maturity and mechanical processing of two hybrids of whole plant corn silage on DM and OM digestibility, nitrogen metabolism, ruminal fermentation, and milk production and composition in lactating Holstein cows. In the first experiment, Pioneer hybrid 3845 whole plant corn was harvested at hard dough, one-third milkline, and two-thirds milkline with a theoretical length-of-cut of 6.4 mm. At each stage of maturity, corn was harvested with (1-mm roll clearance) and without (15.9-mm roll clearance) mechanical processing using a John Deere 5830 harvester with an on-board kernel processor. In the second experiment, Pioneer hybrids 3845 and Quanta were harvested at one-third milkline, two-thirds milkline, and blackline stages of maturity with and without mechanical processing. The theoretical length-of-cut was 12.7 mm. Total tract DM and OM digestibilities were lower for cows fed diets containing processed corn silage in experiment 1, and tended to be lower for cows fed diets containing unprocessed corn silage in experiment 2. Ruminal acetate concentrations were greater and ruminal propionate concentrations were lower 2 and 6 h after feeding for cows fed diets containing corn silage harvested at physiological maturity in experiment 2. This was due to decreased digestion of starch at advanced maturities in experiment 2. Ruminal pH tended to decline rapidly after feeding for cows fed hybrid Quanta (2 h) compared to hybrid 3845 (5 h) corn silage based diets. Ruminal acetate concentrations decreased and ruminal propionate concentrations increased 2 and 6 h after feeding for cows fed diets containing hybrid Quanta corn silage compared to hybrid 3845 corn silage. This was related to a greater starch concentration in the corn silage, greater starch intake, and increased rate of starch digestion for cows fed hybrid Quanta corn silage-based diets. Microbial nitrogen flow was lower and feed nitrogen flow was greater for cows fed diets containing hybrid Quanta corn silage. The lower microbial nitrogen flow was due to lower microbial nitrogen concentration and nonammonia nitrogen flow to the duodenum. Milk fat and protein concentrations had a strong quadratic relationship with forage NDF intake as a percentage of body weight. When forage NDF intake as a percentage of body weight dropped below 0.70%, there was a rapid decline in milk fat and protein concentrations.