-The objective of this research was to characterize the nutritive value of corn silage made on intensive dairy farms and demonstrate the nutritional variations between silages located at the top and at the center of a bunker silo. Thirty-two dairy farms were visited in four Brazilian states. One corn bunker silo of each farm was chosen and samples were collected from the top and center parts. The nutritive value, fermentation end-products, and microbial counts were assessed. The predicted milk was determined by Milk2006 spreadsheet. The mean, standard deviation, maximum, minimum, and 95% confidence interval of all data were calculated. The ash, neutral detergent fiber (NDF), starch, in vitro NDF, and dry matter (DM) digestibility data were compared with reference value. Both statistical procedures were performed through the PROC MEANS of SAS. The mean values found at the center for NDF, starch, total digestible nutrients (TDN -1x ), and estimated milk were 503 g kg −1 DM, 308 g kg −1 DM, 583 g kg −1 , and 1,124 kg t −1 , respectively. The top silages presented a mean TDN -1x and predicted milk of 559 g kg −1 and 1046 kg t −1 , respectively. For NDF digestibility and starch concentration, 53.1% and 62.5% of the center samples presented a value equal to or above the reference value (500 g kg −1 and 300 g kg −1 DM for NDF digestibility and starch concentration, respectively). Overall, the corn silage produced on intensive dairy farms in Brazil has satisfactory nutritive value, especially in terms of starch concentration. Some parameters, such as the concentration of fiber and its digestibility, should be improved. This study also shows that a silo may contain two different types of silage: top and center. This alerts nutritionists and farmers when feeding and sampling corn silage from bunker silos.

The objective of this study was to evaluate 2 systems for covering corn silage in bunker silos. The first system consisted of a sheet of 45-μm-thick oxygen barrier film (OB, polyethylene + ethylene-vinyl alcohol) placed along the length of the sidewall before filling. After filling, the excess film was pulled over the wall on top of the silage, and a sheet of polyethylene was placed on top. The second system involved using a standard sheet (ST) of 180-μm-thick polyethylene film. Eight commercial bunker silos were divided into 2 parts lengthwise so that one-half of the silo was covered with OB and the other half with a ST system. During the filling, 3 net bags with chopped corn were buried in the central part (halfway between the top and bottom of the silo) of the bunkers (CCOR) in 3 sections 10 m apart. After filling, 18 net bags (9 per covering system) were buried 40 cm below the top surface of the 3 sections. These bags were placed at 3 distances from the bunker walls (0 to 50 cm, 51 to 100 cm, and 101 to 150 cm). During unloading, the bags were removed from the silos to determine the dry matter (DM) losses, fermentation end products, and nutritive value. The Milk2006 spreadsheet was used to estimate milk per tonne of DM. The model included the fixed effect of treatment (7 different locations in the bunker) and the random effect of the silo. Two contrasts were tested to compare silages in the top laterals (shoulders) with that in the CCOR (CCOR vs. OB and CCOR vs. ST). Three contrasts compared the corresponding distances of the silage covered by the 2 systems (OB50 vs. ST50, OB100 vs. ST100 and OB150 vs. ST150). Variables were analyzed with the PROC MIXED procedure of the SAS at the 5% level. The OB method produced well-fermented silages, which were similar to CCOR, whereas the OB system showed less lactic acid and greater pH and mold counts compared with CCOR. The ST method had 116.2 kg of milk/t less than the CCOR, as the OB system and the CCOR were similar (1,258.3 and 1,294.0 kg/t, respectively). Regarding the distances from the walls, the effects were more pronounced from 0 to 101 cm. The OB50 and OB100 silages had better quality and lower mold counts and DM losses than ST50 and ST100. The OB system reduced DM and nutrient losses at the shoulders in farm bunker corn silages compared with no sidewall plastic. The OB film should lap onto the crop for at least 200 cm so that 150 cm are covered outward from the wall.

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Our objective was to assess maize fields in two growing seasons to determine the factors that affect the yield and nutritive value of maize silage produced in Brazil.Seventy-four commercial maize fields, 49 in the first growing season (FGS) and 25 in the second (SGS), were sampled over two crop years. In each field, 12 linear meters of plants were cut by hand at 25 cm above ground. Characteristics of the field, plants, and their components (stalk, leaves, husk, cob, and grains) were evaluated. Farmers were interviewed regarding the crop management practices applied. Chopped maize forage was dried to assess its chemical composition, in vitro dry matter digestibility, and in vitro fibre digestibility. Descriptive statistics was carried out for agronomic and nutritional variables. To determine the factors that affected yield and nutritive value in maize fields, artificial neural networks were used. The dry matter yield (DMY), NDF concentration, starch concentration, NDF digestibility, and DM digestibility were chosen as response variables. Then, the top 10 main parameters were used to explain the results. Overall, the association between grain and stover yield maximized DMY. Plant population (plants/ha) and plant maturity were also important to explain yield. Grain depth and number of grains per row were the two most important parameters linked to genetic traits. Plant maturity was decisive in altering the nutritive value of forage maize. Maize grown in the FGS had both greater yield and nutritive value than maize in the SGS.

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