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Introduction and Objective: Corn grain is recognized as the primary source of energy in dairy cow diets and accounts for a major portion of feed costs. Given the fluctuations in the prices of agricultural inputs and the necessity of improving economic efficiency in dairy herds, enhancing the digestibility and optimal utilization of this energy source plays a key role in reducing production costs and improving performance. The physical structure of corn grain, particularly the pericarp layer and the protein matrix surrounding starch granules, is among the factors limiting the accessibility of rumen microorganisms to nutrients. Therefore, the use of thermo-mechanical processing methods such as steam flaking, by breaking these structural barriers and gelatinizing starch, can significantly increase the rate and extent of ruminal fermentation. Although numerous studies have investigated the effects of corn processing on animal performance, comprehensive information regarding the simultaneous effect of steam flaking on ruminal and intestinal degradability, especially using fistulated animals (with ruminal fistulas and intestinal cannulas), in Holstein cows is lacking. Thus, the aim of this study was to compare the effects of steam-flaked corn grain versus whole corn grain (unprocessed) on chemical composition, gas production parameters, as well as the degradability of dry matter, crude protein, starch, and neutral detergent fiber (NDF) in different sections of the digestive tract (rumen, small intestine, and total tract).
Materials and Methods: This research was conducted at the Animal Nutrition Laboratory, Department of Animal Science, University of Zabol. Two experimental treatments included: 1) whole and intact corn grain (without any processing) as the control treatment, and 2) steam-flaked corn grain. To prepare the flaked treatment, corn grains were steamed in an autoclave at 95°C for one hour and then processed using a flaking machine with a roller gap of 2 mm. After processing, all samples were dried and ground. Chemical composition including dry matter, organic matter, crude protein, ether extract, neutral detergent fiber (NDF), and acid detergent fiber (ADF) were measured using standard AOAC methods and the Van Soest method, respectively. To evaluate degradability, two fistulated Holstein cows (with ruminal fistulas and duodenal cannulas) were used. Feed samples (6 g) were placed in nylon bags with dimensions of 12×6 cm and pore size of 42 μm, and incubated in the rumen for 12 hours. After removing the bags from the rumen, washing and drying, the residues in the bags were inserted into the small intestine through the duodenal cannula for 16 hours to measure intestinal degradability, and finally collected from the feces. Gas production parameters (including the fermentable fraction (b), gas production rate constant (c), metabolizable energy (ME), organic matter digestibility (OMD), and organic matter digestibility in dry matter (DOMD)) were determined using the Menke and Steingass method and in vitro incubation. Data obtained from chemical composition and degradability were analyzed in a completely randomized design using the GLM procedure of SAS software, and means were compared using Tukey's test at a significance level of 5%.
Results: Among the chemical components, crude protein, ether extract, neutral detergent fiber, and acid detergent fiber showed no significant differences, and only dry matter percentage was significantly higher in flaked corn compared to whole corn. In dry matter degradability, flaked corn performed better than whole corn in the ruminal section, but this difference was not significant in intestinal and total tract degradability. Degradability of crude protein, starch, and neutral detergent fiber showed no significant differences in any of the sections. Regarding gas production parameters, the fermentable fraction (b) was higher in flaked corn than in whole corn, and metabolizable energy, organic matter digestibility, and organic matter digestibility in dry matter were significantly higher in the flaked treatment. Gas production rate (c) showed no difference between treatments.
Conclusion: Based on the findings of this study, processing corn grain by steam flaking, although having limited effects on chemical composition and the degradability of some components (such as protein, starch, and fiber) in the lower parts of the digestive tract, effectively improves the fermentation process in the rumen. This is accompanied by increased gas production from the fermentable fraction and improved indices of metabolizable energy and organic matter digestibility. Therefore, it appears that using steam-flaked corn grain instead of whole grain, due to increased microbial access to starch and improved energy utilization efficiency, has higher nutritional value and can be used as a high-quality energy feed in the diet of high-producing dairy cows, especially under conditions where increasing feed efficiency and reducing costs are important. Ultimately, given the improved ruminal digestibility and increased metabolizable energy, the use of flaked corn can be an effective step toward enhancing productivity and reducing feed costs in the dairy cattle industry of the country.
Introduction and Objective: Corn grain is recognized as the primary source of energy in dairy cow diets and accounts for a major portion of feed costs. Given the fluctuations in the prices of agricultural inputs and the necessity of improving economic efficiency in dairy herds, enhancing the digestibility and optimal utilization of this energy source plays a key role in reducing production costs and improving performance. The physical structure of corn grain, particularly the pericarp layer and the protein matrix surrounding starch granules, is among the factors limiting the accessibility of rumen microorganisms to nutrients. Therefore, the use of thermo-mechanical processing methods such as steam flaking, by breaking these structural barriers and gelatinizing starch, can significantly increase the rate and extent of ruminal fermentation. Although numerous studies have investigated the effects of corn processing on animal performance, comprehensive information regarding the simultaneous effect of steam flaking on ruminal and intestinal degradability, especially using fistulated animals (with ruminal fistulas and intestinal cannulas), in Holstein cows is lacking. Thus, the aim of this study was to compare the effects of steam-flaked corn grain versus whole corn grain (unprocessed) on chemical composition, gas production parameters, as well as the degradability of dry matter, crude protein, starch, and neutral detergent fiber (NDF) in different sections of the digestive tract (rumen, small intestine, and total tract).
Materials and Methods: This research was conducted at the Animal Nutrition Laboratory, Department of Animal Science, University of Zabol. Two experimental treatments included: 1) whole and intact corn grain (without any processing) as the control treatment, and 2) steam-flaked corn grain. To prepare the flaked treatment, corn grains were steamed in an autoclave at 95°C for one hour and then processed using a flaking machine with a roller gap of 2 mm. After processing, all samples were dried and ground. Chemical composition including dry matter, organic matter, crude protein, ether extract, neutral detergent fiber (NDF), and acid detergent fiber (ADF) were measured using standard AOAC methods and the Van Soest method, respectively. To evaluate degradability, two fistulated Holstein cows (with ruminal fistulas and duodenal cannulas) were used. Feed samples (6 g) were placed in nylon bags with dimensions of 12×6 cm and pore size of 42 μm, and incubated in the rumen for 12 hours. After removing the bags from the rumen, washing and drying, the residues in the bags were inserted into the small intestine through the duodenal cannula for 16 hours to measure intestinal degradability, and finally collected from the feces. Gas production parameters (including the fermentable fraction (b), gas production rate constant (c), metabolizable energy (ME), organic matter digestibility (OMD), and organic matter digestibility in dry matter (DOMD)) were determined using the Menke and Steingass method and in vitro incubation. Data obtained from chemical composition and degradability were analyzed in a completely randomized design using the GLM procedure of SAS software, and means were compared using Tukey's test at a significance level of 5%.
Results: Among the chemical components, crude protein, ether extract, neutral detergent fiber, and acid detergent fiber showed no significant differences, and only dry matter percentage was significantly higher in flaked corn compared to whole corn. In dry matter degradability, flaked corn performed better than whole corn in the ruminal section, but this difference was not significant in intestinal and total tract degradability. Degradability of crude protein, starch, and neutral detergent fiber showed no significant differences in any of the sections. Regarding gas production parameters, the fermentable fraction (b) was higher in flaked corn than in whole corn, and metabolizable energy, organic matter digestibility, and organic matter digestibility in dry matter were significantly higher in the flaked treatment. Gas production rate (c) showed no difference between treatments.
Conclusion: Based on the findings of this study, processing corn grain by steam flaking, although having limited effects on chemical composition and the degradability of some components (such as protein, starch, and fiber) in the lower parts of the digestive tract, effectively improves the fermentation process in the rumen. This is accompanied by increased gas production from the fermentable fraction and improved indices of metabolizable energy and organic matter digestibility. Therefore, it appears that using steam-flaked corn grain instead of whole grain, due to increased microbial access to starch and improved energy utilization efficiency, has higher nutritional value and can be used as a high-quality energy feed in the diet of high-producing dairy cows, especially under conditions where increasing feed efficiency and reducing costs are important. Ultimately, given the improved ruminal digestibility and increased metabolizable energy, the use of flaked corn can be an effective step toward enhancing productivity and reducing feed costs in the dairy cattle industry of the country.
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