Starch is a polysaccharide or complex carbohydrate, and it is the predominant form of energy storage in plants (seeds, roots, tubers). It’s composed of long chains of glucose molecules linked by α-1,4-glycosidic bonds. The digestion of starch is made possible by an enzyme, amylase, which aids the breakdown of the α-1,4-glycosidic bonds to yield individual glucose. According to Yu & Moon (2021), corn, which is the third most important grain crop in the world, is a major source of energy in livestock feed. It’s made up of approximately 75% starch on a dry matter basis. Hence, the concept of feeding an amylase-enabled corn silage to livestock would be to enhance the breakdown of starch and increase nutrient availability to the animals for optimal performance. Amylase is present in the kernel during maize germination (Oliveira et al., 2013), and starch degradation can be enhanced during processing such as ensiling. After ingestion by the cow, starch digestion occurs in the rumen (microbes) and in the small intestine (pancreatic amylase).
A study conducted by Cueva et al. (2021) at The Pennsylvania State University evaluated the lactational performance, rumen fermentation, and enteric methane emission of dairy cows fed an amylase-enabled corn silage. A total of 48 lactating Holstein dairy cows were fed either a control diet (corn silage from isogenic corn without α-amylase trait) or a treatment diet (corn silage from Enogen hybrid amylase-enabled corn) in a randomized complete block design. Both corn hybrids contained similar dry matter (DM) contents and were fed to the cows at 40% inclusion of their diet on a dry matter basis. The isogenic corn silage contained 41.8% DM, 37.5% neutral detergent fiber (NDF), 8.1% crude protein (CP), and 33.1% starch, while the Enogen hybrid corn silage contained 43.3% DM, 36.7% NDF, 7.59% CP, and 36.1% starch.
Alongside the production parameters that were evaluated in this study, the researchers also measured the impact of the treatment on enteric methane emissions, and this is important considering the Global Methane Pledge that was launched in November 2021 at the United Nations Global Climate Summit, where 105 countries (including the USA), gave their commitment to reduce the 2020 methane emissions by 30% in 2030. Therefore, it is essential to incorporate the effect of various dietary treatments on enteric methane gas emissions in studies involving ruminant animals. A wholistic CH4 measurement according to Fouts et al. (2022) should include three components; CH4 production (g of CH4 produced per day), CH4 yield (g of CH4 produced per kg of dry matter intake), and CH4 intensity (g of CH4 per kg of milk or animal product), and these were considered in this study.
The results obtained from this study indicate that there was no statistical difference in dry matter intake, nitrogen utilization, CH4 production, CH4 yield, milk fat concentration, body weight, body weight change and ruminal volatile fatty acids (acetate and propionate) between the control and treatment diets. However, the amylase enabled Enogen hybrid corn silage had a positive impact on milk yield, milk protein and lactose yield, feed efficiency, and CH4 intensity. They also observed a decrease in butyrate production and a trend in increased dry matter degradability in the cows that were fed the treatment diet. The increase in milk yield of 2kg/d (4.4lbs) and lactose yield by the Enogen hybrid corn silage may be attributed to the increased starch intake of cows that received the treatment compared to the control cows. An increase in starch intake and hydrolysis is expected to yield more glucose for milk synthesis in the mammary gland. Glucose is the precursor of lactose during milk synthesis, and the lactose content of milk determines the milk osmolarity and by extension, the milk yield.
The environmental benefit of the Enogen hybrid corn silage can be seen from the improvement in methane intensity. Although there is a production benefit of an increase in milk yield, it cannot be concluded that this increase would translate to more profit because a comparison needs to be made between the cost of procuring the amylase enabled Enogen hybrid corn and the isogenic corn.
— Gift Omoruyi