Authors
1
Department of Animal Science, Colleges of Agriculture and Natural Resources, University of Tehran, Karaj, Alborz, 31587–77871, Iran
2
Assistant Professor, Department of Animal Science, Faculty of Agricultural Science and Engineering, College of Agricultural and Natural Resources, University of Tehran, Karaj, Iran
3
Department of Animal Science, Campus of Agriculture and Natural Resources, University of Tehran, Karaj, Alborz, 31587–77871, Iran
4
Agricultural Research, Education and Extension Organization (AREEO)
Abstract
Background and Objective: One of the most important goals in the dairy industry is to increase milk production and quality, which requires the use of high-quality feedstuff with a high concentration of nutrients, especially for high-producing cows. Consequently, the proportion of concentrate in the diet of high-producing cows has reached its maximum, and improving nutrient digestibility and reducing nutrient loss through feces has become critically important. Starch is one of the most important nutrients affecting milk production. Therefore, the aim of this study was to investigate the relationship between feed parameters and their effect on fecal starch excretion, which is one of the most important nutrients in high-producing Holstein cows at the herd level in the country.
Materials and Methods: The current study was conducted in 76 Holstein dairy herds. In each herd, one pen of high-producing Holstein cows was selected as the index pen based on milk yield, days in milk, and parity. From the selected index pen, 10 cows were chosen with a body condition score of 3 ± 0.25, days in milk of 80 ± 10, a milk yield of 47 ± 2.5, and a parity of 2.5 ± 0.5. For three consecutive days, samples were collected from the total mixed ration, feed ingredients, and cow feces. During this period, data such as dry matter intake (DMI), concentrate intake (CI, kg/day), and forage intake (alfalfa and corn silage) were measured. Finally, the collected data were used to estimate fecal starch excretionusing single and multi-variable linear regression models. The priority of each parameter's effects was determined using the coefficient of determination.
Findings: The results of the current study, based on single-variable regression analysis, showed that starch intake (kg/day) had the highest impact on fecal starch excretion (R2=0.56), followed by CI (R2=0.50), feed starch percentage (R2=0.43), and forage-to-concentrate ratio (R2=0.38). Additionally, the multi-variable regression analysis demonstrated that the equation including CI, feed starch percentage, and DMI (kg/day) provided the highest estimation of fecal starch percentage, with a coefficient of determination of 0.84. The second estimated model, with the next highest coefficient of determination, included DMI, starch intake, and silage starch (R2= 0.67), while the third estimated model included DMI and CI (R2= 0.65).
Conclusion: The current study revealed that fecal starch concentration in high-producing cows was significantly high (average 11.6% based on fecal dry matter) and that the amount of fecal starch can be predicted with high accuracy and precision using dietary variables such as CI, starch ratio in the diet, and DMI.
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