Document Type : Research Paper
Authors
- Ayub Mohammadi 1
- Farhang Fatehi 1
- Kamran Reza-yazdi 1
- Farhad Parnian-khajehdizaj 2
- Ali sadeghi-sefidmazgi 1
1 Department of Animal Science, University college of Agriculture and Natural Resources, University of Tehran, Karaj, Alborz, Iran
2 Agricultural Research, Education and Extension Organization (AREEO), Tabriz, East Azerbaijan, Iran.
Abstract
Objective: One of the most important goals in dairy cattle farming is increasing milk production and quality. This important goal is achieved when high-quality feed with high nutrient concentration is used in dairy cows, especially high-producing cows. However, understanding the importance of starch in cattle feed is vital for maximizing their performance and ensuring their health and welfare, from increasing energy levels for milk production to affecting rumen health and digestive system efficiency. Therefore, the increase in concentrate consumption has reached its maximum, and consequently, increasing nutrient digestion and reducing nutrient waste through feces in dairy cattle herds is of particular importance, requiring better herd management. Thus, the objective of this study was to investigate the relationship between total mixed ration (TMR) nutrient compositions and their effects on fecal starch excretion, as one of the most widely used nutrients in high-producing Holstein cows across the country's herds.
Method: This study was conducted on 76 Holstein dairy herds. In each herd, one pen of high-producing Holstein cows was selected as the index pen based on average milk production, average days in milk, and average parity. From each pen, 10 cows with body condition score of 3±0.25, days in milk of 80±10, milk production of 47±2.5, and parity of 2.5±0.5 were selected. Samples were collected from TMR, feed ingredients, and cow feces for three consecutive days. Finally, data such as dry matter intake, forage-to-concentrate ratio, and amounts and ratios of dietary starch, crude protein, neutral detergent fiber (NDF), crude fat, non-fiber carbohydrates, and organic matter in TMR were measured. The resulting data were used to estimate fecal starch excretion using single and multiple linear regression models. The prioritization criterion for the effects of each parameter was determined using the coefficient of determination.
Results: Based on univariate prioritization, the results showed that in addition to the amount and percentage of dietary starch (coefficient of determination of 0.56 and 0.43, respectively), the amount of NDF, amount of crude protein intake, dietary protein percentage, dry matter intake, and dietary NDF percentage with coefficients of determination of 0.42, 0.36, 0.36, 0.34, and 0.33, respectively, had significant effects on fecal starch excretion (P-value ≤0.01) and had the greatest impact on fecal starch excretion in that order. Additionally, based on the multivariate model, it was determined that including two factors - dietary starch percentage and dietary protein percentage - in the model equation provided the highest estimation of fecal starch percentage with a coefficient of determination of 0.73. It should be noted that the next priorities were for dry matter intake, dietary starch percentage, and dietary protein percentage (R² = 0.68), as well as dry matter intake, protein percentage, and dietary NDF percentage (R² = 0.65).
Conclusions: This study showed that fecal starch concentration in the country's high-producing cows is significantly high (average 11.5% based on fecal dry matter). Also, based on univariate prioritization, it was shown that increases in dietary starch amounts and percentages, dietary crude protein, and daily dry matter intake (in kilograms) lead to increased fecal starch excretion, while increases in dietary NDF amount and percentage resulted in decreased fecal starch excretion. Furthermore, based on multivariate prioritization, the best estimation of fecal starch excretion was achieved using a model including dietary starch percentage and dietary protein percentage variables, which could predict fecal starch concentration with a coefficient of determination of 0.73.
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