1- Department of Animal Science, Faculty of Agricultural Science and Engineering, College of Agricultural and Natural Resources, University of Tehran, Karaj, Iran
Abstract: (35 Views)
Introduction and Objective: Previous studies have shown that in dairy cow nutrition, besides having a balanced diet in terms of nutrient content, the physical form of diets, including particle size, is also an effective factor in proper rumen function and consequently animal production performance. On the other hand, climate change, global warming, and subsequent heat stress in various forms affect the performance and production efficiency of dairy cows. Although it has been shown that dry matter intake decreases under heat stress conditions compared to normal temperature conditions, it is not clear how feed particle size during heat stress can affect feeding behavior, performance, and blood and ruminal parameters in cows. In fact, no study has simultaneously examined the interaction between environmental temperature and forage particle size on nutrient consumption and digestibility in lactating cows. Therefore, the aim of the present study was to simultaneously investigate the interaction between season (spring and summer) and forage particle size (coarse and fine) on nutrient intake and digestibility in High producing Holstein cows.
Materials and Methods: A total of 100 High producing Holstein cows were used in two seasons, spring and summer, with 50 cows per season divided into two treatments: one containing alfalfa forage with coarse particle size (geometric mean 7.7 mm) and one containing alfalfa forage with fine particle size (geometric mean 4.2 mm). Throughout the sampling period, to calculate dry matter intake, the feed offered and the amount remaining the next day before fresh feed was offered were weighed. Also, to examine the feed intake pattern, the amount of feed remaining in the trough was weighed at 2, 4, 8, and 24 hours after the morning feeding and then returned to the trough. Apparent nutrient digestibility was measured using acid-insoluble ash as a marker in feed and fecal samples.
Results: The results showed that dry matter intake was significantly higher in spring compared to summer (P < 0.01). Additionally, there was a significant difference between seasons in terms of feed intake rate parameters, with the amount of feed consumed (in kg) during the first two hours after morning feeding being significantly higher in summer than in spring (P = 0.02), while feed intake during 2-4 hours and 4-8 hours after morning feeding was higher in spring. Overall, in the present study, dairy cows during spring (normal temperature conditions) had a more uniform feed intake rate throughout the day compared to summer (heat stress conditions). It should be noted that the results showed no significant difference in daily feed intake between treatments containing forage with different particle sizes (fine versus coarse). It is worth mentioning that forage particle size had no significant effect on nutrient digestibility, while digestibility of dry matter, organic matter, and crude protein was significantly higher in summer compared to spring
General Conclusion: The results of the present study showed that the season variable had more tangible effects on dry matter intake, feed intake pattern, and nutrient excretion in high-producing dairy cows compared to forage particle size. Furthermore, the lack of effect of feed particle size demonstrates the flexibility of the ruminant digestive system when confronted with different forage particle sizes. These results highlight the importance of nutritional management under different climatic conditions and indicate that animals possess complex adaptive mechanisms to maintain nutritional efficiency under challenging conditions.
Materials and Methods: A total of 100 High producing Holstein cows were used in two seasons, spring and summer, with 50 cows per season divided into two treatments: one containing alfalfa forage with coarse particle size (geometric mean 7.7 mm) and one containing alfalfa forage with fine particle size (geometric mean 4.2 mm). Throughout the sampling period, to calculate dry matter intake, the feed offered and the amount remaining the next day before fresh feed was offered were weighed. Also, to examine the feed intake pattern, the amount of feed remaining in the trough was weighed at 2, 4, 8, and 24 hours after the morning feeding and then returned to the trough. Apparent nutrient digestibility was measured using acid-insoluble ash as a marker in feed and fecal samples.
Results: The results showed that dry matter intake was significantly higher in spring compared to summer (P < 0.01). Additionally, there was a significant difference between seasons in terms of feed intake rate parameters, with the amount of feed consumed (in kg) during the first two hours after morning feeding being significantly higher in summer than in spring (P = 0.02), while feed intake during 2-4 hours and 4-8 hours after morning feeding was higher in spring. Overall, in the present study, dairy cows during spring (normal temperature conditions) had a more uniform feed intake rate throughout the day compared to summer (heat stress conditions). It should be noted that the results showed no significant difference in daily feed intake between treatments containing forage with different particle sizes (fine versus coarse). It is worth mentioning that forage particle size had no significant effect on nutrient digestibility, while digestibility of dry matter, organic matter, and crude protein was significantly higher in summer compared to spring
General Conclusion: The results of the present study showed that the season variable had more tangible effects on dry matter intake, feed intake pattern, and nutrient excretion in high-producing dairy cows compared to forage particle size. Furthermore, the lack of effect of feed particle size demonstrates the flexibility of the ruminant digestive system when confronted with different forage particle sizes. These results highlight the importance of nutritional management under different climatic conditions and indicate that animals possess complex adaptive mechanisms to maintain nutritional efficiency under challenging conditions.
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