نوع مقاله : مقاله پژوهشی
نویسندگان
1 گروه علوم دامی دانشکده کشاورزی دانشگاه بیرجند
2 مرکز آموزش عالی جهاد کشاورزی خراسان رضوی (شهید هاشمی نژاد)
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
Introduction: In feeding of dairy cows, well balanced diet and the proper amount of dietary fiber and particle sizeare necessary. Also, management of feed and feed intake is very important. On the other hand, increasing the intake of dry matter in lactating cows during early lactation is vital for improving milk production, animal health, and physical condition (Grant and Albright, 1995). One of the factors affecting animal health, is the physical properties of the feed, which has a strong relationship with the health of the digestive tract and animal feeding behaviors. Many researches have shown that cows tend to consume fine-grained components of their diet and makes selective consumption against larger components of the diet, while coarse components of the diet and long pieces are essential for animal health, because it increases rumination and chewing activity in animals (Stone, 2004). This experiment was carried out to evaluate effect of feeding frequency on feeding behavior, milk yield, and composition in dairy cows.
Material and methods: Twenty Brown Swiss dairy cows (average milk yield of 26.56 ± 5.2 Kg/d and 44.95 days in milk) were used in a completely random design for two periods. Two experimental treatments were applied. The experimental treatments were: 1- delivery of feed twice per day at 08:00 am and 8:00 pm and 2- delivery of feed three times per day at 08:00, 16:00 and 24:00. Each experimental period consisted of 21 days adaptability and 4 days recording of feeding behavior, milk yield, and composition. For all cows, eating activity and ruminating were recorded by visual method within 48 hours (first and second days during four-day sampling) at intervals of five minutes. Total chewing activity was calculated from the total time spent eating and ruminating. Sleep duration was measured at intervals of 10 minutes. Distribution of particle size was determined through PSPS (Penn State Particle Seprator). Approximate analysis of samples was undertaken by AOAC (2005). Neutral detergent fiber and acid detergent fiber were determined by the method of Van Soest (1991). Milk production was recorded on the third and fourth days of two sampling periods. Samples were taken at these days used to determine fat, protein, lactose, fat-free solids and urea by the means of milko scan system. Measurement of milk casein nitrogen, non-casein nitrogen, non-protein nitrogen of milk and true protein of milk were calculated by Raveland method (1938).
Results and discussion: The results of this experiment showed that increasing the feeding frequency from two to three times a day increased the duration of eating, ruminating, chewing activity. Eating activity (minute / day) was significantly affected by experimental treatments (p < 0.05). Delivery of feed three times a day increased the amount of time consumed for feeding. The increase in feed intake significantly increased the activity of chewing (734 vs. 771 minutes per day) (p < 0.05). The most important feed-related factor affecting the activity of chewing is the physical structure and the chemical nature of the feed (Frooghi, 2005). With increasing feeding frequency, the activity of ruminant in standing position was reduced by approximately 10 minutes (p < 0.05). This means that fewer frequency of feeding increased the level of ruminant activity in the standing position (Phillips and Rind, 2001). Also, the ruminant activity in the resting position was affected by experimental treatments and increased with increasing in feed delivery per day (P <0.0001). The results of this experiment showed that with increasing feed intake from two to three times a day, the selective consumption of feed components decreased and the consumption of NDF and long particles also increased (p < 0.05). Therefore, increasing feeding has a more favorable effect on animal performance and prevents the separation of feed components (Jeziersky and Podluzny, 1984). The feeding frequency had a significant effect on the percentage of selection on screen 1.18 mm (short pieces) (p < 0.05). This means that with increasing feed frequency, consumption from this screen was decreased. However, increasing feed intake, milk production was non significantly increased by 900 g/day. Also, increasing in the frequency of feed provision increased percent of protein, casein N and true protein of milk. However, increasing in the frequency of feed provision significantly decreased percent of milk urea (p < 0.05). Perhaps the reason for the increase in milk protein with increasing feeding frequency is attributed to an increase in eating time and an increase in energy consumption in the form of concentrate or forage (Phillips and Rind, 2001). Feeding frequency had no significant effect on the percentage of milk solids- non- fat.
Conclusion: The results of this study showed that increasing feeding frequency can improve rumination and chewing activity and decrease the selective consumption of feed components. As the results of previous experiments showed, low feed intake increases competition between cows and also causes cows to wait for access to the feeder. So, excessive standing time can increase the risk of acidosis and laminits and reduce animal economic useful life.
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