| Summary: | 碩士 === 國立臺灣大學 === 動物科學技術學研究所 === 105 === Period from 3 weeks before to 3 weeks after parturition is usually called transition period. In this period, dairy cows will inevitably face lots of health problems like ketosis, mastitis, retained placenta, displaced abomasum and so on. The reasons are negative energy balance and decreasing concentrations of many trace elements due to decreasing dry matter intake and increasing energy demand caused by growing fetus and lactation. Therefore, how to help dairy cows get through transition period safely has become an important issue.
The objective of this experiment was to investigate the effects of supplementing transition dairy cows with experimental additives to prevent ketosis and mastitis. Experiment was divided into 2 parts. Treatment group was daily supplemented with additives consisted of Vit. A, D, E, Se and powder made from glycerol and propylene glycol from 3 weeks before to 3 weeks after calving. Blood samples were collected on the day right after calving and 1, 2 and 3 week after calving. Milk samples were collected on the day of 3 week after calving. Besides, daily milk yield, days from calving to first AI and health information were recorded. Experiment I was aimed at the difference between primiparity and multiparity, and experiment II was aimed at primiparity with different body condition score (BCS) due to supplementation effects on primiparity were more obvious in experiment I.
Results showed that primiparity faced more severe negative energy balance than multiparity did. There were improvements in negative energy balance, milk yield, milk components and reproductive performance when cows are supplemented with experimental additives. Although there was no statistically significant difference, but the effects were more obvious and consistent in primiparity. Results of experiment II showed that cows with lower BCS faced more severe negative energy balance than cows with higher BCS according to blood parameters. This finding is different from literatures, and the reason may be related to the feeding competition among cows with different body sizes. Although there was no significant difference, but there were improvements in negative energy balance, milk components and loss of BCS in cows with higher BCS. As to reproductive performance, improvement in cows with lower BCS was more obvious than cows with higher BCS. There was no obvious effect of preventing mastitis in experiment I and II due to high dose of trace elements in original daily rations of dairy farms.
In conclusion, grouping in farms during transition period is important to prevent inevitable feeding competition among cows, and it will be easier to provide proper management to different groups of cows. In addition to this, supplementation with experimental additives can help alleviating negative energy balance and improving milk yield, milk composition and reproductive performance.
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