Managing heat stress to sustain producing dairy cows in the tropics

in National workshop (full text oral presentation), 國內研討會(全文口頭發表)
標題Managing heat stress to sustain producing dairy cows in the tropics
AuthorsLiang Chou Hsia, 夏良宙

The climate in this area can be divided into the following four categories: 1. dry and high temperature, 2. high humidity and high temperature, 3. high temperature but with dry and wet seasons, and 4. moderately cold temperature in winter but high temperature in summer. The most important differences among the four kinds of weather are: 1. Dry and high temperature not only cause heat stress for cattle directly, but also cause low quantity and quality of roughage production. 2. High temperatures usually cause higher cell wall content and lower digestibility of cell wall. High temperatures also cause early maturation of plants which also cause lower digestibility of cell wall. 3. High roughage diet for cattle usually produces higher heat increment, which may cause higher heat stress or lower feed intake. 4. Reproductive performance can be more easily achieved in wet, cool, or moderate cold weather. The result is that milk production can not be easily evenly distributed over 12 months; as a result, the price of milk will be low when cattle produce more milk. This will influence the total income of farmers. 5. Cattle grazing on the range is more difficult if the land is very wet. Excess precipitation can also easily cause land erosion. 6. A high roughage diet for cattle usually produces a higher percentage of methane (CH4), one of the important greenhouse gases. 7. Over-grazing easily causes desertification, and social problems, especially in dry tropical areas. 8. Higher milk-producing dairy cattle have higher heat increment; that is, they are very sensitive to heat stress and not easy to manage. It is not too difficult to find heat-resistant cattle or buffaloes but with lower milk production. How to make a decision as to whether a farmer should choose high- or low-milk yield cattle totally depends on (1) the economic situation of the farmers, (2) available technology to raise high-yield milk cattle, and (3) social and climatic environments.

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