Bos indicus is also highly resistant to parasites. For Bos indicus net energy requirements for maintenance are lower than in Bos taurus, but requirements for growth are higher. The greater ability of Bos indicus to recycle urea to the rumen makes it less dependent on feed nitrogen. Bos indicus can also store heat during the day and then dissipate it nonevaporatively at night, thus reducing the need for watering.ĭry matter intake relative to body weight is higher in Bos indicus than in Bos taurus when coarse forages are fed, but the contrary holds for good-quality forages. Humidity has no adverse effect on Bos indicus sweating rate, while water vapor trapped in the air spaces between the hairs of Bos taurus impedes evaporation. This tolerance is due to the high heat resistance of their sleek, dense coat, which prevents heat gain from the environment low tissue resistance to heat transfer from the body core to the surface and high sweating competence. Adaptation Traitsīos indicus tolerates heat better than Bos taurus, and this is reflected in a lower rise of body temperature under hot conditions.
Solar radiation, which might be seen as a hindrance for dairy production, is in fact the main asset of tropical systems, because it allows intense photosynthesis and plant growth however, to make good use of it, adapted animals are required. This result was due mainly to the high stocking rate of 4.2 cows ha -1 and to the low input in terms of machines, buildings and veterinary costs. As an example, a model private farm in Brazil, keeping F 1 Holstein × Guzera crosses on irrigated, fertilized pasture and feeding 3 kg concentrates day -1, had a production cost US$0.08 l -1, which is extremely low on a world basis. On the other hand, improved systems based on pasture may be extremely efficient economically although, in these conditions, milk yield per cow is not as high as in temperate countries. Also, systems based on high concentrate consumption are not feasible if cows are competing with humans for cereals. However, these expensive systems are not generally economic in developing countries, where capital is scarce and unemployment severe, favoring systems with a lower input. Use of purebred Bos taurus has been advocated for dairy systems that use coolers and ponds to alleviate heat and freestalls or other types of buildings to keep the cattle indoors. Thus, the main interest in crossing is to combine milk yield and adaptation. Bos indicus breeds, on the other hand, while adapted to the environmental challenges, showed little response in milk yield to improved management. For example, in Venezuela, it was estimated that imported and locally born Holstein cows produced only 0.6 and 0.7 replacement females respectively in their lifetimes.
Madalena, in Encyclopedia of Dairy Sciences (Second Edition), 2002 Bos indicus × Bos taurus Crosses Breeds/Crosses and Production Systemsīos taurus breeds, highly selected for milk yield in developed temperate countries, do not perform well under the prevailing production systems in the tropics, where they are unable to cope with the stresses of heat, humidity, parasites and low-quality forages, to the point of being unable to sustain their numbers.
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