Stonaker H H, Villar J, Osorio G, Salazar J
Trop Anim Health Prod. 1976 Aug;8(3):147-54.
In the tropical savannas of Colombia, the Llanos Orientales, a field survey of 40 beef herds leased by farmers through a cooperative indicated that these herds had mean annual calving rates of 52 and 55 per cent in the Plains and Piedmont zones, respectively. Within zones, very large differences in reproductive rates were found between herds. The differences seemed to be associated with the soils and climates of the areas, condition and weight of cows and breed of cow. Only 9 to 13 per cent of nursing cows were found to be pregnant. Conception was seasonal, occurring mostly in the dry and early rainy seasons. Control of the time of weaning of calves, routine mineral supplementation and improved pasture management appeared to offer immediate possibilities for economically improving output of calves.
在哥伦比亚的热带稀树草原——东方平原，一项针对农民通过合作社租赁的40个肉牛群的实地调查表明，这些牛群在平原和山麓地区的年平均产犊率分别为52%和55%。在各区域内，不同牛群之间的繁殖率存在很大差异。这些差异似乎与各地区的土壤和气候、母牛的状况和体重以及母牛品种有关。仅发现9%至13%的哺乳母牛怀孕。受孕具有季节性，大多发生在旱季和雨季初期。控制犊牛断奶时间、常规补充矿物质以及改善牧场管理似乎为经济上提高犊牛产量提供了直接的可能性。
