Analysis on summer milk production of heat-tolerant ten-tons cows and age at first calving of their daughter.

The Hsinchu Branch of TLRI and Dairy Association Taiwan R.O.C. implemented the national DHI program. In 2014, the DHI daity farmers were encouraged to improve cattle breeding performance and cow fertility with lower caving ease and higher rate of pregnancy. Of the 28,399 cows from DHI farms in 2018, there were 51 farms to raise 250 head of high-prolific ten-tons cows. In the summer of 2019 (June-September), the daily milk yield decreased by 2.9- 6.5% compared with the amount of daily milk in April-May (25.28 kg). In 2019, there were 158 high-prolific ten-tons cows, which were raised in 35 households. Their daily milk yield in April and May was 33.51 and 31.34 kg, respectively, and daily milk yield from June to September were 31.26, 29.93, 29.49 to 30.36 kg. It shows that summer heat stress can cause a 12% reduction in milk production. In 2019, the ratio of primiparous cows was 35.0% (5,045/14,404) and the average age of primipara was 26.2 months. [ABSTRACT FROM AUTHOR]