Dairy cattle suffer reproductive irregularities
BEEF cattle suffer fewer irregularities during reproductive heat cycles than dairy cattle and also have higher conception rates to first service, according to a MAFF-funded trial.
Using milk progesterone levels as a measure of fertility in dairy and beef cows, researchers at ADAS Redesdale, Northumber-land, monitored 107 Simmental and Belgium Blue cross Holstein Friesian suckler cows. They found only 5% of beef cows suffered irregularities in heat cycles compared with 27% of dairy cows from other research studies.
Of the 5% of abnormalities recorded, less than 3% of beef cows suffered longer cycles, compared with about 14% of dairy cows recorded in separate studies. Similarly, less than 1% of beef cattle failed to cycle compared with about 13% of dairy cows. The remaining 2% of beef cows had irregular cycles, although the small number of cases makes drawing conclusions difficult, researcher George Mann told delegates.
But beef cows returned to heat later, typically 40 days after calving compared with 27 days for dairy cows. This was due to the presence of a suckling calf and lower progesterone levels, which are required at a certain level to induce a follicle to ovulate, added Dr Mann.
Most beef cows resumed cycling 27 to 40 days after calving, with 85% cycling by 54 days.
Also 77% conceived to first AI service and a further 79% to second AI service. Potential for AI use in beef cows – to cut bull costs and speed up genetic improvement – was good, he suggested. *