Extended calving interval in combination with milking two or three times per day: effects on milk production and milk composition

Abstract

This study was conducted to examine the effect of an extended, 18 months, calving interval (CI) in comparison with a traditional 12 months CI, on milk production and milk composition. In addition, the cows had different milking frequencies (MF), either two or three times per day. This resulted in four treatment groups; referred to as 12-2, 12-3, 18-2 and 18-3. Cows of Swedish Red and White breed were used in the experiment, and the analyses extended over a period of 3 years. Thus, three complete lactations were monitored for cows with 12 months CI and two lactations for cows with 18 months CI, unless the cows were culled during the experiment. The first experimental year, there were 13 cows in each group, and during the second year another five cows were included in each treatment, giving a total of 72 cows for the entire experiment. The achieved calving intervals for the 12 and 18 months CI were 12.2 and 17.5 months, respectively. Cows with 18 months CI had, of course, higher lactation yield, but when the longer lactations were considered there were no differences in milk yield per day of CI. The cows in group 18-3 had higher milk production than 18-2 measured in ECM/day (energy corrected milk) of CI ( P<0.05). There was no significant difference between 12-2 and 12-3 in ECM/day of CI, but 12-3 had a higher cumulative ECM ( P<0.05). Cows milked three times per day had a slightly longer lactation than those milked twice per day. When comparing CI, MF and parity, the primiparous cows had a lower cumulative ECM than multiparous cows in 12 months CI, irrespective of MF, while it was the opposite for the cows with 18 months CI. This study shows that by combining longer calving intervals with increased milking frequency, the milk production per day from one calving to another might be higher than in a traditional calving interval. Our results also indicates that prolonged calving interval in combination with milking three times per day gives a more tenable production system, therefore this should be an interesting option for the farmer.