5.1 Conclusions
§ On Farm 1, a difference in live weight between heifers reared in a suckling system compared to heifers reared in a bucket system was found at an age between 400 and 500 days. No difference in live weight was found on this farm when using corrected live weights. Growth on this appeared to be affected by the use of genetically superior bulls in the suckling group. Heifers on Farm 2, reared in a suckling system, reached a significant higher live weight, at a comparable age, compared to heifers reared in a bucket system
§ Heifers reared in a suckling system can be inseminated or introduced to the bull earlier, than those reared in a bucket system. Hence, age at first calving can be reduced for heifers reared in a suckling system.
§ Live weight at first calving was not measured in this study. The data could not prove if live weight at first calving of heifers reared in a suckling system, was higher compared to those reared in a bucket system, when calving at a comparable age.
§ Milk production data on Farm 1 was not fully comparable, because it was affected by the use of genetically superior bulls in the bucket reared heifers. As well, the reduction of age at first calving of heifers reared in a suckling system was affecting milk production. No difference in milk production between heifers reared in a suckling system and heifers reared in a bucket system was found on Farm 2.
§ Data about mastitis incidence was not fully comparable on Farm 1. Heifers in the bucket and suckling groups were born in different years, while there was a lot of variation in average SCC of the herd within years. No difference in mastitis incidence between suckled and bucket groups was found on Farm 2.
§ Farms using suckling systems have more risk for transmitting Paratuberculosis compared to farms using conventional rearing methods. It is important to test farms were suckling systems are used on the presence of the disease. The Parawijzer is not useful to prevent Paratuberculosis on farms were suckling systems are used, because a number of measures is not applicable on farms using suckling systems.
§ Loss of saleable milk was totally repaid by lower rearing costs on Farm 1, and almost repaid by lower rearing costs on Farm 2.
§ This study is providing a good method for the evaluation of the data from heifers in the QLIF- project.
The general conclusion is: suckling systems can decrease age at first calving of heifers reared in a suckling system. Milk production and mastitis incidence of heifers reared in a suckling system is not different from heifers reared in a bucket system.
5.2 Recommendations
Further research within the project Kalf bij koe already started with the QLIF-project. The recommendations can be taken along in this project.
Concerning the collection of data it is recommended to collect data of suckling calves that received the same treatment. In this study, there was a lot of variation in suckling periods and weaning age. Registration have to be made of heifers that suckled their calf. Furthermore, more data have to be collected. More data makes it possible to compare heifers that start lactating in the same season. And so, there will be less seasonal effects. In addition, measurements have to be done more consistent. The following parameters have to be measured or registered:
§ General information: birth date, weaning date, period of single suckling, period of multiple suckling, calving date;
§ Growth: live weight at birth, at 2,4,6 months, 1 year and at first calving;
§ Milk production: total production, 305-day production, % milk fat and milk protein, DIM, SCC, LW and ISK.
Remaining parameters as age at weaning, age at first calving, etc. can be calculated from this data.
A suckling system is a more expensive rearing method compared to the bucket system. However, this expensive rearing period can be repaid by an earlier age at first calving. It would be interesting to study what will be the (economically) most optimal suckling period and reduction in age at first calving. Another interesting subject for further research is: causes contact of calves with farm specific bacteria more disease or is it resulting in a stronger herd; Since attention is paid by the Louis Bolk Institute and other institutes to suckling systems, the number of farmers that start experiment with suckling systems is increasing. If this increase is going on, special attention has to be paid by the NRS, to the effect of suckling on the lactation curves of suckling cows. When calves drink part of the milk, the beginning of the lactation curves become de-shaped. Parameters which are calculated from measured milk production (ISK-values, LW) become deviated as well. When many farmers start using suckling systems this could even influence breeding values of bulls.
Paratuberculosis can be a threat for a more widely acceptance of suckling systems within the agricultural sector. Therefore, it is important to encourage farmers that use suckling systems to monitor the Paratuberculosis status at their farms.