Inverkan av utfodringsnivå och miljö på reproduktion och hållbarhet hos rekryteringskvigor

Abstract: This study is based on an earlier interdisciplinary study made by Redbo et al., (2000), Extensive cattle production systems – out wintering, which lasted over two winters, 97/98 and 98/99, with two groups of heifers indoors and two groups of heifers outdoors raised in different environments, indoors or outdoors during their second winter. Both indoor and outdoor heifer groups were fed grass silage ad libitum throughout the experimental period that lasted from October until May. The objective of this study was to evaluate the long term effects of being raised in these two environments. This study includes data collected during the period lasting from the start of the experiment of Redbo et al., (2000) until the heifers had calved a second time and the results mainly deal with the performance of the animals after the experiment during their first two calvings and their first lactation. The effects of earlier environment on a number of traits such as reproduction, leg- and hoof health, sustainability and production ability were studied. The material is based on data from the animals in the experiment of Redbo et al., (2000) and two control groups, of animals reared indoors on restricted feeding. Data from a total of 141 animals were analysed. The data, which was collected afterwards, contains weight and age at the first insemination and at calving, longevity, leg- and hoof health, calving problems and milk yield in the first lactation. Statistical analysis was performed on the data, with the exception of health data which has been presented as mean values for the treatment groups. This study found no differences between the different treatments, i.e. environments indoors or outdoors, the same year with regard to production traits such as number of inseminations, milk yield and longlivety. However, in the most cases significant differences were found between the same treatments in different years. The control group differed considerably between years and was not directly comparable to the other groups and therefore it was difficult to make any comparisons with the indoor group from the experiment of Redbo et al., (2000) as was originally planned. Remarks about calving difficulties were shown to be 10 % higher among the outdoor animals than among the indoor animals during both the first and second calving. Ten percent was equivalent to 4 and 3 animals at first and second calving, respectively. No significant differences were found in milk yield between the indoor and outdoor groups the same year which implies that the different treatments did not affect milk yield. The milk yield increased with calendar year and the probable reason was breeding progress and improved feeding regimes. The reason for culling in the two groups varied, the most frequent reason in the indoor group was failure to become pregnant and in the outdoor groups the main reason was mastitis that accounted for approximately 20 % of the culling. No animal in the outdoor group was culled because of hoof diseases or leg disorders and comparatively few animals in the indoor group were culled due of hoof diseases and none for leg disorders. When a comparison was made between the groups about the mean value of longevity no significant differences was found in longelivety between the two treatments. The animal lived between 4.4 and 5.2 years. A large variation was observed between the number of remarks for the same treatment group at different hoof trimming occasions and differences between treatments therefore are uncertain but the outdoor animals somewhat less remarks compared with the indoor group at hoof trimming on three of the four hoof trimming occasions studied. However, no obvious differences could be observed. Over the period studied mastitis was the dominating disease in all groups. Most cases were observed in the outdoor group which had approximately 28 % of the animals affected at some occasion while the corresponding figure for the indoor group was 13 %. With the results from this study it can be concluded that there are difficulties in the analysis of data from post-experimental animals due to the large variations that occur under non-experimental conditions. There were large seasonal variations, i.e. significant differences between the same treatments in different years. However, the results indicate that a high level of animal welfare and good production results can be obtained in both indoor and outdoor systems when rearing heifers, provided that both indoor and outdoor management and practices give the animals access to sufficient feed of good quality and clean conditions for resting and walking and some type of shelter from bad weather.