The breeding goal for dairy production is a high performance cow, which can be used many lactations and is characterized by steady health and high fertility. Social behavior was not of interest to breeders thus far. However, animals which can cope better in difficult situations, e. g., when introduced into a new group, might perform continuously on a high level.
The introduction into the milking herd is a challenging situation for pregnant heifers. Besides adapting to an unfamiliar environment, they have to cope with unfamiliar conspecifics. The presence of familiar animals in the herd, e.g., their mother, can reduce the stress level. It has been shown, that with regard tp their behavior, dam-reared calves were more interested in unfamiliar conspecifics and sought contact earlier than artificially reared control calves. Therefore, we tested whether dam reared animals, which had spent the beginning of their lives in the cows’ herd, show a better social compatibility towards unfamiliar animals when introduced into the herd. In a first study we observed that dam reared heifers showed more submissive postures during the introduction procedure. However, the repetition of the trial did not reveal any differences between the rearing systems. After the animals were fully integrated into the herd, we separated them for 15 minutes to assess their reaction to social isolation. Dam-reared animals more actively explored their surroundings, which can be interpreted as higher motivation to clarify uncertainties and to get back to the herd.
Since some studies reported a relation between the amount of milk ingested as calf and the milk yield in first lactation, it can be assumed that dam-reared animals, which were allowed to suckle high amounts of milk, would have a higher milk yield compared to artificially-reared ones. To verify this hypothesis we compared the performance (milk yield, milk quality, fertility traits) of dam-reared to artificially-reared animals over their first lactation. There was no effect of the rearing system on either milk yield or milk quality. Furthermore, the amount of ingested milk during rearing could not show an effect on yield or quality.
However, a tendency of the rearing system and of the amount of milk fed during rearing could be shown in some fertility traits: Dam-reared animals had a better index for first insemination, a longer calving and gestation interval as well as a higher calving rate compared to cows reared under restricted feeding management (eight liters per day). When animals were reared with a milk allowance of 16 liters, no differences could be detected between dam and artificial rearing.
Long-term studies addressing the effects of the rearing system on lifetime production beyond the first lactation are still missing.