Is rearing calves with the dam a feasible option for dairy farms?—Current and future research

In the dairy industry it is common practice to separate cow and calf shortly after birth but this practice is disputed because of animal welfare concerns. Some producers, in many countries, milk cows that also nurse dairy calves. These cow–calf systems allow nursing as well as affiliative and other natural behaviours. In this review paper we describe cow–calf systems used in practice and/or in research, discuss the benefits and challenges documented by research, and identify areas where more research is needed. Four cow–calf systems are described: (1) free contact systems where cow and calf have unrestricted access to each other; (2) restricted suckling systems allowing short daily contact only to nurse; (3) half day contact where cow and calf are housed together during the day or night; and (4) foster cow systems where one cow nurses 2–4 calves usually without milking. In free and half day cow–calf contact systems the calf drinks large amounts of milk and has high daily weight gains. High pre-weaning calf weight gains have been shown to lead to higher milk yield during that animal's first lactation. One issue with cow–calf systems is the depressed weight gain of calves at weaning. The premature separation of cow and calf, compared to the natural situation, may cause stress especially in free contact systems. Weaning and separation should therefore occur in two steps. Half day contact seems particularly promising because animals get used to being separated, they experience positive human handling, and calves can learn to use a milk feeder which will prevent the growth check following weaning. Nursing cows yield less saleable milk during the suckling period, can have problems with milk ejection during machine milking and have a lower fat content of the milk, compared to non-nursing cows. Udder health of the cow may be positively affected by nursing. A rich social rearing environment has recently been shown to improve cognitive skills of calves. Still, studies on long term effects of dam rearing on behaviour, health, production and farm economics are few. There is also a need to address ways to control transmissible diseases when dairy cattle are kept in mixed age groups. Increased knowledge will help us design functional high tech dairy management systems that respect the natural behaviour of cows and calves during the calf rearing period.