Recipients must be selected for reproductive performance, ability to calve, disposition and milking ability. Virgin beef heifers should be cycling and be a minimum of 13 - 14 months old. Pregnancy rates are good and handling of recipients when synchronizing them tends to be easier because of the lack of calves at side. Calving and milking ability tend to be the downside. If heifers are used the genetics for milk should be known and use should be limited to embryos from low birth weight matings.
Cows with calves at side that have calved at least 50 days and are on an increasing plane of nutrition with access (preferably force fed) to vitamins and minerals work well. Attention should be paid to disposition and udder. First calf heifers work well providing they are in good condition and are at least 70 days post partum. Thin first calf heifers should be fed well and given more time post partum or not used. Open cows are not recommended unless they have a known non-reproductive reason for being open (exposed to a problem breeding bull).
Dairy heifers work well from a pregnancy standpoint, but can be a problem at calving and require high level of care. Lactating dairy cows that are managed like beef cows tend to be difficult to re-use as recipients when nursing an ET calf. Dairy cattle tend to have a higher incidence of leucosis titers which will show up in your ET calf and cause problems with future health testing for entry to bull studs. I don't recommend using dairy heifers and cows for beef ET and if they are used insist on negative leucosis test.
Leasing of recipients works well providing the management in the lease herd is excellent. In such cases a bonus (10-20%) above the price for commercial calves is usually paid based on the weight of the weaned ET calf. It is best to pay a higher bonus for good weights, but build in a penalty clause for frozen ears, swollen joints, frozen feet (things that make the calf not marketable as a purebred). The owner of the embryo pays implanting and synchronization costs.