So much for using wolves and coyotes as a model to argue digestibility and utilization of protein, carbs, and fat in domestic dogs.
http://www.nature.com/...ull/nature11837.html
The wetsuit example fails to consider several points pertinent to most hunting retriever breeds. Assuming you don't wash your hunting retriever every week with a harsh shampoo, your dog has a decent coating of hydrophobic oil on his skin and pelage, enabling it to trap air near the skin when immersed in water. While his or her coat may be wet, the layer near the skin remains dry. Dogs also possess a counter current veinous/arterial supply apparatus in their legs, made more efficient by their fur coat and thoracic structure, enabling them to maintain their core temperatue well in extreme cold. Dogs will "curl up" in extreme cold, minimizing the exposure of their peritoneal body section to heat loss, as well as tucking their nose under a limb to access inspired air that is warmer than ambient. A wetsuit traps the water against a human's skin, maximizing rate of heat loss when ambient temps. are warmer than the water inside the suit. It does, however, slow rate of heat loss when a body is immersed since it adds another layer of insulation, as well as limiting the volume of water next to the wearer's skin that enables body heat loss rate to increase.
http://users.rcn.com/...H/HeatTransport.html
I would suggest you consider keeping the neoprene suit on the dog, dry its belly, legs, and ears well when it is back in the blind or boat, following a retrieve. Also, you may want to consider feeding it low volume high energy content snacks routinely during a cold weather hunt, as well as Warm, not HOT water in a bowl, which aids in maintaining hydration as well as background metabolic function.
A dog kept in a cold ambient air environment has the innate ability to raise its basal metabolic rate, also enhancing its ability to stay warm, since the number of calories burned per unit time, even at rest, is higher when compared to a like-size and breed animal that has been kept indoors for the same interval at a wamer ambient temperature. For humans, resetting basal metabolic rate usually requires about a month or so...