Early in my field work I learned to keep out of the way when medical advice was asked. Not only I am not a veterinarian, but also it was none of my business to further confuse people as I was doing an excellent job at that by giving nutritional advice alone!
Yes, like anyone involved in the pig business, I have an opinion about (almost) everything. But, a personal opinion and a "qualified" opinion are two totally different matters. Feel free to argue to the contrary, but I would not expect a veterinarian to be an expert on nutrition, and, likewise, I would never expect anyone to rely on me for veterinary advice.
In my experience, most nutritionists worldwide tend to follow this approach. In contrast, veterinarians have to differ. In the U.S., for example, most veterinarians would refer any nutrition question (beyond the basics, that is) to a qualified nutritionist (one with a Ph.D. on nutrition). In Europe, however, and any other place where qualified nutritionists are scarce, veterinarians must also play the role of a nutritionist (and that of one with a background on genetics, facilities, etc.). In Spain, for example, where I lived for nine years, the majority of animal professionals are veterinarians, and as you would expect, those taking nutrition decisions are veterinarians as well. Unfortunately, and this is true for most vet schools in Europe, veterinarians only get two or three courses in nutrition -- and nutrition accounts for at least 60 percent of the cost of pig production.
Where am I leading? We need to educate our veterinarians more on nutrition, because whether they want it or not, they often need to become the nutritionist for a producer who cannot access one. Veterinarians will buy books, read magazines and attend seminars on nutrition, but it is best -- in my unqualified opinion, as I am not an academic -- to lay down the foundations of nutrition knowledge early on, before marketing and common practice develop their own roots, often with catastrophic results.