Difference in energy metabolism and protein retention of limit-fed growing pigs of several breeds.

Energy metabolism and protein retention of four pig breeds were studied in three experiments comparing Norwegian (N) landrace with either Finnish (F) landrace (Exp. 1), Great Yorkshire (Y, Exp. 2) or Dutch landrace (D, Exp. 3). An increasing or decreasing temperature regimen (11 to 26 degrees C) was used. The animals were kept at a constant feeding level (about 93 g.kg -.75.d -1). Energy and protein balances were measured at increasing and decreasing temperature conditions separately. The three landrace breeds utilized their dietary energy and protein with similar efficiencies. However, large differences were observed between Y and N pigs in Exp.2. The Y pigs had a higher growth rate, lower feed/gain, lower heat production, and higher protein deposition than the N pigs. These differences were related to a lower level of activity of the Y pigs. This lower activity level resulted in lower maintenance requirements of the Y pigs compared with the N pigs. Growth rate and feed conversion differed between balance periods. When the temperature within a period was being increased, growth rate was higher and feed/gain was lower compared with periods in which the temperature was being decreased. Breeds differ with respect to energy and protein utilization.