Energy balance of lactating primiparous sows as affected by feeding level and dietary energy source

The effects of feeding level and major dietary energy source used during la ctation on sow milk composition, piglet body composition, and energy balanc e of sows were determined. During a 21-d lactation, 48 primiparous sows wer e fed either a Fat-rich (134.9 g/kg fat; 196.8 g/kg carbohydrate) or a Star ch-rich (33.2 g/kg fat; 380.9 g/kg carbohydrate) diet at either a High (44 MJ NE/d; 1,050 g protein/d) or a Low (33 MJ NE/d; 190 g protein/d) feeding level. Within each feeding level, the two diets were fed to provide an isoc aloric and isonitrogenous intake. At the Low feeding level, no differences in milk production, milk composition, or piglet body composition were found as a result of feeding the two dietary energy sources. However, at the Hig h feeding level, sows fed the Fat-rich diet produced higher milk fat (8.4 v s 6.9%) and milk energy (5.38 vs 4.77 kJ/g) concentrations and a higher pig let body fat concentration (152.1 vs 135.4 g/kg! than sows fed the Starch-r ich diet. At the Low feeding level, the energy balance id 6 to d 20) of the sows was similar when fed either the Fat- or the Starch-rich diet (-558 an d -515 kJ . BW-.75. d(-1)), but at the High feeding level, the energy balan ce was more negative in sows fed the Fat than those fed the Starch-rich die t (-544 vs -372 kJ . BW-75. d(-1)). This suggests that at the High feeding level, dietary energy in the form of fat is preferentially used for milk. f at synthesis, resulting in growth and in fatter piglets. Alternatively, at the High feeding level, Starch as the major energy source is used only for growth of the piglets, as confirmed by protein deposition, and also results in a less-negative energy balance for the sows. From this experiment, it c an be concluded that effects of substituting cornstarch for fat in the diet of lactating sows on milk composition, piglet body composition, and energy balance of the sows are dependent on feeding level.