| The quantity of nutrients and greenhouse gases emitted from pig production into the environment can be modulated by different nutritional strategies, but their practical application is dependent upon cost and other biological limitations. This research was conducted to evaluate the nutritional interventions most promising to reduce nutrient excretion and greenhouse gas emissions by pigs. The studies concentrated on sows and growing-finishing pigs, which produce two-thirds of the greenhouse gas emissions by pigs in Canada. The studies evaluated the effect of protein and energy source and protein intake on CO 2 and CH4 emission and nitrogen and carbon excretion and assessed the effect of high- (HP) and low-protein (LP) diets based on corn-soybean (CS) or wheat-barley-canola (WBC) meal. Also, a study was conducted to evaluate the effect of a combined low-protein, low-phosphorus diet supplemented with limiting amino acids and phytase and xylanase, individually or combination, on nutrient digestibility and energy metabolism in growing-finishing pigs using indirect calorimetry.;LP diets led to a significant reduction in CH4 production from WBC diet, but emissions were not affected by protein level in the corn diets. The CO2-equivalents emitted by nonpregnant sows fed at maintenance was lower for the WBC-LP than the WBC-HP diet, while the protein reduction had no effect for the CS diets. Overall, the CO2-equivalents were reduced by 16.4% by reducing dietary protein contents. The gestating and lactating sow data showed that LP diets supplemented with limiting amino acids significantly reduced N and C excretion (Trial 1). From trial 2, average daily gain was not affected by diet type or protein level. N retention was similar for WBC-LP and WBC-HP, but lower for CS-LP than CS-HP. WBC-LP had non-significantly similar fecal N, but a significantly lower urinary N than WBC-HP. N excretion for CS-LP and CS-HP were similar. CO2-equivalent (CO2 and CH4) emission by pigs was numerically lower for LP than HP diets of CS and WBC. Carbon excretion was lower for CS than WBC diets, but similar for LP and HP diets. Daily gain, daily feed intake and gain to feed were not affected by protein level. O2 consumption and CO2 emission were significantly influenced by dietary protein. Dietary protein reduction reduced CH4 emission numerically. Heat production was less in pigs fed VLP than HP (Trial 3). Similarly, in trial 4, daily gain, feed intake, gain to feed, O2 consumption, CO2 and CH4 emission, and nitrogen retention were not affected by combined protein and phosphorus reduction. N intake was significantly lower in the protein-reduced diets compared to control. Fecal and urinary N were significantly lower for pigs fed reduced protein diets compared to the control. Heat production was non-significantly affected by dietary treatments.;Reducing dietary protein concentration maintained animal performance and reduced nutrient excretion by growing-finishing pigs fed WBC. LP reduced CH4 emission, but had little effect on CO2 emission. The CO2-equivalent arising from the animals (CO2 and CH4) tended to be lower for LP. VLP improved heat production, an indication of improved nutrient utilization, and potential for reduced greenhouse gas emission. Such feeding regimens offer substantial benefits in maintaining sustainable environmentally-friendly pork production. Understanding the effect of synthetic AA and exogenous enzyme supplementation on utilization of nutrients (e.g., N and P) and energy will not only encourage swine producers and feed manufacturers to use these nutritional interventions, but also challenge the feed industry to reconsider their diet formulation practices to reduce environmental impact of pork production. |
