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Novel approaches to estimating amino acid requirements and amino acid ratios in diets fed to gestating sows
Nutrition of pregnant sows has received little attention in the recent past, in part because of the time needed to conduct conventional experiments in sows. We conducted experiments specifically designed to determine requirements in early (EG) and late gestation (LG) for amino acids (AA), using the indicator AA oxidation technique, and for energy using indirect calorimetry. Because the indicator AA oxidation technique only needs 2 - 3 days of adaptation, 6 × 6 Latin square experiments to determine AA requirements could completed within a 3-week period, and the same animals could be tested in EG and LG. The implantation of subcutaneous vascular access ports allowed to study protein turnover and metabolomic profiles in the same sows in consecutive parities.
New models for pregnant sow requirements add up the AA and energy deposition in body components, together with estimates of maintenance, and then apply estimates of the efficiency of AA and energy utilization to calculate requirements. These models can calculate requirements for a wide range of physical and performance characteristics of sows. Although there is some disagreement among models and empirical data regarding the absolute values of requirements, the core results are similar. In agreement with our empirical data, these models predict much greater requirements for AA in LG vs. EG, and a decrease in AA requirements with increasing parity number. Models and empirical data indicate that the changes in requirements from EG to LG and with sow age differ among AA, so that the ideal AA pattern changes throughout a sows’ reproductive life. While the ideal protein for pregnant gilts resembles that for growing pigs, it will be closer to that needed for maintenance for adult sows in EG. Therefore, the same diet may be first-limiting in different AA in EG vs. LG, and in gilts vs. adult sows.
Experiments manipulating AA and/or energy allowances showed that optimal subsequent sow and piglet performance is likely achieved by feeding pregnant sows close to requirements modelled or determined based on the growth of the sow-fetal unit. Therefore, pregnant sows should be fed to their changing individual needs throughout their reproductive to achieve optimal performance return from both sows and offspring.
Keywords: Amino acids, Pig, Pregnancy,