Abstract
Abstract. To estimate long-term effects of dietary protein quality on energy metabolism and thyroid hormone Status in growing pigs two experiments were carried out, each using 6 growing German Landrace barrows (40 to 90 kg body weight (BW)) per treatment group, which were fed semisynthetic isoenergetic diets based on either casein or soy protein isolate at 1875 kJ ME/(kg BW0,62 x d). Casein was tested with (CAS+) amino acid (AA) supplementation (methionine + cystine, threonine, tryptophane) and soy protein isolate was tested without (SPI-) AA supplementation at the recommended protein supply of 100% (normal protein level (NP)) and at a protein supply of 50% of NP. During experiments pigs were housed individually in metabolic cages at 23 ± 1 °C. At both protein supply levels, SP1- in comparison to CAS+ caused a lower protein energy retention (PER), which was compensated mainly by an increased fat energy retention (FER). The reduction of the protein supply to 50% caused a lower PER by 30 to 50% in both dietary qualities, which was compensated by a significantly higher FER. However, the heat production (HP) was neither affected by the protein quality nor by the quantity, and resulted in nearly similar values of 60% of ME intake. The thyroid hormone concentrations were dependent primarily on the amount of protein supply, and after decrease of supply to 50% secondly on the dietary protein quality. The increased thyroid hormone concentrations at the 50% protein level were in euthyroid range of pigs and obviously not associated with HP.
Highlights
Long-term feeding of diets, which meet the energy requirements for maintenance and growth, but not the requirement for essential amino acids (AA), decreases growth rate and protein deposition in growing animals
The objective of the present study was to investigate the influence of dietary protein quality (AA pattern) on energy metabolism and thyroid hormone Status, as well as to explore whether differences in energetic efficiency are associated with changes in circulating thyroid hormone levels
At NP the values for CAS+ fed pigs in the lst and 2nd period were 504 and 567 g, respectively, which was in both periods approximately 90 g higher than the daily gain of the SPI- pigs
Summary
Long-term feeding of diets, which meet the energy requirements for maintenance and growth, but not the requirement for essential amino acids (AA), decreases growth rate and protein deposition in growing animals. It is known that thyroid hormones may play a role in mediating the thermogenic response to low protein diets. Less research has been done in examining the effect of feeding dietary proteins with a low biological value on energy metabolism of growing animals. The question arises whether a higher T4 level in AA deficient fed animals represents a true change in biological activity and does play a role in dissipating excess dietary energy. The objective of the present study was to investigate the influence of dietary protein quality (AA pattern) on energy metabolism and thyroid hormone Status, as well as to explore whether differences in energetic efficiency are associated with changes in circulating thyroid hormone levels
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
