Abstract
Protein restriction in utero may give rise to restricted growth as well as induce metabolically related diseases. In order to determine the suitability of mink as an animal model for metabolism studies, the effects of protein restriction during gestation on dam and kit performance must first be determined. Mink dams were fed an adequate protein (AP; crude protein:fat:carbohydrate ratio of 31:55:14% of metabolizable energy, ME) or a low protein diet (LP; 19%:49%: 32% of ME) during the last 21.2 ± 3.3 days of gestation, followed by an adequate diet during lactation. Respiration and balance experiments were performed during late gestation and twice during lactation. The dietary treatment only affected energy metabolism traits significantly during the treatment period in late gestation, such that LP dams oxidized less protein (12% vs 23% of heat production, HE, P = 0.001) but more carbohydrate (37% vs 26% of HE, P -0.75.day-1, P < 0.05) than AP dams. Reproductive performance and kit organ growth were not affected by diet. Kit losses up to weaning were higher in LP than AP dams (2.0 vs 1.4, P < 0.05). LP fetuses weighed less (8.3 vs 11.6 g, P < 0.001) and were shorter (6.2 vs 7.6 cm, P < 0.001) than AP fetuses, however, differences might have been due to different implantation times. LP kits weighed 8.5% less than AP kits at birth, and remained lighter until 21 days of age. The LP diet caused growth restriction and increased kit mortality indicating that the dietary protein supply during late gestation was suboptimal to re-quirements. The long-term consequences of protein restriction in utero in terms of permanent metabolic changes in adulthood now need to be investigated.
Highlights
It is widely recognized that adequate intrauterine and early postnatal nutrient and energy supply is of utmost importance for adult animal performance, health, and life span
Results concerning nutrient intake and various metabolic parameters are given in relation to metabolic body size for comparative purposes, while results regarding organ data are given as the mass of the organ and as the percentage of organ to body weight
Protein restriction during gestation had no effect on nutrient intake during lactation, nutrient intake increased from gestation and throughout the lactation period, reflecting the increasing demand for nutrients for lactation purposes
Summary
It is widely recognized that adequate intrauterine and early postnatal nutrient and energy supply is of utmost importance for adult animal performance, health, and life span. Malnutrition in utero may cause metabolic adaptations or “programming”, which can be exemplified by “the thrifty phenotype” theory. Excess postnatal nutrient supply may cause the development of metabolically related diseases in later life 1. Fetal plasticity allows for adaptations to a compromised nutritional environment in utero by reducing growth and development of the fetus 2. In humans, such a reduction in birth weight is closely correlated with the development of diseases in adulthood, e.g. Type 2 diabetes 3 , heart disease 4 , and hypertension 5. The longterm effects of metabolic programming may differ according to the period during gestation in which a nutritional challenge is imposed, as well as whether this challenge occurs at a sensitive time period for fetal organ and endocrine system development 6
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