Abstract
The major goal of animal production is to obtain abundant and healthy meat for consumers. Maternal food restriction (MFR) is often applied in farms to reduce production costs. However, the suitability of MFR in livestock animals is questionable, as this management may compromise maternal fitness due to a severe negative energetic balance and can induce Intrauterine Growth Restriction (IUGR) and prenatal programming in the offspring. Here, we sought to determine, using pregnant rabbits, the consequences of MFR on maternal endocrine and metabolic status and conceptus development. Pregnant dams were distributed into three groups: CONTROL (ad libitum feeding throughout the entire pregnancy; mean pregnancy length being around 31 days), UNDERFED (50% MFR during the entire pregnancy) and EARLY-UNDERFED (50% MFR only during the preimplantation period, Days 0–7). Maternal leptin concentrations and glycemic and lipid profiles were determined throughout pregnancy, whilst conceptus development was assessed ex-vivo at Day 28. Placental parameters were determined by macroscopic and histological evaluations and apoptotic assessments (TUNEL and Caspase-3). The main results of the study showed that, despite MFR altered maternal plasma lipid concentration (P<0.05), there were no effects on maternal bodyweight, plasma leptin concentration or glycemic profile. Fetal crown-rump lengths were reduced in both undernourished groups (P<0.001), but a significant reduction in fetal weight was only observed in the UNDERFED group (P<0.001). Growth in both undernourished groups was asymmetrical, with reduced liver weight (P<0.001) and significantly increased brain: fetal weight-ratio (P<0.001) and brain: liver weight-ratio (P<0.001) when compared to the CONTROL group. A significant reduction in placental weight was only observed in the UNDERFED group (P<0.001), despite both undernourished groups showing higher apoptotic rates at decidua and labyrinth zone (P<0.05) than the CONTROL group. Thus, these groups evidenced signs of placental degeneration, necrosis and stromal collapse. In summary, MFR may encourage the mother to make strategic decisions to safeguard her metabolic status and fitness at the expense of growth reduction in the litter, resulting in enhanced apoptotic and pathological processes at placental level and IUGR.
Highlights
The major goal of animal production is to obtain abundant and healthy meat for consumers, which relies on adequate management of breeding animals and pregnancy periods [1]
Early-maternal food restriction (MFR) induced maternal food intake compensation in later gestation and circumscribed changes in lipid metabolism without affecting bodyweight, leptin concentrations or glycemic profile. Both undernourished groups had similar food intake during the 1st week of pregnancy and showed significant differences compared with the CONTROL group (Fig 2a)
EARLY-UNDERFED group significantly increased its food intake compared to the CONTROL group during the 2nd and 3rd weeks of pregnancy, but not during the last week of gestation, in which both groups significantly decreased their food intake (Fig 2a)
Summary
The major goal of animal production is to obtain abundant and healthy meat for consumers, which relies on adequate management of breeding animals and pregnancy periods [1]. Thereby, affecting the quality of their meat (muscle fibers and marbling), athletic performance or fleece production [2, 8] and lastly resulting in poorer incomes for the livestock producer and lower quality products for the consumers Despite these inconveniences, MFR protocols applied in specific periods of the pregnancy, such as the preimplantation period, in which the embryo’s requirements are low and the mother presents an anabolic status, could reduce productive costs and be an alternative strategy in farms [9, 10]. Experimental studies suggest that impaired placental structure or function (e.g. placental insufficiency) may contribute to IUGR in response to undernutrition [12, 13] Most of these studies have been performed in rodents [14], whilst the use of large animals is scarce. Large animals (sheep, pig or rabbit) offer a wider range of benefits for the purpose of this assessment, as the results obtained from these trials, especially those based on MFR protocols, can be useful for biomedicine and to unravel the aforementioned advantages and disadvantages of the application of MFR regimens to livestock animals
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