Enhanced or Reduced Fetal Growth Induced by Embryo Transfer into Smaller or Larger Breeds Alters Post-Natal Growth and Metabolism in Pre-Weaning Horses

Abstract

In equids, placentation is diffuse and nutrient supply to the fetus is determined by uterine size. This correlates with maternal size and affects intra-uterine development and subsequent post-natal growth, as well as insulin sensitivity in the newborn. Long-term effects remain to be described. In this study, fetal growth was enhanced or restricted through ET using pony (P), saddlebred (S) and draft (D) horses. Control P-P (n = 21) and S-S (n = 28) pregnancies were obtained by AI. Enhanced and restricted pregnancies were obtained by transferring P or S embryos into D mares (P-D, n = 6 and S-D, n = 8) or S embryos into P mares (S-P, n = 6), respectively. Control and experimental foals were raised by their dams and recipient mothers, respectively. Weight gain, growth hormones and glucose homeostasis were investigated in the foals from birth to weaning. Fetal growth was enhanced in P-D and these foals remained consistently heavier, with reduced T3 concentrations until weaning compared to P-P. P-D had lower fasting glucose from days 30 to 200 and higher insulin secretion than P-P after IVGTT on day 3. Euglycemic clamps in the immediate post-weaning period revealed no difference in insulin sensitivity between P-D and P-P. Fetal growth was restricted in S-P and these foals remained consistently lighter until weaning compared to S-D, with elevated T3 concentrations in the newborn compared to S-S. S-P exhibited higher fasting glycemia than S-S and S-D from days 30 to 200. They had higher maximum increment in plasma glucose than S-D after IVGTT on day 3 and clamps on day 200 demonstrated higher insulin sensitivity compared to S-D. Neither the restricted nor the enhanced fetal environment affected IGF-1 concentrations. Thus, enhanced and restricted fetal and post-natal environments had combined effects that persisted until weaning. They induced different adaptive responses in post-natal glucose metabolism: an early insulin-resistance was induced in enhanced P-D, while S-P developed increased insulin sensitivity.

Maternal Nutrition during Pregnancy Affects Testicular and Bone Development, Glucose Metabolism and Response to Overnutrition in Weaned Horses Up to Two Years

“…Consistent with these results, saddlebred foals that suffered IUGR through embryo transfer in ponies had higher fasting glycemia until 1.5 year of age [10,11]. …”

Evidence for placental compensation in cattle

“…In both beef and dairy cattle, BW is a determining factor for dry matter intake (NRC, 2000 and, so a better nutrient supply of the dam and thus the pregnant uterus might be expected in heavier dams. In addition, crossbreeding experiments in horses have shown that the size of the uterus is of major importance for intra-uterine development (Allen et al, 2002;Peugnet et al, 2014) which, combined with the higher feed intake, could explain the heavier offspring born out of dams with a larger HG.…”

Does maternal size, nutrition and metabolic status affect offspring production traits in domestic species?

“…After Walton and Hamon (1938);Joubert and Hamon (1958);Ferrel. (1991);Biensen et al (1999);Tischner et al (2000); Allen et al (2004); Peugnet et al (2014).…”

“…More recently, the transfer of pony embryos into mares of larger breeds was shown to consistently increase fetal and postnatal growth until adulthood. Conversely, foals from a larger breed born to pony mares were small at birth and only partially caught-up to controls of the same breed (Allen et al, 2004;Peugnet et al, 2014). Moreover, both excess and reduced fetal growth were associated with osteoarticular lesions and metabolic perturbations, some of which still present at 2 years of age (Peugnet et al, 2014(Peugnet et al, , 2016.…”

“…Other production and health traits, such as immunity, feeding behavior but also fertility may also be affected (Chadio and Kotsampasi, 2014;Chavatte-Palmer et al 2014). This pleads for a very careful choice of embryo recipients in terms of breed and size but also underlines the importance of the management of these animals before and during pregnancy.…”