~ 4334 ~ International Journal of Chemical Studies 2019; 7(3): 4334-4335 P-ISSN: 2349–8528 E-ISSN: 2321–4902 IJCS 2019; 7(3): 4334-4335 © 2019 IJCS Received: 13-03-2019 Accepted: 15-04-2019 Safeeda Sultana Begum State Level VRDL, Department of Microbiology, Gauhati Medical College and Hospital, Narakasur Hill Top, Guwahati, Assam, India Mokhtar Hussain Department of Animal Reproduction, Gynaecology and Obstectrics, College of Veterinary Science, Khanapara, Guwahati, Assam, India Prithviraj Chakravarty ICAR- National Research Centre on Yak, Dirang, West Kameng District, Arunachal Pradesh, India Dr. Ajanta Sharma Professor and Head, PI cum Nodal Officer, State Level VRDL, Department of Microbiology, Gauhati Medical College & Hospital, Guwahati, Assam, India Correspondence Safeeda Sultana Begum State Level VRDL, Department of Microbiology, Gauhati Medical College and Hospital, Narakasur Hill Top, Guwahati, Assam, India Neonatal physiology in animals: A short discussion Safeeda Sultana Begum, Mokhtar Hussain, Prithviraj Chakravarty and Dr. Ajanta Sharma Abstract The term “neonate” is derived from the Latin word natus (to be born) and refers to a newborn during the first weeks of life during the physiologic transition. Although strictly speaking it should encompass the entire period until the transition is complete for all organ systems, by convenience it is usually defined as the first 3 to 4 weeks of life in most domestic species. Since neonates are not miniature adults, their physiology is unpredictably different from adults and hence needs a detailed study to know it. Keywords: Adaptation, neonatal, physiology, postnatal Introduction The mechanics of birth require a change in the newborn for extrauterine survival by attaining homeostasis with regards to respiratory gas exchange, along with circulatory and other related modifications. Such modifications depends on a complex change in major organ system, which although transition, usually takes place within the first 6-10 hours of life or may take many weeks for adaptation. The neonate possesses glycogen stores which are depleted shortly after birth and makes adequate nourishment from nursing vital. Fasting, even in the minimal sense can result in hypoglycemia apart from other causes like endotoxemia, septicemia, portosystemic shunts, and glycogen storage abnormalities. If the neonate is clinically fit and has an adequate swallowing and other related reflexes, then oral fluid and glucose replacement may be preferable, provided the animal is not clinically compromised. Just like in the humans, the caloric requirement of neonates of animals is also age (in days) depended, and though mother’s/dam’s milk is always superior, yet commercially manufactured milk replacement formulas are also available for them in case of necessity. Gastrointestinal System There is a rapid increase in development of the gastrointestinal tract (GIT) to about 80% in length and 30% in diameter in the first 10 days of life with maturation being incomplete until after weaning. It takes at least 24 hours for gastric acid secretion to occur in most of the species, but in the rat, this acid secretion occurs only after the first 18 days of birth (until weaning). Among numerous extracellular trophic signals, nutrients present in amniotic fluid, colostrum and fresh milk are mainly responsible for initial GIT development. Although nutrition is perhaps the most potent trophic stimulus of GIT growth, extracellular signals like hormones, mammary secretions, microbes, secretions from autocrine or paracrine mechanisms etc. from surrounding cells influences the cells of the fetal and neonatal GI tract and liver. The microbes which are present in the intestinal gut plays a critical role in development of mucosal immune function, while growth factors in colostrum augment the proliferation of the commensal enteric bacteria, and may also play a major function in initiating or augmenting immunity development of certain species of animals which are otherwise poorly expressed in the neonates. In some species certain immune functions that are initially absent in neonates are replaced by factors in colostrum, as in the equine, wherein neutrophils become mature killing cells only after exposure to substances present in the colostrum. Fluid Physiology During the last few days of gestation fetal blood pressure increases significantly (by 20% in fetal lambs) although fetal blood pressures are still much lower than adult blood pressure (Greenough and Milner, 2005) [3] .