There are quite significant variations observed in the birth weight within the same litter, primarily due to increased sow prolificacy, leading to larger litter size. As hyperprolific sows farrow larger litters, pig producers are challenged by a frustrating trend toward more low birthweight piglets, characterized as poorly developed gut and hence reduced nutrient intake and reduced overall performance. It has recently been reported that birth weight plays an essential role in intestinal development of the neonatal pigs.
Such that piglets born with relatively lower birth weight have challenges with intestinal development due to differences in efficiency of several metabolic pathways. Creep feeding is a supplementation strategy that aims to help piglets (most especially, low birth weight piglets) navigate these developmental challenges by providing complex nutrition to improve nutrient intake, accelerating gut development and preparing the piglet to manage more efficiently, the subsequent effects of weaning.
Several research projects conducted at the Trouw Nutrition Swine Research Centre in the Netherlands have evaluated the effects of creep feeding in large litters. Much of this research has built on studies evaluating how different feeding programmes influence intestinal cell proliferation, development of the small intestine and the gut microbial diversity of the neonate. However, some particularly interesting insights extend beyond the gut development and microbial diversity and abundance but relates to metabolic changes as investigated using a plasma metabolomic analysis approach.
To evaluate the effects of a lower cost versus a premium feeding programme, including supplemental creep feed, researchers analyzed blood samples from piglets. One group of piglets received an inexpensive diet that supplied adequate nutrients with limited in-feed gut health additives. A second group received supplementation with a creep feed formulated to support optimal digestion and prepare the piglet’s gut for post-weaning intake. The analysis included a broad array of nutrients and intermediates to help researchers glean insights on metabolic processes occurring in the pig. In reviewing findings, researchers noted differences in blood concentrations for metabolites related to amino acid synthesis and catabolism. Among these findings, differences due to the feeding programme were observed for bioactive amines and key neurotransmitters including epinephrine and 4-aminobutyric acid (GABA).
The hormone epinephrine is known to play a role in the fight-or-flight response of mammals. High levels of epinephrine have been associated with an increase in blood flow to the muscles, a faster heart rate, dilation of the pupils, and a higher blood sugar level. Epinephrine also acts as a catabolic signal, as its secretion leads to increased blood glucose and fatty acids, aimed at providing substrates for energy production within cells throughout the body. As physiological reactions inside the animal consume energy, they may also negatively impact feed intake.
In contrast to epinephrine’s stimulatory properties, GABA is the main inhibitory neurotransmitter in mammals, and its secretion is associated with a reduction in neuronal excitability. Feelings of relaxation, reduced anxiety, and anti-convulsive effects are commonly reported after GABA is administered to humans.
While it is difficult to assess the effect of blood epinephrine and GABA levels on metabolic processes and behavior in pigs, it is likely that lower epinephrine and higher GABA levels are the product of improved feed intake due to higher feed quality, leading to improved gut function, nutrient digestibility, and a balanced microbial diversity in the GI tract. It is conceivable that lower epinephrine and greater GABA concentrations in the blood may indicate a sense of relaxation that allows more nutrients for fat and protein deposition, which would otherwise be converted to energy in stress-inducing situations. A sense of pleasure may also exert a positive feedback on feed intake regulation, which is desirable during the critical days post-weaning when high intake is particularly desirable.
The practice of creep feeding, along with an optimal weaner diet, have been shown to benefit both feed intake and gain post-weaning. An analysis of metabolomics indicates that blood metabolite concentrations related to amino acid, lipid and the energy metabolism of piglets receiving creep feed with a luxury weaner diet were altered in ways that suggest improved animal performance. Additionally, animals’ levels of neurotransmitters were also different between animals in the two feeding programmes. Changes in neurotransmitter profiles may have contributed to better feed intake post-weaning and to the nursery pigs’ improved overall wellbeing.
Author details - Michael Wellington Swine Nutrition Research Scientist at Trouw Nutrition