The importance of the use of exogenous butyrate in calves’ diets is due to its role as a factor stimulating the functional development of ruminal epithelium and improving calf performance during the transition from preruminant to ruminant status. Our review will first present results related to effects of the administration of butyrate in calves’ diets on the development of ruminal epithelium toward a more effective absorption and metabolism of fermentation products from the rumen. The introduction of sodium butyrate at a level of about 0.3% of diet dry matter is accompanied by an increase to 35% in butyrate concentration in the rumen of 33-day-old calves. Mutual reliance between an enhanced ruminal concentration of butyrate and the activities of transcription factors, genes and proteins involved in cell proliferation, ketogenesis and the maintenance of cell pH homeostasis in the ruminal epithelial cells has been clearly confirmed in many experiments. Second, the review presents results related to the effects of the introduction of butyrate salts in the diet on calf performance. Of 11 studies a positive effect was found in six; five of these were obtained from the calves that started receiving butyrate supplement at a level of about 0.3% diet dry matter from the age of 3 to 5 days. Results indicate that when a supplement is given to calves soon after birth the functional development of ruminal epithelium in cooperation with the endocrine and digestion systems is transferred into improving the efficiency of rearing. There have been no studies on the effects of greater amounts of butyrate salts in milk replacer; butyrate constitutes about 1.2% of the whole cow’s milk dry matter. In older calves, when butyrate administration is provided as a component of a starter concentrate at the increasing inclusion rate from 0.3% to 3.0%, the practical effect in calf performance relates to the risk of depression of rumen pH below 5.5 and accompanying disruption of the organization of the ruminal epithelial tissue. The higher risk is noted in calves received starter with substantial content of a rapidly degradable starch. At present, the insufficient number of positive results confirming the beneficial effect of butyrate supplements in terms of an improvement in performance does not allow their recommendation for use in the practical feeding of calves.

The aim of the present study was to investigate the number of cocaine- and amphetamine-regulated transcript-like immunoreactive (CART-LI) nerve structures in the large intestine of juvenile pigs. The distribution pattern of CART-LI structures was studied by immunohistochemistry in the circular muscle layer, myenteric (MP), outer submucous (OSP) and inner submucous plexus (ISP) as well as in the mucosal layer of six regions of the large bowel: caecum, centripetal and centrifugal turns of the proximal colon, transverse colon, descending colon and rectum. CART-LI neural structures were observed in all gut fragments studied. CART-LI nerve fibres were numerous within the circular muscle layer and in the MP of all the regions studied, while they were moderate or few in number in other layers of the intestinal wall. The numbers of CART-LI neurons within the MP amounted to 2.02% in the caecum to 7.92% in the rectum, within the OSP from 2.73% in the centrifugal turns of the proximal colon to 5.70% in the rectum, and within the ISP from 2.23% in the transverse colon to 5.32% in the centrifugal turns of the proximal colon. The present study reports for the first time a detailed description of the CART distribution pattern within the enteric nervous system (ENS) of the porcine large intestine.

In recent years, a supplementation of livestock animals, including poultry, with β-Hydroxy-β-methylbutyrate (HMB) has gained attention for its effects on protein and fat metabolism. This study investigates the effects of HMB in the laying hen diet on egg quality, focusing on amino acid and fatty acid composition. Laying hens were supplemented with 0.02% HMB, with performance parameters and egg components analyzed. HMB supplementation led to increased albumen weight, influencing egg weight while also reducing feed intake per egg without affecting laying rate, yolk indices, fat, or cholesterol content. Notably, the study revealed significant changes in egg amino acid and fatty acid profiles due to HMB supplementation. Various amino acids, including glycine, serine, and isoleucine, were altered in the yolk, impacting nutritional value and potential health benefits. Regarding fatty acids, the study observed changes in both saturated as well as n-6 and n-3 fatty acids, affecting the overall lipid profile of egg yolks. However, the shifts in fatty acid composition could have implications for cardiovascular health due to altered ratios of n-6/n-3 fatty acids. Further research is required to comprehensively understand the implications of these findings for consumer-oriented egg quality and health benefits.