Abundance of message for insulin-like growth factors-I and -II and for receptors for growth hormone, insulin-like growth factors-I and -II, and insulin in the intestine and liver of pre- and full-term calves

Colostrum insulin supplementation to neonatal Holstein bulls affects small intestinal histomorphology, mRNA expression, and enzymatic activity with minor influences on peripheral metabolism

The objectives of this study were to evaluate how varying colostral insulin concentrations influenced small intestinal development and peripheral metabolism in neonatal Holstein bulls. Insulin was supplemented to approximately 5× (70.0 μg/L; n = 16) or 10× (149.7 μg/L; n = 16) the basal colostrum insulin (12.9 μg/L; BI, n = 16) concentration to maintain equivalent macronutrient intake (crude fat: 4.1 ± 0.06%; crude protein: 11.7 ± 0.05%; and lactose: 1.9 ± 0.01%) among treatments. Colostrum was fed at 2, 14, and 26 h postnatal and blood metabolites and insulin concentration were measured at 0, 30, 60, 90, 120, 180, 240, 360, 480, and 600 min postprandial respective to the first and second colostrum meal. At 30 h postnatal, a subset of calves (n = 8/treatment) were killed to excise the gastrointestinal and visceral tissues. Gastrointestinal and visceral gross morphology and dry matter and small intestinal histomorphology, gene expression, and carbohydrase activity were assessed. Insulin supplementation tended to linearly reduce the glucose clearance rate following the first meal, whereas after the second meal, supplementation linearly increased the rate of glucose absorption and nonesterified fatty acid clearance rate, decreased the time to maximum glucose concentrations, and decreased the time to reach minimum nonesterified fatty acid concentrations. Additionally, insulin clearance rate was linearly increased by insulin supplementation following the second colostrum feeding. However, there were no overall differences between treatments in the concentrations of glucose, nonesterified fatty acids, or insulin in plasma or serum. With respect to macroscopic intestinal development, dry rumen tissue mass linearly decreased when insulin was supplemented in colostrum, and supplementation linearly increased duodenal dry tissue density (g dry matter/cm) while tending to increase duodenal dry tissue weight. Increasing the colostrum insulin concentration improved small intestinal histomorphological development in the distal small intestine, as ileal villi height and mucosal-serosal surface area index were increased by supplementing insulin. Lactase enzymatic activity linearly increased in the proximal jejunum while ileal isomaltase activity linearly decreased with insulin supplementation. These data indicate that changes in colostrum insulin concentrations rapidly affect gastrointestinal growth prioritization and carbohydrase activity. The changes in gastrointestinal ontology result in minor changes in postprandial metabolite availability and clearance.

Effects of colostrum management on transfer of passive immunity and the potential role of colostral bioactive components on neonatal calf development and metabolism

Neonatal dairy and beef calves are required to ingest adequate volumes of high-quality colostrum during their first hours of life to acquire transfer of passive immunity (TPI). As such, immunoglobulin G (IgG) has largely been the focus of colostrum research over recent decades. Yet, little is known about the additional bioactive compounds in colostrum that potentially influence newborn calf development and metabolism. The purpose of this narrative review is to synthesize research regarding the effects of colostrum management practices on TPI, as well as to address the potential role of additional colostral bioactive molecules, including oligosaccharides, fatty acids, insulin, and insulin-like growth factor-I, in promoting calf development and metabolism. Due to the importance of IgG in ensuring calf immunity and health, we review past research describing the process of colostrogenesis and dam factors influencing the concentrations of IgG in an effort to maximize TPI. We also address the transfer of additional bioactive compounds in colostrum and prepartum management and dam factors that influence their concentrations. Finally, we highlight key areas of future research for the scientific community to pursue to ultimately improve the health and welfare of neonatal dairy calves.

Effects of branched-chain volatile fatty acids and fibrolytic enzyme on rumen development in pre- and post-weaned Holstein dairy calves

The study evaluated the effects of branched-chain volatile fatty acids (BCVFA) and fibrolytic enzyme (FE) on rumen development in calves. Forty Holstein male calves at the same ages (15 ± 2.5 days of age) and weights (45 ± 3.3 kg of body weight [BW]) were assigned randomly to four groups with a 2 × 2 factorial arrangement of treatments. Supplemental BCVFA (0 g/d or 18 g/d) and FE (0 g/d or 1.83 g/d) were fed to calves. Data were analyzed as a 2 × 2 factorial arrangement random design by the mixed procedure of SAS. The BCVFA × FE interaction was observed for ruminal propionate, blood growth hormone (GH) and insulin-like growth factor-1 (IGF-1), and GH receptor (GHR) and IGF-1 receptor (IGF-1R) expression in the rumen mucosa. Dry matter intake was higher for BCVFA addition. The higher average daily gain and ruminal volatile fatty acids were observed for BCVFA or FE addition. Stomach weight and the length and width of rumen papillae were higher for BCVFA addition. The higher expression of GHR, IGF-1R and 3-hydroxy-3-methylglutaryl-CoA synthase 1 in rumen mucosa, and blood GH and IGF-1 were observed with BCVFA or FE addition. Blood β-hydroxybutyrate and acetoacetate were higher for BCVFA addition. The results indicated that rumen development was promoted by BCVFA, but was not affected with FE addition in calves.

Effects of isovalerate supplements on morphology and functional gene expression of rumen mucosa in pre- and post-weaning dairy calves

Isovalerate supplements could stimulate rumen development by improving morphology and function of rumen mucosa, and then promote the growth of calves. This study was done to evaluate the effects of isovalerate supplements on morphology and functional gene expression of rumen mucosa in dairy calves. In total, 48 Chinese Holstein male calves with 15 days of age and 45.1±0.36 kg of BW were randomly assigned to four groups. The treatments were: control, low-isovalerate, moderate-isovalerate and high-isovalerate with 0, 3, 6 and 9 g isovalerate per calf per day, respectively. Supplementary isovalerate was hand-mixed into milk in pre-weaning calves and into concentrate portion in post-weaning calves. The study consisted of a 15-day-adaptation period and a 60-day-sampling period. Calves were weaned at 60 days of age. Three calves were slaughtered from each of the four treatments at 30, 60 and 90 days of age. The weight of body and stomach were measured, samples of ruminal tissues and blood were analyzed. Total stomach weight, total stomach to BW ratio, rumen wall and keratinized layer thickness, serum growth hormone and IGF-1 for both pre- and post-weaning calves increased linearly with increasing isovalerate supplements. Rumen to total stomach weight ratio, the length and width of rumen papillae, and serum β-hydroxybutyrate increased linearly for post-weaning calves. However, abomasum weight to total stomach weight ratio decreased linearly for both pre- and post-weaning calves. The relative messenger RNA expression for growth hormone receptor, IGF-1 receptor and 3-hydroxy-3-methylglutaryl-CoA synthase 1 in rumen mucosa increased linearly for post-weaning calves. Our results suggested that isovalerate supplements promoted rumen development in a dose-dependent manner. The optimum dose was 6.0 g isovalerate per calf per day.

Effects of starter feeding and early weaning on GHR mRNA expression in liver and rumen of lambs from birth to 84 days of age

The growth hormone receptor (GHR) is associated with animal growth and development. To investigate such effects on GHR gene expression, a total of 102 Hu lambs were randomly allocated to one of three groups (Group 1: starter diet from 7 d of age, weaning at 56 d of age; Group 2: starter diet from 42 d of age, weaning at 56 d of age; Group 3: starter diet from 7 d of age; weaning at 28 d of age). Six lambs from each group were sacrificed every 14 d to investigate the effects of starter feeding and weaning age on GHR mRNA expression in the liver and rumen. The results revealed that GHR mRNA expression was significantly higher in the liver and rumen (p < 0.05) than in other tissues. Early starter feeding up-regulated hepatic GHR mRNA expression on days 14, 28, 42 and 56 and ruminal GHR mRNA expression on days 28, 42, 70, and 84 (p < 0.05). Early weaning up-regulated hepatic GHR mRNA expression on days 56, 70 and 84 and ruminal GHR mRNA expression on days 42, 56, 70 and 84 (p < 0.05). Dietary and weaning regimes and age affected the hepatic and ruminal GHR mRNA expression.

Invited review: Growth-promoting effects of colostrum in calves based on interaction with intestinal cell surface receptors and receptor-like transporters

The postnatal development and maturation of the gastrointestinal (GI) tract of neonatal calves is crucial for their survival. Major morphological and functional changes in the calf's GI tract initiated by colostrum bioactive substances promote the establishment of intestinal digestion and absorption of food. It is generally accepted that colostrum intake provokes the maturation of organs and systems in young calves, illustrating the significance of the cow-to-calf connection at birth. These postnatal adaptive changes of the GI tissues in neonatal calves are especially induced by the action of bioactive substances such as insulin-like growth factors, hormones, or cholesterol carriers abundantly present in colostrum. These substances interact with specific cell-surface receptors or receptor-like transporters expressed in the GI wall of neonatal calves to elicit their biological effects. Therefore, the abundance and activity of cell surface receptors and receptor-like transporters binding colostral bioactive substances are a key aspect determining the effects of the cow-to-calf connection at birth. The present review compiles the information describing the effects of colostrum feeding on selected serum metabolic and endocrine traits in neonatal calves. In this context, the current paper discusses specifically the consequences of colostrum feeding on the GI expression and activity of cell-receptors and receptor-like transporters binding growth hormone, insulin-like growth factors, insulin, or cholesterol acceptors in neonatal calves.

Lactation Biology Symposium: role of colostrum and colostrum components on glucose metabolism in neonatal calves

In neonatal calves, nutrient intake shifts from continuous glucose supply via the placenta to discontinuous colostrum and milk intake with lactose and fat as main energy sources. Calves are often born hypoglycemic and have to establish endogenous glucose production (eGP) and gluconeogenesis, because lactose intake by colostrum and milk does not meet glucose demands. Besides establishing a passive immunity, colostrum intake stimulates maturation and function of the neonatal gastrointestinal tract (GIT). Nutrients and nonnutritive factors, such as hormones and growth factors, which are present in high amounts in colostrum of first milking after parturition, affect intestinal growth and function and enhance the absorptive capacity of the GIT. Likely as a consequence of that, colostrum feeding improves the glucose status in neonatal calves by increasing glucose absorption, which results in elevated postprandial plasma glucose concentrations. Hepatic glycogen concentrations rise much greater when colostrum instead of a milk-based colostrum replacer (formula with same nutrient composition as colostrum but almost no biologically active substances, such as hormones and growth factors) is fed. In contrast, first-pass glucose uptake in the splanchnic tissue tended to be greater in calves fed formula. The greater plasma glucose rise and improved energy status in neonatal calves after colostrum intake lead to greater insulin secretion and accelerated stimulation of anabolic processes indicated by enhanced maturation of the postnatal somatotropic axis in neonatal calves. Hormones involved in stimulation of eGP, such as glucagon and cortisol, depend on neonatal diet, but their effects on eGP stimulation seem to be impaired. Although colostrum feeding affects systemic insulin, IGF-I, and leptin concentrations, evidence for systemic action of colostral insulin, IGF-I, and leptin in neonatal calves is weak. Studies so far indicate no absorption of insulin, IGF-I, and leptin from colostrum in neonatal calves, unlike in rodents where systemic effects of colostral leptin are demonstrated. Therefore, glucose availability in neonatal calves is promoted by perinatal maturation of eGP and colostrum intake. There may be long-lasting effects of an improved colostrum supply and glucose status on postnatal growth and development, and colostrum supply may contribute to neonatal programming of performance (milk and growth) in later life, but data proving this concept are missing.

Somatotropic gene response to recombinant growth hormone treatment in buffalo leucocytes

The use of recombinant bovine growth hormone (rbGH) to increase milk yield in cows is banned in some countries. In others, where it is authorised, it has triggered harsh debates on labelling of dairy products. If many studies have been performed on bovines, there is a lack of information on buffaloes, which are sometimes treated with rbGH and re-present an important economical resource for dairy products in some countries. Analytical methods with legal value for surveillance of rbGH treatments do not yet exist. Research on gene expression biomarkers is one of the most promising approaches to this purpose. For this reason, we treated five buffaloes for 10 weeks with a sustained-release formulation of rbGH and analysed the response of 20 somatotropic axis genes in leucocytes by real-time polymerase chain reaction. Overall changes in gene expression levels were of low magnitude and sometimes affected by the 'time' factor. Only the IGFBP-1 gene showed a significant under-expression (about two-fold; p <0.001) in treated animals. Taken together, these results give evidence that expression analysis of the somatotropic axis genes in leucocytes is little helpful for discrimination of rbGH-treated buffaloes, but do not exclude that another array of genes could provide useful patterns of variation.

Somatotropic gene response to recombinant growth hormone treatment in buffalo leucocytes

The use of recombinant bovine growth hormone (rbGH) to increase milk yield in cows is banned in some countries. In others, where it is authorised, it has triggered harsh debates on labelling of dairy products. If many studies have been performed on bovines, there is a lack of information on buffaloes, which are sometimes treated with rbGH and re-present an important economical resource for dairy products in some countries. Analytical methods with legal value for surveillance of rbGH treatments do not yet exist. Research on gene expression biomarkers is one of the most promising approaches to this purpose. For this reason, we treated five buffaloes for 10 weeks with a sustained-release formulation of rbGH and analysed the response of 20 somatotropic axis genes in leucocytes by real-time polymerase chain reaction. Overall changes in gene expression levels were of low magnitude and sometimes affected by the 'time' factor. Only the IGFBP-1 gene showed a significant under-expression (about two-fold; p <0.001) in treated animals. Taken together, these results give evidence that expression analysis of the somatotropic axis genes in leucocytes is little helpful for discrimination of rbGH-treated buffaloes, but do not exclude that another array of genes could provide useful patterns of variation.

Insulin-like growth factors (IGFs), IGF binding proteins, and other endocrine factors in milk: role in the newborn

The role of colostrum and milk in the neonate has been chiefly recognized as a comprehensive nutrient foodstuff. In addition, the provision of colostrum-the first milk-for early immune capacity has been well documented for several species. Colostrum is additionally a rich and concentrated source of various factors that demonstrate biological activity in vitro. Three hypotheses have been proposed for the phenotypic function of these secreted bioactive components: (1) only mammary disposal, (2) mammary cell regulation, and (3) neonatal function [gastrointestinal tract (GIT) or systemic]. Traditionally, it was assumed that the development of the GIT is preprogrammed and not influenced by events occurring in the intestinal lumen. However, a large volume of research has demonstrated that colostrum (or milk-borne) bioactive components can basically contribute to the regulation of GIT growth and differentiation, while their role in postnatal development at physiological concentrations has remained elusive. Much of our current understanding is derived from cell culture and laboratory animals, but experimentation with agriculturally important species is taking place. This chapter provides an overview of work conducted primarily in neonatal calves and secondarily in other species on the effects on neonates of selected peptide endocrine factors (hormones, growth factors, in part cytokines) in colostrum. The primary focus will be on insulin-like growth factors (IGFs) and IGF binding proteins (IGFBPs) and other bioactive peptides, but new interest and concern about steroids (especially estrogens) in milk are considered as well.

Gut responses to enteral nutrition in preterm infants and animals

Preterm birth is associated with immature digestive function that may require the use of total parenteral nutrition and special oral feeding regimens. Little is known about the responses to oral food in the preterm neonate and how enteral nutrients affect the immature gastrointestinal tract (GIT). In vivo studies are difficult to perform in laboratory rodents because of their small body size and that of immature organs at birth, and this makes the large farm animals (e.g., pigs, cattle, sheep) more attractive models in this field. In these species, preterm delivery at 88%-95% gestation is associated clinical complications and degrees of GIT immaturity similar to those in infants born at 70%-90% gestation. Studies in both animals and infants indicate that the immature GIT responds to the first enteral food with rapid increases in gut mass and surface area, blood flow, motility, digestive capacity, and nutrient absorption. To a large extent, the enteral food responses are birth independent, and can be elicited also in utero, at least during late gestation. Nevertheless, preterm neonates show compromised GIT structure, function, and immunology, particularly when delivered by caesarean section and fed diets other than mother's milk. Formula-fed preterm infants are thus at increased risk of developing diseases such as necrotizing enterocolitis, unless special care is taken to avoid excessive nutrient fermentation and bacterial overgrowth. The extent to which results obtained in preterm animals (most notably the pig) can be used to reflect similar conditions in preterm infants is discussed.

Nutritional physiology of neonatal calves*

The gastrointestinal tract of neonatal calves is relatively mature but still requires morphological and functional changes. The intake of colostrum with its nutrient and non-nutrient components exerts marked effects on gastrointestinal development and function. Colostrum intake provides immunoprotection (passive immunity by immunoglobulins) and is essential for survival of neonates of most species. Furthermore, there are important transient as well as long-lasting systemic effects on the nutritional status, on metabolism, and on various endocrine systems due to intake of nutrient and non-nutrient colostral components that contribute to survival in the stressful postnatal period. Colostrum is much more than just a supplier of immunoglobulins.

Abundance of mRNA encoding for components of the somatotropic axis and insulin receptor in different layers of the jejunum and ileum of neonatal calves1,2

Insulin-like growth factors-1 and -2, IGFBP-2 and -3, and receptors for IGF type-1 and type-2 (IGF-1R, IGF-2R), growth hormone (GHR), and insulin (InsR) in neonatal calves are variably expressed among gastrointestinal sites and thought to exert site-specific physiological functions. We studied by real-time reverse-transcription PCR, whether there are differences in the abundance of mRNA coding for IGF-I, IGF-2, IGFBP-2, IGFBP-3, IGF-1R, IGF-2R, GHR, and InsR in compartmentalized layers (fractions) of jejunum and ileum of 5-d-old calves fed colostrum. Samples of jejunum consisted primarily of villi and crypts; samples from ileum consisted mainly of villus tips, crypts, and lamina propria (LP; containing mainly Peyer's patches). After slaughter, segments of middle areas of jejunum and ileum were flushed with 154 mM NaCl. Pieces (5 mm x 5 mm) of jejunal (n = 9) and ileal walls (n = 5) were placed on glass slides and snap-frozen in liquid N before being cut horizontally into 10-mum-deep slices using a cryotome at -20 degrees C. Fifteen consecutive and morphologically similar slices were collected as fractions of villus, crypt, and LP layers, respectively. Fractions were characterized by use of 5'-bromo-2-deoxyuridine (BrdU) that labeled proliferating cells, and by expression of lactase mRNA. The BrdU-labeled cells were present in crypts and LP, but not in tips of villi. Lactase mRNA levels were greater in villus than crypt fractions, but lactase mRNA was absent in LP. In jejunum, mRNA levels, relative to levels of housekeeping genes (sum of levels of mRNA coding for ubiquitin, glyceraldehyde phosphate dehydrogenase, beta-actin, and ribosomal RNA), differed (P < 0.05) between fractions for InsR (crypts > villi), IGFBP-2 (crypts > villi), and IGFBP-3 (crypts > villi), and total RNA levels were greater (P < 0.05) in crypt than villus fractions. In ileum, mRNA levels, expressed relative to housekeeping genes, differed (P < 0.05) between fractions for IGF-I (LP > villi, crypts), IGF-2, and IGFBP-3 (villi > crypts, LP), GHR and InsR (crypts > LP), IGFBP-2 (crypts > villi, LP), and total RNA levels were greater (P < 0.05) in LP and crypt than in villus fractions. In conclusion, the tested fractionation technique is quite applicable for gene expression studies in the intestine of calves. Members of the somatotropic axis and of the insulin receptor are not equally expressed in different jejunal and ileal layers of neonatal calves.

Preterm as Compared with Full-Term Neonatal Calves Are Characterized by Morphological and Functional Immaturity of the Small Intestine

Intestinal diseases in neonatal calves may be due to morphological and functional immaturity. We have studied histomorphology, crypt cell proliferation rates (based on incorporation of 5-bromo-2'-deoxyuridine into DNA), presence of apoptotic cells (based on terminal deoxynucleotidyl transferase-mediated X-dUTP nick end labeling), and brush border enzyme activities in preterm calves (277 d of gestation), euthanized on d 1 (P0) or 8 (P8), and in full-term calves (290 d of gestation), euthanized on d 1 (F0) or 8 (F8). Vacuolated epithelial cells were present in ileum of P0 and F0 but not in P8 and F8. During the first 8 d, villus sizes, crypt depths, and proliferation rates of crypt cells in the small intestine of preterm calves did not significantly change. In contrast, in full-term calves during the first 8 d, villus sizes in jejunum decreased, crypt depths increased in small intestine and colon, and crypt cell proliferation increased in duodenum and jejunum. Submucosal thickness in jejunum was highest in P0, but in ileum it increased with gestational age and feeding. Gestational age x feeding interactions indicated increased activities of aminopeptidase N and reduced lactase activities only in F8 and reduced dipeptidylpeptidase IV activities only in P8. In conclusion, in preterm calves the small intestinal epithelium was immature and brush border enzyme activities differed in part from those in full-term calves.

Effects of colostrum feeding and dexamethasone treatment on mRNA levels of insulin-like growth factors (IGF)-I and -II, IGF binding proteins-2 and -3, and on receptors for growth hormone, IGF-I, IGF-II, and insulin in the gastrointestinal tract of neonatal calves

The somatotropic axis regulates growth of the gastrointestinal tract (GIT). In addition, colostrum feeding and glucocorticoids affect maturation of the GIT around birth in mammals. We have measured mRNA levels of members of the somatotropic axis to test the hypothesis that colostrum intake and dexamethasone treatment affect respective gene expression in the GIT. Calves were fed either colostrum or an isoenergetic milk-based formula, and in each feeding group, half of the calves were treated with dexamethasone (DEXA; 30 microg/kg body weight per day). Individual parameters of the somatotropic axis differed (P < 0.05) among different GIT sections and formula feeding increased (P < 0.05) mRNA levels of individual parameters at various sites of the GIT. Effects of DEXA on the somatotropic axis in the GIT partly depended on different feeding. In colostrum-fed calves, DEXA decreased (P < 0.05) mRNA levels of IGF-I (esophagus, fundus, duodenum, and ileum), IGF-II (fundus), IGFBP-2 (fundus), IGFBP-3 (fundus), IGF1R (esophagus, ileum, and colon), IGF2R (fundus), GHR (fundus), and InsR (esophagus, fundus), but in formula-fed calves DEXA increased mRNA levels of IGF-I (esophagus, rumen, jejunum, and colon). Furthermore, DEXA increased (P < 0.05) mRNA levels of IGF-II (pylorus), IGFBP-3 (duodenum), IGF2R (pylorus), and GHR (ileum), but decreased mRNA levels of IGFBP-2 (ileum), and IGF1R (fundus). Whereas formula feeding had stimulating effects, effects of DEXA treatment on the gene expression of parameters of the somatotropic axis varied among GIT sites and partly depended on feeding.