We tested the hypothesis that the dietary energy-dependent alterations of the rumen papillae size are accompanied by corresponding changes in systemic insulin-like growth factor (IGF)-1 concentration and in rumen papillary IGF type 1 receptors (IGF-1R). Young male goats (n=24) were randomly allocated to two groups (n=12) and fed a high level (HL) metabolizable energy [1200 kJ/(kg(0.75).d)] or a low level (LL) [500 kJ/(kg(0.75).d)] diet for 42 d. The concentration of ruminal total SCFA did not differ between the groups, but the molar proportion of butyric acid was enhanced by 70% in the HL group (P<0.05). Both the length and width of the papillae were greater (P<0.05) in the HL group, and the surface was 50-100% larger (P<0.05) in the tissue sampled from the artrium ruminis, the ventral ruminal sac and the ventral blind sac. Transport of Na+ across the rumen epithelium, which is amiloride sensitive, was higher (P<0.05) in the HL than in the LL group. Furthermore, the plasma IGF-1 concentration was about twofold higher in the HL group (P<0.05), and the maximal rumen epithelial IGF-1R binding was also higher in the HL (P<0.05) than in the LL group. IGF-1R mRNA and IGF-1 mRNA were detected in rumen papillae; however, they were unaffected by dietary treatments. DNA synthesis and cell proliferation of cultured rumen epithelial cells were higher (P<0.05) after IGF-1 treatment (25 or 50 microg/L) compared with those in the medium without IGF-1. Thus dietary energy-dependent alterations of rumen morphology and function are accompanied by corresponding changes in systemic IGF-1 and ruminal IGF-1R.

Bovine colostrum contains various essential nutrients, antibodies, hormones and growth factors that are important for nutrient supply, host defense, growth and for general neonatal adaptation. We have studied effects of colostrum fed for different durations on selected metabolic and endocrine traits in the first week of life in calves. Calves were fed colostrum twice daily for 3 d (group C6) or colostrum only as their first meal (group C1), followed by milk replacer up to d 7, or they were only fed milk replacer but no colostrum (group M). Plasma concentrations of immunoglobuline G and activities of enzymes (gamma-glutamyltransferase, aspartate-aminotransferase, lactate-dehydrogenase, glutamate-dehydrogenase) increased in groups C6 and C1 after first feeding, but not in group M. Postprandial plasma glucose concentrations on d 2 increased significantly more in groups C6 and C1 than in group M. Plasma triglycerides on d 2 and plasma phospholipid and cholesterol concentrations on d 7 were significantly higher in group C6 than in groups C1 and M. Plasma insulin concentrations on d 2 tended (P = 0.07) to increase more postprandially in group C6 than in group M and postprandial plasma glucagon concentrations on d 1 increased more in groups C6 and C1 than in group M and remained elevated on d 2 only in group C6. Plasma cortisol concentrations decreased postprandially in all three groups and were highest on d 2 and d 7 in group M. Plasma triiodthyronine and thyroxine concentrations decreased in the first week of life in all calves, whereas plasma prolactin concentrations were greatest on d 7 in group C6. In conclusion, various metabolic and endocrine traits were influenced by whether colostrum was fed and the duration of colostrum feeding.

Summary 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.

In milk-fed calves, the effects of sodium-butyrate (Na-butyrate) to replace flavomycin on growth performance and some mechanisms involved were studied. Pancreatic and intestinal morphology, digestive enzyme activities, plasma gut regulatory peptide concentrations, and expression of their receptors in the gastrointestinal tract were measured. Gastrointestinal tract defense systems were examined by measuring protein levels of 2 heat-shock proteins (HSP27 and HSP70). The calves were randomly allocated into 2 groups fed the same basic diet with flavomycin as an antimicrobial growth promoter or with Na-butyrate (3 g/kg of dry matter). Sodium-butyrate disappeared quickly in the upper gut and was not found in circulating blood. Supplementation with Na-butyrate enhanced growth rate and improved feed conversion into body weight gain compared with the flavomycin group. Supplementation with Na-butyrate was likely associated with an improvement in efficacy of the gastrointestinal tract digestive capacities expressed by enhanced production of digestive enzymes and increased absorptive capacities in the upper small intestine. The effects could have been controlled by insulin-like growth factor-1 but probably not by any of the cholecystokinin/gastrin peptide family. Concentrations of HSP27 and HSP70 were increased in stomach and colon of calves receiving Na-butyrate, thereby assuring protection of cells with intensive metabolism (chaperone function). In conclusion, beneficial effects of Na-butyrate on maturation of gastrointestinal functions were shown in milk-fed calves and may be applied to young mammals of other species.

Effects on metabolic and endocrine traits of feeding colostrum on d 1 and 2, then mature milk up to d 7, or glucose or water on d 1, colostrum on d 2 and 3 and then mature milk up to d 7 were studied in calves. Calves fed colostrum within the first 24 h after birth had significantly higher rectal temperatures, heart rates and respiratory frequencies than calves provided only water or glucose. Significantly elevated plasma nonesterified fatty acid and bilirubin concentrations on d 1 and 2 of life in calves fed only water on d 1 compared with calves of the other groups mirrored reduced energy intake. Fecal consistency was significantly higher during wk 1 of life, and gastrin and glucose-dependent insulinotropic polypeptide increased only on d 1 and/or 2 of life in calves already fed colostrum on d 1, expressing improved functioning of the gastrointestinal tract. Significantly higher plasma globulin levels up to d 7 in calves fed colostrum on d 1 than in those starting colostrum intake only on d 2 demonstrated significantly enhanced efficiency of gamma-globulin absorption. Furthermore, significantly higher circulating glucose, albumin, insulin, insulin-like growth factor-I concentrations and significantly lower urea levels in calves fed colostrum on d 1 compared with those fed colostrum starting on d 2 of life indicated stimulation of anabolic processes. In conclusion, colostrum intake by calves within the first 24 h of life is needed not only for an adequate immune status, but also to produce the additional important and favorable effects on metabolic and endocrine traits and on vitality.

Experiments were designed to study compositional differences in colostrum and mature milk and during the course of milk removal. Fractionized milk samples during the course of machine milking were analyzed in single (right rear) quarters in the cisternal fraction, after 25, 50, 75, and 100% of spontaneously removed milk, in residual milk, and in composite samples from all quarters on d 2 (colostrum) and in wk 4 (mature milk) of lactation. Somatic cell counts; concentrations of dry matter, total protein, insulin-like growth factor-I, insulin, prolactin, tumor necrosis factor-alpha, Na, and Cl; gamma-glutamyltransferase activity; and electrical conductivity were higher, whereas lactose concentration was lower on d 2 than in wk 4. Concentrations of fat, potassium chloride, and osmolarity did not differ between lactational periods. During the course of milking, concentrations of dry matter, fat, lactose, and potassium, and osmolarity increased, whereas somatic cell counts, protein, insulin like-growth factor-I, insulin, prolactin, and sodium concentrations, electrical conductivity and gamma-glutamyltransferase activity decreased on d 2, and protein, sodium, and electrical conductivity decreased in wk 4. In conclusion, various milk constituents differed considerably between lactational periods (colostrum and mature milk). Milk isotonicity was only in part associated with lactose concentration. Electrical conductivity was associated with Na, K, and fat concentrations and was highest in the cisternal fraction. Changes in milk constituents during milking need to be considered if milk samples are taken for analytical purposes and to evaluate the health status of the udder.

The effect of intestinal glucose supply on whole body rate of glucose appearance (WBGRa) and mammary utilization of glucose was studied in four lactating dairy cows. Glucose (0, 443, 963 and 2398 g/d) was continuously infused in the duodenum over 14-d periods using a Latin square design. A grass silage-based diet was formulated so that treatments were isoenergetic and isonitrogenous and contained 100 and 110% of energy and protein requirements according to INRA (1989). The WBGRa was measured by the [6,6-(2)H2]glucose dilution technique, and mammary glucose balance by arteriovenous differences and blood flow measurements. Duodenal glucose infusion increased arterial glucose concentrations linearly, whereas arterial concentrations of insulin, growth hormone, and glucagon were not changed. The WBGRa increased linearly with increasing glucose loads. The increase represented 42% of the intestinal glucose supplement. Mammary blood flow dramatically increased (up to 45%) and was associated with a significant increase of arterial insulin-like growth factor-1 concentrations. Mammary gland rate of glucose disappearance ([6,6-(2)H2]glucose measurement) increased linearly, whereas net mammary balance of glucose, lactose, and milk yields increased quadratically. Net mammary balance of glucose accounted for 60% of WBGRa, except for the greatest dose (47.6%). The decrease in milk yield with 2398 g/d of glucose may be explained by an imbalance in intracellular intermediate concentrations. The milk ratio of glucose-1-phosphate to glucose-6-phosphate decreased significantly at the greatest infusion of glucose. In conclusion, exogenous glucose supply to a grass silage-based diet increased WBGRa, mammary utilization of glucose and milk synthesis.

Feed intake, growth performance, and metabolic and endocrine traits were studied in male calves fed unlimited (GrAL; n = 7) amounts of colostrum for 3 d after birth and mature milk up to d 28 and were compared with calves fed commonly recommended amounts of colostrum and milk (GrRS; n = 7). Calves were fed by automates, and software was available to continuously register the time points and amounts of ingested feed up to 11 d of age. Body weight was measured on d 1, 4, 7, 14, 21, and 28, and blood samples were taken on d 1, 2, 3, 7, 14, 21, and 28 to measure several metabolites and hormones. Feed intake of calves fed GrAL increased from d 1 to 4, then remained stable and was always higher than for calves fed GrRS. Total visits (visits with and without milk intake) were higher for GrRS than GrAL, but visits with milk intake were comparable between groups and meal sizes per visit with milk intake were greater in GrAL than in GrRS. Body weight gain was greater in GrAL than in GrRS in wk 1, but not later. There were significant group differences in plasma concentrations of albumin (GrRS > GrAL), nonesterified fatty acids (GrRS > GrAL), cholesterol (GrRS > GrAL; d 28), insulin (GrAL > GrRS), and cortisol (GrRS > GrAL), but not of immunoglobin G, urea, glucose, triglycerides, growth hormone, and glucagon. In conclusion, calves fed ad libitum were capable of ingesting very large amounts of colostrum and milk, even during wk 1 of life, accompanied by a greater body weight gain in GrAL in the first week, whereas in GrRS, the high number of visits without feed intake indicate that these calves reached no repletion. Compared with calves provided restricted amounts of feed, calves with free access to colostrum and milk were characterized by reduced plasma concentrations of nonesterified fatty acids and by a transiently enhanced insulin and reduced cortisol status.