Postprandial blood hormone and metabolite concentrations influenced by feeding frequency and feeding level in veal calves.

This study hypothesized that increased feeding frequency (FF) decreases problems with glucose homeostasis seen at high feeding levels (FL) in heavy veal calves. Effects of FF and FL on hormone and metabolite concentrations were studied in 15 heavy veal calves fed once (FF1; at 12:00), twice (FF2; at 12:00 and 24:00) or four times daily (FF4; at 06:00, 12:00, 18:00 and 24:00). In period 1, all calves were fed at a low FL (FL(low); 1.5 x metabolizable energy requirements for maintenance, ME(m)). In period 2, FF2 and FF4 calves were fed at high FL (FL(high); 2.5 x ME(m)), whereas FF1 calves were still fed at FL(low). Blood was sampled every 30 min from 12:00 to 18:00 and postprandial integrated plasma hormone and metabolite concentrations (AUC(12-18 h)) were calculated. Glucose AUC(12-18 h) increased with increasing FL, but decreased with increasing FF, urea AUC(12-18 h) increased with increasing FL, whereas non-esterified fatty acid AUC(12-18 h) were unaffected by FL and FF. Insulin AUC(12-18 h) decreased with increasing FF and decreasing FL. Glucagon AUC(12-18 h) increased with increasing FL and FF. Growth hormone AUC(12-18 h) decreased, whereas insulin-like growth factor-1 and leptin AUC(12-18 h) increased with increasing FL. Mean thyroxine and 3,5,3'-triiodothyronine concentrations were modified by FF and FL. There were no FF x FL interactions, except for plasma glucose. In conclusion, postprandial hormone and metabolite responses were differentially affected by FF and (or) FL. Glucose and insulin concentrations were maximally increased at high FL and low FF. Hyperglycemia, glucosuria and excessive insulinemia were prevented by increasing FF and decreasing FL.

Separation of protein and lactose intake over meals dissociates postprandial glucose and insulin concentrations and reduces postprandial insulin responses in heavy veal calves.

The present study examined, at identical daily nutrient intakes, the impact of separating protein and lactose intakes across two daily meals on the metabolic and endocrine status in heavy veal calves. Calves were assigned to one of six degrees of separating protein and lactose over the two meals (termed nutrient synchrony, SYN 1-6; 6 calves/treatment). They were fed the protein-rich (P-)meal and the lactose-rich (L-)meal at 06:00 and 18:00h, respectively, or vice versa. At SYN 1, calves were fed with 50% of the daily protein and 50% of the daily lactose intake in each meal. Protein and lactose were iso-energetically exchanged between the two daily meals from SYN 1 to 6. At SYN 6, 85% of the daily protein and 20% of the daily lactose was fed in the P-meal and the remainder in the L-meal. Blood samples were collected hourly during 24h. Mean 24h glucose concentrations increased and insulin concentrations decreased from SYN 1 to 6. Postprandial 5h areas under concentration curves (AUC(0-5h)) of glucose increased with increasing meal lactose content. AUC(0-5h) of non-esterified fatty acids increased after P- and L-meals from SYN 1 to 6. Urea concentrations increased after L-meals from SYN 1 to 6, but decreased after P-meals from SYN 1 to 6. Insulin AUC(0-5h) decreased after L-meals and after P-meals from SYN 1 to 6. Nutrient asynchrony did not affect insulin-like growth factor-1, glucagon, growth hormone, leptin, 3,5,3'-triiodothyronine and thyroxine. In conclusion, separation of protein and lactose intake over meals inhibited insulin responses to a lactose-rich meal in heavy veal calves despite high plasma glucose concentrations.

Ruminal drinkers: endocrine and metabolic status and effects of suckling from a nipple instead of drinking from a bucket.

In ruminal drinkers (RD) ingested milk is transported into the rumen and not into the abomasum. Because this is followed by changes in digestibility and absorption, we have tested whether this is associated with postprandial metabolic and endocrine changes. Unweaned, bucket-fed calves (one RD, two controls) were studied on seven farms. On d 1, after metabolic and endocrine 12-h profiles were studied, RD and one control calf were fed for 10 d by nipple, whereas the other control calf was fed by bucket. On d 11, metabolic and endocrine 12-h profiles were again studied. On d 1, mean plasma concentrations of glucose, triglycerides, urea, insulin, insulin-like growth factor-1 (IGF-1), 3,5,3'-triiodothyronine (T3), thyroxine (T4) and leptin were significantly different between RD and controls, whereas mean concentrations of non-esterified fatty acids (NEFA), total protein, albumin, and glucagon did not differ significantly among groups. In RD concentrations of glucose, NEFA, insulin, growth hormone, IGF-1, and T4 were higher, and of urea were lower on d 11 than on d 1. Glucose and insulin concentrations increased postprandially in healthy calves on d 1, but barely in RD and remained lower than in controls, and there was no rise of NEFA and triglyceride concentrations on d 1 after the initial postprandial decrease in RD, in contrast to controls. But on d 11 postprandial responses of these four traits were similar in RD and controls and urea and T4 concentrations on d 11 became normalized. However, glucose and T3 concentrations in RD on d 11 were still lower than in one or both control groups. In conclusion, various metabolic and endocrine traits in RD differed from healthy controls. Drinking by floating nipple instead of drinking from bucket for 10 d normalized several metabolic and endocrine traits in RD.

Ontogenesis of mRNA levels and binding sites of hepatic alpha-adrenoceptors in young cattle.

Catecholamines affect hepatic glucose production through (alpha- and beta2-) adrenoceptors (AR). We studied mRNA abundance and binding of hepatic alpha-AR in pre-term (P0) calves and in full-term calves at day 0 (F0), day 5 (F5) and day 159 (F159) to test the hypothesis that gene expression and numbers of hepatic alpha-AR in calves are influenced by age and associated with beta2-AR and selected traits of glucose metabolism. mRNA levels of alpha1- and alpha2-AR were measured by real time RT-PCR. alpha1- and alpha2-AR numbers (maximal binding, Bmax) were determined by saturation binding of (3H)-prazosin and (3H)-RX821002, respectively. alpha1- and alpha2-AR subtypes were evaluated by competitive binding. alpha1A-AR mRNA levels were lower in P0 than in F0, F5 and F159 and alpha(2AD)-AR mRNA levels were lower in F159 than in P0, F0 and F5, while alpha2C-AR mRNA levels increased from P0 and F0 to F5 and F159. Bmax of alpha1-AR increased from P0 to F5, then decreased in F159. Bmax of alpha2-AR decreased from F0 to F159. Bmax of alpha1-AR was positively associated with mRNA levels of alpha1A-AR (r = 0.7), Bmax of beta2-AR (r = 0.5) and negatively with hepatic glycogen content (r = -0.6). Bmax of alpha2-AR was negatively associated with Bmax of beta2-AR (r = -0.4). In conclusion, mRNA levels and binding sites of alpha1- and alpha2-AR in calves exhibited developmental changes and were negatively associated with hepatic glycogen content.

Effects of colostrum feeding and glucocorticoid administration on insulin-dependent glucose metabolism in neonatal calves.

Colostrum feeding and glucocorticoid administration affect glucose metabolism and insulin release in calves. We have tested the hypothesis that dexamethasone as well as colostrum feeding influence insulin-dependent glucose metabolism in neonatal calves using the euglycemic-hyperinsulinemic clamp technique. Newborn calves were fed either colostrum or a milk-based formula (n=14 per group) and in each feeding group, half of the calves were treated with dexamethasone (30 microg/[kg body weight per day]). Preprandial blood samples were taken on days 1, 2, and 4. On day 5, insulin was infused for 3h and plasma glucose concentrations were kept at 5 mmol/L+/-10%. Clamps were combined with [(13)C]-bicarbonate and [6,6-(2)H]-glucose infusions for 5.5h (i.e., from -150 to 180 min, relative to insulin infusion) to determine glucose turnover, glucose appearance rate (Ra), endogenous glucose production (eGP), and gluconeogenesis before and at the end of the clamp. After the clamp liver biopsies were taken to measure mRNA levels of phosphoenolpyruvate carboxykinase (PEPCK) and pyruvate carboxylase (PC). Dexamethasone increased plasma glucose, insulin, and glucagon concentrations in the pre-clamp period thus necessitating a reduction in the rate of glucose infusion to maintain euglycemia during the clamp. Glucose turnover and Ra increased during the clamp and were lower at the end of the clamp in dexamethasone-treated calves. Dexamethasone treatment did not affect basal gluconeogenesis or eGP. At the end of the clamp, dexamethasone reduced eGP and PC mRNA levels, whereas mitochondrial PEPCK mRNA levels increased. In conclusion, insulin increased glucose turnover and dexamethasone impaired insulin-dependent glucose metabolism, and this was independent of different feeding.

In vitro embryo production: growth performance, feed efficiency, and hematological, metabolic, and endocrine status in calves.

The potential management benefits of in vitro embryo production have been offset by an increased incidence of health-related problems in resulting calves [increased birth weight, congenital abnormalities, and peri- and postnatal mortality (large-offspring syndrome)] and of recipient cows (prolonged gestation, dystocia, increased hydroallantois, abortion). The aim of the present research was to determine whether relevant metabolic, endocrine, or hematological traits could be related to the causes of enhanced growth performance of in vitro fertilized calves. Growth performance and feed efficiency as well as hematological, metabolic, and endocrine traits studied in calves derived from in vitro-produced embryos (IVP; n = 11) and in calves derived from artificial insemination (AI; n = 8). Donor cows from which oocytes for in vitro fertilization were obtained had a heterogeneous background, thus excluding genetic maternal influences. On the other hand, semen for in vitro fertilization and for artificial insemination was from the same bull, and recipient cows were held under the same husbandry and feeding conditions as AI cows, thus reducing the variability. Blood samples were collected preprandially on d 1, 2, 3, 4, 7, 14, 28, 56, and 112 of life and every 20 min between 0830 and 1630 h on d 7 and 112 for the evaluation of growth hormone secretory patterns. Gestation of IVP cows was longer than that of AI cows, but birth weights were similar in both groups. Feed intake, average daily gain, and body length during the experimental period, body weight from wk 8 to 16, and gain/feed ratio during the first month of life were higher in IVP than in AI calves. At birth, potassium, 3,5,3'-triiodothyronine, and thyroxine concentrations were lower in IVP than in AI calves. Concentrations of sodium and potassium on d 7, of triglycerides on d 28, and of albumin on d 56 were higher in IVP than in AI calves. In conclusion, IVP calves had higher feed intake and growth rate during the entire growth period and improved feed efficiency in the first month of life than AI calves, but this was not mirrored by consistent changes of hematological, metabolic, or endocrine traits, whose concentrations were in the normal range. Additional work is needed to study IVP calves under field conditions.

Effects of dexamethasone and growth hormone treatment on hepatic gluconeogenic enzymes in calves.

The hypothesis was tested that dexamethasone (DX) and bovine somatotropin (bST) alter expression or activity of gluconeogenic enzymes in neonatal calves. Holstein dairy calves (n = 24) were randomly divided in 4 groups and were treated with saline (control group), with DX at 30 microg/kg body weight per d (CDX), with 500 mg of sustained-release recombinant bST every 14 d (CbST), and with the combination of DX and bST from d 3 through 42 of life (CbSTDX). Plasma glucose and insulin concentrations were elevated throughout the study in CbSTDX, and insulin concentrations were elevated in CDX from d 7 to 28. Treatment with DX and the combination of DX and bST increased plasma glucagon concentrations from d 14 to 42, but decreased plasma cortisol concentrations on d 7 and 14 when compared with control calves. In liver, phosphoenolpyruvate carboxykinase (PEPCK) mRNA levels were reduced in CDX and CbSTDX when compared with control calves or CbST. The activity of PEPCK on d 14 was higher in CbSTDX compared with control calves. Pyruvate carboxylase mRNA levels were decreased on d 7 in CDX and CbSTDX. Pyruvate carboxylase activities on d 14 and 28 were lower in CDX and CbSTDX than in control calves or CbST. These data indicate an age-dependent response to DX for blood metabolites, expression and activities of hepatic PEPCK and pyruvate carboxylase, and for effects of bST, suggesting that glucocorticoid status is important.

Plasma leptin status in young calves: effects of pre-term birth, age, glucocorticoid status, suckling, and feeding with an automatic feeder or by bucket.

Plasma leptin concentrations depend on energy intake and fat stores and are modified by hormones, such as glucocorticoids. We have measured plasma leptin concentrations in pre-term calves (born on day 277 of gestation) during the first week of life, in full-term calves (290 days of gestation), fed similar amounts of nutrients with colostrum or a milk-derived formula, combined with or without dexamethasone treatment (to simulate a high glucocorticoid status), during the first five days of life, and in calves fed with an automatic feeder or by bucket or suckling on dams up to day 28. Leptin concentrations increased (P<0.05) from birth to day 7 in pre-term calves. In full-term calves leptin concentrations were stable from day 1 to day 4 in colostrum-fed animals, but decreased (P<0.05) and were lower (P<0.05) if fed a formula with similar amounts of energy and macronutrients as colostrum. Concentrations increased (P<0.05) from day 1 to day 2 in calves suckling on dams and then remained elevated, but did not change and were lower in calves fed with the automatic feeder or by bucket than in suckling calves. Dexamethasone only slightly elevated leptin concentrations. There was no episodic secretion pattern, and there were no consistent associations of leptin with various metabolites and hormones. In conclusion, plasma leptin in young calves with respect to effects of nutrition (low energy intake) and hormones (glucocorticoids) and in association with metabolic changes behaved differently from what is known in mature cattle.

Dexamethasone and colostrum feeding affect hepatic gluconeogenic enzymes differently in neonatal calves.

Plasma glucose concentrations in neonates are influenced by colostrum feeding and by glucocorticoids. We have tested whether a high-glucocorticoid status after birth, as well as colostrum feeding, influences glucose metabolism in association with changes of hepatic expression and activities of gluconeogenic enzymes phosphoenolpyruvate carboxykinase (PEPCK; EC 4.1.1.32) and pyruvate carboxylase (PC; EC 6.4.1.1) in neonatal calves. Calves (n = 14 per group) were fed either colostrum or a milk-based formula with nutrient and energy contents similar to colostrum. Half the calves in each feeding group were treated with dexamethasone (DEXA; 30 microg/[kg BW x d]). Pre- and postprandial blood samples were taken on d 1, 2, 4, and 5 and liver samples were collected on d 5 of life. Dexamethasone treatment increased (P < or = 0.05) plasma concentrations of glucose, insulin, and glucagon more in colostrum-fed than in formula-fed calves but increased (P < or = 0.05) urea concentrations and decreased (P < or = 0.05) concentrations of NEFA, ACTH, and cortisol independent of colostrum vs. formula feeding. Colostrum feeding increased (P < 0.05) plasma glucose, but decreased (P < 0.05) plasma urea concentrations. Glucagon-to-insulin ratios in DEXA-treated and colostrum-fed calves were decreased (P < 0.05). Dexamethasone treatment decreased hepatic mRNA levels and activities of PC (P < 0.001 and P < 0.10) and activities of PEPCK (P < 0.001) but increased (P < 0.001) the glycogen content. Colostrum feeding increased (P < 0.05) mitochondrial PEPCK mRNA levels and PEPCK activities in calves not treated with DEXA but decreased (P < 0.1) amounts of PC mRNA. In conclusion, increased plasma glucose concentrations after DEXA treatment were not associated with a stimulation of hepatic gluconeogenic enzyme activities; however, colostrum feeding probably raised plasma glucose concentrations because of increased hepatic gluconeogenic activities.

The response of the hepatic insulin-like growth factor system to growth hormone and dexamethasone in calves.

Glucocorticoids inhibit postnatal growth and yet can stimulate the somatotropic axis around birth. The aim of the present study was to investigate the effects of dexamethasone on the somatotropic axis and on the responses of the insulin-like growth factor (IGF) system to growth hormone treatment in calves. Calves (n=24) were randomly divided into four groups. Group DX was injected with dexamethasone (30 micro g/kg body weight per day), group GH was injected with 500 mg slow-release bovine growth hormone at 14-day intervals, group GHDX was injected with dexamethasone and bovine growth hormone, and group CNTRL (serving as control) was injected with saline from day 3 to day 42 of life. Blood samples were taken on day 3 and blood and liver samples were obtained on days 7, 14, 28 and 42. Body weight increased in the CNTRL and GH groups up to the end of the study and in the DX and GHDX groups up to the fourth week. Dexamethasone treatment decreased (P<0.05) plasma IGF binding protein (IGFBP)-1 on days 7 and 14, but increased (P<0.05) plasma IGFBP-1, decreased (P<0.05) plasma IGF-I and IGFBP-3, and decreased hepatic mRNA for growth hormone receptor (GHR) and IGF-I on day 42. Growth hormone treatment increased (P<0.05) plasma growth hormone concentrations on days 7 and 14, tended to increase (P<0.1) plasma IGF-I concentrations on day 42, and increased (P<0.05) hepatic mRNA levels of GHR on day 14 and IGF-I mRNA levels on days 7 and 14. The combined dexamethasone and growth hormone treatment increased plasma growth hormone concentrations on day 7 and resulted in the highest plasma concentrations of IGF-I and IGFBP-3 (day 7 to day 28) as well as the greatest abundance of hepatic GHR (day 14) and IGF-I (days 7 and 14) mRNA. Plasma IGFBP-1 concentrations in the GHDX group behaved in a similar manner as in the DX group. In conclusion, the response of the somatotropic axis to growth hormone treatment could be greatly enhanced by dexamethasone treatment during the neonatal and early postnatal period, but body weight gain was not improved. Dexamethasone alone inhibited the somatotropic axis and postnatal growth after the first Month of life.

Physiological traits in preterm calves during their first week of life.

Morbidity and mortality of preterm neonatal calves are higher than of calves born at normal term, possibly and in part due to immaturity of physiological functions. Physiological parameters were therefore studied during the first week of life in seven preterm calves, born on day 277 of gestation after dams were injected prostaglandin F2alpha and flumethason. Calves were fed colostrum of the first milking for the first 3 days and from day 4 to day 7 the same colostrum diluted with milk replacer. Body weight increased during the first week of life by 2.2 kg. Heart rate and respiratory rate were always relatively high, whereas values of rectal temperature, blood gases, haematological, metabolic and endocrine traits were in the range and behaved similarly as is the experience in full-term neonatal calves. Major exceptions were glucose and insulin, the concentrations of which barely rose postprandially, and growth hormone, the responses of which to growth hormone releasing factor analogue 1-29 were extremely variable and in part very small. In conclusion, calves born 2 week before normal term that survived the first week of life, although physiologically immature, were well able to handle ingested nutrients and to control their metabolism.

Estimation of energy balance at the individual and herd level using blood and milk traits in high-yielding dairy cows.

This study aimed to estimate individual and herd-level energy balance (EB) using blood and milk traits in 90 multiparous high-yielding Holstein cows, held on a research farm, from wk 1 to 10 postpartum (p.p.) and to investigate the precision of prediction with successively decreased data sets simulating smaller herd sizes and with pooled samples. Dry matter intake, milk yield, and BW were measured daily from parturition through wk 10 p.p. Milk composition was determined 4 times per week, and milk acetone was measured weekly. Blood samples for the determination of metabolites, hormones, electrolytes, and enzyme activities were taken weekly from wk 1 to 10 p.p. between 0730 and 0900. Body condition scores and ultrasonic measurements of backfat thickness and fat depth in the pelvic area were evaluated in wk 1, 4, and 8 p.p. Concentrations of glucose, cholesterol, urea, insulin, insulin-like growth factor-1, triiodothyronine, and thyroxine (T4) in blood plasma and of lactose and urea in milk were positively correlated with EB, whereas concentrations of nonesterified fatty acids (NEFA), creatinine, albumin, beta-hydroxybutyrate, and growth hormone and enzyme activities in blood, and concentrations of fat, protein, fat:lactose ratio, and acetone in milk were negatively correlated with EB. Leptin concentration was not correlated to EB over the first 10 wk p.p. To estimate EB linear mixed-effects, models were developed by backward selection procedures. The most informative traits for estimation of EB were the fat:lactose ratio in milk and NEFA and T4 concentrations in blood. The precision of estimation of EB in individual cows was low. Using blood in addition to milk traits did not result in higher precision of estimation of herd-level EB, and decreasing sample sizes considerably lowered the precision of EB prediction. Estimation of overall mean herd-level EB over the first 10 wk p.p. using pooled samples was precise even with small sample sizes, but does not consider the level of EB in particular weeks. In conclusion, estimation of herd-level EB at individual weeks using milk traits only has practical implication with herd sizes of > or = 100 cows if calving is highly seasonal and of or = 400 cows if calving is uniformly distributed. Using blood in addition to milk traits does not improve precision of estimation of herd-level EB, regardless of sample size.

Growth performance, metabolic and endocrine traits, and absorptive capacity in neonatal calves fed either colostrum or milk replacer at two levels.

Colostrum (CO) contains high amounts, whereas whole milk and milk replacer (MR) contain small amounts, of bioactive and growth-promoting substances, such as IGF-I. An experiment was designed to study the effects of feeding CO or MR on the first 3 d to neonatal calves, followed by whole milk up to d 7, at low and high density. Intestinal absorptive capacity, plasma metabolite and hormone concentrations, and growth performance were measured during the 1st wk of life. Body weight increased (P < .05) similarly in calves fed low or high amounts of CO but did not rise in MR-fed calves. Loose feces were more frequent (P < .05) and absorption of xylose on d 5 was lower (P < .01) in MR- than in CO-fed calves, but there were no effects of feeding density within CO-fed or within MR-fed groups. However, high feeding density within CO-fed groups enhanced (P < .05) total protein, globulin, triglyceride, cholesterol, and insulin concentrations, whereas in the initially high and low MR-fed groups only plasma glucose and insulin after the first meal and plasma NEFA on d 2 were modified (P < .05) by different feeding density. Thus, feeding different amounts of CO partly influenced protein and fat metabolism in calves during the 1st wk of life, but it did not measurably affect intestinal function. However, feeding different amounts of MR, in the absence of CO, barely affected metabolic and endocrine traits and absorptive capacity. Thus, high density CO feeding, and therefore a high supply of nutrients, together with greater amounts of bioactive and growth-promoting substances influenced neonatal metabolism and growth more than a high density of MR feeding containing only small amounts of bioactive and growth-promoting substances. Factors in addition to nutrient density seem to be important for the development of neonatal calves.