Delayed colostrum feeding affects IGF-I and insulin plasma concentrations in neonatal calves

In the neonatal calf, insulin-like growth factor I (IGF-I) concentrations are markedly influenced by the amount of colostrum intake after birth, although colostral IGF-I is barely absorbed. In this study we have investigated effects of delayed colostrum intake in neonatal calves on metabolic traits and on IGF-I, IGF binding proteins (IGFBP), growth hormone (GH), and insulin concentrations in plasma. Calves received colostrum of first milking starting at 2 (GrA), 6 (GrB), 12 (GrC), and 24 h (GrD) after birth. Before third colostrum intake plasma total protein concentrations were higher in GrA than in GrD and plasma glucose concentrations were higher in GrC than GrD. Plasma IGF-I concentrations at first and third colostrum intake were higher in GrA than in GrD. Plasma IGFBP-2 concentrations before first colostrum intake were higher in GrD than in GrA and GrC, and were higher before third colostrum intake in GrD than in GrA. Plasma IGFBP-3 concentrations before first colostrum intake were lower in GrD than in GrA, and before third colostrum intake were lower in GrD than in GrA and GrB. Postprandial plasma insulin concentrations after first colostrum intake were higher in GrA than in GrC and GrD. In conclusion, the plasma IGF-I and insulin status are markedly, albeit transiently, decreased in calves fed colostrum with a delay of 12 to 24 h, and the decreased concentrations of plasma IGF-I were associated with decreased IGFBP-3/IGFBP-2 ratios.     

Postprandial metabolism and endocrine status in veal calves fed at different frequencies

Veal calves fed by bucket often develop postprandial insulin resistance, hyperglycemia, and glucosuria during fattening. Automatic feeding systems allow feed intake for 24 h, and small ingested portions are expected to decrease postprandial glucose loads. We have studied metabolic and endocrine traits in calves that were either 1) fed identical daily amounts of whole milk plus milk replacer by a computer-programmed automatic feeder (> or =6 portions from 0800 to 2400 h) (GrA) or 2) fed by bucket at 0800 and 1630 h (GrB). Calves started at a body weight of 118 kg, and the experiment lasted for 3 wk. During wk 3, lactose was supplemented to stress postabsorptive glucose homeostasis. Feed intake and average daily gains in GrA and GrB were similar. Plasma concentrations during an 8-h period of glucose (in part), lactate, urea, and somatostatin (in wk 3), and of glucagon and insulin (wk 2 and 3) were smaller in GrA than in GrB, whereas growth hormone, insulin-like growth factor I, insulin-like growth factor binding protein-1 (wk 2), and prolactin concentrations (wk 2 and 3) were higher. Lactose supplementation in wk 3 enhanced transient postprandial hyperglycemia and hyperinsulinemia. Thus, there were marked metabolic and endocrine differences when calves sucked their feed in six or more portions during a 16-h period from an automatic feeder compared with twice daily drinking from a bucket. Ingestion of small portions by calves avoided marked hyperglycemia and lactate increments, and lower plasma urea concentrations mirrored enhanced nitrogen utilization, possibly mediated by the altered growth hormone, IGF-I and insulin status.     

Extending lactation in pasture-based dairy cows. II: Effect of genetic strain and diet on plasma hormone and metabolite concentrations

Fifty-six genetically divergent New Zealand and North American Holstein-Friesian (HF) cows grazed pasture, and were offered 0, 3, or 6 kg of concentrate DM/cow per day for an extended lactation (605 ± 8.3 d in milk; mean ± standard error of the mean). Weekly blood samples collected from individual cows from wk 1 to 10 postpartum (early lactation), and from wk 47 to 63 postpartum (extended lactation) were analyzed for nonesterified fatty acids (NEFA), glucose, insulin, leptin, growth hormone (GH), insulin-like growth factor-I (IGF-I), calcium, and urea. During early lactation, NEFA and GH concentrations were greater and IGF-I concentrations were less, and increased at a slower rate in North American HF. During this 10-wk period, there were no strain effects on plasma glucose, leptin, insulin, or calcium. During the extended lactation period, North American HF had greater NEFA and GH concentrations; there were strain × diet interactions for insulin and leptin, and a tendency for a strain × diet interaction for glucose. These interactions were primarily due to greater plasma insulin, leptin, and glucose concentrations in the New Zealand HF fed 6 kg of concentrate DM/cow per day, a result of excessive body condition in this treatment. In this period, there was no strain effect on plasma IGF-I, calcium, or urea concentration. During early lactation, there was a linear increase in glucose and IGF-I, and a linear decrease in GH and urea with increasing concentrate in the diet. However, plasma calcium, NEFA, insulin, and leptin remained unchanged. During the extended lactation period, there was an effect of feed supplementation on GH and urea, which decreased linearly with increasing concentrate in the diet. There was, however, no supplementation effect on NEFA, calcium, or IGF-I. These data indicate potential strain differences in recoupling of the somatotropic axis, insulin resistance, and energy partitioning, and may help explain the physiology behind the previously reported greater milk production and body condition score loss in North American HF. The results have implications for breeding and diet management during an extended lactation.     

Developmental changes in the kinetics of glucose and urea in Holstein calves

Because weaning is the point when the nutrient composition of feed changes for the neonatal ruminant, the present experiment was conducted to assess the developmental changes in the kinetics of glucose and urea over this period, using stable isotopes of glucose and urea, at 4, 13, and 24 wk in calves. Plasma concentrations of nonesterified fatty acids, amino-N, urea-N, and insulin-like growth factor-I increased, but that of growth hormone decreased with age. The plasma glucose concentration increased at 13 wk of age and thereafter decreased at 24 wk of age. The glucose irreversible loss and recycling rates were significantly higher at 4 wk of age than at 13 and 24 wk of age. On the other hand, the irreversible loss and recycling rates of urea, as well as the urea pool size, were higher at 24 wk of age than at 4 and 13 wk. It is concluded that weaning at 6 wk is the pivotal time for the alteration of glucose kinetics. However, the aging process, but not weaning, is important for changes in the kinetics of urea in calves.     

Effects of recombinant bovine somatotropin on nutritional status of dairy cows during pregnancy and of their calves

Objectives of this trial were to evaluate effects of rbST on the nutritional status of 24 Holstein cows during pregnancy and of their calves from birth to weaning. All cows conceived during injection with either a placebo or 350 mg of rbST in a sustained-release vehicle every 14 d commencing 98 to 112 d postpartum for their entire lactation. In Experiment 1, blood samples were collected at 90, 180, and 270 d postconception in cows. Concentrations of urea, glucose, albumin, total proteins, Ca, P, insulin, cortisol, hemoglobin, and hematocrit were unaffected by treatment as well as BW, body condition scores, and energy balances at conception and during pregnancy. Days open and calving interval were not significantly different but were numerically increased by 31 d in rbST-injected cows. Nonesterified fatty acids, bST, and insulin-like growth factor-I in plasma were elevated significantly in rbST-injected cows. In Experiment 2, blood samples were collected at birth and at 1, 3, 5, and 7 wk in calves born from cows of Experiment 1. Circulating concentrations of glucose, nonesterified fatty acids, albumin, total proteins, hemoglobin, insulin, cortisol, bST, insulin-like growth factor-I, and hematocrit, blood pH, blood gases and buffer capacity, birth weight and rate of weight gain, height at withers, and heart girth from birth to weaning were not different due to treatment of dam. However, some parameters were significantly different based on age and sex. These data support previous assumptions that the magnitude of the modifications in nutrient partitioning produced by rbST do not affect the hierarchy of the partitioning process for the calf.     

Slow release somatotropin in dairy heifers and cows fed two levels of energy concentrate. 2. Plasma hormones and metabolites

Fifty Holstein dairy cows (26 primiparous) were used to evaluate effects of level of concentrate and of slow release recombinant bST on plasma hormones and metabolites. Blood was sampled at wk 14 and 20 of lactation, which was 5 and 11 wk after the first bST injection. In addition, at d 3 and 10 after the third bST injection, diurnal profiles of somatotropin and metabolites were studied in 7 bST cows and 5 control cows by blood sampling every 20 min over 6 h. Supplementation by bST enhanced plasma somatotropin and insulin-like growth factor-I but did not significantly affect plasma concentrations of triiodothyronin and insulin. The bST supplementation increased plasma NEFA at wk 14 and reduced uremia at wk 20. Primiparous cows showed higher plasma NEFA and triiodothyronin than multiparous cows at both sampling periods, higher insulin-like growth factor I, and lower beta-hydroxybutyrate at wk 14, and higher glucose and lower insulin at wk 20. In the diurnal kinetic study, bST supplementation did not alter bST spike frequency and duration but increased spike magnitude, the area under the curve above the baseline, and the baseline mean. Sixty-one to 56% of the increase over controls in plasma bST total area was due to increase in the area under the curve above baseline. Preprandial NEFA were increased by bST at d 10.     

Duodenal rapeseed oil infusion in early and midlactation cows. 3. Plasma hormones and mammary apparent uptake of metabolites

Rapeseed oil was infused continuously (1.0 to 1.1 kg/d) into the duodenum of Holstein x Friesian multiparous cows during the first 3 wk of lactation (oil treatment, 6 cows versus 6 controls, early lactation trial) or after 100 d of lactation (midlactation trial, 9 cows in a crossover design). In the midlactation trial, plasma glucose, 3-hydroxybutyrate, and free glycerol were not affected by oil infusion. Postprandial plasma NEFA were higher in oil-infused than in control cows; plasma triglycerides, phospholipids, and cholesterol were significantly increased in oil treatment. Plasma insulin was lower and somatotropin higher in oil-infused cows, whereas insulin-like growth factor-I and triiodothyronine were not affected. During the early lactation trial, there were few significant effects of oil infusion on measured plasma metabolites and hormones. Preprandial glucose and NEFA were lower in oil treatment during wk 2, preprandial phospholipids were higher in wk 1 and 3, and free cholesterol was higher in wk 1. Responses of plasma glucose and NEFA to insulin challenge were not clearly affected by oil treatment during either trial. Differences in plasma triglycerides between jugular and mammary veins were higher in oil treatment in both trials. Oil infusion did not affect jugular-mammary differences of other metabolites except for a slight increase in cholesterol esters in midlactation. The relationships between jugular-mammary differences and jugular plasma concentrations showed that up to 24, 27, 54, and 17% of jugular glucose, NEFA, triglycerides, and 3-hydroxybutyrate apparently were taken up by the mammary gland.     

Effects of sometribove on performance, carcass composition, and chemical blood characteristics of dairy calves.

Ten intact male Holstein calves averaging 75 kg of BW and 59 d of age were used to study the effects of daily injections of 0 (control) or 10 mg of sometribove (recombinant methionyl bST) for 6 wk on performance, health, carcass composition, N metabolism, chemical blood characteristics, and hormone profiles. Average daily gain, feed intake, feed:gain ratio, and height at withers, hip, and hock were not influenced by bST. Carcasses from bST-treated calves contained 5% more protein and 36% less lipid than controls. Circulating concentrations of Ca, P, glucose, urea N, alkaline phosphatase, creatine phosphokinase, insulin-like growth factor-I, and insulin were not affected by bST. Packed cell volume was decreased about 7% (29.9 vs. 32.4%) in the bST calves. Hormone injection did not adversely affect health of the calves as measured by body temperature and by pulse and respiration rates. The most profound effects of sometribove were a reduction in carcass lipid and an increase in body proteins. These effects may be of some practical importance when leanness of carcass is desirable.     

Hematological, metabolic, and endocrine effects of feeding vitamin A and lactoferrin in neonatal calves

There are reports of important interactions among vitamin A, lactoferrin (Lf), and components of the insulin-like growth factor (IGF) system. Newborn calves are deficient in vitamin A and have a low Lf status. Colostrum contains vitamin A, Lf, and members of the IGF system, including IGF binding proteins (IGFBP), and these compounds may exert mutual interactions in neonatal calves. Effects of feeding different amounts of vitamin A and Lf on hematological, metabolic, and endocrine traits during the first 5 d of life were studied in neonatal calves. Calves were fed a milk-based formula without (F) or with added vitamin A [F(A); 351, 402, 490, and 490 micromol/kg dry matter (DM) on d 1, 2, 3, and 4, respectively], Lf (F(L); 3850, 1990, 660, and 660 mg/kg DM on d 1, 2, 3, and 4, respectively), or vitamin A + Lf (F(AL)) and colostrum (C). Blood samples were taken preprandially on d 1 to 5 and postprandially on d 1, 2, and 4 for the study of hematological, metabolic, and endocrine traits. As intestinal absorption of Lf in formula-fed calves was obviously lower than in colostrum-fed calves, Lf supplementation did not influence the metabolic and endocrine status. Plasma vitamin A concentrations increased from d 1 to 5 in F(A), F(AL), and C, but remained low in F and F(L). Addition of vitamin A to F affected concentrations of vitamin A from d 2 to 5; hemoglobin and triglycerides on d 3; and tended to influence IGFBP-3 levels on d 5. On d 1, preprandial insulin concentrations in F and F(L) were higher than those in F(A) and F(AL) and growth hormone concentrations on d 3 in F(A) were higher than in F(AL). In C, plasma Lf concentrations increased on d 1 and then decreased until d 5, whereas plasma urea and IGF-I concentrations remained stable. Compared with F-fed calves, C-fed calves had higher plasma concentrations of Lf from d 1 to 4, higher concentrations of vitamin A on d 5, higher concentrations of total protein from d 2 to 5, higher concentrations of triglycerides on d 3 and 4, and higher concentrations of IGF-I on d 4 and 5, but lower urea concentrations on d 4 and 5 and lower basal growth hormone concentrations than in F, F(L), and F(A). In conclusion, metabolite and hormone concentrations were influenced by differences in feeding. Addition of vitamin A influenced concentrations of vitamin A, hemoglobin, and triglycerides and tended to affect IGFBP-3 levels. Lactoferrin and vitamin A did not interact with respect to the IGF-I and IGFBP-3 status.     

Hormonal responses to bovine somatotropin and dietary protein in early lactation dairy cows

The effects of bST injection and dietary protein level on blood hormone and metabolite concentrations were examined in four mature Holstein cows in a double crossover design. Cows were assigned at d 5 to 9 postpartum to receive daily injections of either a control (saline) solution or 20.6 mg of bST. Four 3-wk periods were used during which one cow from each group was fed a medium protein diet (17.1% CP), and the other received a high protein diet (23.6% CP). Injections of bST or control solutions began on d 0 of the second period. Intakes of DM were not influenced by dietary protein or bST injection. Milk yield tended to increase with increased CP level but was not affected by bST injection. Based on the rate and extent of decline in milk production after cessation of bST injection, the cows assigned to bST had lower milk production potential than control cows. Thus, the effect of bST injection apparently was to enhance milk yield to levels similar to those of controls. There were no significant CP level or bST injection effects on glucose, FFA, somatostatin, or somatotropin concentrations. Glucagon concentrations were higher in bST-treated cows. Concentrations of insulin-like growth factor-I were increased with increased CP level and also with bST injection. Significant effects of days on bST were observed for insulin, insulin-like growth factor-I, glucose, and FFA. Cows given bST injections and producing equal amounts of milk as control cows did not show major physiological differences in hormones and metabolites with the exception of insulin-like growth factor-I.     

Intramammary infusion of insulin or long R3 insulin-like growth factor-I did not increase milk protein yield in dairy cows

Two experiments investigated the regulation of milk protein synthesis in well-fed cows (n = 4) using 1) a hyperinsulinemic-euglycemic clamp and 2) intramammary infusion of insulin or long R3 insulin-like growth factor-I plus supplementary amino acids. In experiment 1, insulin was infused at 1.0 microg x kg BW(-1) x h(-1) to increase circulating levels fourfold, and euglycemia was maintained by infusion of glucose. An insulin clamp increased the yields of casein and whey protein both with and without supplementary amino acids. Plasma concentrations of insulin-like growth factor-I were increased and insulin-like growth factor binding protein-2 decreased during insulin clamp, while both insulin and insulin-like growth factor-I in milk were elevated by this treatment. Milk concentrations of insulin peaked on day 4, but insulin-like growth factor-I concentrations in milk peaked on day 1 of the insulin clamp. In experiment 2, intramammary infusion of insulin had no effects on any measured variables, while yields of milk, protein, and fat were slightly lower following long R3 insulin-like growth factor-I treatment. This could be associated with an increase in somatic cell count, which occurred following long R3 insulin-like growth factor-I treatment. Results from experiment 1 suggest insulin and insulin-like growth factor-I are likely candidates responsible for the increased milk protein yields during the insulin clamp. However, in experiment 2 neither hormone enhanced milk protein yield when administered using an intramammary technique.     

The association between metabolic parameters and oocyte quality early and late postpartum in Holstein dairy cows

The objective of this was to study the association between metabolic parameters and oocyte quality in postpartum lactating dairy cows as assessed by oocyte morphology and development after fertilization and culture in vitro. Holstein-Friesian spring-calving cows were used (n = 16, parity 3.0 ± 0.36, weight at calving 611 ± 16.2 kg, previous 305-d milk yield 6,454.0 ± 276.4 kg). Bodyweight (BW) and body condition score were recorded at approximately 2 wk before expected calving date, at calving, and then weekly until the end of the experiment (approximately 80 d postpartum). Blood plasma samples were collected weekly, starting 2 wk before the expected calving date and continuing until the end of the experiment and were analyzed for nonesterified fatty acids (NEFA), β-hydroxybutyrate (BHBA), insulin, insulin-like growth factor-I, and glucose. Transvaginal oocyte recovery was carried out twice weekly on each cow for a period of approximately 12 wk starting 14 d after calving until approximately 80 d postpartum. A linear decrease in BW was observed from calving (d 0) to d 28, after which it remained stable. Body condition score decreased from 14 d precalving, reaching a nadir at approximately d 35 to 42, after which it increased to the end of the period. Nonesterified fatty acid concentrations were significantly elevated from the week before calving until d 42 postcalving, whereas BHBA concentration was significantly elevated from calving to d 49 postcalving. Insulin-like growth factor-I concentration dramatically decreased from d -14 to a nadir on d 7. A significant increase in glucose concentration occurred from d -7 to d 0, followed by a precipitous decrease to d 7. Based on the metabolic profiles (particularly NEFA and BHBA concentrations), data from d 0 to 42 postpartum (period 1) were compared with corresponding data from d 42 to 80 (period 2). Apart from body condition score, all of the physiological parameters measured (milk yield, BW, and blood metabolites) differed significantly between the 2 periods. In particular, insulin-like growth factor-I, insulin, and glucose concentrations were higher post-d 42, whereas BHBA and NEFA were lower compared with pre-d 42 postpartum. The number of oocytes recovered per session and oocyte quality grade did not differ between periods. Positive associations of follicles aspirated and insulin, BHBA, and NEFA were detected. The number of oocytes recovered was positively associated with milk yield, BW, and glucose and NEFA concentrations. The number of cleaved oocytes was positively associated with BW and NEFA concentration. In conclusion, the data do not provide evidence of an effect of lactation-induced metabolic stress on oocyte developmental competence in the postpartum dairy cow assessed in terms of morphological quality and ability to develop following in vitro fertilization.     

Effects of prenatal dietary rumen-protected choline supplementation during late gestation on calf growth,metabolism, and vaccine response

The objective of this study was to examine the effects of prenatal supplementation and dose of rumen-protected choline (RPC) on neonatal calf growth, metabolism, and vaccine response. Parous Holstein cows were blocked by calving month and randomly assigned within block to receive 45 g/d of RPC [20.4 g/d of choline ions (CHOL45), n = 19], 30 g/d of RPC [13.6 g/d of choline ions (CHOL30), n = 22], or no RPC (CON, n = 19) as a top-dress, starting 24 d before expected calving. Calf body weights were recorded for the first 3 wk of life. All calves were fed colostrum replacer (300 g of IgG) at birth, and apparent efficiency of IgG absorption was calculated. On d 1, 7, 14, and 21, blood samples were taken to quantify plasma reactive oxygen and nitrogen species, antioxidant potential, haptoglobin, nonesterified fatty acids (NEFA), β-hydroxybutyrate, and glucose. Calves received an intranasal vaccine at birth, and nasal secretions were collected on d 0, 7, 10, 14, and 21 to quantify bovine respiratory syncytial virus-specific IgA. Data were analyzed using linear mixed models including the fixed effects of treatment, time (when applicable), calf sex, and prepartum dam data (?24 d) along with interactions. Treatment did not affect calf body weight, β-hydroxybutyrate, or glucose concentrations. For apparent efficiency of IgG absorption, treatment interacted with the dam's prepartum body condition score. Where the dam's body condition score was ≤3.25, IgG absorption was reduced in calves born from CHOL45 dams as compared with calves from either CHOL30 or CON dams. Calves from CHOL30 dams had a lesser oxidative stress index (OSi; reactive oxygen and nitrogen species/antioxidant potential) than calves from CON dams. Haptoglobin concentrations were less in heifer calves from CHOL45 dams as compared with heifers from CON dams. The dam's prepartum NEFA concentration interacted with treatment. When dam NEFA was minimal, calves from CHOL45 and CHOL30 dams had greater or tended to have greater NEFA, respectively. Conversely, when dam NEFA was greater, calves from CHOL30 and CHOL45 dams had lesser or tended to have lesser NEFA than calves from CON dams, respectively. For vaccine response, treatment interacted with the dam's prepartum OSi. Among calves born from dams with a greater OSi, calves from CHOL45 and CHOL30 dams had lesser bovine respiratory syncytial virus-specific IgA concentrations in nasal secretions as compared with CON. Prenatal RPC supplementation during late gestation affected IgG absorption, neonatal calf metabolism, and vaccine response with some effects dependent on the dam's prepartum parameters.     

Effects of lipid-encapsulated conjugated linoleic acid supplementation on milk production, bioenergetic status and indicators of reproductive performance in lactating dairy cows

Conjugated linoleic acid (CLA) reduces mammary milk fat synthesis in a dose-dependent manner. Our objective was to determine the effects of lipid-encapsulated CLA (LE-CLA) supplementation on milk production, reproductive performance and metabolic responses in lactating dairy cows fed a grass silage-based diet. Seventy-two Holstein-Friesian cows (32 primiparous and 40 multiparous) were used in a completely randomized block design. Cows received either 80 g of LE-CLA daily or 60 g of calcium salts of palm fatty acids daily (control) from parturition until 60 days in milk. LE-CLA contained a 50:50 mix of cis-9,trans-11 CLA and trans-10,cis-12 CLA, resulting in a daily intake of 6 g of each isomer. Milk production and dry matter intake were recorded daily, and blood samples were collected 3-times a week. Blood samples were analysed for circulating concentrations of glucose, non-esterified fatty acids (NEFA), β-hydroxybutyrate (BHBA), insulin and insulin-like growth factor-I (IGF-I). Progesterone was measured in blood samples collected after the first post-partum insemination. Ovarian ultrasound examinations commenced at 8-10 d post partum and were carried out 3-times a week until first ovulation. LE-CLA treatment resulted in decreased milk fat concentration, with consequent improvements in energy balance and body condition score (BCS). The peak concentration of NEFA in blood was reduced by LE-CLA, but circulating concentrations of insulin, glucose, IGF-I, BHBA and progesterone were not affected. There was no effect of LE-CLA supplementation on the post-partum interval to first ovulation. Services per conception tended to be reduced. The reduction in milk energy output and improvement in energy status and BCS in LE-CLA-supplemented cows provides a strong rationale for further studies with greater cow numbers to test effects on reproductive performance.     

Milk production,nutrient utilization,and endocrine responses to increased postruminal lysine and methionine supply in dairy cows

The effect of increased postruminal supply of lysine and methionine was investigated in a production trial involving 64 dairy cows in early lactation. Within each of two basal rations, based on either corn silage or grass silage, rations were either naturally deficient in lysine or fortified with 24 g of lysine in a rumen-protected form and naturally deficient in methionine or fortified with 12 g of methionine in a rumen-protected form. The data were analyzed separately for the four lysine and the four methionine treatment groups. Milk production, body weight gain, and plasma concentrations of insulin-like growth factor-I, bovine somatotropin, insulin, glucose, nonesterified fatty acids, and urea were monitored over a 12-wk period. Supplementation with protected methionine led to increases in milk fat and protein contents of 2.4 and 1.8 g/kg of milk, respectively. Supplementation with protected lysine or methionine numerically increased protein yield comparable to values reported in the literature, but the treatment effects were not statistically significant. Efficiency of utilization of absorbed amino acids for milk protein synthesis and efficiency of utilization of metabolizable energy for milk production were not significantly altered in response to increased postruminal lysine and methionine flow, but a numerically increased efficiency of utilization of total amino acids was observed. No significant effect of lysine or methionine supplementation was observed on endocrine parameters nor on plasma metabolite concentrations. However, across treatment groups, high milk yield was correlated with low plasma insulin-like growth factor-I concentrations (r = -0.44) and partially with low plasma nonesterified fatty acids concentration and insulin levels (r = -0.26), while body weight gain was negatively correlated (r = -0.33) with elevated plasma bovine somatotropin concentrations.     

Stimulation of milk yield and feed intake by bovine placental lactogen in the dairy cow.

A 6 x 6 Latin square design was used to test the effects of recombinant bovine placental lactogen on milk yield, milk composition, feed intake, and blood hormone and metabolite levels in nonpregnant lactating cows. The six treatments (5, 10, 20, and 40 mg/d of placental lactogen, water as negative control, and 20 mg/d of bST as positive control) were administered by subcutaneous injection twice daily for 9 d. Blood samples were taken during the last 5 d of the treatment period. The three highest doses of placental lactogen increased milk yield, and there was a linear dose effect, although placental lactogen was less potent than bST. Milk concentrations of lactose, protein, and fat were not altered by any of the treatments. Dry matter intake was increased by two of the doses of placental lactogen, but not by bST. Blood urea N concentration was decreased in a dose-dependent manner by placental lactogen and was also decreased by bST. Similarly, serum insulin-like growth factor-I was increased in a dose-dependent manner by placental lactogen and was also increased by bST. Plasma concentrations of NEFA and glucose were increased by bST, but placental lactogen had little or no effect on either of these parameters. Thus, placental lactogen appears to act, in part, as a weak somatotropin agonist; however, it also appears to have specific activities, e.g., stimulating feed intake.     

Performance and behaviour of calves reared in groups or individually following an enhanced-growth feeding programme

Nineteen calves were reared in individual pens (IP), and twenty calves were grouped in four pens of five calves each (GP) to study the effects of grouping on behaviour and performance. All calves were on an enhanced-growth feeding programme and had unlimited access to starter. Total dry matter intake (DMI) body weight (BW), serum urea, non-esterified fatty acid (NEFA), cortisol, insulin, and glucose concentrations, and immune response to vaccination were measured. Behaviour patterns categorized as: non-nutritive oral behaviour, cross-sucking, inter-sucking, and self-grooming, were monitored 20 min following the morning and afternoon milk replacer consumption, and at the same times after weaning. There were no differences in final BW and starter DMI between treatments. The decrease of average daily gain (ADG) during the week following weaning was more pronounced in GP than in IP calves. Serum NEFA concentration increased at the beginning of the study in IP calves but serum urea concentrations were greater in GP than in IP calves the week after weaning. Self-grooming increased in both treatments throughout the study but GP calves increased non-nutritive oral behaviour and decreased cross-sucking and inter-sucking behaviours throughout the study. Rearing calves in groups following an enhanced-growth feeding programme did not increase starter intake. Furthermore, cross-sucking and inter-sucking behaviours in calves reared in groups did not seem to cause increased metabolic or immunological distress.     

Effects of additional milk replacer feeding on calf health, growth, and selected blood metabolites in calves

The objective of the experiment was to evaluate effects of increased milk replacer feeding on growth, intake, feed efficiency, and health parameters in stressed calves. Holstein bull calves (n = 120; approximately 3 to 8 d of age) were purchased from sale barns and dairy farms and housed in fiberglass hutches. In addition, wood shavings contaminated with coronavirus were mixed with clean shavings and added to each hutch before the start of the experiment. Calves were fed either a fixed amount (454 g/d) of a 20% crude protein (CP), 20% fat milk replacer to weaning at 28 d or a variable amount (454, 681, 908, and 454 g/d on d 0 to 7, 8 to 14, 15 to 31, and 32 to 41, respectively) of a milk replacer containing 28% CP and 17% fat without or with added dietary supplement containing bovine serum. Calves were also fed commercial calf starter and water ad libitum. Plasma IgG concentration in most calves on arrival at the facility was < 10 g/L. Intake, change in body weight, feed efficiency, morbidity and mortality, and selected plasma metabolites were determined. Body weight at 28 d, 56 d, daily body weight gain, intake of milk replacer, fecal scores, days with diarrhea, and days treated with antibiotics were increased with feeding variable amount of milk replacer over the 56-d study. Starter intake from d 1 to 56 was reduced from 919 to 717 g/d in calves fed fixed and variable amounts of milk replacer, respectively. Morbidity, measured as the number of days that calves had diarrhea, was increased by 53% when a variable amount of milk replacer was fed. Calves fed variable milk replacer were treated with antibiotics for 3.1 d compared with 1.9 d for calves fed 454 g of milk replacer/d. Concentrations of plasma glucose, urea N, and insulin-like growth factor-I were increased when calves were fed variable amount of milk replacer. Dietary supplement containing bovine serum had no effect on any parameter measured. There was no effect of milk replacer feeding on concentrations of nonesterified fatty acids, total protein, or growth hormone concentrations. Plasma tumor necrosis factor-α was highest in calves with the highest plasma IgG concentrations on the day of arrival and might be related to the calf's ability to identify pathogens in the environment. Under conditions of this study, calves fed variable amount of milk replacer and exposed to immunological challenge before weaning had greater BW gain, but also increased incidence of diarrhea that required added veterinary treatments.     

Effects of feeding milk replacer once versus twice daily on glucose metabolism in Holstein and Jersey calves

Eighteen Holstein (experiment 1) and 15 Jersey (experiment 2) heifer calves were fed milk replacer once or twice daily to determine effects of feeding frequency on weight gain, starter intake, and glucose metabolism. Body weights were measured weekly from birth to 8 wk. Blood samples were collected at wk 1 through 6 from all calves before and at 30, 60, 90, 120 and 180 min after the morning feeding. Plasma was analyzed for glucose, insulin, glucagon, and nonesterified fatty acids (NEFA). Urine was collected 90 min postfeeding to measure glucose concentration. Treatment did not affect mean starter intake or body weight. In experiments 1 and 2 mean plasma glucagon, glucose, NEFA, and insulin and urinary glucose concentrations were not affected by treatment. There was an interaction of sampling time and treatment for plasma insulin concentrations but not for glucose concentrations in both experiments. Following feeding, calves fed milk replacer once daily had higher insulin concentrations than those fed twice daily. There was an interaction of sampling time and treatment for plasma NEFA concentrations in Jersey calves only. Jersey calves fed milk replacer once daily had higher plasma NEFA concentrations before the morning milk replacer feeding. At wk 3 and 6, frequently sampled intravenous glucose tolerance tests were performed to assess glucose effectiveness, insulin sensitivity, and acute insulin response. In experiments 1 and 2 glucose effectiveness and insulin sensitivity were similar regardless of milk replacer feeding frequency. In Holstein and Jersey calves fed milk replacer twice daily, acute insulin response was greater than in calves fed once daily. However, insulin sensitivity decreased with age, while acute insulin response increased with age. These data suggest that feeding calves milk replacer once daily did not deleteriously affect performance or glucose metabolism regardless of breed.     

The effect of 2 liquid feeds and 2 sources of protein in starter on performance and blood metabolites in Holstein neonatal calves

The aim of present study was to investigate the effect of 2 liquid feeds and 2 protein sources in starter on the performance and blood metabolite responses of Holstein neonatal calves from birth to 6 wk of age. Calves (20 males and 20 females) based on sex were randomly assigned to 4 treatments in a 2 × 2 × 2 factorial arrangement, including soybean meal (SBM) and meat and bone meal (MB) with either fermented colostrum (or fresh milk. Although sex and liquid feed had no significant effect on feed intake, calves consumed more feed intake on the diet containing SBM (15 ± 0.2 kg) than MB (13 ± 0.2 kg) during the experimental period; also, weight gain was affected by both liquid feed and starter. Liquid feed and starter had significant effects on calf body size, including pin width, hip width, withers height, hip height, and stomach size, but no significant effects were observed on calf body size between the sexes. Plasma glucose concentration was not affected by sex, liquid feed, or starter. Plasma urea nitrogen concentration decreased in the first 3 wk and then started to increase during the last 3 wk, but it was only affected by starter and calves receiving SBM (10.18 mg/dL) had a higher concentration of plasma urea nitrogen than calves receiving MB (9.6 mg/dL) at the end of the experiment. Plasma growth hormone and insulin-like growth factor I concentrations decreased in all treatment groups from d 0 to the end of the study. No significant effects were observed on plasma growth hormone and insulin-like growth factor I concentrations between the 2 sexes, but they were significantly affected by both liquid feed and starter. Results of the present study provide useful information to apply to Holstein neonatal calves during the first 6 wk of life when liquid feed and 2 sources of protein in starter are considered.