Duodenal flow of digesta in preruminant calves fed clotting or nonclotting milk replacer

Four Holstein male calves each were fitted with a reentrant duodenal cannula and fed a low heat milk replacer with or without an oxalate-NaOH buffer known to prevent curd formation in the abomasum. Animals were used in a crossover design to study the effect of milk clotting on duodenal flow of DM, fat, protein, lactose, and Ca. Clotting affected the flow of DM, protein N, total N, and fat as shown by the more uniform gastric emptying of the clotting milk replacer compared with the nonclotting one. For both treatments, the flow rate of these components reached a peak 2 h after feeding. Clotting did not alter the flow rate of free amino N, lactose, and Ca. The cumulative flow of DM, lactose, and Ca was similar for the clotting and nonclotting milk replacers rising gradually during the first 4 h postfeeding and tending to plateau thereafter. The clotting milk replacer resulted in a more linear cumulative flow of fat, protein N, and total N than the nonclotting one. Proteolysis of milk protein in the abomasum was the same for the two milk replacers as indicated by the total flow of free amino N measured over 24 h. Data suggest that milk clotting modifies abomasal flow of milk constituents retained in the abomasal clot but does not alter the flow of constituents in the whey fraction.     

Influence of supplemental, dietary vitamin A on retinol-binding protein concentrations in the plasma of preruminant calves

Transport of retinol (vitamin A alcohol) from retinoid stores in the liver to target tissues is accomplished exclusively by a specific plasma protein, retinol-binding protein. Within individuals, retinol-binding protein concentrations in plasma are regulated and remain constant except in extremes of vitamin A nutriture or in disease. In the present study, retinol-binding protein concentrations in plasma from preruminant calves supplemented with 0, 1700 (i.e., current NRC requirement), 34,000, or 68,000 IU of vitamin A daily from birth to 27 d of age (n = 6/treatment) were quantified. Retinol-binding protein concentrations at birth averaged 21 microg/ml (n = 24) or approximately 50% of concentrations in dairy heifers and cows. Plasma retinol and retinol-binding protein concentrations were correlated positively, corroborating the role of vitamin A nutriture in the regulation of retinol-binding protein secretion from the liver. In this regard, dietary vitamin A influenced positively retinol and retinol-binding protein concentrations and, as a consequence, the degree of saturation of retinol-binding protein with retinol. At 27 d of age, calves fed > or = 34,000 IU of vitamin A had substantially higher retinol and retinol-binding protein concentrations than did calves fed < or = 1700 IU of vitamin A, indicating that dietary vitamin A effects positively vitamin A status. The data also suggest that the current NRC requirement may not be sufficient to assure vitamin A adequacy in preruminant calves. Percent saturation of retionol-binding protein with retinol in all calves was < 35%, much lower than anticipated and suggests that the retinol requirement of vitamin A-responsive tissues exceeded vitamin A availability.     

Plasma lipid concentrations in preruminant calves fed whole milk with whey protein isolate

The objective was to investigate the acute effects of retinol acetate added to whey protein isolate (WPI) on postprandial changes in plasma retinol (experiment 1) and the acute effects of milk fat added to WPI on triglyceride (TG), chylomicrons and very low density lipoprotein (VLDL), and fatty acid concentrations (experiment 2) in suckling calves at 1 and 6 wk of age. In experiment 1, 16 Holstein male calves were alloted to 2 equal groups. On the days of measurement, the calves were fed at 0900 h whole milk [4% of body weight (BW)] mixed with vitamin A acetate (500,000 IU) with or without WPI (0.04% of BW). At 1 wk of age, significantly higher postfeeding concentrations of plasma retinol were observed in the calves fed milk with WPI. At 6 wk of age, no differences in the plasma retinol concentrations were observed between 2 groups. On the days of measurement in experiment 2, 16 male calves were fed at 0900 h whole milk (4% of BW) with added milk fat prepared by centrifugation from whole milk (2% of BW) with or without WPI (0.04% of BW). The milk supplemented with fat was prepared on the day before the measurement. At 1 wk of age, significant higher postfeeding concentrations of plasma TG concentrations were obtained in the calves fed WPI than in the control calves, immediately after the meal or from 7 h later onward. Plasma chylomicrons and VLDL concentrations at 1 wk of age were significantly higher in the WPI-fed group than in the control group at 8 h postfeeding. In the calves with the WPI diet, plasma concentrations of myristic, palmitic, stearic, oleic, and linoleic acids at 1 wk of age were significantly higher than those in the control calves at 8 h after feeding. However, chylomicrons and VLDL, and fatty acid concentrations did not differ between the 2 groups after feeding at 6 wk of age. Results indicate that WPI increases plasma lipid concentration of preruminant calves only at 1 wk of age. These data are interpreted to indicate that WPI enhances mainly lipid uptake in the intestines of neonatal calves.     

Performance and visceral tissue growth and development of Holstein calves fed differing milk replacer allowances and starch concentrations in pelleted starter

The objectives of this study were to investigate how milk replacer (MR) allowance and differing concentrations of starch and neutral detergent fiber in starter alters visceral tissue and overall growth of the calf. Calves were randomly assigned to 1 of 4 dietary treatments (n = 12 per treatment) arranged in a 2 × 2 factorial based on daily MR allowance (MRA) and amount of starch in pelleted starter (SPS) as follows: 0.691 kg of MR/d [dry matter (DM) basis] with starter containing low or high starch (12.0% and 35.6% starch, respectively) and 1.382 kg of MR/day (DM) with starter containing low or high starch. All calves were housed in individual pens with straw bedding until wk 5 when bedding was covered to minimize intake. Calves were fed MR twice daily (0700 and 1700 h) containing 24.5% crude protein (DM) and 19.8% fat (DM), and had access to pelleted starter (increased by 50 g/d if there were no refusals before weaning, and then 200 g/d during and after weaning) and water starting on d 1. Calves arrived between 1 and 3 d of age and were enrolled into an 8-wk study, with calves undergoing step-down weaning during wk 7. Intakes were measured daily, and body weight (BW) and blood samples were recorded and collected weekly. Calves were dissected in wk 8 for visceral tissue measurements. Overall, there was increased MR DM intake for the high- (0.90 ± 0.01 kg/d; ± SE) compared with the low-MRA (0.54 ± 0.01 kg/d) calves, whereas starter DM intake increased in low- (0.47 ± 0.05 kg/d) compared with high-MRA (0.20 ± 0.05 kg/d) calves, which was driven by increases in wk 6, 7, and 8. High-MRA calves had increased BW during wk 2, 3, 4, 5, 6, and 7. The difference in BW disappeared by wk 8, with overall average daily gain having a tendency to be increased in high (0.57 ± 0.04 kg/d) compared with low-MRA (0.50 ± 0.04 kg/d) calves, whereas average daily gain was increased in high-MRA calves during wk 2 and 3 and increased in low-MRA calves during wk 7 and 8. There were several differences throughout visceral tissue measurements, but most notably, an increase in rumen mass (i.e., full, empty, and digesta weights) in low- compared with high-MRA calves, as well as in low- compared with high-SPS calves was observed. The length, width, and 2-dimensional area of rumen papillae were also increased in low- (area: 0.88 ± 0.03 mm²) compared with high-MRA (0.46 ± 0.03 mm²) calves. The majority of differences were attributed to increased MR allowance, which contributed to reduced pelleted starter intake by more than 50% and reduced rumen development, whereas differences in starch intake from the completely pelleted starter had minimal effects on overall growth and tissue measurements.     

Digestibility measured by fecal and ileal collection in preruminant calves fed a clotting or a nonclotting milk replacer

Eight Holstein male calves, each fitted with an ileal reentrant cannula at 7 to 10 d of age, were fed a milk replacer based on low heat skim milk powder with or without an oxalate-NaOH buffer known to prevent curd formation in the abomasum. The calves were used to study the effects of milk clotting on digesta flow at the ileum and apparent digestibility measured by fecal and ileal collection. Patterns of ileal flow of total digesta, DM, N, and fat were similar for the clotting and the nonclotting milk replacers. The apparent digestibility of DM and N was higher when measured by fecal than ileal collection for both milk replacers. Digestibility of DM was higher for the clotting than for the nonclotting milk replacer when measured by ileal collection. Clotting did not affect N digestibility measured by either fecal or ileal collection. The concentration of amino acids differed generally in the ileal digesta compared with concentration in feces. In the ileal digesta, some amino acids showed lower concentrations in the clotting milk replacer fed calves compared with those fed the nonclotting milk replacer. The coefficients of digestibility of each amino acid were similar when measured by either fecal or ileal collection. Clotting had no effect on amino acid digestibility measured by both fecal and ileal collection. The data suggest that fecal collection might indicate higher digestibility as compared with ileal collection and that the absence of milk replacer clotting does not affect ileal flow and digestibility of milk replacer N and fat.     

Abomasal pH, nutrient digestibility, and growth of Holstein bull calves fed acidified milk replacer

Our objective was to compare nutrient digestion and utilization, amount and pattern of intake, and pH profile over time of abomasal contents in calves offered acidified milk replacer ad libitum or regular (sweet) milk replacer twice daily at 10% of body weight per day. Ten Holstein bull calves were fed replacers reconstituted to 13% dry matter for 4 wk. Daily milk replacer and water consumption and weekly body weight were recorded. Other variables were measured during the 2nd and 4th wk. Calves offered acidified replacer consumed more dry matter and gained more body weight than did calves fed sweet replacer; however, there was no difference in feed conversion ratio. Apparent digestibility of dry matter, ether extract, nitrogen, and retention of absorbed nitrogen were not affected by treatment. Acidified milk replacer offered ad libitum lowered the pH of abomasal contents and feces compared to regular replacer offered at 10% of body weight per day. Feeding patterns of calves offered acidified replacer ad libitum were variable. No adverse effects of feeding acidified milk replacer were noted.     

Composition of growth of Holstein calves fed milk replacer from birth to 105-kilogram body weight

Sixty calves were assigned to a comparative slaughter study to determine the changes in composition of milk replacer-fed Holstein bull calves from birth to 105-kg body weight (BW). Six calves were slaughtered on day of birth and served as a baseline for comparison of compositional changes. Fifty-four calves were assigned to one of three treatments (18 calves per treatment). Calves were fed milk replacer containing 30% crude protein (CP) and 20% fat. Target growth rates for treatments 1, 2, and 3 were 500, 950, and 1400 g/d, respectively. Six calves from each treatment were slaughtered and analyzed for energy, nitrogen, ether extract, and ash when they reached 65, 85 and 105 kg of BW. Actual daily gains from birth to slaughter were 560, 973, and 1100 g, and net deposition of CP and fat were 140 and 44, 204 and 154, and 247 and 161 g/d for treatments 1, 2, and 3, respectively. Results were used to develop equations to predict retained energy [retained energy = (empty BW(0.223)) x (empty BW gain(1.32))], and retained protein, [retained protein = (184 x empty BW gain (kilograms/d)) + (17.2 x (retained energy)/empty BW gain] where retained energy is in Mcal/d, retained protein is in g/d, and empty BW and gain are in kilograms. The composition of gain observed was compared to predictions from the 1989 Dairy NRC and 1996 Beef NRC equations and demonstrated the equations do not represent the composition of gain in calves of this weight.     

Passive transfer of immunoglobulin G and preweaning health in Holstein calves fed a commercial colostrum replacer

The objective of this study was to describe passive transfer of IgG and preweaning health in newborn calves fed a commercially available plasma-derived colostrum replacement (CR) product or maternal colostrum (MC). Twelve commercial Holstein dairy farms enrolled singleton newborn heifer calves to be fed fresh MC (n = 239 calves) or one dose of CR containing 125 g of Ig (n = 218 calves) as the first colostrum feeding. For 7 of these farms that routinely provided a second feeding of 1.9 L of MC to their calves 8 to 12 h after the first colostrum feeding, calves assigned to the CR treatment group were offered a second feeding consisting of 1.9 L of commercial milk replacer supplemented with one dose of a commercially available plasma-derived colostrum supplement, containing 45 g of Ig per dose, 8 to 12 h after the first colostrum feeding. A blood sample was collected from all calves between 1 to 8 d of age for serum IgG and total protein (TP) determination, and records of all treatment and mortality events were collected until weaning. Serum IgG and TP concentrations were significantly higher in calves fed MC (IgG = 14.8 ± 7.0 mg/mL; TP = 5.5 ± 0.7 g/dL) compared with calves fed CR (IgG = 5.8 ± 3.2 mg/mL; TP = 4.6 ± 0.5 g/dL). The proportion of calves with failure of passive transfer (serum IgG <10.0 mg/mL) was 28.0 and 93.1% in the MC and CR treatment groups, respectively. Though a trend was present, the proportion of calves treated for illness was not statistically different for calves fed MC (51.9%) vs. CR (59.6%). Total number of days treated per calf (MC = 1.7; CR = 2.0), treatment costs per calf (MC = $10.84; CR = $11.88), and proportion of calves dying (MC = 10.0%; CR = 12.4%) was not different between the 2 colostrum treatment groups. The mean serum total protein concentration predictive of successful passive transfer (serum IgG = 10 mg/mL) was 5.0 g/dL in calves fed MC or CR. Long-term follow-up of these calves (to maturity) is ongoing to describe the effects of feeding CR on longevity, productivity, risk for Johne's disease, and economics.     

Health and performance of calves with forestomach-bypass fed milk replacer.

Ten male Holstein calves were placed in groups of two calves each on similarity of age. On calf in each group was subjected to forestomach-bypass surgery at about 1 mo of age. Fortified commercial milk replacer with added minerals and vitamins was fed as the sole diet. The calves were housed indoors on slatted platforms. Weight gain was determined biweekly. Feed intake was determined daily. Necropsies were performed upon termination of the study. Recurrent ruminal bloat, fever, and anorexia of varying degrees and combinations occurred in four of the calves with forestomach bypass. Two of these calves showed slow weight gain. One of the four calves died following acute bloat while the other three calves were sacrificed following repeated episodes of bloat. The time of termination varied between 3 and 10 mo. One calf with forestomach bypass and all control calves appeared healthy throughout the experiment. Necropsies indicated that the ruminal bloat, seen in most of the forestomach-bypass calves, could be attributed to the back-flow of ingesta via the omasal-abomasal orifice. This ingesta appeared to produce gas which became trapped in the bypassed rumen.     

An oxalate-sodium hydroxide buffer to study the role of milk replacer coagulation in preruminant calves

An oxalate-NaOH buffer, which prevents coagulation in the abomasum of young calves, was added to a nonclotting milk replacer based on high heat skim milk powder, to investigate effects of this buffer on digestibility and metabolism of dietary components. Twelve Holstein male calves were allotted at random in two groups of six animals each and fed the experimental milk replacers from 3 to 17 d of age. Digestibility of dry matter, protein, and fat was similar for both control and buffered milk replacers. Concentrations of plasma glucose, triglycerides, alpha-amino nitrogen, and urea were the same in animals receiving buffer treated milk replacer and control diets. The data suggests that this oxalate-NaOH buffer would be suitable to prevent milk clotting in studies dealing with the importance of coagulation in digestion and metabolism in preruminant calves.     

Performance, health, and postweaning growth on calves fed cold, acidified milk replacer ad libitum

Holstein calves were assigned to one of three regimens from d 4 to 35 of age, then abruptly weaned (program 1): A) conventional, all-milk protein milk replacer fed individually twice daily; B) ad libitum feeding of cold, acidified milk replacer to calves housed and fed individually in pens, and C) same as B, except calves were housed and fed in group pens. From d 36 of age to 136 kg of body weight calves were in group pens by treatment. Program 2 utilized the same treatments; however, acidified milk replacer calves were gradually weaned starting d 22 of age. For program 1, calves fed acidified milk replacer for ad libitum intake consumed more dry matter from liquid and less from grain than those fed conventionally. Calves fed acidified milk replacer showed improved gains of 8.7 and 8.4 kg up to d 35 of age. For program 2, dry matter intake from liquid was higher, and grain was lower for calves fed acidified milk replacer; however, differences were not as large as in program 1. Body weight gains were 1.1 and 2.8 kg higher for calves fed acidified milk replacer through d 35 of age. No mortality occurred with either program during preweaning. In both programs, fecal consistency was more fluid for calves fed acidified milk replacer; however, days calves were treated were less. Regardless of preweaning program, calves on all treatments reached 136 kg of body weight in approximately the same number of days.     

Growth and health of Holstein calves fed milk replacers supplemented with antibiotics or Enteroguard

Forty-five Holstein calves were fed milk replacers containing either antibiotics [MRA (oxytetracycline at 138 mg/kg and neomycin at 276 mg/kg), n = 22)] or Enteroguard [MRE, a blend of fructooligosaccharides, allicin, and gut-active microbes at (129 mg/kg, n = 23)] from birth to 5 wk of age to compare effects on average daily gain and on incidence of scours. Performance was evaluated by measuring weight gain, feed efficiency, and fecal scores. The overall body weight gains and severity of scours were not different between treatments, nor were there differences in starter intake or mean body weight gain. During wk 2, the average gain of calves fed MRA was less than that of calves fed MRE (0.07 vs. 0.09 kg/d, P = 0.09), and greater during wk 5 (0.62 vs. 0.51 kg/d, P < 0.01); however, total gain for calves fed MRE was not different from calves fed MRA. Likewise, average feed efficiencies (gain/dry matter intake) were not different. Severity of scours, as measured by fecal scores, and concentrations of serum proteins, an indirect measure of immunoglobulins, were similar for calves fed MRA and MRE. The results suggest that antibiotics in milk replacers can be replaced with compounds such as fructooligosaccharides, probiotics, and allicin to obtain similar calf performance.     

Soy protein concentrate and heated soy flours as protein sources in milk replacer for preruminant calves

Thirty-two male calves (8/treatment) in Trial 1 and 41 male and female calves (10 or 11/treatment) in Trial 2 were fed milk replacers containing 100% of the total protein from milk sources or 25% from milk and 75% from a soy product: soy protein concentrate; commercial heated (fully cooked) soy flour; or experimental soy flour for 6 wk. The experimental flour received moist heat sufficient to reduce trypsin inhibitor to 1 unit/mg. Calf performance improved with age on all diets. Growth, protein and dry matter digestibility, nitrogen retention, and morphology of the intestinal mucosa of calves on the all milk-protein diet were superior to those of calves on diets containing a soy product. All soy-fed groups had a humoral but no cell-mediated immune reaction to soy proteins. Soy protein concentrate and the experimental heated soy flour were superior to the commercial heated soy flour as protein sources for milk replacer.     

Supplementation of lysolecithin in milk replacer for Holstein dairy calves: Effects on growth performance,health, and metabolites

Lysolecithin is an antiinflammatory emulsifier associated with improved apparent digestibility of total dietary fat and improved feed efficiency in dairy cattle. However, it is unknown if lysolecithin (LYSO) improves performance in calves. Moreover, since many conventional milk replacers use vegetable-sourced fat (e.g., palm oil), nutrient absorption and fecal score may be affected in neonatal calves. Thus, the objective of this study was to evaluate the effects of LYSO supplemented in milk replacer on performance, metabolites, and gut health of preweaned dairy calves. Holstein calves (n = 32) with adequate passive transfer were assigned in pairs (16 blocks) balanced by birth weight, date of birth, and sex at 1 d of age to randomly receive either LYSO (mixed in 2 milk replacer feedings at a rate of 4 g/d Lysoforte, Kemin Industries Inc., Des Moines, IA) or a milk replacer control (nothing added). Both treatments were fed 6 L/d milk replacer [22.5% crude protein, 16.2% crude fat (vegetable oil fat source) on a dry matter basis with 14% solids] by bucket in 2 daily feedings for 56 d. Calves were individually housed in wooden hutches and offered a commercial calf starter (24.6% crude protein and 13.9% neutral detergent fiber) and water by bucket ad libitum. Feed refusals and calf health was assessed daily. Weights and blood metabolites (glucose, total serum protein, albumin, creatinine, triglycerides, and cholesterol) were sampled weekly, and calves completed the study before weaning at 56 d of age. The effects of LYSO on calf average daily gain, feed efficiency, and blood metabolites were evaluated using a linear mixed model with time as a repeated measure, calf as the subject, and block as a random effect in SAS (SAS Institute Inc., Cary, NC). The effect of LYSO to improve the odds of abnormal fecal score was evaluated using a logistic model. Supplementation of LYSO increased average daily gain (control 0.28 ± 0.03 kg; LYSO 0.37 ± 0.03 kg; least squares means ± standard error of the mean) and increased feed efficiency (gain-to-feed; control 0.25 ± 0.03; LYSO 0.32 ± 0.03). Similarly, LYSO calves had a higher final body weight at d 56 (control 52.11 ± 2.33 kg; LYSO 56.73 ± 2.33 kg). Interestingly, total dry matter intake was not associated with LYSO despite improved average daily gain (total dry matter intake control 1,088.7 ± 27.62 g; total dry matter intake LYSO 1,124.8 ± 27.62 g). Blood glucose, albumin, creatinine, triglycerides, and cholesterol were not associated with LYSO. Indeed, only total serum protein had a significant interaction with LYSO and age at wk 5 and 6. Moreover, control calves had a 13.57 (95% confidence interval: 9.25–19.90) times greater odds of having an abnormal fecal score on any given day during the diarrhea risk period from d 1 to 28. The inclusion of LYSO as an additive in milk replacer in a dose of 4 g/d may improve performance, and calf fecal score, preweaning. Further research should investigate the mechanisms behind the effects of LYSO on fat digestibility in calves fed 6 L/d of milk replacer with vegetable-sourced fat.     

Immune responses of Holstein and Jersey calves during the preweaning and immediate postweaned periods when fed varying planes of milk replacer

The objective was to determine the influence of breed and planes of preweaned milk replacer (MR) nutrition on the immune responses of pre- and postweaned dairy calves. Forty-two bull calves (n = 20 Holstein and n = 22 Jersey, 2 ± 1 d old) were studied. Holstein and Jersey calves came from separate dairies. Calves were fed either a higher plane of MR nutrition or a lower plane of MR nutrition. Holstein and Jersey calves on the lower planes of MR nutrition were fed 454 g (as fed)/d of a 20% crude protein (CP)/20% fat MR. Holstein calves on the higher plane of MR nutrition were fed 810 and 1,180 g (as fed)/d of a 28% CP/20% fat MR for wk 1 and wk 2 to 6, respectively. Jersey calves on the higher plane of nutrition were fed 568 and 680 g (as fed)/d of a 28% CP/25% fat MR for wk 1 and wk 2 to 6, respectively. On d 4, 42, and 77, peripheral blood was collected for ex vivo immunological analyses, and on d 7 all calves were challenged subcutaneously with commercially available lipopolysaccharide (LPS) from Escherichia coli (4 µg/kg of body weight); clinical and biochemical responses were evaluated at 0, 1, 2, 3, 4, 5, 6, 9, 12, 24, and 72 h. We observed a breed difference in total serum protein, wherein Jersey calves had higher concentrations than Holsteins. Holsteins and calves fed the higher plane of MR nutrition had greater glucose concentrations following the LPS challenge. With the exception of plasma haptoglobin concentrations at 24 h postchallenge, we observed no treatment × time interactions following the LPS challenge. Calves fed higher planes of MR nutrition had greater plasma haptoglobin concentrations 24 h following the LPS challenge. Isolated mononuclear cells from Holstein calves secreted more tumor necrosis factor-α than did cells from Jersey calves when stimulated ex vivo with LPS on d 77. In addition, when whole blood was incubated with a live enteropathogenic E. coli culture, blood from Holsteins had a greater killing capacity than did whole blood from Jerseys. Calves fed higher planes of MR nutrition had greater neutrophil oxidative burst intensities at d 77 when cocultured with E. coli for 10 min. In addition, Jersey calves fed the lower plane of MR nutrition had reduced neutrophil oxidative burst capacity and whole blood E. coli killing at d 77 compared with the other groups. These data indicate that Jersey calves had lower measures of many innate immune variables despite likely having greater passive transfer, as evidenced by greater total serum protein concentrations. Furthermore, feeding a higher plane of MR nutrition to Jersey calves improved some postweaning innate immune responses.     

Diurnal pattern of plasma cortisol in preruminant calves fasted or fed different milk proteins

The objective was to clarify the possible role of meals in the nycthemeral evolution of cortisol and the influence of intestine absorption kinetic of nutrients. Preruminant calves were fed two kinds of diets, a conventional curdled milk and a milk that did not curdle in the abomasum. These calves were also fasted for 24 h. Blood was sampled regularly during a 24-h period under three different dietary situations. Daily mean plasma cortisol was lower in calves fed uncurdled milk than in those fed curdled milk or fasted. Diurnal changes in plasma cortisol were characterized in fed animals by sharp postprandial decreases; the morning meal induced a more intense decrease than the evening one, which was followed by a regular increase of cortisol concentrations overnight. Between meals, several peak values were detected at the same times in all animals with both kinds of meals. The postprandial decreases did not occur in fasted animals, and peak values could not be linked to those occurring when animals were fed. Thus, cortisol secretion by adrenals seemed to be influenced by nutrient intestinal absorption, whereas during fasting different mechanisms were involved.     

Tolerance of the preruminant calf for selenium in milk replacer

Calves were fed skim milk powder-based milk replacer containing either .2, 1, 3, 5, or 10 ppm selenium (added as sodium selenate) in the dry matter from 3 to 45 d of age to estimate the lowest amount of dietary selenium that would reduce calf performance and feed utilization. Only at the highest selenium (10 ppm) did calves show reduced average daily gain and feed efficiency and lower blood packed cell volume. Apparent digestibility of dry matter, nitrogen, and lipid, and plasma creatine phosphokinase activity were not affected by any of the selenium intakes. In general, selenium in blood, bile, duodenal mucosa, liver, kidney, and muscle reflected selenium intakes with liver and kidney reaching the highest selenium concentrations. Postmortem examinations of calves revealed no gross abnormalities for any of the selenium treatments. The preruminant calf is very tolerant of high inorganic selenium concentrations in skim milk powder-based milk replacer.     

Modulation of fat-soluble vitamin concentrations and blood mononuclear leukocyte populations in milk replacer-fed calves by dietary vitamin A and beta-carotene

Dairy calves (n = 18), separated from dams at birth, were fed 1 L of pooled-colostrum. For the remaining 7 wk of the study, they were fed one of three diets consisting of either a custom-formulated milk replacer without vitamin A (controls), or supplemented with retinyl palmitate (equivalent to 32,000 IU of vitamin A/d) or with beta-carotene (equivalent to 20,000 IU of vitamin A/d). Plasma retinol, beta-carotene, and RRR-alpha-tocopherol concentrations were lowest at birth, and increased substantially from birth to 1 wk postpartum in all groups, a probable consequence of ingestion of colostrum. From 1 to 7 wk of age, retinol concentrations were greatest in retinyl palmitate-supplemented calves, intermediate in beta-carotene-supplemented calves and lowest in control calves. At 2, 3, 5, 6, and 7 wk, RRR-alpha-tocopherol concentrations were lower in retinyl palmitate-supplemented calves than in control calves. A negative correlation between plasma retinol and vitamin E concentrations existed from wk 2 to 7, suggesting vitamin A influences the absorption and distribution of RRR-alpha-tocopherol. Supplemental retinyl palmitate, but not beta-carotene, was associated with a reduction in the percentage of blood mononuclear leukocytes expressing CD2, CD4, and CD8-T cell antigens and interleukin-2 receptors. By wk 7, leukocyte populations from retinyl palmitate-supplemented calves were more similar to those from adult cattle than those from control calves, suggesting that supplemental vitamin A, as retinyl palmitate, affects the maturation of the neonatal immune system. Differences in the composition of blood mononuclear leukocyte populations may represent changes in immune competency.     

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.     

Growth characteristics of calves fed an intensified milk replacer regimen with additional lactoferrin

The objective of this study was to evaluate the effect of lactoferrin addition to milk replacer varying in crude protein (CP) on dry matter intake, growth, and days medicated. Thirty-four Holstein heifer calves were assigned to 4 treatments in a 2 × 2 factorial arrangement of treatments in a randomized complete block design. Treatments were as follows: 562 g daily of a nonmedicated conventional milk replacer (20% CP:20% fat) feeding regimen with or without 1 g of supplemental bovine lactoferrin (n = 9 for both treatments) or a nonmedicated intensified milk replacer feeding regimen (28% CP:20% fat) fed on a metabolizable energy basis (0.2 Mcal/kg BW^0.75) from d 2 to 9, and at 0.27 Mcal/kg BW^0.75 from d 10 to 42 with or without 1g supplemental bovine lactoferrin (n = 8 for both treatments). Calves were fed pelleted starter (25% CP) in 227.5-g increments beginning on d 2 and had free access to water. Calves remained on the study for 14 d postweaning. Dry matter intake was determined daily. Growth measurements were taken weekly. Blood samples were taken twice weekly for determination of blood urea N. On d 10 of life, calves were subjected to a xylose challenge. Calves on conventional treatments ate more starter preweaning, during weaning, and postweaning. Preweaning, intensively fed calves had higher dry matter intakes. Weights of intensified-fed calves were greater at weaning. Intensified milk replacer-fed calves had greater average daily gain preweaning and overall and higher gain:feed ratios preweaning, but conventionally fed calves had higher gain:feed ratios during weaning. Intensified milk replacer-fed calves had greater hip heights during weaning and postweaning and greater heart girths preweaning, weaning, and postweaning. Days medicated were greater preweaning and overall for intensified-fed calves. There were no differences among treatments for xylose absorption. Calves on conventional treatments had increased blood urea nitrogen concentrations preweaning. There were no effects of lactoferrin on any experimental variable. Intensified milk replacer-fed calves consumed less starter but had higher average daily gains overall and larger frames and greater BW than conventionally fed calves. An intensified milk replacer feeding regimen promotes faster growth during the preweaning period when compared with calves fed conventional treatments, but supplemental bovine lactoferrin was not beneficial under these experimental conditions.