Macronutrient profile in milk replacer or a whole milk powder modulates growth performance, feeding behavior, and blood metabolites in ad libitum-fed calves

Performance, nutrient digestibilities, and metabolic profiles of Holstein calves fed whole milk or milk replacer at 2 feeding levels

The macronutrient composition of common milk replacers (MR) largely differs from bovine whole milk (WM). These differences are more nutritionally relevant when calves receive higher milk allowances. Therefore, the present study compared fresh WM with a conventional MR fed at 2 level of feeding allowances evaluating growth performance, apparent total-tract nutrient digestibilities, N balance, and serum metabolite profiles in calves. Newborn male Holstein calves (n = 48; 1.96 ± 0.99 d of age; 45.0 ± 4.37 kg BW) were blocked by arrival date and age. Calves in each block were then randomly assigned to the 4 treatments (n = 12 per treatment): MR or WM at a high (9.0 L/d) or low feeding allowance (4.5 L/d) fed 3 times daily. Calves were weaned between wk 6 and 10 following the introduction of the starter feed in wk 6. The study ended 13 wk after the arrival at the facility. Blood and body weights were collected on arrival, and weekly thereafter. Total 24h-collection periods of feces and urine was performed at wk 2, 4, 5, 7, 9, 11, and 13. Remarkably, no interactions were observed between liquid feed and level of supply. Calves fed MR had higher ADG during the preweaning phase than to calves fed WM. However, calves fed WM had an increased growth rate postweaning, resulting in no difference in BW at the end of the study. Calves fed WM had a higher apparent crude fat digestibility during the weaning period. Metabolic N efficiency, expressed as N balance relative to digestible N supply, was higher during the preweaning phase, but tended to be lower during the postweaning phase for calves fed MR as compared with calves fed WM. In the preweaning period, serum glucose, BHB, nonesterified fatty acids (NEFA), total protein (TP), urea, albumin, globulin, triglyceride (TG), and cholesterol were influenced by liquid feed source. Carryover effects of milk source on TG and TP were observed during the postweaning period. As expected, calves fed a high milk allowance showed better ADG at preweaning and were consistently heavier throughout the study than calves fed a low milk allowance. Feeding a high milk allowance did not negatively affect nutrient digestibility during the postweaning phase. In the preweaning phase, milk allowance affected glucose and cholesterol metabolism, whereas TG, TP, albumin, and NEFA concentrations were affected during the postweaning period. From a single oral dose of indigestible markers (Cr-EDTA, lactulose, and d-mannitol), calves fed a high milk allowance showed greater urinary recovery of all markers after 6 h of collection, but not after 24 h. Calves fed a high milk allowance had a higher proportion of days with lower fecal scores during the preweaning phase. In conclusion, the serum metabolite profiles of calves throughout the study were highly influenced by milk source. Higher milk allowance increased growth performance and had no adverse effects on starter feed intake or nutrient digestibility in the postweaning phase. The multiple effects described for milk source and level of supply were overall independent, presenting no relevant interactions.

Nutritional value of black soldier fly larvae oil in calf milk replacers

Sustainable alternatives to high-environmental-input feed ingredients are important to reducing the environmental impact of animal agriculture. Protein and oil extracted from cultivation of black soldier fly (Hermetia illucens) larvae (BSFL) on waste feedstocks such as manure, food waste, and plant residues could be a suitable source of nutrients. The oil from BFSL contains large amounts of saturated fatty acids, particularly lauric acid, and may be a more sustainable alternative to palm and coconut oils that are currently used in calf milk replacers in many parts of the world. The objective of this study was to evaluate animal performance in neonatal calves fed calf milk replacers (CMR) containing oil from BSFL. Holstein heifer calves (n = 100) were assigned randomly at birth to receive one of 4 experimental CMR containing 24% CP and 18% fat from a blend of 80/20 palm/coconut oil (B0), 80/20 palm/BSFL oil (B20), 70/30 palm/BSFL oil (B30), or 60/40 palm/BSFL oil (B40). Calves were fed up to 900 g/d of CMR powder reconstituted to 15% solids daily to d 55, then 600 g/d to d 63 and 300 g/d to the end of the trial at d 70. Commercial calf starter, wheat straw, and water were available for ad libitum consumption. Intake, growth, fecal scores, and feed efficiency were monitored and reported weekly. There were no effects of experimental treatments on growth or feed efficiency. Consumption of CMR during the first 2 wk of the study was lower when calves were fed B20 (wk 1 and 2) or B30 (wk 2). Calves were generally healthy and there were no indications of feed refusal or maldigestion. Probability of a non-normal fecal event (fecal score >0) was lower when calves were fed B20 during the first 3 wk of the study. Oil from BSFL may be an attractive alternative to palm and coconut oil in CMR.

Pasteurized waste milk vs. milk replacer at the same crude protein:metabolizable energy ratio with different energy sources (fat vs. lactose) to pre-weaning Holstein calves: Effects on growth performance, feeding behavior, and health

The improved growth performance of calves at weaning results from an effective pre-weaning feeding strategy. The type and pasteurization process of liquid feed are among the most variable feeding practices affecting calves' growth and health. In previous studies that compared waste milk (WM) vs. milk replacer (MR), little consideration has been given to the variations in chemical composition and feeding behavior between them, and there has been a lack of justification for the crude protein: metabolizable energy (CP:ME) ratio adopted. Hence, this study aimed to evaluate the effects of feeding pasteurized WM or MR differing in energy source (fat vs. lactose, respectively) with similar CP:ME ratio on intake, growth, feeding behavior, and health of newborn Holstein calves. Thirty-two male calves (4-d-old; 40.0 ± 0.58 kg BW) were assigned to the trial and randomly allocated to each liquid feed diet (WM or MR). Calves were housed in individual pens with free access to starter feed and fresh water. Calves were weaned on d 61 and assessed until d 101 as the postweaning period. WM-fed calves had greater total nutrient intake (DM, CP, EE, and ME), weight gain, final BW, skeletal growth parameters, and feed efficiency (d 30). Calves WM-fed sorted less against particles retained on the 2.36-mm sieve but more against particles retained on the sieve of 0.6 mm. In WM-fed calves, the sorting index decreased for feedstuff retaining on the bottom pan compared with MR-fed calves. Irrespective of the type of the liquid feed, all calves sorted for particles retaining on the sieve of 4.75 mm and the bottom pan, and against the particles that were retained on the sieves of 2.36- (MR-fed calves only), 1.18- and 0.6-mm. Starter feed nutrient intake and particle size intake from the sieves of 4.75-, 2.36-, and 1.18-mm increased in WM- vs. MR-fed calves. Eating rate and meal size but not meal frequency and length were greater in WM-fed calves, leading to higher pre- and post-weaning starter feed intake. Calves WM-fed spent less time eating and standing but more time ruminating and lying than MR-fed calves. Calves WM-fed had a lower likelihood of having elevated general appearance (score ≥2; hazard ratio = 2.79), diarrhea (score ≥3; hazard ratio = 1.35), and pneumonia (hazard ratio = 4.77). Calves WM-fed experienced shorter days with elevated general appearance, diarrhea, and pneumonia. Overall, feeding WM led to increased starter feed intake by boosting the eating rate and meal size, promoting greater growth than MR. Additionally, compared with MR, WM feeding increased time spent ruminating and lying and reduced susceptibility to diarrhea and pneumonia.

Core microbe Bifidobacterium in the hindgut of calves improves the growth phenotype of young hosts by regulating microbial functions and host metabolism

BACKGROUND

The growth and health of young ruminants are regulated by their gut microbiome, which can have lifelong consequences. Compared with subjective grouping, phenotypic clustering might be a more comprehensive approach to revealing the relationship between calf growth state and core gut microbes. However, the identification of beneficial gut bacteria and its internal mechanisms of shaping host phenotype differentiation remains unclear.

RESULTS

In this study, calves were divided into two clusters, cluster1 and cluster2, based on 29 phenotypic indicators using cluster analysis. Calves in cluster2 showed better growth performance, including higher body weight (BW), average daily gain (ADG), and dry matter intake (DMI), as well as better serum indicators with a high level of total superoxide dismutase (T-SOD), interleukin-6 (IL-6), and insulin-like growth factor-1 (IGF-1) compared to those in cluster1. Multi-omics was used to detect microbial features among calves in different phenotypic clusters. Distinct differences were observed between the two clustered gut microbiomes, including microbial diversity and composition. The close relationships between growth performance, blood metabolites, and microbiome were also confirmed. In cluster2, Bifidobacterium members were the dominant contributors to microbial metabolic functions with a higher abundance. Furthermore, pathways involved in carbohydrate degradation, glycolysis, and biosynthesis of propionate and proteins were active, while methane production was inhibited. In addition, the diversity and richness of hindgut resistome in cluster2 were lower than those in cluster1. The isolation and culture of Bifidobacterium strain, as well as the mice experiment, indicated that B. longum 1109 from calf feces in cluster2 could promote the growth of young hosts, enhance their blood immunity and antioxidation, and improve the development of hindgut.

CONCLUSIONS

In summary, cluster analysis has proved to be a feasible and reliable approach for identifying phenotypic subgroups of calves, prompting further exploration of host-microbiome interactions. Bifidobacterium as a core microbe in the hindgut of calves may play a crucial probiotic role in host phenotypic differentiation. This study enhances our comprehension of how gut core microbe shapes the host phenotype and provides new insights into the manipulation of beneficial gut colonizers to improve the growth performance and productivity of young ruminants. Video Abstract.

A Framework for Comprehensive Dairy Calf Health Investigations

The objective of this narrative review is to provide a systematic framework for veterinarians to investigate dairy calf health, focusing on critical control points and key performance indicators (KPIs) to address morbidity and mortality challenges in preweaned calves. Recommendations target prenatal maternal nutrition, heat stress abatement, and optimal calving management to minimize risks associated with perinatal mortality and preweaning morbidity. Further, comprehensive colostrum management is discussed to ensure excellent transfer of passive immunity, which includes prompt collection and feeding within two hours of birth at a volume of 8.5-10% of calf body weight. Nutritional guidance emphasizes the importance of transition milk and feeding higher planes of nutrition to support immunity, with recommendations that milk total solids exceed 10% to meet energy needs. Environmental management recommendations include a minimum of 3.3 m2 of space per calf, the use of low-dust bedding, and air quality controls to reduce respiratory disease. Lastly, regular health data collection and KPI monitoring, such as average daily gain and morbidity rates, are essential for data-driven improvements. By implementing these evidence-based recommendations, veterinarians can support dairy farmers in reducing calf morbidity and mortality, ultimately enhancing calf welfare and lifetime productivity.

Temperature preferences of dairy calves for heated calf hutches during winter in temperate climate

Newborn calves face challenges adapting from the warm uterine environment to cold ambient temperatures, often experiencing cold stress. The objective of this study was to assess the preferred inside hutch temperature of dairy calves in their first week after birth during Central European winter and to compare lying behavior in heated and non-heated hutches. Sixteen matched pairs of dairy calves (2.6 ± 1.3 d old) were enrolled in 7d replicates with a preference and a control phase. During preference phase the calf could choose between 4 different hutches with access to a shared paddock. Inside the hutches either 0, 1, 2 or 3 heat lamps (HL0, HL1, HL2, HL3) were switched on. The control calf was kept in a non-heated hutch with an enclosed paddock. Calves were observed for 3 to 4 d, then switched from preference to control phase (or vice versa) and observed again for 3 to 4 d. Location of calves was documented once per minute by a time-lapse camera. Lying times and lying bouts were monitored by a 3D accelerometer data logger attached to the calves' metacarpus. With each additional heat lamp switched on, the temperature inside the hutches rose by 2.6 ± 1.0°C. Calves spent 90% of their time inside a hutch, irrespective of the number of heat lamps switched on. No preference for a specific inside hutch temperature existed. There was, however, a tendency for the location of the hutches closest to the control calf. Lying behavior did not differ between preference and control phase, but decreased marginally with increasing age. These findings could indicate that there is a need of shelter for calves in winter, but without a preference for a certain inside hutch temperature under the prevailing conditions of deep straw bedding, highly sufficient milk supply and an ambient temperature of 5.4 ± 3.3°C.

Early Life Nutrition and its Effects on the Developing Heifer: Growth, nutritive intakes, and metabolism

We aimed to assess the effects of preweaning nutrition and postweaning growth rates on the metabolic characteristics of replacement dairy heifers until 20 mo of age. At birth heifers, were allocated to one of 4 treatment groups which were a combination of preweaning (high or low preweaning nutritional treatment), and postweaning treatments (high or low postweaning growth rate). In the preweaning phase (birth until weaning at 10 weeks of age) heifers were subject to either a High (8 L/day) or Low (4 L/day) milk feeding strategy, then at weaning either a high or low postweaning growth rate. Heifers in the high preweaning treatment groups recorded greater growth rates until weaning compared with heifers in the low preweaning treatment groups. Heifers in the high preweaning groups consumed approximately twice the amount of milk and half the amount of concentrate. Blood samples taken at 6 weeks of age had lower BHB and higher glucose and IGF-1 concentrations in the high preweaning treatment in the preweaning phase; these differences disappeared postweaning. Additionally, insulin levels were also higher, and QUICKI index results were lower for heifers on the high preweaning treatment and for those on the high postweaning treatment, at 6 weeks and 13 mo of age. No differences between treatments were detected at 8 mo of age. Results indicate a positive effect of accelerated preweaning nutrition and post weaning growth rate (at 13 mo of age) on these metabolic biomarkers, however these treatment effects were independent of one another and reflected the nutritional input at the time.

Serum lipidomic profiling of dairy calves fed milk replacers containing animal or vegetable fats

Vegetable fat blends are commonly used as fat sources in milk replacers (MR) for calves, but their composition differs considerably from that of bovine milk fat. The aim of this study was to investigate the serum lipid profile of preweaning calves fed twice-daily MR containing 30% fat (% DM). Upon arrival, 30 male Holstein-Friesian calves (BW = 45.6 ± 4.0 kg, age = 2.29 ± 0.8 d) were randomly assigned to 2 experimental diets (n = 15 per treatment): one MR was derived from either vegetable fats (VG; 65% rapeseed and 35% coconut fats) or animal fats (AN; 65% packers lard and 35% dairy cream). The 2 MR formulas contained 30% fat, 24% CP, and 36% lactose. Calves were housed indoors in individual pens with ad libitum access to chopped straw and water. Daily milk allowances were 6.0 L from d 1 to 5, 7.0 L from d 6 to 9, and 8.0 L from d 10 to 35, divided into 2 equal meals and prepared at 13.5% solids. An untargeted liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) method was employed to analyze the lipid profiles in the serum of calves sampled from the jugular vein at 35 d of age. In total, 594 lipids were characterized, comprising 25 different lipid classes. Principal component analysis (PCA) showed significant separation between VG and AN, indicating different lipid profiles in the serum. An orthogonal partial least squares discriminant analysis (OPLS-DA) classification model was used to further validate the distinction between the 2 treatment groups. The model exhibited a robust class separation and high predictive accuracy. Using a volcano plot (fold change threshold ≥1.5 and false discovery rate ≤0.05), it was observed that calves fed AN had higher levels of 39 lipid species in serum than calves fed VG, whereas 171 lipid species were lower in the AN group. Lipid classes, such as phosphatidylcholine (PC), phosphatidylethanolamine (PE), sphingomyelin (SM), triglycerides (TG), lysophosphatidylcholine (LPC), and lysophosphatidylethanolamine (LPE), were different. In particular, PC and PE were observed at lower levels in calves fed AN, possibly indicating shifts in cell membrane characteristics, intracellular signaling, and liver functions. In addition, a decrease in certain triglyceride (TG) species was observed in calves fed AN, including a decrease in TG species such as TG 36:0 and TG 38:0, possibly related to variations in the content of certain fatty acids within the AN MR, such as C10:0, C12:0, C14:0, and C18:0, compared with the VG MR. Calves fed AN had lower levels of LPC and LPE, and lysophosphatidylinositol, SM, and phosphatidylinositol species than calves fed VG, suggesting shifts in lipoprotein and lipid metabolic pathways. In conclusion, these results deepen the understanding of how lipid sources in MR can modulate the serum lipidome profiles of dairy calves.

Impact of different levels of lactose and total solids of the liquid diet on calf performance, health, and blood metabolites

OBJECTIVE

This study aimed to evaluate the effect of feeding milk replacer (MR) with varying levels of lactose and the increased supply of total solids (from 750 to 960 g/d) on performance, blood metabolites, and health of Holstein male calves during the preweaning period.

METHODS

Forty newborn Holstein calves (10 per treatment) were blocked according to birth weight and date of birth and distributed in a randomized block design to different liquid diets: Whole milk powder (WMP) diluted to 125 g/L solids; MR with 48% lactose (48L), diluted to 125 g/L solids; MR with 53% lactose (53L), diluted to 125 g/L solids; 53L MR corrected to 160 g/L solids (16TS) by the inclusion of a solid corrector. Calves were individually housed in wood hutches, fed 6 L/d of the liquid diet, and had free water and starter concentrate access. The study lasted 56 days.

RESULTS

Liquid diet intake was higher for calves fed 16TS than for other treatments. Calves fed 16TS presented higher protein and fat intake, followed by those fed WMP and the 48L or 53L MRs. Lactose intake was higher for 16TS-fed calves, followed by 53L, 48L, and WMP-fed calves. Starter and total dry matter intake did not differ among liquid diets. The average daily gain was higher for 16TS than 48L-fed calves, with the other treatments being intermediary. The lowest feed efficiency was observed for calves fed 48L. No effects on health were observed, as well as on selected blood metabolites, except for albumin concentration, which was higher for calves fed 16TS and WMP.

CONCLUSION

Higher total solids content (160 g/L) in MR increases nutrient intake and consequently improves the performance of dairy calves. Feeding MRs with levels of lactose up to 53% of the DM had no deleterious effect on the performance or health of the calves.

Fat composition of milk replacer influences growth performance, feeding behavior, and plasma fatty acid profile in ad libitum-fed calves

Fat composition in milk replacers (MR) for calves differs from bovine milk fat in multiple ways. The aim of the study was to investigate the impact of different approaches of formulating fat in MR on growth, ad libitum intakes of MR and solid feeds, as well as blood metabolites in dairy calves. Upon 24 to 96 h after birth, 63 calves were acquired from dairy farms and incorporated into the study. Calves were blocked based on arrival day and randomly assigned within each block to one of 3 treatments differing in MR fat composition (n = 21 per group): VG was based on vegetable fats including 80% rapeseed and 20% coconut fats; AN was formulated with animal fats including 65% lard and 35% dairy cream; and MX with a mixture of 80% lard and 20% coconut fats. All 3 MR contained 30% fat, 24% crude protein, and 36% lactose and were formulated to have a fatty acid profile resembling that of milk fat. From arrival onward (3.1 ± 0.84 d of age; means ± standard deviation), calves were group housed and were offered an ad libitum supply of MR at 135 g/L (13.5% solids). Weaning was gradual and induced between wk 7 and 10, after which calves were fed only solid feeds. Starter feed, chopped straw, and water were offered ad libitum throughout the study. Calves were weighed, and blood was collected weekly until d 84 after arrival. Preweaning average daily gain was greater in calves fed AN (915 g/d) than other treatments (783 g/d), whereas no differences were detected in the weaning and postweaning phases. Preweaning MR intake was greater in calves fed AN than MX from wk 2 to 6 and was also higher in calves fed AN than VG in wk 5 and 6. Consistently, the number of rewarded visits during the ad libitum phase was greater in calves fed AN than MX, whereas VG showed no differences. This led to a higher preweaning total metabolizable energy intake in calves fed AN than in calves fed VG and MX. Serum cholesterol was higher, and serum albumin was lower in calves fed VG than other treatments. The proportion of high-density lipoprotein cholesterol in total plasma cholesterol was lower and that of low-density lipoprotein (LDL) cholesterol was higher in calves fed VG compared with other treatments. Overall, the fatty acid profile of plasma largely mirrored the MR fat composition during the preweaning period. Feeding AN enhanced MR intake and improved preweaning growth compared with other treatments. Feeding VG resulted in a marked increase in plasma cholesterol, particularly in the form of LDL cholesterol, which could be linked to an excessive intake of polyunsaturated fatty acids. These findings underscore the importance of formulating the fat content of MR to be similar to bovine milk fat.

Fat composition of milk replacer influences postprandial and oxidative metabolisms in dairy calves fed twice daily

Milk replacers (MR) for calves contain alternative fat sources as substitute for milk fat. This substitution leads to differences in fat properties, such as the fatty acid profile and the triglyceride structure. This study evaluated how fat composition in MR affects gastrointestinal health, blood redox parameters, and postprandial metabolism in calves fed twice daily. Forty-five individually housed male Holstein-Friesian calves (2.3 ± 0.85 d of age) were assigned to 1 of 15 blocks based on the age and the day of arrival. Within each block, calves were randomly assigned to 1 of 3 experimental diets and received their respective diet from arrival until 35 d after arrival. The 3 experimental diets (n = 15 per treatment group) consisted of an MR with a blend of vegetable fats containing rapeseed and coconut (VG), an MR with only animal fats from lard and dairy cream (AN), and an MR containing a mixture of animal and vegetable fats including lard and coconut (MX). The fatty acid profile of each MR was formulated to resemble that of bovine milk fat while using only 2 fat sources. All MR were isoenergetic, with 30% fat (% DM), 24% crude protein, and 36% lactose. Chopped straw and water were available ad libitum from arrival onward but no starter feed was provided. Daily milk allowances were 6.0 L from d 1 to 5, 7.0 L from d 6 to 9, and 8.0 L from d 10 to 35, divided into 2 equal meals and prepared at 135 g/L (13.5% solids). Fecal appearance was scored daily; calves were weighed and blood was drawn on arrival and weekly thereafter. Urine and feces were collected over a 24-h period at wk 3 and 5 to determine apparent total-tract digestibility and assess gastrointestinal permeability using indigestible markers. Postprandial metabolism was evaluated at wk 4 by sequential blood sampling over 7.5 h, and the abomasal emptying rate was determined by acetaminophen appearance in blood. Fat composition in MR did not affect growth, MR intake, gastrointestinal permeability, nor nutrient digestibility. The percentage of calves with abnormal fecal scores was lower at wk 2 after arrival in calves fed VG than MX, whereas AN did not differ from the other treatments. Calves fed AN and MX had higher thiobarbituric acid reactive substances measured in serum than VG, whereas plasma ferric-reducing ability was greater in calves fed MX than VG. Postprandial acetaminophen concentrations did not differ across treatment groups, but the area under the curve was smaller in calves fed VG than in the other 2 treatments, which is indicative of a slower abomasal emptying. Postprandial serum triglyceride concentration was greater in calves fed AN than VG, whereas MX did not differ from the other treatments. Based on these outcomes, all 3 fat blends can be considered suitable for inclusion in MR for calves.

Postprandial metabolism and gut permeability in calves fed milk replacer with different macronutrient profiles or a whole milk powder

Significant differences exist in the composition of current milk replacers (MR) and bovine whole milk. This study investigated how the macronutrient profile of 3 different MR formulations containing varying amounts of fat, lactose, and protein, and a whole milk powder (WP), affect postprandial metabolism and gut permeability in male Holstein calves. Sixty-four calves (45.4 ± 4.19 kg [mean ± SD] and 1.8 ± 0.62 d of age) were blocked in order of arrival to the facility and within each block, calves were randomly assigned to 1 of 4 treatments. Treatments included a high-fat MR (HF: 25.0% dry matter [DM] fat, 22.5% protein, 38.6% lactose; n = 14), a high-lactose MR (HL: 44.6% lactose, 22.5% protein, 18.0% fat; n = 17), a high-protein MR (HP: 26.0% protein, 18.0% fat, 41.5% lactose; n = 17), and WP (26.0% fat, 24.5% protein, 38.0% lactose; n = 16). Calves were fed 3.0 L (135 g/L) 3 times daily at 0600, 1200, and 1800 h with a teat bucket. Milk intake was recorded daily for the first 28 d after arrival, and blood sampling and body weight measurements were performed at arrival and on d 7, 14, 21, and 27. Gut permeability was estimated from fractional urinary excretion of indigestible markers (Cr-EDTA, lactulose, and d-mannitol) administered as a single dose on d 21 instead of the morning milk meal. Digestibility was determined simultaneously from a total collection of feces over 24 h. Postprandial dynamics were measured on d 28 by sequential blood sampling over 7.5 h. Dry matter intake of MR over 28 d was slightly greater in calves fed HL and HP than in WP. Recovery of Cr-EDTA and d-mannitol over a 24-h urine collection was greater in calves fed WP and HP than HL calves. Apparent total-tract digestibility of crude ash, protein, and fat did not differ among treatments; however, DM digestibility was lower in calves fed WP than in other treatment groups. In addition, abomasal emptying, as indicated by the area under the curve (AUC) for acetaminophen, was slower in calves fed WP than in calves fed HF and HL. The AUC for postprandial plasma glucose was lower in calves fed HL than WP and HF and lower in calves fed HP than WP. The AUC for postprandial serum insulin was greater in calves fed HP than WP and HF, whereas calves fed HL did not differ from the other treatments. Postprandial triglycerides were greater in calves fed WP, and postprandial adiponectin was higher in calves fed HL than other treatments. The high content of lactose and protein in MR had a major effect on postprandial metabolism. This raises the possibility of optimizing MR formulations to maintain metabolic homeostasis and influence development.

Water, mineral, and blood acid-base balance in calves with naturally occurring diarrhea receiving two alternative oral rehydration solutions or a placebo

Quantifying the water and mineral losses in feces is essential to determine the optimal composition of oral rehydration solutions (ORS) for diarrheic animals. In a randomized complete block design, this study evaluated water, mineral, and blood acid-base balance of calves with naturally occurring diarrhea receiving ORS or a placebo. On d 0, 45 calves (age: 18 ± 3.2 d; mean ± SD) were selected based on the presence of visual signs of diarrhea, such as dirty tail or wet feces, along with clinical symptoms evaluated by measuring the skin turgor and the degree of enophthalmos. On d 1, calves were divided into blocks of 3 animals based on blood base excess (BE) measured at 0900 h, and within each block, calves were randomly assigned to 1 of 3 treatments (15 calves per treatment) including (1) a hypertonic ORS (HYPER; Na+ = 110 mmol/L; 370 mOsm/kg; strong ion difference [SID] = 60 mEq/L), (2) a hypotonic ORS with low Na+ (HYPO; Na+ = 77 mmol/L; 278 mOsm/kg; SID = 71 mEq/L), and (3) a placebo consisting of lukewarm water with 5 g/L of whey powder (CON). Milk replacer (MR) was fed through teat buckets twice daily at 0630 h and 1700 h in 2 equally sized meals of 2.5 L from d 1 to 3 and of 3.0 L on d 4 and 5. Treatments consisting of 2.0 L lukewarm solutions were administered between milk meals from d 1 to 3 at 1200 h and 2030 h through teat buckets. Refusals of MR and treatments were recorded daily, and blood samples were collected from the jugular vein once daily at arrival in the afternoon of d 0 and at 0900 h from d 1 to 5 after arrival. Urine and feces were collected quantitatively over a 48-h period from 1200 h on d 1 to 1200 h on d 3, and a representative sample of each 24-h period was stored. In addition, the volume of extracellular fluid was evaluated on d 2 by postprandial sampling over a 4-h period relative to the injection of sodium thiosulfate at 1300 h. Total daily fluid intake (MR, treatment, and water) from d 1 to 3 was greater in HYPER (LSM ± SEM; 8.9 ± 0.36 L/d) and HYPO (7.8 ± 0.34 L/d) than in CON (6.6 ± 0.34 L/d). This resulted in a greater water balance (water intake - fluid output in urine and feces) in calves receiving ORS (59.6 ± 6.28 g/kg BW per 24 h vs. 39.6 ± 6.08 g/kg BW per 24 h). Fecal Na+ losses were greater in HYPER than in the other treatments (81 ± 12.0 mg/kg BW per 24 h vs. 24 ± 11.8 mg/kg BW per 24 h). Blood pH was higher in HYPO (7.41 ± 0.016) than CON (7.35 ± 0.016) over the 5 monitoring days, whereas HYPER (7.37 ± 0.017) did not differ with other treatments. In this experimental model, diarrheic calves were likely unable to absorb the high Na+ load from HYPER, resulting in greater Na+ losses in feces, which might have impaired the alkalinizing capacity of HYPER. In contrast, HYPO significantly sustained blood acid-base balance compared with CON, whereas HYPER did not. This suggests that low tonicity ORS with a high SID are more suitable for diarrheic calves.

Gastrointestinal structure and function of preweaning dairy calves fed a whole milk powder or a milk replacer high in fat

The composition of milk replacer (MR) for calves greatly differs from that of bovine whole milk, which may affect gastrointestinal development of young calves. In this light, the objective of the current study was to compare gastrointestinal tract structure and function in response to feeding liquid diets having a same macronutrient profile (e.g., fat, lactose, protein) in calves in the first month of life. Eighteen male Holstein calves (46.6 ± 5.12 kg; 1.4 ± 0.50 d of age at arrival; mean ± standard deviation) were housed individually. Upon arrival, calves were blocked based on age and arrival day, and, within a block, calves were randomly assigned to either a whole milk powder (WP; 26% fat, DM basis, n = 9) or a MR high in fat (25% fat, n = 9) fed 3.0 L 3 times daily (9 L total per day) at 135 g/L through teat buckets. On d 21, gut permeability was assessed with indigestible permeability markers [chromium (Cr)-EDTA, lactulose, and d-mannitol]. On d 32 after arrival, calves were slaughtered. The weight of the total forestomach without contents was greater in WP-fed calves. Furthermore, duodenum and ileum weights were similar between treatment groups, but jejunum and total small intestine weights were greater in WP-fed calves. The surface area of the duodenum and ileum did not differ between treatment groups, but the surface area of the proximal jejunum was greater in calves fed WP. Urinary lactulose and Cr-EDTA recoveries were greater in calves fed WP in the first 6 h post marker administration. Tight junction protein gene expression in the proximal jejunum or ileum did not differ between treatments. The free fatty acid and phospholipid fatty acid profiles in the proximal jejunum and ileum differed between treatments and generally reflected the fatty acid profile of each liquid diet. Feeding WP or MR altered gut permeability and fatty acid composition of the gastrointestinal tract and further investigation are needed to understand the biological relevance of the observed differences.