The effect of timing of oral meloxicam administration on physiological responses in calves after cautery dehorning with local anesthesia

Dehorning is a painful husbandry procedure that is commonly performed in dairy calves. Parenteral meloxicam combined with local anesthesia mitigates the physiological and behavioral effects of dehorning in calves. The purpose of this study was to determine the influence of timing of oral meloxicam administration on physiological responses in calves after dehorning. Thirty Holstein bull calves, 8 to 10 wk of age (28–70 kg), were randomly assigned to 1 of 3 treatment groups: placebo-treated control group (n = 10), calves receiving meloxicam administered orally (1 mg/kg) in powdered milk replacer 12 h before cautery dehorning (MEL-PRE; n = 10), and calves receiving meloxicam administered as an oral bolus (1 mg/kg) at the time of dehorning (MEL-POST; n = 10). Following cautery dehorning, blood samples were collected to measure cortisol, substance P (SP), haptoglobin, ex vivo prostaglandin E₂ (PgE₂) production after lipopolysaccharide stimulation and meloxicam concentrations. Maximum ocular temperature and mechanical nociceptive threshold (MNT) were also assessed. Data were analyzed using noncompartmental pharmacokinetic analysis and repeated measures ANOVA models. Mean peak meloxicam concentrations were 3.61 ± 0 0.21 and 3.27 ± 0.14 μg/mL with average elimination half-lives of 38.62 ± 5.87 and 35.81 ± 6.26 h for MEL-PRE and MEL-POST, respectively. Serum cortisol concentrations were lower in meloxicam-treated calves compared with control calves at 4 h postdehorning. Substance P concentrations were significantly higher in control calves compared with meloxicam-treated calves at 120 h after dehorning. Prostaglandin E₂ concentrations were lower in meloxicam-treated calves compared with control calves. Mechanical nociceptive threshold was higher in control calves at 1 h after dehorning, but meloxicam-treated calves tended to have a higher MNT at 6 h after dehorning. No effect of timing of meloxicam administration on serum cortisol concentrations, SP concentrations, haptoglobin concentrations, maximum ocular temperature, or MNT was observed. However, PgE₂ concentrations in MEL-PRE calves were similar to control calves after 12 h postdehorning, whereas MEL-POST calves had lower PgE₂ concentrations for 3 d postdehorning. These findings support that meloxicam reduced cortisol, SP, and PgE₂ after dehorning, but only PgE₂ production was significantly affected by the timing of meloxicam administration.     

The effect of meloxicam on behavior and pain sensitivity of dairy calves following cautery dehorning with a local anesthetic

Effects of a single injection of meloxicam on calf behavior, pain sensitivity, and feed and water intakes were examined following dehorning. Sixty Holstein heifer calves were blocked by age and randomly assigned to receive an i.m. injection of meloxicam (0.5 mg/kg) or a placebo. All calves were given a lidocaine cornual nerve block (5 mL per horn). Treatments and nerve blocks were administered 10 min before cautery dehorning. Continuous sampling of behavior was performed during five 1-h intervals using video recordings, and total daily activity was monitored using an accelerometer. A pain sensitivity test was administered with a pressure algometer, and feed and water intakes were recorded daily. Calves were sham-dehorned 24 h before actual dehorning to establish baseline values, and all variables were assessed at the same times following dehorning and sham dehorning for up to 48 h post-dehorning. Meloxicam-treated calves displayed less ear flicking during the 44 h following dehorning (increases of 4.29 ± 1.10 and 1.31 ± 0.66 ear flicks/h in the first 24 h, and increases of 3.27 ± 0.89 and 0.55 ± 0.50 ear flicks/h during the second 24 h, for control and meloxicam calves, respectively) and less head shaking during the first 9 h following dehorning (increase of 2.53 ± 0.54 and 0.85 ± 0.46 headshakes/h over baseline for control and meloxicam, respectively). Meloxicam-treated calves were less active than controls during the first 5 h following dehorning (activity 34.1 ± 3.2 and 30.6 ± 2.6 for control and meloxicam, respectively) and displayed less sensitivity to pressure algometry 4 h after dehorning (pressure tolerance of 1.62 ± 0.13 kg of force and 2.13 ± 0.15 kg of force for control and meloxicam calves, respectively). Changes in behavior suggest that meloxicam was effective for reducing post-surgical pain and distress associated with calf dehorning.     

Effects of a concentrated lidocaine solution on the acute phase stress response to dehorning in dairy calves

The objective of this study was to more fully define the surgical stress response to dehorning by heat cauterization in dairy calves by measuring behavioral, hormonal, inflammatory, and immunological markers of stress and to determine whether a nerve block of the surgical site with a concentrated solution of lidocaine (5%) reduces the degree of stress. Thirty-two 10- to 12-wk-old female Holstein calves were randomly allotted to 1 of 4 treatments: 5% lidocaine followed by dehorning, 2% lidocaine followed by dehorning, saline followed by dehorning, or 5% lidocaine followed by sham dehorning. Plasma cortisol concentration was measured in blood samples collected via a jugular catheter at −0.5, 0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 6, 9, 12, 24, 48, and 72 h. Various other blood constituents were measured in samples collected at −0.5, 12, 24, 48, and 72 h. Feeding, drinking, scratching, grooming, rubbing, licking, and inactivity behaviors were observed in the standing and recumbent positions using a 10-min scan sampling method analyzed on a time period and daily basis for 72 h following the dehorning procedure. The frequency of vocalization, kicking, and lying in the chute during the dehorning procedure were also assessed. The overall plasma cortisol concentrations were higher in calves subjected to dehorning than in control calves. Compared with the control group, the saline-treated calves had a higher cortisol concentration at 30 and 60 min postdehorning. Plasma cortisol concentrations were higher in all groups at 30 min postdehorning than at other sampling times. The percentage of circulating neutrophils and the neutrophil:lymphocyte ratio were increased in the saline and 2% lidocaine group. Total plasma protein, fibrinogen, and α₁-acid glycoprotein concentrations were similar among treatments. The behavioral response to dehorning, as manifested by kicking while in the chute, was greater in the saline and 2% lidocaine group than in the control or 5% lidocaine treatment groups. In the postdehorning period, the percentage of time calves spent performing various maintenance behaviors did not differ among treatments. Thus, injection of 5% lidocaine may not provide any added comfort after the dehorning but may decrease the overall stress response during the procedure.     

Effects of twice-daily nursing on milk ejection and milk yield during nursing and milking in dairy cows

Milk production and hormonal responses to milking in Holstein cows that were milked twice daily, and that either also nursed calves twice daily 2 h after milking for 9 wk after calving (n = 10) or that served as nonnursing controls (n = 8) were examined to assess how nursing affected responses to machine milking. Milk yield at milking during the 9 wk of nursing was lower in nursing cows compared with control cows (26.1 ± 1.0 vs. 35.5 ± 1.1 kg) that were only machine milked. During nursing, the amount drunk by calves increased from 6.5 ± 0.7 kg/d on wk 1 to 12.5 ± 1.4 kg/d on wk 9. When this was added to the amount of milk obtained at milking, nursing cows did not differ from control cows in total milk produced (35.5 ± 1.0 vs. 35.5 ± 1.0 kg). Residual milk yield, after i.v. injection of oxytocin after milking, was higher in nursing cows than in control cows (8.7 ± 0.8 vs. 3.2 ± 0.8 kg). During the 6 wk after weaning, milk production was the same for the nursing and control cows (34.0 ± 1.35 vs. 34.7 ± 1.42 kg). Plasma oxytocin levels during milking were greater for control cows than for nursing cows (31.7 ± 5.4 vs. 18.0 ± 2.8 pg/mL), but were equivalent to concentrations in nursing cows during nursing (35.5 ± 7.5 pg/mL). Plasma concentrations of prolactin and cortisol increased after both milking (control vs. nursing: prolactin: 40.2 ± 6.8 vs. 32.9 ± 6.1 ng/mL; cortisol: 6.4 ± 1.23 vs. 7.4 ± 1.10 ng/mL) and nursing (control vs. nursing: prolactin: 18.6 ± 7.3 vs. 38.9 ± 6.6 ng/mL; cortisol: 2.34 ± 1.15 vs. 7.37 ± 1.04 ng/mL). In contrast to previous studies, there was no obvious advantage for milk production by keeping a calf with the cow. This appears to result from the reduced oxytocin secretion during milking for the nursing cows.     

Effects of pair versus single housing on performance and behavior of dairy calves before and after weaning from milk

This experiment tested the effects of pair versus single housing on the performance and behavior of dairy calves before and after weaning. Twenty-seven Holstein calves were separated from the dam within 6 h of birth, housed in individual pens for 4 d, and then assigned to either continued individual housing (n = 9 calves) or pair housing (n = 9 pairs). Calves had ad libitum access to starter, hay, and water via buckets. Pasteurized whole milk was fed via teat twice a day for 2 h at ad libitum volumes until d 36. During the milk-feeding period, paired calves showed higher intakes of starter than did the individually housed calves (averaging 93 vs. 59 ± 11 g/d per calf). Calves were weaned from milk from d 37 to 41 by progressive dilution of milk with water, and the teat was removed on d 49. Calves in both treatments vocalized in response to teat removal but this response was less in paired calves than in individually housed calves (84 vs. 194 ± 12 calls/2-h period per calf on d 49). On d 56, calves were moved to group pens, mixed with other calves, and observed for 15 d. Starter, water, and hay were available ad libitum via automatic feeders. Compared with calves previously housed in single pens, paired calves had a shorter latency to start feeding (9.1 ± 2.6 vs. 49.5 ± 4.1 h/calf), visited the starter feeder more frequently (41.6 ± 3.0 vs. 26.4 ± 3.3 visits/d per calf), spent more time at the feeder (87.8 ± 2.5 vs. 65.3 ± 2.9 min/d per calf), and consumed more starter (3.4 vs. 2.3 ± 0.2 kg/d per calf). Weight gains at mixing were higher for paired than for individually housed calves on d 2 and 3 after mixing (0.5 vs. −2.4 ± 0.3 kg/d per calf; and 0.8 vs. −0.9 ± 0.3 kg/d per calf, respectively). The results indicate that pair housing during the milk-feeding stage reduces calf responses to weaning and improves performance after weaning when calves are housed in groups.     

Reducing pain after dehorning in dairy calves

We investigated behavioral responses after dehorning and a sham procedure in 20 Holstein calves aged 4 to 8 wk. Calves either received a nonsteroidal antiinflammatory drug (ketoprofen) before dehorning as well as 2 and 7 h after the procedure or were assigned to a control group. All calves received a sedative (xylazine) and local anaesthetic (lidocaine) before dehorning, and responses were scored over 24 h after the procedure. After hot-iron dehorning, calves treated with ketoprofen also demonstrated little head shaking or ear flicking, but control animals demonstrated higher frequencies of these behaviors; both responses peaked 6 h after dehorning. Differences between the treatment groups remained statistically significant until 12 h (head shaking) and 24 h (ear flicking) after dehorning. A low frequency of head rubbing was observed in both treatment groups, but control calves were more frequently observed engaged in this behavior. There was no statistically significant effect of treatment on any of the other behavioral measures. Calves treated with ketoprofen also tended to gain more weight (1.2+/-0.4 kg) during the 24 h after dehorning than did control calves (0.2+/-0.4 kg). There was no effect of treatment on any of the response variables when calves were sham dehorned. These results indicate that ketoprofen mitigates pain after hot-iron dehorning in young dairy calves.     

Effect of treatment with the nonsteroidal antiinflammatory meloxicam on milk production, somatic cell count, probability of re-treatment, and culling of dairy cows with mild clinical mastitis

It was hypothesized that treatment of clinical mastitis with a combination of a nonsteroidal antiinflammatory treatment (meloxicam) and a parenteral antibiotic (penethamate hydriodide) would result in lower somatic cell counts (SCC), reduced milk yield losses, improved clinical outcomes, and reduced culling rates compared with antibiotic therapy alone. Cows in 15 herds with clinical mastitis during the first 200 d of lactation (median = 13 d) were treated with 5 g of penethamate hydriodide daily for 3 d, and one-half these cows were treated with 250 mg of the nonsteroidal antiinflammatory drug meloxicam (n = 361 cows), whereas the other half (n = 366 cows) were treated with the vehicle (control group). Milk samples for bacteriology were collected from clinically affected glands before treatment, and samples were collected at 7 (±3), 14 (±3), and 21 (±3) d after commencement of treatment for SCC determination. Additionally, the rectal temperature, udder edema score, California Mastitis Test score, and milk clot score were determined before treatment and daily milk yield data were collected across the lactation. There were no differences between the treatment groups in calving date, days in milk, age, breed, rectal temperature, California Mastitis Test score, clot score, udder edema score, or bacterial pathogens isolated before treatment. There was no difference between treatment groups in the number of cows that were defined as treatment failures (i.e., re-treated within 24 d of initial treatment, died, or the treated gland stopped producing milk); 79 (21.9%) vs. 92 (25.1%) cows in the meloxicam and control groups failed, respectively. The SCC was lower in the meloxicam-treated group compared with the control group after treatment [550 ± 48 vs. 711 ± 62 geometric mean (×1,000/mL) ± standard error of the mean SCC for quarters after treatment with meloxicam vs. control, respectively]. There was no difference in milk yield for the cows treated with meloxicam compared with the control cows within 28 or 200 d after treatment. Fewer meloxicam-treated than control cows were removed (culled) from the herds [39/237 (16.4%) vs. 67/237 (28.2%) for meloxicam vs. control cows, respectively; odds ratio = 0.42, 95% confidence interval = 0.26 to 0.68]. It was concluded that treatment of cows with clinical mastitis with a combination of meloxicam and penethamate resulted in a lower SCC and a reduced risk of removal from the herd (culling) compared with treatment with penethamate alone.     

Effects of handling, administration of a local anesthetic, and electrical dehorning on plasma cortisol in Holstein calves

Effects of handling, administration of a local anesthetic, and electrical dehorning on plasma cortisol were measured in Holstein heifer calves. Jugular blood was sampled from 24 calves (age, 7 to 16 wk) within 1 to 2 min after entering their pen (baseline, 0800 h). All calves were then haltered, placed in a restraint chute, an unheated electrical dehorner applied to each horn stump, and a second jugular blood sample obtained 30 min later (handling). Calves were then divided into control and test groups (12 calves). For the next 2 consecutive d the sequence of sampling blood and handling were the same except that 1) for control calves a heated dehorner was used on d 2 (dehorning), and 2) for test calves the cornual nerve of each horn stump was injected with 5 ml lidocaine prior to applying an unheated dehorner on d 2 (administration of anesthetic) and a heated dehorner on d 3 (combination of anesthetic and dehorning). Handling, injection of an anesthetic, and dehorning were stressful and increased plasma cortisol of calves 5.4, 16.8, and 28.3 ng/ml above baseline, respectively. Dehorning and the combination of injecting lidocaine and dehorning resulted in similar increases in plasma cortisol. Different responses in plasma cortisol in individual calves exposed to similar stimuli suggest that synthesis and release of cortisol can be modified.     

Effects of continuous versus periodic milk availability on behavior and performance of dairy calves

Dairy calves fed milk ad libitum engage in feeding activity throughout the day and night. However, providing calves with continuous access to milk can present practical problems with milk quality, particularly during warm weather. One way to maintain milk quality in ad libitum feeding regimens is to limit the time that milk is available, but no research to date has addressed how this might affect calves. The objectives of this study were to quantify the effects of continuous access to milk (24 h/d) vs. access during only part of the day on milk feeding behavior and performance. Twenty-eight female Holstein calves were randomly assigned to treatments at 5 ± 3 d of age and monitored for 28 d. All calves had milk delivered through a teat. Treatments were 1) access to milk for 24 h/d; 2) access to milk for 2 feedings per day (each of 2 h), with water available through the teat the remainder of the day (4-h wet treatment); and, 3) access to milk for 2 feedings per day (each of 2 h), but with no water available through the teat (4-h dry treatment). Calves given 24-h access to milk consumed 11.2 ± 0.5 kg/d on average. Milk intake tended to be lower for the 4-h wet and 4-h dry treatments, averaging 10.0 ± 0.3 kg/d, with no difference between these 2 treatments in this or any other variable. Average daily gain over the course of the experiment did not vary with treatment and averaged 1.1 ± 0.04 kg/d. Calves in the 24-h treatment spent more time on the teat than those calves on the 4-h treatments, but during the 4 h/d when milk was available to all calves, calves in the 4-h treatments spent more time on the teat. These results show that individually housed calves fed milk ad libitum for only 4 h/d compensate by changing their milk feeding behavior and are able to achieve similar weight gains to animals fed milk continuously.     

Effects of local anesthetic and a nonsteroidal antiinflammatory drug on pain responses of dairy calves to hot-iron dehorning

This study examined the effects of a nonsteroidal antiinflammatory agent (NSAID) on physiological responses of calves immediately after hot-iron dehorning (DH) and during the time that local anesthetic (LA) wears off (2 to 3 h) after this procedure. Forty-six calves (33 ± 0.3 d of age) were randomly assigned to 6 treatments: hot-iron DH versus sham DH with either no pain mitigation, LA alone, or LA with NSAID (i.v. Meloxicam). Eye temperature (measured using infrared thermography) was recorded every 5 min for 3 h after treatments. Heart rate (HR) and heart rate variability (HRV) were recorded continuously; for analysis of HRV, short segments of 512 interbeat intervals were examined. After DH without LA or NSAID, HR increased by 35 ± 3.0 beats/min in the first 5 min and remained elevated above baseline for 3 h. The HRV around the time of DH did not differ between treatments; however, the root mean square of successive differences decreased from 68 to 41 ± 12.6 ms immediately following DH without pain relief, suggesting a decrease in vagal tone at this time. Between 2 and 3 h following DH with LA, there was a decrease in eye temperature (−0.6 ± 0.1°C), an increase in HR (8 ± 3.0 beats per min) and changes in HRV. Changes in HRV at this time included a decreased high-frequency power and an increase in the low-frequency power and low-frequency/high-frequency ratio, indicating a change in sympatho-vagal balance. The changes in eye temperature, HR, and HRV between 2 and 3 h following DH with LA indicated the onset of pain coinciding with the time that the LA effects wear off. In addition, this study demonstrated that the combination of LA and NSAID mitigated the onset of pain responses when the LA wanes.     

Noninvasive assessment of autonomic activity for evaluation of pain in calves, using surgical castration as a model

The role of the autonomic nervous system (ANS) in mediating eye temperature responses during painful procedures was examined in thirty 4-mo-old bull calves randomly assigned to 4 treatments: 1) sham handling control (C; n = 8), 2) surgical castration (SC; n = 6), 3) local anesthesia with sham handling (LAC; n = 8), and 4) local anesthesia with surgical castration (LASC; n = 8). Maximum eye temperature (°C), measured by infrared thermography, heart rate (HR), and heart rate variability (HRV) were recorded continuously from 25 min before to 20 min after castration. The HRV was analyzed by examining segments of 512 interbeat intervals before and after treatments and comparing the root mean square of successive differences (RMSSD), high and low frequency (HF and LF, respectively) power, and the ratio of LF and HF powers (LF:HF). Jugular blood samples were analyzed for norepinephrine and epinephrine in C and SC treatments and for cortisol during all treatments. There was an immediate increase in HR following castration in SC (+15.3 ± 2.8 beats/min) and LASC (+6.3 ± 2.4 beats/min) calves. Eye temperature increased during the 20-min observation period in SC and LASC calves (+0.47 ± 0.05°C and +0.28 ± 0.05°C, respectively), and there was a small increase in C calves (+0.10 ± 0.05°C). Following castration in SC calves, there was an increase in RMSSD (+25.8 ± 6.4) and HF power (+11.0 ± 6.5) and LF:HF decreased (−2.1 ± 0.7). Following castration in LASC, there was an increase in RMSSD (+18.1 ± 4.9) and a decrease in LF power (−10.2 ± 5.0). Cortisol increased above baseline within 15 min following treatment in both castrated groups, but was greater for SC calves (+18.4 ± 2.3 ng/mL) than for LASC calves (+11.1 ± 1.9 ng/mL). After castration, norepinephrine increased 3-fold and epinephrine increased by half in SC calves but not in C calves. There were no changes in HR, HRV, or cortisol responses to C or LAC treatments. Local anesthetic reduced, but did not eliminate, responses to surgical castration. The synchronized increase in catecholamine and HR responses immediately following SC treatment suggests the initial response was mediated by the sympathetic branch of the ANS. The subsequent changes in RMSSD, HF power, and LF:HF ratio indicated this was followed by an increase in parasympathetic activity. The use of HR, HRV, and infrared thermography measurements together provide a noninvasive means to assess ANS responses as indicators of acute pain in cattle.     

Milk cortisol concentration in automatic milking systems compared with auto-tandem milking parlors

Milk cortisol concentration was determined under routine management conditions on 4 farms with an auto-tandem milking parlor and 8 farms with 1 of 2 automatic milking systems (AMS). One of the AMS was a partially forced (AMSp) system, and the other was a free cow traffic (AMSf) system. Milk samples were collected for all the cows on a given farm (20 to 54 cows) for at least 1 d. Behavioral observations were made during the milking process for a subset of 16 to 20 cows per farm. Milk cortisol concentration was evaluated by milking system, time of day, behavior during milking, daily milk yield, and somatic cell count using linear mixed-effects models. Milk cortisol did not differ between systems (AMSp: 1.15 ± 0.07; AMSf: 1.02 ± 0.12; auto-tandem parlor: 1.01 ± 0.16 nmol/L). Cortisol concentrations were lower in evening than in morning milkings (1.01 ± 0.12 vs. 1.24 ± 0.13 nmol/L). The daily periodicity of cortisol concentration was characterized by an early morning peak and a late afternoon elevation in AMSp. A bimodal pattern was not evident in AMSf. Finally, milk cortisol decreased by a factor of 0.915 in milking parlors, by 0.998 in AMSp, and increased by a factor of 1.161 in AMSf for each unit of ln(somatic cell count/1,000). We conclude that milking cows in milking parlors or AMS does not result in relevant stress differences as measured by milk cortisol concentrations. The biological relevance of the difference regarding the daily periodicity of milk cortisol concentrations observed between the AMSp and AMSf needs further investigation.     

Short communication: Glutamine increases autophagy of liver cells in weaned calves

The objectives of this study were to determine the effects of an increased jugular supply of l-Gln on the autophagy of weaned calves. At 35 d of age, 24 Holstein calves (initial body weight of 50 ± 0.5 kg; 35 ± 2 d of age) were randomly allocated to 4 treatments, with each treatment including 5 male calves and 1 female calf. Holstein calves were assigned to treatments of (1) intravenous infusion of 2 d of 0.85% NaCl (control group) (2) intravenous infusion of 8 g/d of l-Gln mixed with 2 d of 0.85% NaCl solution, (3) intravenous infusion of 16 g/d of l-Gln mixed with 2 d of 0.85% NaCl solution, and (4) intravenous infusion of 32 g/d of l-Gln mixed with 2 d of 0.85% NaCl. The infusion was administered 2 h/d for 7 consecutive days starting on d 1 after weaning. Feed and water were freely available to all calves. All calves were killed on d 7 postweaning to measure the autophagy of liver cells. The level of autophagy in liver cells was improved when the Gln infusion dose increased.     

The effects of early weaning on innate immune responses of Holstein calves

The objectives of this study were to compare innate immune responses of calves weaned early (EW; n = 23; weaned at 23.7 ± 2.3 d of age) with those of conventionally weaned calves (CW; n = 22; weaned at 44.7 ± 2.3 d of age). All calves were fed 3.8 L of colostrum within 12 h of birth and were subsequently fed milk replacer twice daily. The weaning process began by withdrawal of the afternoon milk-replacer feeding. Milk was fully withdrawn, and the calf was considered completely weaned when it consumed 900 g of calf starter as-fed for 2 consecutive days. Blood samples were collected from all calves at 24, 27, 31, 45, 48, 52, and 66 ± 2.3 d of age. Early weaned calves took a variable amount of time to completely wean from milk replacer; therefore, data were also analyzed by comparing calves grouped by latency to completely weaned (fast = 1 to 5 d; intermediate = 6 to 8 d; slow = 15 to 17 d). Slow-EW calves weighed less than either the fast- or intermediate-EW calves before initiating weaning. At 27 d of age, circulating neutrophils were greater among EW calves than CW calves. Moreover, fast-EW calves had lower neutrophil:mononuclear cell ratios at 45 d of age than other EW calves. Slow-EW calves had lower TNF-α concentrations from whole blood stimulated with endotoxin at 27 and 31 d of age compared with fast- and intermediate-EW calves. All EW calves had decreased neutrophil L-selectin at d 27 and increased neutrophil L-selectin at 31 d of age. At 31 d of age, neutrophil β₂-integrin was the greatest among the fast-EW calves. All EW calves had decreased neutrophil oxidative burst at 27 and 31 d of age. Three days after CW calves were weaned they had higher neutrophils, hematocrit percentages, and circulating cortisol than EW calves. In addition, 3 d after CW calves were weaned they had decreased neutrophil oxidative burst responses to Escherichia coli. Weaning, irrespective of age, suppressed many innate immune responses. In addition, early weaning transiently suppressed L-selectin expression on neutrophils; however, the immunological significance in the context of the resistance to disease is unknown because EW calves likely had greater protection from passively derived immunoglobulins when they were weaned. Finally, calves with lower BW around 24 d of age may not be suitable for early weaning programs as evident in the suppressed secretion of TNF-α from whole blood cultures during the week following the initiation of weaning.     

Effect of bupivacaine liposome suspension administered as a cornual nerve block on indicators of pain and distress during and after cautery dehorning in dairy calves

Dehorning is performed on a high percentage of dairies worldwide. Concern about the negative effect of dehorning on animal welfare has contributed to the development of new guidelines that require the use of pain management at the time of disbudding in the United States. However, livestock producers are limited in how to address this requirement due to a lack of (1) approved analgesic drugs, (2) analgesic options that control pain for an extended duration, and (3) analgesic formulations that are practical for producers to administer. The objective of this study was to evaluate the effectiveness of bupivacaine liposome suspension, a novel, long-acting, local anesthetic formulation administered as a nerve block at dehorning, compared with current industry standard analgesic approaches using lidocaine nerve blocks alone or in combination with the nonsteroidal anti-inflammatory drug meloxicam. Fifty male Holstein calves, 10 to 14 wk of age, were enrolled and randomly assigned to 1 of 5 treatment groups before cautery dehorning as follows: (1) bupivacaine liposome suspension block, oral placebo (BUP); (2) lidocaine block, oral placebo (LID); (3) lidocaine block, oral meloxicam (1 mg/kg of body weight; LID + MEL); (4) saline block, oral placebo (CON); and (5) saline block, oral placebo, sham dehorn (SHAM). Biomarkers were collected from 0 to 120 h postdehorning and included infrared thermography, mechanical nociceptive threshold (MNT), pressure mat gait analysis, chute defense and behavior scoring, and blood sampling for serum cortisol and prostaglandin E₂ metabolites. Responses were analyzed using repeated measures with calf nested in treatment designated as a random effect, and treatment, time, and their interaction designated as fixed effects. At 2 h postdehorning, the BUP group had a higher MNT compared with the CON group. Furthermore, at 24 h postdehorning, the BUP group had a higher MNT compared with the LID group. Gait distance differed significantly between treatment groups; the CON, LID, and LID + MEL groups had an increased gait distance relative to the SHAM group. The CON group exhibited a higher chute defense behavior score during the dehorning procedure compared with all other treatments. Furthermore, the CON group exhibited more ear flicks than the BUP and LID + MEL groups postdehorning. At 4 h and 24 h after dehorning, the LID + MEL group had a lower average prostaglandin E₂ metabolites concentration compared with all other treatment groups. These data showed that administration of bupivacaine liposome suspension as a cornual nerve block at the time of dehorning was as effective at controlling pain as a multimodal approach of lidocaine and meloxicam.     

Photoperiod affects gene expression of leptin and leptin receptors in adipose tissue from lactating dairy cows

Leptin is mainly secreted by adipocytes and is implicated in the regulation of metabolic status, feed intake, and body condition. Day length (DL) can affect leptin gene expression and secretion. The aim of the study was to evaluate the effect of DL on gene expression of leptin and leptin receptors in adipose tissue (AT). Four lactating and pregnant Holstein cows were housed in a climate-controlled chamber for 51 d. The first 30 d were used to adapt animals to the new housing conditions. During that period the DL adopted was 12 h light:12 h dark (12:12). The experimental period included 3 different and consecutive phases: 7 d of neutral DL (12:12); 7 d of long DL (18 h light:6 h dark); and 7 d of short DL (6 h light:18 h dark). Subcutaneous AT biopsies were performed at the end of each phase. Prolactin, growth hormone, cortisol, leptin, glucose, nonesterified fatty acids, β-OH-butyrate, and cholesterol were determined in plasma samples. Abundance of leptin mRNA, and Ob-Ra and Ob-Rb leptin receptor mRNA were determined in AT samples by ribonuclease protection assay. Day length did not affect feed intake or body condition score. Exposure to short DL significantly reduced milk yield (13.1 ± 2.2 vs. 15.8 ± 1.7 and 16.0 ± 2.0 kg/d for short vs. neutral and long DL, respectively). Plasma leptin, growth hormone, cortisol, nonesterified fatty acids, β-OH-butyrate, and glucose were not affected by DL; cholesterol was lowest under short DL (3.93 ± 0.38 vs. 4.36 ± 0.39 and 4.07 ± 0.38 mmol/L for short vs. neutral and long DL, respectively). Prolactin increased under long DL (134.82 ± 16.94 vs. 81.98 ± 20.25 and 96.16 ± 0.38 ng/mL for long vs. neutral and short DL, respectively). Gene expression of leptin and its receptors was affected by DL. Leptin mRNA increased under long DL (11.91 ± 0.84 vs. 7.82 ± 0.84 and 7.56 ± 0.84 pg of mRNA/μg of total RNA for long vs. neutral and short DL, respectively). Leptin receptors Ob-Ra and Ob-Rb mRNA were higher under long DL, whereas Ob-Ra and Ob-Rb mRNA were lower under short DL (Ob-Ra: 1.91 ± 0.41, 2.49 ± 0.41, and 0.65 ± 0.41 pg of mRNA/μg of total RNA for neutral, long, and short DL, respectively; Ob-Rb: 5.29 ± 0.79, 5.98 ± 0.68, and 2.02 ± 0.70 pg of mRNA/μg of total RNA for neutral, long, and short DL, respectively). Results of the present study appear to exclude an effect of feed intake and metabolic status on leptin gene expression. A prolactin-mediated effect of photoperiod on AT leptin modulation may be proposed in lactating dairy cows.     

Hay intake improves performance and rumen development of calves fed higher quantities of milk

Research to date has suggested that access to forage before weaning can limit rumen development in calves, but no research has yet addressed the role of forage for calves fed higher quantities of milk. This study compared performance and rumen development of calves provided high volumes (equivalent to approximately 20% of calf birth weight) of milk with and without access to hay. At d 3 of age, individually housed calves were randomly assigned to treatment (either ad libitum access to chopped grass hay or no forage; n = 15 calves per treatment, 10 heifers, and 5 bulls). All calves were provided ad libitum access to water and starter throughout the study. All calves were offered 8 L of milk/d from a nipple bottle from d 3 to 35, 4 L/d from d 36 to 53, and 2 L/d until weaning at d 56. Solid feed intake and growth parameters were monitored from d 3 to 70. At d 70, males from both treatments were slaughtered to measure rumen development parameters. Overall dry matter (DM) intake from solid feed did not differ between treatments before wk 5. However, during wk 6 to 10, calves fed forage consumed more total DM (starter plus hay) than did calves fed no forage. Hip and wither height, heart girth, and body barrel at d 3, 56, and 70 did not differ between treatments. Reticulorumen weight was heavier in calves fed hay versus those fed only starter (12.77 ± 1.29 vs. 7.99 ± 0.69 kg with digesta; 1.89 ± 0.05 vs.1.60 ± 0.09 kg without digesta). Body weight without digesta was similar in calves fed forage or no forage. Mean rumen pH was higher in calves fed hay compared with those fed no forage (5.49 ± 0.08 vs. 5.06 ± 0.04). In conclusion, provision of chopped hay to calves fed high volumes of milk can promote solid feed DM intake and rumen development without affecting BW gain.     

What do preweaned and weaned calves need in the diet: A high fiber content or a forage source?

The objective of this study was to determine whether the improvement of performance of young calves associated with the supplementation of chopped grass hay reported in some studies is due to an increase in the total neutral detergent fiber (NDF) content of the consumed diet or to the provision of chopped grass hay. Sixty-three Holstein calves [9 ± 4.4 d old; mean ± standard deviation (SD)] were randomly distributed in 4 treatments resulting from the combination of 2 levels of NDF content of a pelleted starter and the supply or absence of forage provision: low-NDF starter (18%) with or without chopped oat hay, and high-NDF starter (27%) with or without chopped oat hay. All animals were fed the same milk replacer (21% crude protein and 19.2% fat) at the rate of 4 L/d at 15% dry matter from d 1 to 34, and 2 L/d at 15% dry matter from d 35 to 42 (weaning). The study finished 2 wk after weaning. Body weight was measured weekly and individual calf starter and hay intake was recorded daily. On d 50, blood samples were drawn 2 h after the morning concentrate offer to determine serum glucose and insulin concentrations. On d 52, samples of ruminal fluid were obtained via an esophageal tube, and pH was measured immediately. During the preweaning period, pelleted starter intake was similar among treatments, but average daily gain tended to be greater in low- than in high-NDF treatments (0.69 vs. 0.63 ± 0.020 kg/d, respectively; mean ± SD). However, during the 2 wk after weaning, supplementation of forage improved pelleted starter intake and average daily gain without affecting the gain-to-feed ratio. Probably, the greater pelleted starter intake observed in forage-supplemented calves was mainly due to the greater ruminal pH found in forage-supplemented calves compared with forage-deprived calves (5.81 vs. 5.05 ± 0.063, respectively). Blood insulin-to-glucose ratio was greater in forage-supplemented compared with unsupplemented calves [mean ± SD; 6.53 vs. 4.24 ± 0.125 insulin (ng/L)-to-glucose (mg/dL) ratio, respectively]. In conclusion, a low-NDF pelleted starter is recommended during the preweaning period, and the provision of chopped hay is necessary right after weaning to improve calf performance.     

Short communication: Maternal heat stress during the dry period alters postnatal whole-body insulin response of calves

Heat stress during the dry period not only negatively affects a cow's performance but also affects her offspring. Previous studies indicate that calves born to cows heat-stressed during late gestation have lower birth weight but similar overall weight gain during the prepubertal period compared with those cooled in utero. However, it is unclear if whole-body insulin response, and thus metabolism, of calves is altered in their postnatal life after in utero heat stress. The aim of the present study was to examine the effects of maternal heat stress during the dry period on whole-body insulin response of calves after weaning. Calves (10/treatment) were born to cows exposed to heat stress (HT) or cooling (CL) when dry. Calves were immediately separated from their dams and fed 3.8 L of high-quality colostrum within 1 h after birth and then 1.9 L 12 h later. All calves were fed 1.9 to 3.8 L of pasteurized milk in the morning and afternoon from 2 to 42 d of age and then only in the morning until weaning at 49 d. Calf starter and water were offered ad libitum starting at 2 d of age. All calves were managed in the same manner throughout the study. All calves were subjected to a glucose tolerance test (GTT) and an insulin challenge (IC) at 55 d of age. Calves heat-stressed in utero were born lighter (40 ± 1.4 vs. 45 ± 1.4 kg) compared with CL calves. Both groups of calves had similar weaning weights (HT: 68 ± 3.2 kg; CL: 71 ± 3.3 kg) and body weight gain from birth to weaning (HT: 28 ± 2.2 kg; CL: 26 ± 2.3 kg). Compared with those cooled in utero, HT calves had a similar insulin response to GTT and insulin clearance during IC but faster glucose clearance during GTT and IC. In conclusion, in addition to impaired fetal growth, maternal heat stress during the dry period enhances the whole-body insulin response of calves after weaning, which suggests the possibility of accelerated lipogenesis and fat deposition in early life.     

Performance and health responses of dairy calves offered different milk replacer allowances

Eighty female Holstein calves (12 ± 4.1 d of age and 42 ± 4.3 kg of BW) were collected from different herds, brought to the study site, and blocked by age and assigned to either a 6 L/d maximum daily milk replacer (MR) allowance (LMR) or a maximum MR allowance of 8 L/d (HMR). Calves were kept in individual hutches until 52 d of age and then moved into pens, forming groups of 10. All calves had ad libitum access to a mash starter feed. Calves in both treatments received the MR distributed in 3 separate allotments between 1 wk after the beginning of the study and 52 d of age. Then, all calves were moved to group pens and preweaned by offering 2 L/calf of the same MR twice daily in a trough until the age of 59 d, when MR offer was further reduced to a single dose of 2 L until the age of 73 d, when all calves were completely weaned. Individual starter feed and MR consumption was recorded on a daily basis until 52 d of age, and on a group basis until weaning time. Body weight was measured at the beginning of the study and at 52 (preweaning), 73 (weaning), and 110, 160, and 228 d of age. Solid feed consumption (mean ± SE) was greater in LMR (821 ± 42.1 g/d) than in HMR calves (462 ± 42.1 g/d) between 42 d of age and 52 d (preweaning). As expected, as age increased, solid feed consumption increased, and LMR showed a more marked increase than HMR calves. Despite the greater solid feed intake of LMR calves, HMR grew faster than LMR calves until preweaning time, but from preweaning to weaning, LMR calves grew more than HMR calves (977 vs. 857 ± 30.7 g/d, respectively; mean ± SE). No differences in feed efficiency were observed. While calves were individually housed, no differences were observed in the incidence of bovine respiratory disease or diarrhea between treatment groups. We concluded that, under the milk regimen, age range of calves, and weaning method used in the current study, before preweaning, HMR calves grow more than LMR calves, but between preweaning and weaning, LMR grow more than HMR calves, overcoming the difference in BW at preweaning. As a result, with the weaning scheme followed herein, providing more milk does not ensure greater performance; no differences are obtained in BW at weaning and at 228 d of life. Also, based on solid feed consumption patterns seen in this study, we determined that the optimum age to reduce MR allowances and foster solid feed intake is around 45 d of age.