Response of anemic calves to exertion

Twenty-one calves, 16 weeks of age, comprised 3 treatment groups. All calves in 2 of these groups were anemic. Several variables were measured before and immediately after an imposed exertion period. The anemic calves had significantly faster heart rates than did nonanemic calves, but there was no significant difference either in respiratory rates or acid-base variables. However, anemic calves became more acidic when made to work and also showed greater increase in respiratory rate than did nonanemic calves. The partial pressure of oxygen in venous blood was significantly lower in the anemic calves than in nonanemic calves both before and after exertion, but still represented adequate saturation of hemoglobin with oxygen.     

Growth response of steer calves treated with zeranol, oestradiol 17β or progesterone-oestradiol benzoate implants before and after weaning

This experiment compared the growth response of untreated steer calves with those given a long acting oestradiol-silicone rubber implant or implants of zeranol or oestradiol-progesterone pellets either singly, or repeated after 79 days. The experiment extended through the 6 weeks prior to weaning at 8 months of age, 5 weeks of grazing oat stubble and a 16-week finishing phase on a feedlot. The oestradiol-silicone rubber implant was the only product to significantly increase weight gains compared to controls (0.69 vs 0.52 kg/head/day, 18.2% advantage) in the pre-weaning phase. All anabolic agents produced higher weight gains ranging from increases of 0.16 to 0.19 kg/head/day (18.2-21.6%) above controls in the first 60 days of the feedlot phase. Responses did not differ significantly among the products and were the same whether or not steers had been previously implanted. Lower planes of nutrition in the late suckling and post-weaning periods were accompanied by smaller and non-significant responses to both the short acting anabolics, zeranol and oestrogen-progesterone, compared to the increased weight gains of steers given oestradiol-silicone rubber implants. Implanting with oestradiol in a silicone rubber matrix resulted in similar increases in weight gain both before and during the feedlot phase. This may have been due to the implant maintaining a continuously high level of circulating anabolic agent for the 190 days of the experiment.     

Response to transplanted adult Ostertagia ostertagi in calves

Plasma pepsinogen levels became elevated in groups of recipient calves immediately after transplant with adult Ostertagia ostertagi. These rises occurred in both previously parasite-naive calves and in calves which had experienced prior infection terminated with an anthelmintic either seven or 21 days before transplant. From the results it appears that adult O ostertagi play a significant role in the elevated plasma pepsinogen levels associated with bovine ostertagiasis.     

Response of calves to exposure with swine influenza virus

In calves inoculated with live swine influenza virus (SIV) A/sw/IL/75 (H1N1) intranasally, SIV was isolated for 7 days, and respiratory tract disease was observed. Antibody was detected in serum of inoculated calves from postinoculation day 9, and virus-neutralization antibody was demonstrated on postinoculation days 14 and 21. The primary response was low, but readily differentiated from the secondary response after calves were challenge exposed with homologous SIV. Pneumonic lesions were observed at necropsy, and histopathologic changes in airways and lungs were consistently found. Fluorescent staining revealed viral activity in epithelial cells of airways. The virus was transferred to healthy calves housed with inoculated calves.     

Response to elemental sulfur by calves and sheep fed purified diets

Free amino acid profiles in plasma and liver as well as body, organ and gastrointestinal growth were compared in 20 weanling bulls (four per treatment) fed diets deficient (.04%), excessive (.94 and 1.72%) or adequate (.34%) in S. Body, organ and gastrointestinal comparisons also were made with yearling rams fed .04 and .34% S diets. The .34% S diet was fed at two levels, one ad libitum, the other in amounts equal on a body weight.75 basis to that consumed by animals fed the .04% S diet ad libitum. Animals were allowed to consume other diets ad libitum. The calves fed the .04% S diet had negative S, but slightly positive N, balance and were unable to maintain body weight. As dietary S content was increased, plasma and liver methionine increased linearly. An increased histidine in plasma of calves fed the .04% S diet may be due to reduced intake because the calves restricted-fed the .34% S diet also had high plasma histidine. Plasma citrulline, cystine, serine and total nonessential amino acids decreased markedly as dietary S intake became adequate. Intermediate S diets resulted in reduced concentrations of plasma alanine, serine, proline and total nonessential amino acids. Calves restricted-fed the .34% S diet were the most efficient in retaining N with less urinary N. Excesses of S were not detrimental to growth, but plasma valine increased linearly as S intake increased. The S deficiency in calves reduced the ratio of the rumen-reticulum tissue to body weight, and in rams it reduced the ratio of gastrointestinal tissue and preintestinal tissue to body weight. Per kilogram of intestinal-free body weight, there was a linear decrease in liver and testes but an increase in adrenals as S was decreased for calves. The kidney, adrenals and pituitary were increased by S deficiency in rams. Of the amino acids assayed, only methionine from the plasma and liver in calves reflected both an excess and a deficiency of S independent of feed intake effects.     

Effects of zeranol implants on post-castration response in calves

SUMMARY Suckling and yearling calves were surgically castrated and one half of each group implanted with 36 mg zeranol at time of castration. Both treated and control cattle of each class were maintained as a group and evaluated for swelling of the scrotum, inflammation and healing, plasma prostaglandin levels and weight gain. Swelling and inflammation of the scrotum were less in treated suckling calves than in controls at both 7 and 14 d after castration, though this difference was not statistically significant. In yearlings at 7 d after castration, treated cattle had more swelling than controls; however at 14 d, treated cattle had less swelling and inflammation with only one treated yearling having an open scrotal wound versus 6 (P <.03) in the control group. Plasma prostaglandin levels as indicated by plasma malondialdehyde increased from d 0 to 14; however no significant treatment differences were observed for either age group. Suckling calves treated with zeranol gained 9.79 kg more (P <.03) than non-treated calves during the 97 d of trial while the yearlings treated with zeranol gained 16.78 kg more (P <.01) than controls during 102 d. It is concluded from the increased growth and reduced scrotal swelling and inflammation in treated cattle that zeranol implantation could possibly have a beneficial effect in improving the healing process after castration.     

Weaning and post-weaning performance by fall-born beef calves weaned on different dates in the spring from Neotyphodium coenophialum-infected tall fescue pastures

Fall-born calves grazing Neotyphodium coenophialum-infected tall fescue [E+; Lolium arundinaceum (Schreb.) Darbysh.] pastures should benefit from early weaning because of reduced exposure to fungal toxins. However, fall-born calves that grazed E+ and were weaned in mid-April had reduced post-weaning performance compared with calves managed similarly but weaned in early June. Gelbvieh × Angus calves (n = 238) were used in a 3-year study to determine the optimal time to wean fall-born calves grazing E+. Cow/calf pairs were allocated randomly to one of four weaning date treatments: 1) March 16 (177 ± 4.7 days of age; MarW), 2) April 13 (204 ± 4.7 days of age; AprW), 3) May 11 (236 ± 4.7 days of age; MayW), and 4) June 8 (264 ± 4.8 days of age; JuneW). On their assigned weaning date, calves were weighed, vaccinated, blood samples were collected, and calves were moved to 3.2-ha pastures adjacent to their dams for 14 days. After the weaning period, calves were weighed, blood samples were collected, and then calves were moved to pastures containing non-toxic forages. Birth weight and calf weights on MarW, AprW, and MayW weaning dates did not differ (P ≥ 0.21) across weaning date treatments. However, calf weaning weights on their respective weaning dates, weight on JuneW and on June 22 (14 days following the JuneW), daily gain between birth and June 22, and weight change between MarW and JuneW increased linearly (P < 0.05) across weaning dates. Linear decreases (P < 0.05) across weaning dates were noted for antibody titers to bovine virus diarrhea (BVD) and infectious bovine rhinotracheitis (IBR), serum Cu, and platelets at the time of actual weaning. Linear increases (P < 0.05) across weaning dates were noted for: i) total antioxidant potential and eosinophils at weaning; ii) changes in antibody titers to BVD and IBR, total antioxidant potential, and serum Zn during the 14-day post-weaning period; and iii) and changes in BVD and BRSV titers and serum Cu between actual weaning date and June 22. Heifer weight at breeding increased (P < 0.05) and steer weight at shipping, hot carcass weight and backfat thickness tended (P ≤ 0.10) to increase linearly across weaning dates. Final feedlot weight and gain did not differ (P ≥ 0.18) among weaning dates. Therefore, delaying weaning of fall-born calves grazing E+ pastures until early June may be beneficial for calf weight and immune function at weaning, and heifer weight at breeding, but those benefits in steers may be mitigated through the feedlot period.     

Response of Pasteurella haemolytica to erythromycin and dexamethasone in calves with established infection.

A subcutaneous soft tissue infection model in calves was used to study the in vivo response of Pasteurella haemolytica to erythromycin and dexamethasone. Two tissue chambers were implanted SC in each of 12 calves. At 45 days after implantation, all tissue chambers were inoculated with an erythromycin-sensitive strain of P haemolytica. Starting 24 hours after inoculation, calves were allotted to 4 groups of equal size and a 2 x 2-factorial arrangement of treatments was applied: 3 calves were given erythromycin (30 mg/kg of body weight, IM, for 5 days), 3 calves were given dexamethasone (0.05 mg/kg, IM, for 2 days), 3 calves were given erythromycin and dexamethasone, and the remaining calves served as nontreated controls. Chamber fluids were tested daily, and the response to treatment was measured. Neither erythromycin nor dexamethasone affected viability or growth of bacteria within tissue chambers. Dexamethasone had no effect on the influx of neutrophils into infected chambers. Despite repeated administration of a high dose of erythromycin and attainment of adequate concentration in serum, erythromycin concentration in chamber fluids did not exceed the minimal inhibitory concentration established in vitro. These results indicate that the clinical efficacy of erythromycin against P haemolytica sequestered in consolidated pneumonic lesions may not be well correlated with predictions based on serum pharmacokinetic and in vitro susceptibility data.     

Response of ewes of mediterranean sheep breeds to subcutaneous implants of melatonin

This study was done to examine whether pregnancy rates and prolificacy could be improved by treatment with melatonin before introduction of rams during seasonal anestrus. Three trials were conducted on four farms with a total of 481 ewes of three breeds, Rasa Aragonesa, Churra and Talaverana. Ewes isolated from rams since lambing were treated for 5 weeks with subcutaneous melatonin implants (Regulin®), or served as controls.Percentages of ewes with luteal activity at ram introduction did not differ between melatonin-treated and control groups (tested in Trial 1 and on Farm A in Trial 2). No differences were found in the mean interval from ram introduction to lambing or the distribution pattern of lambing.Significant differences in pregnancy rates were found only in Trial 1, 53% in treated vs. 38% in control ewes (P < 0.05). Rasa Aragonesa ewes which had lambed previously an average of 10 days earlier had a 19% higher pregnancy rate in Trial 1 (P < 0.01). Melatonin increased prolificacy only in Churra ewes (Trial 2, P < 0.10), by 0.24 on Farm A and 0.13 on Farm B.It is concluded that the potential of Spanish sheep to respond to supplementary melatonin varies in relation to breed, month and reproductive history.     

Growth and sexual characteristics of suckling beef calves as influenced by age at castration and growth implants

A 2-yr study using crossbred male calves (n = 228) evaluated castrating at birth or at 4 mo of age and use of anabolic growth implants (none, zeranol or estradiol-17 beta). Angus, Hereford and Brahman crossbred calves produced in seven cow-calf units that varied by breed component, stocking rate and calving season were allotted to treatment at birth in a 2 x 3 factorial arrangement. Growth implants decreased (P less than .01) testicular weight and expression (P less than .05) of male secondary sex characteristics in suckling bull calves at 4 mo. Implanted calves were shorter (P less than .05) at the hips and had shorter front legs (P less than .01) at both 4 mo and at weaning. Cannon bone circumference at weaning was increased (P less than .05) by growth implants. Age at castration did not affect (P greater than .05) calf performance or body characteristics. Calves given growth implants had higher (P less than .05) rates of gain from birth to 4 mo than did nonimplanted calves (.75 vs .71 kg/d). Implanted calves were heavier (P less than .01) at weaning and had higher (P less than .01) ADG from 4 mo to weaning than did nonimplanted calves. These data indicate no benefit from delaying age at castration, but implanting increased weaning weight an average of 8.2 kg.     

Response to reimplanting beef steers with estradiol benzoate and progesterone: performance, implant absorption pattern, and thyroxine status.

This study determined the influence of the estrogenic ear implant Synovex-S on feedlot performance, tissue deposition, and thyroid status of growing-finishing beef steers implanted either once or reimplanted. The pattern of implant absorption was also determined. Two 112-d feeding trials were used with 48 Hereford steers per trial. Each trial was a randomized block design with eight groups (lots) of six steers each assigned to four treatments (two lots/treatment). Treatments were 1) no implant or control, 2) implanted on d 0 and reimplanted at 60 d on trial, 3) implanted at 30 d on trial, and 4) implanted on d 0 only. These implant treatments resulted in withdrawal periods before slaughter of approximately 60, 90 and 120 d for Treatments 2, 3, and 4, respectively. All steers were given ad libitum access to water and a 60% concentrate diet. Group intakes were determined daily, BW weekly, estimated body composition every 28 d, plasma thyroid hormone concentrations at 112 d and at slaughter, and carcass measurements and liver tissue deiodinase at slaughter. Approximately 25% of the original implant dose remained in the ear 60 d after implanting and this residual amount was absorbed linearly at the rate of approximately .15% of the original dose per day. Implant treatments increased (P less than .05) DMI, BW gain, feed conversion, and empty body gains for water and protein. Carcass measurements suggested a nonsignificant trend (P greater than .10) for leaner carcasses for implanted steers. An immediate shift toward greater protein and less fat deposition occurred within 28 d after initial implanting (Treatment 3).(ABSTRACT TRUNCATED AT 250 WORDS)     

Efficacy of sustained release needle-less ceftiofur sodium implants in treating calves with bovine respiratory disease

Three experiments were conducted to determine preliminary efficacy of sustained release needle-less implants in effecting cure in calves with bovine respiratory disease. One hundred and twenty beef calves with a rectal temperature > or = 40 degrees C and shallow or labored respiration and coughing were used in these experiments. Four groups (1-ceftiofur sodium injections [days 1, 2, and 3], 2-ceftiofur sodium needle-less implants [days 1, 2, and 3], 3-ceftiofur sodium needle-less implants [days 1 and 3], and 4-ceftiofur sodium needle-less implants [day 1] were included. All treatments contained 250 mg of ceftiofur sodium and were administered intramuscularly in the neck after diagnosis of bovine respiratory disease. Experiment 1 included 20 calves (group 1-10 calves and group 3-10 calves; 213 to 255 kg) and calves were monitored for clinical efficacy. Experiment 2 included five calves per group (all four groups; 164 to 192 kg) and calves were bled frequently after treatment for desfuroylceftiofur (the primary ceftiofur metabolite) concentrations. Experiment 3 included 20 calves per group (all four groups; 160 to 205 kg) and calves were monitored for clinical efficacy. Blood desfuroylceftiofur concentrations remained above the minimum inhibitory concentration for Pasteurella haemolytica, Pasteurella multocida, and Haemophilus somnus for 24 hours after injection and 72 hours after implantation (P < 0.05). Mortalities and the number of calves with a positive response and relapse response were similar (P < 0.25) among the four groups. In summary, the administration of one-250 mg ceftiofur sodium needle-less sustained release implant was as efficacious in treating bovine respiratory disease as three daily 250 mg injections of ceftiofur sodium.     

Response to environmental temperatures in Brahman calves during the first compared to the second day after birth.

Brahman calves (n = 28) were used to evaluate the effect of environmental temperature during the 1st or 2nd d after birth. Calves were removed from their dams within 30 min of birth (newborn; D0) before suckling or at 20 h of age and fasted for 4 h before treatment (day-old; D1). Calves were placed in either a warm (W; 25 degrees C) or a cold (C; 5 degrees C) environment for 2 h and either maintained in or transferred to, respectively, W for 22 h. Blood samples were collected via jugular catheters at 15-min intervals beginning at initial placement in W or C through 3 h and at 4, 5, 6, 8, 10, 12, 14, 18, and 24 h. Rectal temperature (Tr) was recorded with each sample. Following the 60-min and 12-h samples, each calf was administered 1 liter of colostrum from its dam. Serum or plasma was analyzed for glucose, lactate, plasma urea nitrogen, triglycerides, nonesterified fatty acids, insulin, cortisol, triiodothyronine (T3), and thyroxine (T4). Rectal temperature of D0C calves was lower (P less than .05) than that of other calves from 75 min through 3 h. Insulin, lactate, T3, and plasma urea nitrogen concentrations were not different among all calves. Higher (P less than .01) cortisol and T4 concentrations were observed in D0 than in D1 calves. Cortisol (P less than .008) and nonesterified fatty acid (P less than .05) levels were greater in C than in W calves. All D0 calves had lower (P less than .0001) glucose concentrations than D1 calves until the 12-h feeding.(ABSTRACT TRUNCATED AT 250 WORDS)