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1.
By examining cover slips stained at regular intervals the development of primary lymph node tissue cultures from 2 cases of juvenile bovine leukosis and 2 “normal” foetuses was studied. Secondly, comparisons were made between cell lines prepared from 23 bovines — “normal” animals and foetuses, cases of adult leukosis, juvenile leukosis and skin leukosis — with respect to susceptibility to infection with interferon sensitive viruses (VSV and PRV) and/or growth rate in the presence of sera from “normal” and leukotic animals.Nuclear budding, nuclear fragmentation, lymphocyte adsorption and giant cell formation were observed — though to a much greater extent in cultures prepared from the leukosis animals — in all 4 cases studied. No indications of different susceptibility for the test virus infections appeared between cell lines prepared from “normal” and leukotic animals. The growth rate of the cell lines seemed similar irrespective of the kind of serum used.  相似文献   

2.
An experimental oral infection of goats with a caprine isolate of Mycobacterium a. subsp. paratuberculosis was used to investigate immunological and bacteriological events during the subclinical phase of infection. Seven goats at 5–8 weeks of age were given a bacterial suspension in milk-replacement three times weekly for 9 weeks. Six animals were kept as controls.

Cellular recall responses against M. a. paratuberculosis were analysed by means of a lymphocyte proliferation test, an IFN-γ assay and an IL-2 receptor assay. All inoculated animals had detectable CMI responses from 9 weeks post-inoculation and through the 2 years of study, although the responses were highest during the first year. Antibodies against M. a. paratuberculosis could be detected from weeks 15–20 in four of the seven animals, and one additional animal became antibody positive at week 35, while two inoculated animals did not produce significant antibody titres during the experiment. At about 1-year post-inoculation, two animals became faecal shedders, while two others started to excrete bacteria into faeces about 2 years post-inoculation. The appearance of M. a. paratuberculosis in faeces was not associated with a decline in cellular responses as far as could be assessed using the current methods for measuring CMI.

Pathological lesions due to M. a. paratuberculosis infection and presence of bacteria were recorded in the intestine and/or mesenteric lymph nodes of five animals while lymph node changes suggestive of paratuberculosis were observed in one animal. Only the two animals with no signs of an active infection at necropsy showed a considerable decline in the cellular parameters during the last year of the study, particularly in the IFN-γ assay.

The two animals with the highest levels of M. a. paratuberculosis responsive CD8+ lymphocytes in the circulation about 1-year post-inoculation had no detectable lesions in the distal ileum and colon at necropsy, while high numbers of γδ T-cells responsive to M. a. paratuberculosis in the circulation were associated with disseminated lesions in the distal ileum and colon.  相似文献   


3.
Faecal specimens from 200 market swine (115 feeder pigs and 85 butcher hogs) offered for sale at a southern California livestock auction yard during a three-month period, were examined for cryptosporidium oocysts. Of the 10 pigs (5 per cent) found to be excreting the parasite, seven were feeder pigs and three were butcher hogs. Of the feeder pigs four (4.1 per cent) came from the 98 non-diarrhoeic pigs and three (17.6 per cent) from 17 diarrhoeic pigs. The 85 butcher hogs were all apparently healthy.  相似文献   

4.
A prospective cohort study was undertaken in a commercial swine herd to determine the relationship between weight gain and the occurrence of enzootic pneumonia (EP). Estimates of the association between EP and weight gain were obtained from multiple linear regression models, using coughing episodes or slaughter checks as indicators of EP status. Models were estimated for pigs in 2 different age groups: roasters (n = 1084, sold at 32 to 50 kg) and market hogs (n = 1162, sold at 100 to 110 kg). The relationship between presence of lung lesions at slaughter and previous coughing episodes was also investigated. Throughout the study period, clinical evaluations were performed weekly, and coughing episodes recorded for each pig. Lungs were inspected at slaughter, and scores were expressed as the percentage of the lung with gross pneumonic lesions. Coughing and lung scores were significantly correlated, after adjusting for other covariates (R = 0.32 and 0.59, respectively, for market hogs and roasters). However, the agreement beyond chance between coughing history and lung lesions at slaughter was poor among both roasters and market hogs (kappa = 0.17 and 0.07, respectively). Although very specific, weekly assessment of coughing was not a sensitive indicator of lung lesions at slaughter. In multiple regression, lung score was a highly significant predictor of lower final weight in pigs of both age groups (P < 0.001 in the selected regression models).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

5.
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6.
Liver lesions were found in 6/6 pigs 7 months after oral inoculation with 5000 or 35,000 Echinococcus multilocularis eggs. However, lesion morphology differed considerably among the animals. The largest lesions (3–8 mm in diameter) were found in a single pig and smaller lesions (1.5–3 mm) in three pigs. These lesions were clearly circumscribed and had pronounced central necroses and dystrophic calcifications. In contrast, most of the smallest (usually <1.5 mm in diameter) found in two other pigs, had small compact fibrotic areas and blurred borders with obvious fibrous infiltrations into the interlobular tissues. E. multilocularis specific DNA was detected by PCR in all lesion types, but metacestode viability, as assessed by in vivo intraperitoneal inoculations in jirds, could not be demonstrated. Within 1 month post inoculation, all pigs developed specific IgG antibody responses against a battery of different antigens (metacestode, cyst fluid, and protoscoleces-derived native E. multilocularis and E. granulosus antigens, affinity purified Em2G11 antigen, antigen B, recombinant Em II/3–10 antigen). Two different reaction patterns were recorded. In the two pigs with the small lesions, pronounced reactions against all crude antigens with peaks 3–5 months p.i. and clearly elevated levels until the end of the experiment were noted. In all other pigs, antibody reactions remained low in all cases. In conclusion, we demonstrated two types of E. multilocularis metacestode development in pigs with distinct immunological response patterns.  相似文献   

7.
We analysed the individual-animal data from six of the nine outbreaks of tuberculosis in Canadian cattle and cervids from 1985 to 1994. A “positive/reactor” animal was one which had either a positive culture or a positive or suspicious reaction on a mid-cervical, comparative cervical, or gross or histopathological test for tuberculosis. Individual-animal data were collected only for herds which had one or more positive/reactor animals. Data were collected from the outbreak records in the Regional or District offices of Agriculture and Agri-food Canada’s Animal and Plant Health Directorate. The within-herd spread of Mycobacterium bovis was studied by determining the most-likely date at which the herd was first exposed to M. bovis and the number of reactions which had developed by the time the herd was investigated. The animal-time units at risk in the herd were probably overestimated, resulting in conservative estimates of the within-herd incidence rates. Negative-binomial regression was used to investigate factors which might have influenced the within-herd spread of tuberculosis. Increasing age appeared to be a risk factor for being a positive/reactor animal. When compared to animals 0–12 months old, animals 13–24 months old had an incidence rate ratio (IRR) of 7.6, while animals >24 months old had an IRR of 10.4 (p=0.009). Actual and predicted incidence rates for tuberculosis in mature (>24 months old) animals were calculated. Actual and predicted incidence rates were similar for cervids, within an outbreak. There was more variability between actual and predicted rates in the dairy and beef animals. In the one outbreak (Ontario) where there were positive/reactor cervid, dairy and beef herds, the actual incidence rate for cervids (IR=9.3 cases per 100 animal-years) was almost twice that of dairy cattle (IR=5.0) and three times that of beef cattle (IR=3.1).  相似文献   

8.
Malignant theileriosis of sheep is a highly fatal, acute or subacute disease is caused by the tick-borne protozoan parasite, Theileria hirci. In this investigation ten healthy male lambs aged 5-6 months were randomly divided into two groups, A and B and were kept in isolated tick-proof pens. They were treated for internal and external parasite before commencement of the experiment. The lambs were experimentally infected with T. hirci by placing ticks Hyalomma anatolicum anatolicum infected with T. hirci on them. The ticks used in this survey had originally been isolated from sheep and colonies of them were established in an insectarium. Before and after infection rectal temperatures and clinical signs of the lambs were recorded, blood and prescapular lymph node smears were prepared and examined to determine the extent of the parasitaemia, and blood samples were analyzed to evaluate their haemoglobin (Hb) and packed cell volume (PCV) rates. Three days after the commencement of a febrile reaction and appearance of the schizonts in the lymph node smears, treatment of the lambs in Group A with an extract containing the alkaloids of Peganum harmala (wild rue) was commenced. Group B lambs were kept untreated controls. Before treatment there were no significant differences in the rectal temperature, parasitaemia rate, and the Hb and PCV values between animals in the two groups but after treatment significant differences in these values was detected (P < 0.05). After treatment, the clinical signs and parasites in the lymph node smears of the animals in Group A disappeared and they all animals recovered. These parameters in the animals of Group B progressed until their death. Pathological studies showed the characteristic lesions of theileriosis in lambs in Group B, but not in Group A. The results indicate a therapeutic effect of the alkaloids of P. harmala for treatment of ovine malignant theileriosis.  相似文献   

9.
During the period April 1983 to March 1986, lymphoreticular lesions in cattle were surveyed at an Ontario abattoir. Postmortem examination of 171,157 cattle revealed macroscopic lesions in 696 animals (0.4%). The most frequent finding was abscessation of a single lymph node, a finding that was observed in 353 cases (50.7% of animals with lesions/0.2% of total slaughter). Actinobacillary granulomas were present in 252 lymph nodes (36.2%/0.1%). Other specific lesions included mycobacteriosis and mycotic or parasitic lymphadenitis. Cases of nonspecific chronic lymphadenitis or granulomas in lymph nodes, pigmentations, malformations, hyperplasia, and neoplasia were also seen. Abscesses were the most common splenic lesions. One animal had localized lymphangiectasia of the epicardium.  相似文献   

10.
Salmonella in the mesenteric lymph nodes of healthy sows and hogs   总被引：1，自引：0，他引：1  
Mesenteric lymph nodes were collected from healthy sow and slaughter hogs that had been kept in holding pens for an average of 10 and 2 days, respectively, before slaughter at an abattoir. Salmonella was isolated from 58.2% (67/115) of the sows and 31.3% (16/51) of the slaughter hogs. This difference in Salmonella prevalence was significant (chi 2 = 10.22, P less than 0.005); therefore, the hypothesis that there would be no significant difference in the infection rates of sows and slaughter hogs was rejected.  相似文献   

11.
Antimicrobial drug-use was assessed on 34 farrow-to-finish operations that marketed at least 500 hogs/yr. These operations either did not use any antimicrobials or used narrow-spectrum or broad-spectrum antimicrobials in rations of post-weaning pigs. Total antimicrobial use was measured for two months after obtaining inventories and records of all antimicrobials used. The collection of empty medication bottles and inventories of drugs on hand was convenient for producers and useful for estimating or validating recorded treatment rates, particularly for antimicrobials that were used only in one class of pig. Treatment records, however, underestimated by approximately 35% the amounts used for 27/29 farm–antimicrobial combinations. Rates of individual-pig treatment varied from 0–24.1 pigs treated/1000 pig-days, with a median of 5.29. Most individual animal treatments were given to piglets and sows at parturition and penicillin was the most commonly used antimicrobial. Gentamicin was administered to suckling piglets on 19 of the farms.  相似文献   

12.
The financial impact of use of cypermethrin pour-on (EctoporR) in control of animal trypanosomiosis was determined in a trial undertaken by the Kenya Trypanosomiasis Research Institute (KETRI). This trial started in December 1990 and ended in February 1992. It was undertaken in two adjacent ranches in the coast province of Kenya. The trial site was in an area of high apparent density (AD) of tsetse flies, and at the start of the trial no cattle were kept in this area. Cypermethrin was applied fortnightly to the 1100 steers which were kept in pour-on ranch ‘A’ while another 100 steers were kept in control ranch ‘B’ to act as control sentinels. From the main pour-on group, 100 animals were identified as the pour-on sentinels and compared to the control sentinels which received no pour-on.

Pour-on application led to a significant decrease in the tsetse AD in the pour-on ranch A to 90% of the initial AD in some areas. The animals treated with pour-on had a significantly higher mean packed-cell volume (PCV). The weekly prevalence of trypanosome infections in animals treated with pour-on was <4% with only one exception when it was <10%. In the control animals, the prevalence ranged between 10 and 50% (with a few exceptions when it was <10%). The incidence of tick-borne diseases was lower in the pour-on animals. The mean monthly weights of the pour-on animals was significantly higher, and at the end of the trial the pour-on animals had a mean weight gain of 136.70±16.7 kg while the control animals had gained 97.16±22.6 kg.

The financial net return of using cypermethrin pour-on was positive and the financial rate of return of 122.6% indicated that use of the pour-on was highly beneficial despite the high cost of the product.  相似文献   


13.
We investigated the effect of raising runt white sturgeon (Acipenser transmontanus) separately from dominant fish during the initial stages of grow-out in a commercial farm. Runt fish are poor-growers, have underdeveloped muscle mass, swim slowly and are more-frequently found at the top of the water column. The objective of the study was to describe the mortality and recovery rates (and their determinants) of white-sturgeon runts after separating them from dominant fish. Runt white sturgeon were stocked into twelve 2 m × 2 m rectangular tanks and graded periodically during a follow-up of 46–102 days. Overall mortality rates ranged from 0.3 to 7 dead fish per 1000 sturgeon-days at risk and overall recovery rates from 3.9 to 13.5 recovered fish per 1000 sturgeon-days at risk. Period-specific mortality and recovery rates increased over time. The period-specific mortality rates for all three periods were significantly higher for tanks of runts originating from grow-out tanks with high mortality (p-values: first period = 0.06; second period = 0.09; third period = 0.03), but were similar for tanks of runts of high- and low-mean initial weight. The period-specific recovery rates were significantly higher in runts originating from high-mortality grow-out tanks only for the third period (p = 0.05) but not the first and second periods (p-values = 0.33 and 0.25, respectively). Recovery rates were significantly higher in the higher-mean-weight runts tanks for the first and third period but not for the second (p-values: first period = 0.02; second period = 0.65; third period = 0.06). We concluded that the proportion of runts that recover during a 46–89 day period is substantial (16–58%); therefore, it might be worthwhile growing such fish separately in a fish farm for about three months. Financial analysis showed that this practice was profitable, if the value of white sturgeon fish for the farm exceeded $2.05 per kg.  相似文献   

14.
Seven dogs with parasitologically proven clinical visceral leishmaniosis (Leishmania infantum infection) were treated with a combination of allopurinol and sodium stibogluconate. The dogs received first orally 15 mg/kg of allopurinol every 12 h until the clinical signs improved, in the following 1 month period allopurinol at same dose and subcutaneously 30 mg/kg of sodium stibogluconate combination were given daily and at the end of the combined treatment, allopurinol was continued alone at the same dose till the end of 8 months. During the treatment period, dogs were supported by additional proteins, vitamins, and minerals. A long acting insecticide (collar or drop) was also used in order to prevent further parasite transmission. Follow-up was maintained by clinical, clinicopathological evaluation, and parasitological examination of lymph node, serology using the indirect immunofluorescent antibody test (IFAT). Before treatment commenced, the most important clinical signs were exfoliative dermatitis, ulcerations, peripheral lymhadenopathy, pale mucous membranes, weight loss, and ocular lesions. Clinicopathological findings included commonly anaemia, hyperproteinaemia, hyperglobulinaemia and hypoalbuminaemia. Before the treatment, amastigotes were seen in six of the seven dogs by examination of lymph node aspiration, and IFAT-titers were positive in all dogs. At the end of 8 months treatment, remission of clinical signs, restoration to normal of clinicopathological abnormalities were noticed. Lymph node aspiration was performed on three out of the seven dogs at the end of the treatment because of the very small sizes of the lymph nodes, and no amastigotes were observed. Although the mean IFAT-titer of the dogs were significantly (P < 0.001) lower compared with pretreatment, IFAT-titers of dogs were still positive. No relapses occurred during treatment period and a 6-24-month duration after the end of therapy. Based on the above results, long-term use of allopurinol combined with sodium stibogluconate together with support treatment concluded to have enough therapeutic efficacies in the treatment of dogs with visceral leishmaniosis. Observations of the cases for possible relapses were still going on and insecticide application was carefully carrying on in order preventing a possible re-infection.  相似文献   

15.
The levels of production, ascarid burden and respiratory disease were measured on 15 purposively selected swine herds, and the relationships between the various measures of ascarid burden were examined. On each farm 30 randomly selected pigs were weighed and rectal fecal samples were collected at approximately 11, 15, 19 and 22 weeks of age, and at slaughter. Fecal ascarid-egg counts and duration of infection were combined to calculate a composite measure of ascarid burden called "lifetime burden". At the abattoir the carcass weight and levels of anteroventral pneumonia, atrophic rhinitis, and liver lesions were recorded for each hog. The number of ascarids in the small intestines were counted. Study hogs were marketed at an average of 189 +/- 22 days. The average dressed carcass weight was 77.0 +/- 5.9 kg and the mean average daily gain was 0.519 +/- 0.071 kg/day. The percent of hogs with ascariasis varied widely among farms, no matter what measure of ascariasis was used; the percent with intestinal ascarids at slaughter ranged from 0% to 96%, the percent that shed ascarid eggs during their lifetime ranged from 0% to 100%, and the range for hogs with liver lesions ranged from 27% to 100%. Of the hogs slaughtered, 82% had milk spot lesions, 32% shed ascarid eggs during their lifetime and 35% had intestinal ascarids. The latter had an average of 12 intestinal ascarids. Anteroventral pneumonia occurred in 55% of the slaughtered hogs and 9% had atrophic rhinitis scores of five. The percent of hogs per farm with pneumonia ranged from 17% to 96%. The percent of hogs per farm with atrophic rhinitis scores of five ranged from 0% to 57%.  相似文献   

16.
The effects of prednisolone sodium succinate on the responses of porcine lymphocytes to phytohemagglutinin (PHA) and pokeweed mitogen (PWM) were investigated. Sensitivity of peripheral blood lymphocytes (PBL) to the synthetic glucocorticoid, prednisolone, was related to age of the lymphocyte donor. The greatest sensitivity was found in PBL from animals less than one week old; PBL from animals between 2 to 4 months retained some glucocorticoid sensitive cells; whereas, PBL from animals older than 6 months were exceptionally resistant to steroid. Similar age-associated sensitivities were found for lymphocytes from lymph node, spleen and thymus. Significant differential sensitivities among the various lymphoid organs were found with the thymic lymphocyte possessing the greatest sensitivity to steroid and the PBL lymph node and splenic lymphocytes possessing the highest resistance to the suppressive effects of steroid. The age related differences in sensitivity to steroid did not appear to be caused by differences in the number of steroid receptors because lymphocytes from susceptible and resistant animals had similar numbers of receptors. The results suggest that the age related sensitivity may be associated with a higher percentage of sensitive thymic-derived lymphocyte in the PBL, lymph node and spleen of the younger animals. Results of this study also suggest that the adult pig (6 months) should be classified as a steroid resistant species.  相似文献   

17.
A 95-day study (June 25-September 27, 2001) was conducted using 120 steers (311.9+/-2.4 kg) randomly allocated to two treatments: (1) mineral containing 0.55% fenbendazole (FBZ) and (2) control, no FBZ in the mineral. Animals in the FBZ group were individually identified by an electronic tag that was read each time an animal attended the mineral feeder. The feeder was equipped with load cells that enabled individual mineral intakes to be estimated. The FBZ group was provided with non-medicated mineral during a 14-day adaptation period (July 23-August 5) and an 8-day post-medication period (September 17-24). The intake of FBZ was monitored for 14 days during each of the two treatment periods; August 6-19 and September 3-16, separated by a 14-day non-medicated period, August 20-September 2. Control animals had access to non-medicated mineral for the entire 95-day study period. All steers were grazed on alfalfa-grass pasture for the duration of the study and had free access to flocculated, filtered and chlorinated water via an automatic waterer. Fecal samples were collected from steers three times during the experiment July 23, August 27 and September 27, and analyzed for nematode eggs and Giardia sp. cysts. Seventy-five and 83% of the steers in the FBZ group visited the mineral feeder during the first and second treatment periods, respectively. Individual daily mineral and FBZ intake for the first and second treatment periods was 52.9+/-6.6g per day and 10.1+/-1.2mg/kg BW; 72.3+/-8.4 g per day and 11.8+/-1.4 mg/kg BW, respectively. FBZ animals were separated into three groups during each treatment period based on the recommended dose (RD) of FBZ (5 mg/kg/BW), those that received > the RD, those that received < RD but > 50% RD and those that received < 50% of RD. Nematode egg counts and the number of animals infected with nematodes was reduced (p < 0.05) in all cattle that consumed FBZ as compared to control animals. In contrast to nematode eggs, numbers of Giardia cysts was not reduced (p > 0.05) by FBZ as compared to controls in either treatment period. These results may be a reflection of Giardia re-infection occurring following treatment and highlight the need for variation in treatment regimes specifically targeted at the parasite of interest.  相似文献   

18.
Despite many years of testing mink for serum antibodies against the Aleutian mink disease virus (AMDV) by counterimmunoelectrophoresis (CIEP) and elimination of reactors, this virus has remained the number one disease threat for the mink industry in Nova Scotia (NS). The objective of this study was to analyze CIEP test results to determine the success of the AMDV-control strategy in NS. A total of 2,964,920 CIEP test results from 82 ranches, spanning an eight-year period between 1998 and 2005, were analyzed. This survey included approximately 60% of the active ranchers in the province. The number of ranchers that tested their animals was 42 in 1998, gradually increased to 58 in 2003 and then showed some decline. The overall proportion of CIEP-positive mink was 3.34%, and varied between 5.22% in 1999 and 1.35% in 2005. The proportion of infected ranches ranged between 23.8% in 1998 and 70.7% in 2003. The overall trend was for a smaller proportion of infected animals but a larger proportion of infected ranches during this time period. Of the 82 ranches, 24 (29.3%) had negative CIEP in all tests, 15 (18.3%) had CIEP positive animals in every year tested, and 43 (52.4%) had positive and negative results in different years, indicating that AMDV infection was widespread in NS. There were 23 infected ranches with 8years of uninterrupted testing. These ranchers performed 75.8% of the total samples tested (2,246,711), implying that they have diligently been trying to eradicate the virus. Infection persisted on three of these ranches for the entire 8year period, and only two of the ranches remained CIEP negative for longer than four years. The average percentage of CIEP-positive mink on these ranches was 2.2, which was lower than 6.35% for the 33 infected ranches with occasional testing, and 73.6% and 82.4% for two ranches that had never used the CIEP test, showing that persistent test-and-removal strategy has been effective in reducing the prevalence of infected animals but has failed to eradicate the virus from most of the infected ranches.  相似文献   

19.
Three different production systems for autumn born dairy steers, managed more or less intensively, have been investigated. The aim of the production systems were to use a basic diet of grass, either grazed or conserved as silage or hay, combined in various proportions. The animals were slaughtered, aiming for the same degree of fattening, but at three ages. The intensive management aimed at slaughter in January–February at 26–28 months of age after indoor finishing with silage or hay. An “intensive out-of-season” management wished improve at slaughter at 28–30 months of age. Finally an extensive management with finishing at grazing resulted in slaughter in May–June at 30–33 months of age.

In three successive factorial experiments, 106 steers of two genotypes, Holstein and Montbéliard were reared to test the effects of the three production systems. The animals were evaluated for productive traits, carcass quality and biochemical characteristics of m. longissimus thoracis and m. rhomboideus thoracis.

For both breeds, the “extensive” animals produced heavier carcasses (+ 20 kg between “intensive” and “extensive”; P < 0.002). The carcass conformation evaluated by the EUROP classification did not differ between the production systems. The estimated percentage of adipose tissue of the carcass was significantly lower for the “extensive” steers (P < 0.05). The shear force measured on raw meat was not significantly affected by the production system, but after cooking, the shear force was higher for the extensive management as was the total collagen content. The haeminic iron content was always lowest in the intensive management. The results of these three series of experiments show that it is possible to produce steers with a feeding regime consisting mainly of grass (from 87% to 94% of the dry matter intake) grazed or harvested as hay or silage. To make the best use of the herbage resources of the farm and to limit the purchase of concentrates, the production of autumn born steers slaughtered at 32 months seems to be an attractive production system for dairy farmers.  相似文献   


20.
Sixteen male Holstein calves averaging 168 kg body weight (BW) were used to determine the effects of human growth hormone-releasing factor (1–29)NH2 (hGRF (1–29)NH2; .22 μg/kg BW), thyrotropin-releasing factor (TRF; .165 μg/kg BW) or hGRF (1–29)NH2 plus TRF (.22 and .165 μg/kg BW, respectively) on growth hormone (GH) release in animals exposed to 16 hr of light (L): 8 hr of dark (D) (lights on at 0100 hr) and hGRF plus TRF (.22 and .165 μg/kg BW, respectively) in animals exposed to 8L:16D (lights on at 0900 hr). For each treatment, times of iv injection were 0400, 1000, 1600 and 2200 hr. In animals exposed to 16L:8D, average GH peaks reached after hGRF (1–29)NH2 or TRF injections were 49.7 and 32.0 ng/ml while the area under the GH response curve (AUC) were 1247 and 1019 ng/ml*min, respectively. There was no significant effect of times of injection on GH release following the separate injection of hGRF (1–29)NH2 or TRF. In animals exposed to 16L:8D, GH peaks and AUC after hGRF plus TRF injections were 226.4, 189.2 and 116.8 ng/ml, and 4340, 3660 and 2415 ng/ml*min at 0400, 1000 and 1600 hr (lights on), respectively but only 42.3 ng/ml and 1692 ng/ml*min at 2200 hr (lights off). In animals exposed to 8L:16D, GH levels and AUC after hGRF plus TRF injections reached 177.5 and 180.5 ng/ml, and 2759 and 3704 ng/ml*min at 1000 and 1600 hr (lights on) but only 84.0 and 72.7 ng/ml, and 1544 and 1501 ng/ml*min at 0400 and 2200 hr (lights off), respectively. These results demonstrated that hGRF (1–29)NH2 and TRF can act in synergy to potentiate GH release in dairy calves. This synergistic action occurred only when both peptides were injected during the lighted phase of short and long day photoperiods.  相似文献   

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