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1.
Oral administration of 5 mg mestranol daily for 100 days to 70 German Black Peid bulls improved weight gain in 72% of the animals. Average additional increment ranged from 2 to 17%. During the first weeks of administration there was a weak and transient protein-anabolic action and improvement in digestion of crude protein. Appetite was slightly stimulated. Consumption of food and energy per unit of weight gain was improved; better growth led to higher slaughter weight. Treatment had no effect on meat to bone ratio, degree of fulness of the gastointestinal tract, or meat quality. Skeletal mineralization was improved by 10-30%, and there was a noticeable anabolic effect on mineral metabolism. After longer administration an antigonadotropic action became evident. Some veterinary indications for use in fattening cattle were derived from these effects. Further pharmacological and clinical investigation of this and more active anabolics seemed to be required.  相似文献   

2.
The metabolic fate of the anabolic agents, diethylstilbestrol, hexestrol, trenbolone acetate, zeranol and the endogenous steroids are discussed under the headings absorption, distribution and excretion. There is an optimum concentration of anabolic agent in the systemic circulation that results in a maximum increase in growth rate of farm animals. This optimum blood concentration should be maintained over a long period. However, there is rapid metabolism and excretion of anabolic agents with short half-lives in blood, and metabolic clearance rate equals entry rate. The rate of absorption of the agent, which is determined by formulation and site of administration, is most important and is best achieved by the use of slow release implants. The pattern of exponential absorption from compressed pellets of single anabolic agents is not ideal, and a more constant payout of drug, in particular estradiol-17 beta, is best achieved in combined preparations of agents or from silicone rubber implants impregnated with the agent. The high metabolic clearance rate and rapid excretion of anabolic substances influences the distribution of residues. Outside the site of administration, less than 1% of the administered dose is present in the animal. The lowest concentrations of residues are found in muscle and fat, higher concentrations are present in liver and kidney and the highest concentrations are in the bile, urine and feces.  相似文献   

3.
Increasing daily light exposure from 8 to 16 h increases average daily body weight gains of sheep and Holstein cattle but reduces gains of white-tailed doe fawns. Some of these effects on average daily gain in sheep are the result of increased gut fill and pelt weight. Increasing daily exposure to light increases feed intake when sheep or cattle are fed ad libitum. However, increased feed intake is not a prerequisite for the anabolic effects of long duration exposures to light because increased growth occurs in the animals given 16 h light:8 h dark (16L:8D) even when feed intake is restricted. The anabolic effects of increased duration photoperiods in sheep are independent of the gonads, whereas in cattle they are dependent on the gonads. Consistent increases in average daily gains of cattle in response to longer duration photoperiods have not always been achieved. The lack of consistency may be associated with sexual maturity or rate of fattening of the animal. For example, the stimulatory effects of 16L:8D photoperiods on live weight gain are not readily manifested in immature prepubertal heifers, but occur primarily during the peripubertal period. Short days are conducive to deposition of fat, which may account for the stimulatory effects of short days on live weight gain of white-tailed doe fawns and excessively fattened Holsteins. In contrast, long duration photoperiods stimulate protein accretion in cattle. The hormonal signals that mediate the anabolic effects of increasing exposure to light are not associated with change in insulin, thyroxine or growth hormone concentrations in the blood. Glucocorticoid concentrations in serum decrease with longer duration photoperiods which is consistent with an anabolic effect. Increasing daily light exposure to 16 h/d hastens the increase in concentrations of progesterone and testosterone in sera of peripubertal heifers and prepubertal bulls, respectively. Thus, change in secretion of reproductive hormones in the peripubertal period of cattle may be associated with the anabolic effects previously described and is consistent with gonad dependency. Prolactin concentrations in serum increase in sheep and cattle as duration of light exposure increases. But, there is no irrefutable proof that prolactin is responsible for the increased rates of gain or change in carcass composition associated with longer exposures to light. Thus, the hormonal mechanisms involved in photoperiod-induced alterations in growth remain to be established.  相似文献   

4.
The clinical signs, the results of haematological and biochemical analyses and the treatment of 30 cattle with botulism are described, and the signs of the 13 cattle that survived are compared with those of the 17 that were euthanased owing to the disease. The cattle originated from 11 farms that had experienced an outbreak of botulism. The most important clinical sign in all the cattle was a reduction in the strength of the tongue; excessive salivation and difficulty in swallowing were observed in 20 of the animals, and the ears of 15 of them drooped. In 21 of the cattle, reaction to pricking of the head and body with a hypodermic needle was either absent or slight. Twelve of the animals had an unsteady, slow, difficult gait, and nine were unable to stand. A significantly higher proportion of the cattle which were euthanased had marked changes in behaviour and condition, anorexia, severely reduced skin turgor, weak tongues, a low rectal temperature, a high heart rate and a low blood pH; 11 were euthanased immediately after a clinical examination and six were euthanased one to five days after the initiation of treatment because their condition had deteriorated. Thirteen of the animals were treated for three to 23 days and were healthy when they were discharged. The treatment consisted of an intravenous infusion of 10 to 20 litres of glucose saline per day and the daily administration of fresh ruminal juice. Follow-up by telephone several months later revealed that all 13 animals had recovered completely.  相似文献   

5.
Disease or endotoxemia alters the plasma concentrations of anabolic hormones, particularly growth hormone (GH) and insulin-like growth-factor I (IGF-I). In general, these hormones are inhibited during the catabolic disease state. A hypothesis has evolved that anabolic hormones might be useful in patients’ recovery under these and other catabolic circumstances. The treatment of cattle with GH has provided significant improvement in the physiological response of the animals to the subsequent injection of bacterial lypopolysaccharide (LPS), perhaps via inhibition of tumor necrisis factor (TNF) release. However, this improved response to disease was not observed with animals treated with GH and infected with one of two parasitic organisms, Sarcocystis cruzi or Eimeria bovis. Recent attempts with other anabolic hormones, estradiol and progesterone, have proven remarkably effective in improving the adaptive physiological responses of calves to either E. bovis infection or to the injection of LPS. All animals displayed signs of infection, but the intensity and duration of symptoms were reduced. Although a mechanism is not yet known, there were no effects on TNF; cortisol; the percentages of lymphocytes expressing CD2, 4, or 8 antigens; or the production of antibodies.  相似文献   

6.
OBJECTIVE: To determine the rectal temperature response of cattle, following the oral administration of ergot of rye (Claviceps purpurea), under pen conditions of enforced sunlight compared with those of enforced shade. DESIGN AND PROCEDURE: Hereford cross steers were divided into two groups of 18. One group was dosed once, on a Monday morning, with finely ground rye grass ergots at a rate of 180 mg/kg body weight and held in the sun for 7 h each day until Friday afternoon. The other group was not dosed but was similarly held in the sun during the same period. Their rectal temperatures were measured early morning and mid afternoon, from Monday to Friday inclusive. The process was repeated for each group, but this time they were held in the shade. The four treatment options were run concurrently by conducting the experiments over 6 weeks and using 3 animals in each treatment group, each week. RESULTS: The thermic response over all weeks, of the ergot treated, sunlight exposed cattle, was deemed greater than for the other groups, based on the following four parameters. The increase in rectal temperature between early morning and mid afternoon, the size of the mid afternoon rectal temperature rise, the difference between the maximum mid afternoon rectal temperature recorded by an animal in the sun compared with that recorded by the same animal in the shade, and finally the number of animals in a treatment group that recorded rectal temperatures > 40.00 degrees C. The difference in the daily increase in body temperature between the ergot treated, sun exposed cattle and the ergot treated, shaded cattle, was greater than that observed between the sun exposed and shade restricted control cattle. Nine of 18 ergot treated and sun exposed cattle developed hyperthermia; no cattle in the other three groups did. CONCLUSIONS: Some sunlight exposed cattle, dosed with a low amount of ergot of rye, can experience a body temperature elevation above the normal range, even under mild ambient temperature and humidity conditions. Sunlight exposure causes an increase in body temperature in normal cattle that is probably attributable to solar radiant heat. Ergot ingestion causes an increase in body temperature in shaded cattle that is probably attributable to ambient temperature and humidity effects. This response can be increased by sun exposure and this increase is attributable to solar radiant heat effects and possibly also solar radiation. A response to radiant heat is consistent with the known physiological effects of ingested ergot alkaloids, but a response to solar radiation is not.  相似文献   

7.
The effect of two anti-inflammatory drugs on the development and persistence of clinical signs in cattle experimentally infected with bovine ephemeral fever (BEF) virus was investigated by their administration, either before or after the commencement of fever. A total of 16 cattle was given phenylbutazone sodium (PBZ). The drug prevented fever and other clinical signs in six cattle when given daily during the incubation period, and at 8-h intervals for 5 days when clinical disease might be expected. When treatment with PBZ was deferred until 2-4 h after the commencement of fever, the rectal temperature returned to normal within 4 h in four of six cattle and the development of other clinical signs was suppressed. Clinical signs of ephemeral fever occurred in four untreated cattle infected at the same time. Viraemia, the development of neutralizing antibodies (at 8-11 days), resistance to subsequent challenge with BEF virus, neutrophilia, lymphopenia and a rise in plasma fibrinogen occurred in all BEF-infected animals whether treated or untreated, despite different clinical appearances. The mean peak of plasma fibrinogen in the untreated cattle was 6.9 g l-1; 3.2 g l-1 when treated 2-4 h after fever developed and 3.8 g l-1 when treated from 18-h post-infection. BEF virus was isolated from leucocytes of each of the cattle, but the frequency of isolation was lower in the treated group. The results indicate that treatment with PBZ blocked the host response which produces the clinical signs and did not have an anti-viral effect. In a similar experiment, a long-acting anti-inflammatory drug, flunixin meglumine, failed to prevent BEF or to modify the clinical signs once they had developed, except for the rectal temperature which returned to normal within 2-4 h of the administration of the drug. The efficacy of this drug was not improved by increasing the dosage to two or three times the recommended level.  相似文献   

8.
The effect was investigated of the Ralgro preparation with the active substance zeranol on histological and histochemical properties of bull muscles. The anabolic effect was displayed by a trend toward greater thickness of muscle fibres in m. longissimus thoracis, m. semitendinosus and m. triceps brachii, whilst differences between the muscles of experimental and control animals were not statistically significant. The bulls administered zeranol had the higher proportions as well as the higher relative volumes of white (aW) muscle fibres, but neither were these differences statistically significant in comparison with the control. The growth and development of testicles are inhibited by zeranol. The inhibition is significant and persists during 30 days after the last administration. Later on, the rate of development and growth are increased with the testicles reaching the weight of the sexual glands of control animals in 90 days after the last administration; the coiled seminiferous tubules grow and spermiogenesis occurs.  相似文献   

9.
Induction of superovulation using human menopausal gonadotriphin (hMG) in Japanese Black cattle can result in the recovery of a higher percentage of high quality embryos compared with that using porcine follicle stimulating hormone (FSH). In order to clarify the endocrinological mechanism involved in this discrepancy, 30 superovulation sessions of 17 Japanese Black cattle were studied. Fifteen cattle were super‐stimulated with hMG (total 600 IU), and the remaining 15 cattle were given FSH (total 20 mg). The plasma profiles of LH, estradiol‐17β (E2) and progesterone (P4) were correlated, and the embryo quality was investigated. The total number of ova recovered and the number of transferable embryos tended to be larger in the hMG‐treated group than in the FSH‐treated group. The percentage of excellent embryos tended to be higher in the hMG‐treated group than in the FSH‐treated group (54.3 and 28.7%, respectively, p < 0.10). The E2 level increased during the first 3 days after the initial administration of either hMG or FSH and was higher in the hMG‐treated group than in the FSH‐treated group (p < 0.05). During this period, the E2 level could be categorized into one of the following three types according to whether it increased or decreased and according to the degree of increase or decrease: (1) increase by a factor of 1.2 or more (quick increase type) (2) slight increase by a factor less than 1.2 (slow increase type), and (3) no increase (unstable increase type). In the group treated with hMG, 66.7% of the animals (10 of 15 cattle) showed a quick increase in the E2 level. However, in the FSH‐treated group, 40% (six of 15) of the animals showed a slow increase in the E2 level. The plasma LH level increased dramatically 8 h prior to the peak level in both the hMG‐ and FSH‐treated groups, and then it returned to the basal level 12 h later. After the administration of prostaglandin (PG)F2α, the LH peak level was attained within 44 h in 80% of the animals in the hMG‐treated group, whereas in the FSH‐treated group, the LH peak level tended to be reached later. The P4 level did not increase during the period of hMG or FSH treatment and decreased drastically following administration of PGF2α. After the onset of oestrus, the P4 level was higher in the hMG group than in the FSH group, and 5 to 7 days after oestrus, the level remained higher in the hMG group than in the FSH group (p < 0.05). After the first 3 days of hMG administration, the E2/P4 ratio was higher than that after FSH administration. Furthermore, on the day following PGF2α administration, the ratio was significantly higher in the hMG group than in the FSH group (p < 0.05). These results indicate that superovulation in cattle given hMG results in a significant increase in plasma E2 during the first 3 days and that the increase in the plasma P4 level is larger a few days after oestrus and thereafter compared with FSH‐induced superovulation. Therefore, such plasma level profiles may be related to the increased recovery rate of high quality embryos.  相似文献   

10.
The effect of corticosteroids on the reaction to the intradermal injection of phytohemagglutinin was examined in normal cattle. The associated hematological changes were also examined. Normal, untreated cattle responded to an injection of 1 mg phytohemagglutinin in 0.1 mL saline by a 40 to 80% increase in double skin thickness while corticosteroid treated animals had responses approximately one half of the controls. Neutrophils predominated early in the reaction but were replaced by increasing proportions of lymphoid cells towards 72 hours. These results indicate that an intact and functional inflammatory mechanism is required for a cutaneous response to phytohemagglutinin. Normal animals had a physiological leukocytosis characterized by an increase in mature neutrophils and lymphocytes. Corticosteroid treated animals had a mature neutrophilia, lymphopenia, eosinopenia and monocytosis. These hematological changes were qualitatively similar to those seen in other species.  相似文献   

11.
Ceftiofur crystalline-free acid sterile suspension (CCFA-SS), a long-acting formulation of ceftiofur formulated for subcutaneous injection in the middle third of the posterior aspect of the ear, is being developed for the control and treatment of bovine respiratory disease. A study was designed to evaluate average daily gain (ADG) and feed efficiency (FE) for cattle through 140 days in the feedlot after CCFA-SS was administered concurrently in the same ear with a growth-promoting implant. On Day 0, steers (n = 207) averaging 189 kg in weight were randomly assigned to the following treatments: Revalor -S implant (120 mg trenbolone acetate and 24 mg estradiol per implant; Hoechst-Roussel Agri-Vet Company) (n = 64); CCFA-SS at 6.6 mg ceftiofur equivalents/kg and a Revalor -S implant (n = 64); untreated control (no CCFA-SS or implant) (n = 63); or CCFA-SS only (n = 16). On Day 56, an Implus-S implant (200 mg progesterone USP plus 20 mg estradiol benzoate; Pharmacia and Upjohn Animal Health) was administered to all cattle. Tolerance of administration of all materials was observed visually and by palpation of the treated ears. Average daily gain and FE from Day 0 through Day 56 were significantly (P <.001) better for steers of both groups with an implanted growth-promotant than for untreated controls. From Day 0 through Day 140, ADG was significantly (P <.05) better for cattle given an implant or an implant plus CCFA-SS than for untreated controls and FE was significantly (P <.05) better for cattle given an implant plus CCFA-SS than for controls. Mild or moderate, transient swelling of the treated ear was observed in two cattle (CCFA-SS plus implant) on Day 52. On Day 56, 88 % of cattle treated with CCFA-SS, 84 % of the cattle treated with an implant plus CCFA-SS, and 100 % of cattle in other groups were normal. Administration of CCFA-SS in the middle third of the posterior aspect of the ear at the same time as growth-promoting implants did not affect performance of cattle in the feedlot and was well tolerated by the animals.  相似文献   

12.
The immediate as well as the persistent anthelmintic efficacies of topically applied eprinomectin were evaluated in goats against induced infections with Teladorsagia circumcincta (2800 L3) and Trichostrongylus colubriformis (6000 L3). Twenty-three culled dairy goats were allocated to the following groups: control animals (group 1), animals treated 21 days prior to nematode infection (group 2), animals treated 7 days prior to nematode infection (group 3) and animals treated 21 days after nematode infection (group 4). Eprinomectin was applied at twice the cattle dose rate (1.0 mg/kg BW). According to the groups, necropsies were undertaken 28 days after nematode infection (groups 1-3) or 14 days after the anthelmintic treatment (group 4). Worm counts were determined for abomasum and small intestine. The curative anthelmintic efficacy of eprinomectin at 1.0 mg/kg BW on existing worm burdens was 100% against T. circumcincta and T. colubriformis. Quite similar worm burdens reductions were observed when eprinomectin was administered 7 days before infection whereas they were only 52.4 and 17.8% for T. circumcincta and T. colubriformis, respectively, for an administration of the drug 21 days prior to the nematode infection.  相似文献   

13.
The antiviral effects of recombinant bovine interferon-tau (rboIFN-tau) on bovine leukemia virus (BLV) were examined in vitro and in vivo. In the in vitro experiments, BLV titers decreased in FLK-BLV cells and in peripheral blood mononuclear cells of BLV-infected cattle treated with rboIFN-tau at a concentration higher than 10(2) U/ml. In order to examine the in vivo effects of rboIFN-tau, 10 BLV-infected cattle were subcutaneously injected with rboIFN-tau. In the first experiment, 6 cows were administrated with 10(5) U/kg body weight of rboIFN-tau 3 times per week for 4 weeks, while in the second experiment 4 cows were administrated with 10(6) U/kg body weight of rboIFN-tau 3 times per week for 3 weeks. No adverse effects were observed after the administration of rboIFN-tau. In experiment No. 1, the mean BLV titers in cattle decreased in the post-rboIFN-tau administration period compared to the pre-rboIFN-tau administration period. In experiment No. 2, the mean BLV titers in cattle decreased in the rboIFN-tau administration period. These results suggest that rboIFN-tau decreases BLV titers in vitro and in vivo and that rboIFN-tau possibly reduces the degree of BLV titer in cattle without severe side effects.  相似文献   

14.
The results of an experiment to determine the effectiveness of prostaglandin analogues to induce estrous synchronization of cattle are presented. There were 257 experimental animals and 119 control animals. 44 cattle that had histories of fertility disturbances were studied separately to determine if the estrous synchronization could improve fertility. The 257 experimental animals were given 2 .5 mg injections im of ICI 80,996 (ICI) with an interval of 10 or 11 days between injections. Then artificial insemination was administered 63 or 75 hours after the 2nd ICI injection. 1 group of cattle underwent artificial insemination both 75 and 99 hours after the 2nd ICI injection. 47 cattle received a 1.5 mg injection im of gonadotropin-releasing hormone (GnRH) in conjunction with artificial insemination. Fertility was not significantly higher among the animals treated with prostaglandin analogues than among the control animals. 61% of the experimental animals had mature follicles at the time of artificial insemination with a 65% conception rate. The animals given GnRH showed a higher rate of conception compared with the control group, and the animals showed the highest rate of conception. Intensive tests done on 16 cattle showed that a complete luteolysis occurred 15-24 hours after treatment, the luteinizing hormone (LH) peak occurred 51-100 hours after treatment, and ovulation occurred 69-120 hours after treatment. The cattle that received GnRH injections in conjunction with artificial insemination showed a peak LH level 3 hours after the GnRH injection.  相似文献   

15.
Heat stress in cattle results in millions of dollars in lost revenue each year due to production losses, and in extreme cases, death. Death losses are more likely to result from animals vulnerable to heat stress. A study was conducted to determine risk factors for heat stress in feedlot heifers. Over two consecutive summers, a total of 256 feedlot heifers (32/ breed/ year) of four breeds were observed. As a measure of stress, respiration rates and panting scores were taken twice daily (morning and afternoon) on a random sample of 10 heifers/ breed. Weights, condition scores, and temperament scores were taken on 28-day intervals during the experiment. Health history from birth to slaughter was available for every animal used in this study. It was found that at temperatures above 25 °C, dark-hided animals were 25% more stressed than light-colored; a history of respiratory pneumonia increased stress level by 10.5%; each level of fatness increased stress level by approximately 10%; and excitable animals had a 3.2% higher stress level than calm animals. Not only did the stress level increase with these risk factors, but average daily gain was reduced. The Charolais cattle gained significantly more than all other breeds of cattle tested. Calm cattle gained 5% more than excitable cattle. Finally, cattle treated for pneumonia gained approximately 8% slower than non-treated cattle. The results of this study have not only revealed heat stress risk factors of breed (color), condition score (fatness), temperament, and health history (treated or not treated for pneumonia), but have also shown the effectiveness of using respiration rate as an indicator of heat stress.  相似文献   

16.
Contagious bovine pleuropneumonia (CBPP), caused by Mycoplasma mycoides subsp. mycoides SC (MmmSC), is one of the most important diseases of cattle in Sub-Saharan Africa. The live T1/44 vaccine is normally used for its control but produces only transient protection and gives rise to adverse reactions. The present study evaluated the efficacy of danofloxacin (2.5% Advocintrade mark, Pfizer Ltd.) for the treatment of naturally infected cattle and in the prevention of CBPP transmission to in-contact cattle. Adult cattle, taken from a natural outbreak, were placed into two groups of 10 animals and kept on a research farm in paddocks 50m apart. One group was treated with 2.5mg/kg danofloxacin on days 0, 1 and 2; the other group were saline treated. On day 2, 10 CBPP-free, seronegative cattle were placed in contact with each of the two groups. All cattle were monitored for 3.5 months. No differences were seen in clinical improvement of the CBPP-affected cattle treated with danofloxacin compared with the untreated CBPP-affected cattle with approximately half of each group being withdrawn because of CBPP or showing CBPP lesions at post mortem examination. Clinical scores of the two groups were also similar. However cattle kept in contact with the danofloxacin-treated CBPP-affected animals showed significantly fewer lesions, less mortality and fewer animals were seropositive (P<0.02) and had reduced clinical scores (P<0.001) compared to cattle kept in contact with untreated CBPP-affected cattle. MmmSC was also isolated from fewer contact controls kept with the treated group. These findings could have important implications for the control of CBPP in Africa.  相似文献   

17.
Experiments were performed to examine the effects of long‐term treatment with recombinant bovine somatotropin (rbST) on milk plasmin–plasminogen and milk composition by one injection of 500 mg of rbST in every 14 days throughout lactation in crossbred Holstein cattle. The animals receiving rbST gave a greater milk yield and rate of blood flow to the udder during early lactation than the control group. The milk lactose concentration remained constant while the milk protein concentration increased as lactation advanced in both groups. The level of milk fat in rbST‐treated animals was significantly greater than in controls in the early lactation period (P < 0.05). The milk sodium and chloride concentrations of the rbST‐treated animals significantly decreased in early lactation as compared with the control animals. The sodium : potassium ratio of the rbST‐treated animals was significantly lower than those of control animals in the early lactation (P < 0.05) and it markedly increased in late lactation. As lactation advanced, the concentration of plasmin in the milk gradually increased, while the milk plasminogen concentration significantly increased in both groups. The plasminogen : plasmin ratio decreased in the control animals while it increased in the rbST‐treated animals as lactation advanced. These findings demonstrate that rbST is involved the activity of the plasmin–plasminogen system but is not involved in maintaining tissue integrity in the mammary gland during late lactation in crossbred dairy cattle.  相似文献   

18.
To determine the effects of bovine somatotropin (bST) treatment beginning at 3 ages on the growth rate and components of the somatotropic axis, 40 beef cattle (200 +/- 21 d of age) were randomly assigned to 1 of 4 treatments (10 animals/treatment). Three of the treatment groups received bST (33 mug/kg of BW) daily beginning at 200, 250, or 300 d of age until all animals reached 400 d of age; the fourth group served as controls (0 bST). Animals were housed in pens (5 animals per pen; 2 pens per treatment) and fed a diet formulated for an ADG of 1.2 kg/d. Feed intake (per pen) was measured daily, and BW was determined weekly. Blood samples (10 mL) and ultrasound measurements were collected at 200, 250, 300, 350, and 400 d of age. Serum concentrations of ST and IGF-I were determined by RIA and IGFBP-2 and -3 by ligand blot procedures. Overall, cattle gained 284.0 +/- 14.7 kg of BW with a treatment x week interaction (P < 0.01), such that during the treatment period ADG was 11.6, 8.7, and 15.8% greater (P < 0.05) in cattle treated with bST beginning at 200, 250, and 300 d, respectively, relative to controls during the same time frame. Average DMI was 13.6% less (P < 0.05) in bST-treated cattle than in controls. Increases in ADG coupled with a reduction in DMI resulted in 11.7, 14.0, and 26.4% increases (P < 0.01) in the efficiency of gain (G:F) in bST-treated cattle beginning at 200, 250, and 300 d of age, respectively, compared with contemporary controls. Backfat thickness increased (P < 0.05) over time, but the magnitude of the increase was less in the bST-treated cattle (treatment x week interaction; P < 0.05). Area of the LM increased (P < 0.05) over time but was similar across treatment groups. Serum concentrations of ST, IGF-I, and IGFBP-3 increased (P < 0.05), whereas IGFBP-2 decreased (P < 0.05) over time. The changes in the components of somatotropic axis were more pronounced in bST-treated cattle compared with controls, with the greatest magnitude of response in animals that began bST treatment at 300 d of age. In conclusion, the exogenous bST-induced growth response was greater in animals that began to receive bST administration at 300 d of age and received it for a shorter period (100 d) compared with animals that received bST beginning at 200 or 250 d of age.  相似文献   

19.
Ward CJ 《Veterinary parasitology》2006,138(3-4):268-279
A computer model of the population biology of Ostertagia ostertagi in young cattle and the effect of the parasite on animal growth has been constructed. It was validated against results from field trials where worm populations and rate of growth of cattle treated with anthelmintics were compared to similar groups of untreated animals. A close correlation between observed and predicted values for faecal egg and pasture larval counts was seen in the cattle which had been treated with an oxfendazole pulse release bolus at turnout. Timings and peak values were less accurately predicted in the untreated cattle. Although predictions for live weight gain during the grazing season indicated that the model may be overestimating the potential growth rate of cattle, it is considered that the model provides a suitable tool for comparing the effectiveness of different worming programmes under farm conditions. The computer simulation also allowed examination of the underlying influences and interactions between parasitological factors, such as numbers of immature and adult worms, and animal and pasture factors, such as sward height, grass consumption and feed conversion, in the parasite's influence on animal performance.  相似文献   

20.
The goal of the present paper was to establish criteria for the differentiation of thymic lymphoma and haematoma of the ventral neck in cattle. Four cattle with thymic lymphoma and seven with haematoma of the ventral neck underwent physical, haematological, biochemical and ultrasonographic examinations as well as histological evaluation of a biopsy specimen. All of the animals had firm non-painful swellings, which were no warmer than normal and extended from the pharyngeal region to the thoracic inlet. A diagnosis could not be established based on the results of physical examination and palpation of the swellings. Animals with a haematoma had a shorter history of being ill compared to those with thymic lymphoma. In patients with a haematoma, anaemia was present, the heart rate was elevated and the haematocrit was decreased, but not in cattle with thymic lymphoma. A tentative diagnosis was made on the basis of a macroscopic evaluation of the biopsy samples, which were dark red and firm in cattle with a haematoma. All cases of malignant thymic lymphoma were confirmed by histological examination of a biopsy sample. Ultrasonography did not help to differentiate between haematoma and thymic lymphoma. All animals with thymic lymphoma and three of those with a haematoma were euthanased. The four remaining animals with a haematoma were treated successfully.  相似文献   

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