Sympathico-adrenal effects of endotoxaemia in cattle

Intradermal injection of 46 micrograms E coli endotoxin had no effect on the plasma cortisol and noradrenaline concentrations of four dairy cows. Mean values were similar to normal values reported in the literature. Intravenous injection of 75 micrograms of endotoxin on the following day caused a massive increase in plasma cortisol concentrations which lasted for seven hours. Plasma noradrenaline concentrations increased rapidly after the intravenous administration of endotoxin and remained high for at least one hour. A possible relationship between endotoxaemia and the pathogenesis of acute laminitis is discussed.     

Histopathological effects of boldenone in cattle

Histopathology of male cattle previously found positive for béta-boldenone in urine in the Netherlands and in Italy was studied. The animals were derived from practice and several weeks had passed after the finding of béta-boldenone before the animals were examined. The animals consisted of 34 male veal calves and one finishing bull. In the prostate gland hypersecretion, cyst formation (45%) and hyperplasia of the urethral epithelium was observed, in the bulbo-urethral gland similar alterations were present. The testis showed reduced development and degeneration of the germinal epithelium (70%), leading to debris and syncytial cell formation in the lumina. Stromal proliferation was evident. In some animals the liver was sampled and showed periportal fibrosis, bile duct proliferation and sometimes necrosis. The bull also showed degeneration of the germinal epithelium of the testis and absence of sperm production, the prostate gland showed some secretion and had an atrophic appearance. It is concluded that béta-boldenone may lead to degeneration of the germinal epithelium of the testis and hypersecretion and cyst formation in the prostate and bulbo-urethral gland, which alterations may heal in time.     

Hemodynamic effects of unilateral segmented lumbar epidural analgesia in cattle.

Hemodynamic measurements, arterial and mixed venous blood gas tensions, and pH were determined in 12 adult cows (mean weight 538 kg) following the injection of 8 ml of 5% procaine between the first and the second lumber vertebra into the epidural space. Comparison of base-line data with obtained during unilateral segmented lumbar analgesia between T(13) and L(3) segments indicated significant decreases (P is less than 0.05) in total peripheral resistance and diastolic and mean arterial blood pressures, and significant increases (P is less than 0.05) in heart rate and cardiac output. Arterial and mixed venous blood gas tensions and pH, O(2)-uptake, stroke volume, left ventricular stroke work, left ventricular minute work and hematocrit did not change significantly (P is less than 0.05). Cardiovascular and respiratory values in two cows (mean weight 700 kg) given xylazine (50 mg, IM), were depressed from base-line data, but did not change significantly (P is less than 0.05) during unilateral segmental epidural analgesia of segments T(13 to L(3). The nonsedated healthy cow tolerates sympathetic vasomotor blockade between T(13) and L(3) segments well and is able to mobilize circulatory mechanisms effectively.     

Cardiopulmonary effects of position in conscious cattle

The cardiopulmonary effects of 4 positions (standing, right lateral, left lateral, and dorsal recumbency) were evaluated in conscious cattle in which no sedatives or anesthetic drugs were given. Each position was maintained for 30 minutes, during which time there were no significant changes in heart rate, respiratory rate, mean arterial blood pressure, arterial pH, PaCO2, arterial base excess, or venous blood gas values. Significant decreases in PaO2 developed when cattle were in lateral positions and dorsal recumbency. Cardiac index was unchanged in all positions, except in dorsal recumbency at 30 minutes, when it was significantly decreased.     

Clinical and clinico-pathological effects of Escherichia coli endotoxin in mature cattle.

The effects of intravenous administration of Escherichia coli endotoxin were studied in eight mature lactating cows. Three cows were studied following intrammary infection with E. coli. Significant clinical findings are presented. Significant clinico-pathological findings include leukopenia, decreased blood serum calcium concentrations and increased levels of serum glutamic-oxaloacetic transaminase and serum ornithine-carbamyl transferase. Significant elevations of plasma corticosteroids were also noted.     

Direct and maternal genetic effects for carcass traits in beef cattle.

Carcass measurements were taken on 1,537 steers produced over four generations in a rotational crossbreeding study. Breed direct and maternal additive and heterotic genetic effects were estimated for hot carcass weight (HCWT), retail yield (RY), longissimus muscle area (LM), fat thickness (FT), marbling score (MS), and Warner-Bratzler shear force (WBS). Angus (A), Brahman (B), Charolais (C), and Hereford (H) breeds were involved in straightbred, first-cross, and two-, three-, and four-breed rotational crossbred matings with each crossbred combination including the B. Breed direct (Ig) and maternal (Mg) additive genetic effects and direct (Ih) and maternal (Mh) heterotic genetic effects were estimated using a multiple-regression model. The Ig and Mg effects were expressed as deviations from the overall mean. The IgC effects (Ig for C breed) were significant for HCWT, RY, and LM and resulted in leaner, heavier carcasses. The IgA and IgH effects were, in general, negative (P < .05) for HCWT, RY, LM, and WBS, and positive (P < .01) for FT and MS. The IgB effects were large and undesirable for HCWT, RY, LM, MS, and WBS (P < .01). The majority of Ih effects were beneficial (P < .05) for HCWT, RY, LM, and WBS. The Ih effects exhibited by B combinations were of greater (P < .05) magnitude with positive influences for HCWT, RY, and LM and desirable effects for WBS. The maternal additive and heterotic effects were of lesser importance than the direct additive and heterotic effects for the carcass traits studied.     

光周期技术对奶牛的影响

自从1978年报告明暗周期（16小时明期、8小时暗期）光照具有催乳作用以来，许多研究报道长光照促进产奶量增加。可是，与产奶量增加有关的内分泌因素一直无一致的结论。最近研究表明类胰岛素生长因子I（IGF－I）可以调节长光照的催乳反应，长光照确实增加青年牛及泌乳牛IGF－I含量，从而导致产奶量增加。这种IGF－I含量的增加与体内血液激素变化无关，模拟短光照的褪黑素对长光照诱导的IGF－I增加有抑制作用。不过，饲喂褪黑素对奶牛产奶量没有影响，尽管目前对其内分泌机制了解还不够深入，但是奶牛生产者对光周期管理技术如何与其它饲养管理措施相结合很感兴趣，有足够证据表明长光照对奶牛产奶量影响可以持续整个泌乳期，长光照与BST（牛生长激素）结合应用使产奶量增加幅度更大，在干奶期间，长光照处理增加围产期催乳素峰值，可是，与长光照相比，大干奶期间短光照处理可使下一个泌乳期产奶量最大幅度增加，这主要是由于它对奶牛光周期反应系统产生了影响，总之，IGF－I可能是长光照处理增加产奶量的中间调节者，光周期管理可以有效地与其它管理措施相结合（如BST）,在干奶期重视光周期管理对下一个泌乳期获得最大产奶量意义很重大。     

Maternal effects on docility in Limousin cattle

The objective of this study was to quantify the role of maternal effects on docility in Limousin cattle. Docility scores were obtained at weaning while animals were restrained in a squeeze chute. Scores 1 through 6 represented a docile to aggressive temperament, respectively, and were provided by the North American Limousin Foundation. Observations with unknown age of dam, contemporary groups containing less than 10 observations, contemporary groups with no variation, and single-sire contemporary groups were removed, leaving 21,932 observations. A 2-generation pedigree file compiled from animals with observations contained 49,459 animals. Fixed effects were weaning contemporary group and age of dam (2, > or =3 yr). Six animal models encompassed combinations of random factors: direct genetic, maternal genetic, and maternal permanent environmental effects. The model D was the most basic, containing direct genetic and residual effects, and it resembled the method currently used by the North American Limousin Foundation for genetic evaluation of docility. Maternal genetic or permanent environmental effects were separately added to the model D, denoted as models DM and DC, respectively. Model DMC contained all random factors. Models DM-Zero and DMC-Zero were equivalent to models DM and DMC, respectively, but with zero direct-maternal genetic covariance. Direct heritability estimates were moderate for all models (0.29 +/- 0.02 to 0.38 +/- 0.03). Maternal heritability estimates were low, ranging from 0.01 +/- 0.01 (DM-Zero) to 0.05 +/- 0.02 (DM). Negative direct-maternal genetic correlations of -0.41 +/- 0.09 and -0.55 +/- 0.09 were estimated for models DM and DMC, respectively. The proportion of phenotypic variance accounted for by maternal permanent environmental effects was 0.03 +/- 0.01, 0.04 +/- 0.01, and 0.02 +/- 0.01 for models DC, DMC, and DMC-Zero, respectively. Likelihood ratio tests indicated that model DMC best fit the data. Although maternal genetic and maternal permanent environmental effects were significant, they accounted for only 8% (model DMC) of the phenotypic variance, and a Spearman rank correlation of 0.99 between models D and DMC showed sires did not rank differently with or without inclusion of these effects. Given these results, inclusion of maternal effects to the genetic evaluation of docility in Limousin cattle does not seem warranted.     

Excess rumen product anions in cattle. II. Toxic and lethal effects with butyrate.

Toxicity to butyrate was observed in 100-250 kg male Holstein calves following intravenous injection of 0.7-3.6 mmole/kg body weight, intravenous infusion with 0.12-0.53 mmole/min/kg body weight and intraruminal dosage with 19.4 mmole/kg body weight butyrate. Lower doses produced ataxia and serous nasal discharge. Higher doses produced sudden flaccid paralysis and death from asphyxia. No postmortem lesions, gross or histological, were observed. Plasma K+ was reduced to 2.2-2.5 mEq/L. When infusions were stopped, rapid recovery preceded clearance of butyrate and low K+ remained. Nerve depolarization in the central nervous system may be the cause of the toxic effects. Butyrate acidosis is suggested as a factor in unexplained sudden deaths in ruminants.     

Osteochondrosis in cattle.

Osteochondrosis is a poorly understood condition that affects many species, including cattle. Its incidence is not fully appreciated in the cattle industry for many reasons. Most of the reports show a male, purebred predilection, but this may simply be a result of the typical population for which medical attention is sought. With the increasing value of female breeding stock, a less skewed distribution of the disease will most likely result. Distribution of lesions is similar to that in the horse, with the stifle and tarsus most commonly affected. Treatment is divided into medical and surgical options, but neither seem to be strikingly effective as of yet. Surgical techniques include arthroscopy and arthrotomy, and both have their complicating factors. How osteochondrosis as a disease will affect the cattle industry is still to be decided. If the incidence rate does increase with more animals being valued for their economic potential, then treatment options will surely be reevaluated and refined.     

Shade and wind barrier effects on summertime feedlot cattle performance.

In each of three summertime trials conducted over consecutive years, approximately 110 predominantly black and black-white-face steers were blocked by weight and randomly allotted to one of 16 pens in a 2x2 factorial arrangement of treatments. Factors consisted of cattle being fed in facilities with or without wind barriers and with or without shade. Steers were fed dry-rolled corn-based diets (1.43 Mcal/ kg, NEg). Mean starting date and days on feed were June 26 and 79, respectively. In unshaded areas, temperature and humidity averaged 21.6 degrees C and 77.9%, and the blackglobe-humidity index (BGHI) at 1500 averaged between 84.0 and 89.1. Each of four 6.1-x6.1-m structures (mean height = 3.4 m) with white steel roofs provided shade (2.65 m2/steer) for two pens. In facilities with wind barriers provided, airflow was reduced from the north and northwest by a 25-m-wide shelterbelt containing six rows of trees. For cattle fed in pens with wind barriers, shade increased (P<.05) gain from 0 to 56 d and decreased (P<.05) DMI/ADG from 0 to 28 d. Differences (P<.05) in performance were not found between shaded and unshaded cattle in any portion of the feeding period for cattle fed in the pens without wind barriers and over the entire feeding period in either type of facility. The shade response in pens with wind barriers seemed to be greater the 1st yr than in subsequent years. Differences in weather patterns among years, especially air temperature, humidity, and solar radiation, may partially explain this interaction. Also, in yr 1, cattle tended to have greater fat thickness at finish than in yr 2 and 3. Correlations between BGHI and DMI tended to be greater during the early portion of the trial (0 to 28 d) than over the entire trial. Correlations between the difference in BGHI under shade vs no shade and percentage of shade use had the greatest magnitude and were significant only in the first 28 d vs over the entire feeding period. Although no heat-related cattle deaths occurred in this study, results suggest that shade improves cattle performance in the summer when they are fed in facilities with winter wind protection available and have not become acclimated to hot conditions. Once cattle are acclimated or hot conditions subside, compensation by unshaded cattle offsets much of the initial benefits of providing shade.     

Cardiovascular effects of intravenous administration of tetracycline in cattle

Tetracycline chloride dissolved in saline was injected intravenously to seven cows. Two doses of tetracycline were used: 5 and 10 mg/kg b.wt, and the injections were given over a period of either 10, 60 or 300 sec.
A number of the cows collapsed shortly after the injection was completed, usually when the 10 mg dosage was given in 60 sec. When the same dose was given over a period of 5 min none of the cows collapsed. A more or less pronounced drop in blood pressure could be detected during or shortly after the injection; in those cows which collapsed the blood pressure fell almost to zero. The predominant change in pulse rate in connection with the tetracycline administration was a decrease which could be quite marked, pulse rates falling as low as 10–20 per min. Simultaneously with these changes in blood pressure and pulse rate severe abnormalities in ECG could be observed. Pre-treatment with a normal therapeutic dose of calcium borogluconate intravenously prevented collapse in the cows and diminished the drop in blood pressure associated with an ensuing tetracycline injection.
It is concluded that intravenous injection of tetracycline is hazardous, but that collapse can be avoided by giving the injection very slowly over a period of no less than 5 min.     

Environmental effects on pregnancy rate in beef cattle

Ten years of calving records were examined from Bos taurus crossbred cows (mean of 182 cows/yr) to quantify the effects of environmental conditions during the breeding season on pregnancy rate. Estimated breeding dates were determined by subtracting 283 d from the calving date. Relationships were determined between the proportion of cows bred during the periods from the beginning of the breeding season until d 21, 42, and 60 of the breeding season and the corresponding environmental variables. Weather data were compiled from a weather station located approximately 20 km from the research site. Average daily temperature and relative humidity were used to calculate daily temperature-humidity index (THI). Daily averages for each environmental variable were averaged for each period. Minimum temperature (MNTP) and THI for the first 21 and 42 d of the breeding season were negatively associated (P < 0.001) with pregnancy rate. For the 0-to 21-d, 0- to 42-d, and 0- to 60-d breeding periods, respective r2 for average temperatures were 0.32, 0.37, and 0.11, whereas r2 for MNTP were 0.45, 0.40, and 0.10 and r2 for THI were 0.38, 0.41, and 0.11, respectively, for the same breeding periods. The negative associations of temperature and THI with pregnancy rate are most pronounced during the first 21 d of the breeding season, with a -3.79 and -2.06% change in pregnancy rate for each unit of change in MNTP and THI, respectively. A combination of environmental variables increased the R2 to 0.67. In this analysis, windspeed was found to be positively associated with pregnancy rate in all equations and increased the R2 in all breeding periods. Optimum MNTP for the 0- to 21-d, 0- to 42-d, and 0- to 60-d breeding periods was 12.6, 13.5, and 14.9 degrees C, respectively. For the 0- to 60-d breeding period, optimum THI was 68.0, whereas the THI threshold, the calculated level at which cattle will adapt, was found to be 72.9. Reductions in pregnancy rate are likely when the average MNTP and THI equal or exceed 16.7 degrees C and 72.9, respectively, and for Bos taurus beef cows that are pasture bred during a 60-d spring-summer period.