Pharmacokinetics of phenylbutazone given intravenously or orally in mature Holstein bulls

Six mature Holstein bulls were each given 10 mg of phenylbutazone (PBZ)/kg of body weight, PO. Of the 6 bulls, 3 were given 10 mg of PBZ/kg by rapid IV administration 4 weeks later. Plasma concentration-vs-time data were analyzed, using nonlinear regression modeling (sum of exponential functions). The harmonic mean of the biologic half-life of PBZ was 62.6 +/- 12.9 hours after oral administration and 61.6 +/- 7.2 hours after IV administration. The mean residence time was 94.61 +/- 8.44 hours and 90.49 +/- 8.93 hours for oral and IV administration, respectively. The mean total body clearance was 0.0015 +/- 0.0003 L/h/kg, with the mean apparent volume of distribution 0.134 +/- 0.021 L/kg. Mean bioavailability was 73 +/- 2% after oral administration. Phenylbutazone was adequately absorbed from the gastrointestinal tract in bulls. The apparent volume of distribution was small, indicating that PBZ distributed mainly into plasma and extracellular fluid. The total body clearance was also small, which accounted for the long half-life of PBZ in bulls.     

Temporal patterns of growth hormone in blood and seminal plasma of mature dairy bulls

This study was conducted to determine if growth hormone (GH) concentration in bovine seminal plasma would be proportional to but less variable than blood plasma GH. The relationship between GH in blood and seminal plasma was also examined critically. Blood samples were collected at 15-min intervals for 5.75 h, while semen was collected at 30-min intervals over the same time period. Average seminal plasma GH concentrations were 3.2 times higher (P less than .05) than blood plasma GH concentrations (40.4 +/- 15.8 ng/ml vs 12.6 +/- 1.2 ng/ml, respectively). The within animal correlation between blood and seminal plasma was consistently low and nonsignificant (P greater than .05). Overall blood plasma GH and seminal plasma GH concentrations were weakly correlated (r = .418; P greater than .05) among bulls. A predictable relationship between blood and seminal plasma GH concentration does not exist under the conditions of this study.     

Pharmacokinetics of phenylbutazone in mature Holstein bulls: steady-state kinetics after multiple oral dosing

Six mature Holstein bulls were given an 8-day course of phenylbutazone (PBZ) orally (loading dose, 12 mg of PBZ/kg of body weight and 7 maintenance doses of 6 mg of PBZ/kg, q 24 h). Plasma concentration-vs-time data were analyzed, using nonlinear regression modeling. The harmonic mean +/- pseudo-SD of the biologic half-life of PBZ was 61.8 +/- 12.8 hours. The arithmetic mean +/- SEM of the total body clearance and apparent volume of distribution were 0.0021 +/- 0.0001 L/h/kg and 0.201 +/- 0.009 L/kg, respectively. The predicted mean minimal plasma concentration of PBZ with this dosage regimen was 75.06 +/- 4.05 micrograms/ml. The predicted minimal plasma drug concentration was compared with the observed minimal plasma drug concentration in another group of bulls treated with PBZ for at least 60 days. Sixteen mature Holstein bulls were given approximately 6 mg of PBZ/kg, PO, daily for various musculoskeletal disorders. The mean observed minimal plasma concentration of PBZ in the 16 bulls was 76.10 +/- 2.04 micrograms/ml, whereas the mean predicted minimal plasma concentration was 74.69 +/- 3.10 micrograms/ml. Dosages of 4 to 6 mg of PBZ/kg, q 24 h, or 10 to 14 mg of PBZ/kg, q 48 h, provided therapeutic plasma concentrations of PBZ with minimal steady-state concentrations between 50 and 70 micrograms/ml.     

Replication requirements and number of ejaculates needed for assessing treatment effects on sperm output and seminal characteristics of electroejaculated Holstein bulls

Two ejaculates were harvested by electroejaculation on each of 3 d per week for 14 wk from 14, 12- to 24-mo-old Holstein bulls. Ejaculates during the first 2 wk served to stabilize sperm output. Data for the remaining ejaculates were used in a components of variance approach to determine the number of bulls per treatment and ejaculates per bull that would be needed to provide adequate sensitivity and precision for assessing treatment effects on seminal characteristics. The latter included the number of sperm (total and motile), volume and sperm concentrations of the sperm-rich fraction, and the percentage of progressively motile sperm in first and second ejaculates or per day. Replication requirements declined as the number of ejaculates per bull was increased to about 15 to 25 but declined minimally thereafter. The number of bulls needed per treatment varied in relation to the size of the treatment response to be detected but was much greater than the replication used in typical experiments. Replication for assessing sperm output in first ejaculates or per day was approximately one-half as great for experiments in which pretreatment information was used to adjust post-treatment data. Tables should be useful as a guide for designing efficient, cost-effective studies of known sensitivity and precision.     

不同营养水平日粮对奶公牛直线育肥性能的影响

为了研究不同能量和蛋白质水平日粮对奶公牛直线育肥性能的影响。选择4~5月龄左右、平均体重为121 kg的奶公犊36头,随机分成两组,试验Ⅰ组(饲喂低营养水平日粮)、试验Ⅱ组(饲喂高营养水平日粮),每组18头。试验期440 d。整个育肥试验以12月龄划分为前期和后期2个阶段。结果表明,整个育肥期,试验Ⅱ组的平均日增重比试验Ⅰ组提高了5.83%(P>0.05),料重比降低了3.11%(P>0.05)。试验Ⅱ组的粗蛋白质、粗脂肪、中性洗涤纤维、酸性洗涤纤维、钙和磷的表观消化率较高,但是与试验Ⅰ组差异不显著(P>0.05)。试验Ⅱ组的谷草转氨酶、谷丙转氨酶、生长激素、甲状腺素含量比试验Ⅰ组显著提高了8.27%,13.85%,6.70% 和1.26%(P<0.05)。血清尿素氮含量降低了12.22%(P<0.01)。两个营养水平日粮对屠宰率、胴体产肉率和净肉率没有影响。随着营养水平的提高,pH、剪切力、蒸煮损失、失水率有下降的趋势,牛肉中的蛋白质和脂肪含量有上升的趋势,但差异不显著(P>0.05)。与试验Ⅰ组相比,试验Ⅱ组的pH、剪切力、蒸煮损失和失水率分别降低了2.34%,12.97%,18.30%和3.38%,牛肉中粗蛋白和粗脂肪含量分别提高了4.95%和8.55%。养殖效益试验Ⅱ组比试验Ⅰ组多收入0.98元/(日·头),全期效益试验Ⅱ组比试验Ⅰ组多收入431.20元/头。因此,提高日粮的营养水平,可以促进奶公牛的生长、改善肉品质和增加经济效益。     

中国荷斯坦奶公牛肉用研究进展

奶公犊资源的充分利用,不仅能缓解国际市场上牛肉供应不足的紧张局面,而且可以满足广大消费者对高品质牛肉的需求。如何利用现有的奶公犊资源,借鉴国外先进的产业模式和饲养技术,构建我国特色的肉牛产业,成为当前养牛人关注的焦点。我国在奶公犊育肥利用上起步较晚,但随着牛源紧缺,围绕奶公牛生产的相关研究已经陆续展开,在犊牛肉生产技术、小牛肉生产技术、普通牛肉生产技术以及高附加值牛肉生产技术等4个方面取得了长足进展。本文就近几年中国荷斯坦奶公牛在这4方面的研究进展进行了综述。     

Pituitary, adrenal, immune and performance responses of mature Holstein x Friesian bulls housed on slatted floors at various space allowances

The effect of various space allowances on the pituitary, adrenal and immune responses and on performance was investigated in 72 mature Holstein x Friesian beef bulls. The animals (weighing 403+/-3.5 kg) were blocked by weight and randomly assigned to two groups (familiar, F, and unfamiliar, UF) x three treatments (1.2, 2.7 and 4.2m(2) per bull; n=24 per space allowance), and housed for 83 days in 18 pens (n=4 per pen). Blood samples were collected on days -1, 0, 3, 14, 36 and 77 with respect to mixing and housing on day 0. The bulls were given exogenous adrenocorticotrophic hormone (ACTH) on day 3 and corticotrophin-releasing hormone (CRH) on days 14, 36 and 77. Basal plasma cortisol concentration was not affected (P>0.05) by mixing F and UF bulls. On day 3, basal cortisol was greater (P<0.05) in bulls housed at 1.2 than those at 2.7 and 4.2m(2) space allowances while no effect was observed in ACTH-induced plasma cortisol concentration among treatments. Following CRH administration, there was no effect (P>0.05) of treatment and treatment x time on plasma ACTH concentration. On day 14, interferon-gamma production was lower (P<0.05) in the bulls housed at 4.2 vs. 2.7 m(2) and was intermediate but not significantly different (P>0.05) for those housed at 1.2m(2). Animals housed at either space allowances had significant (P<0.05) neutrophilia, lymphopenia, eosinopenia and decreased haemoglobin on day 3 compared with day 0. The liveweight gain from days 0 to 83 was lower (P<0.05) in bulls housed at 1.2 compared with those at 2.7 and 4.2m(2). Housing bulls at 1.2m(2) space allowance had a detrimental effect on their growth and was associated with an acute rise in plasma cortisol concentration (on day 3) compared with those having space allowances of 2.7 and 4.2m(2)/bull.     

Seminal shedding of bluetongue virus in experimentally infected mature bulls

Sixteen bulls ranging in age from 2 to 11 years were experimentally inoculated with bluetongue virus to investigate the frequency and duration of seminal shedding of the virus. All bulls developed typical viremia, lasting 21 to 58 days, and they seroconverted 2 to 3 weeks after inoculation. Virus isolation was attempted from a total of 232 ejaculates, 163 (70%) of which were collected during the period of viremia. Bluetongue virus was not isolated from any of the ejaculates collected from 11 of the 16 bulls. Virus was isolated from 9 of 52 ejaculates collected from the other 5 bulls during the period of viremia. In no instance was virus isolated from semen without concurrent isolation from blood.     

Estimation of genetic parameters and genome scan for 15 semen characteristics traits of Holstein bulls

A QTL detection experiment was performed in French dairy cattle to search for QTL related to male fertility. Ten families, involving a total of 515 bulls, were phenotyped for ejaculated volume and sperm concentration, number of spermatozoa, motility, velocity, percentage of motile spermatozoa after thawing and abnormal spermatozoa. A set of 148 microsatellite markers were used to realize a genome scan. First, genetic parameters were estimated for all traits. Semen production traits were found to have moderate heritabilities (from 0.15 to 0.30) while some of the semen quality traits such as motility had high heritabilities (close to 0.60). Genetic correlations among traits showed negative relationships between volume and concentration and between volume and most quality traits such as motility or abnormal sperm while correlations between concentration and these traits were rather favourable. Percentages of abnormal sperm were negatively related to quality traits, especially with motility and velocity of spermatozoa. Three QTL related to abnormal sperm frequencies were significant at p < 0.01. In total, 11 QTL (p < 0.05) were detected. However, the number of QTL detected was within the range of expected false positives. Because of the lack of power to find QTL in this design further analyses are required to confirm these QTL.     

Development of a RAPD marker-based classification criterion for quality semen production in Holstein crossbred bulls

In cattle production systems, an intense selection pressure for production traits has resulted in the decline of fertility traits. To optimize an efficient reproduction system, the inclusion of both male and female fertility traits in the selection process is very much essential. RAPD (Random Amplified Polymorphic DNA) was developed as a molecular biology tool and has been extensively used, to study intra- and interspecific genetic diversity. The present study was undertaken to utilize RAPD primers to investigate the association between DNA markers and semen quality traits viz. Sperm concentration, total sperm count ejaculate and initial sperm motility and thereby to identify good/poor semen producers. DNA isolated from the blood samples of healthy bulls was subjected to RAPD-PCR. The multiple regression analysis followed by independent t test was carried out to identify suitable markers. Based on the results, only 12 bands were identified as marker suitable for any of the quality trait. This includes, OPA2 ~ 760, OPA2 ~ 700, OPA6 ~ 1,200, OPA9 ~ 400, OPA9 ~ 380, OPA12 ~ 970, OPA14 ~ 715, OPA14 ~ 605, OPA16 ~ 485, OPA17 ~ 860 and OPA18 ~ 480. Multiple regression analysis selected, OPA2 ~ 760 and OPA2 ~ 1,750 for sperm concentration and OPA2 ~ 760, OPA2 ~ 700, OPA9 ~ 620, OPA4 ~ 670 and OPA18 ~ 1,015 for total sperm count/ejaculate. But the t test revealed a significant association between OPA2 ~ 760 and total sperm count. Further, discriminant function analysis also identified this marker in the first step itself. The results of the present study can be exploited as a low-cost alternative strategy for identification of good /poor semen producers in crossbred bulls at an early age.     

Differential promoter methylation of DAZL gene in bulls with varying seminal parameters

In India, cross‐breeding of indigenous cattle with exotic cattle such as Holstein Friesian and Jersey has been going on since last four decades to improve milk production. Although it has led to increased milk yield, the subfertility in male cross‐bred progeny has remained a significant problem. Epigenetic modifications (DNA methylation, histone modifications and chromatin remodelling) are regarded as key players influencing gene expression. DAZL gene plays an important role in germline development and gametogenesis. The methylation and mRNA expression level of this gene have been significantly negatively correlated in the testes of cattle–yak hybrids and their parents. This study analysed the methylation profile of DAZL gene promoter in bull spermatozoa in an attempt to speculate its role in cross‐bred cattle subfertility. Semen samples from Sahiwal, Holstein Friesian and Frieswal bulls (Sahiwal X Holstein Friesian) with varying semen motility parameters were collected, and DNA was isolated. Methylation‐specific primers were used to amplify part of promoter and exon 1 of DAZL gene using bisulphite‐converted DNA. The amplified products were sequenced after cloning in pTZ57R/T vector. Sequence analysis revealed significantly higher DNA methylation of DAZL gene in Frieswal bulls with poor motility (28.26%) as compared to medium (15.21%) and high motility phenotype (6.52%). In pure‐bred counterparts, Sahiwal and Holstein Friesian, epigenetic marks were more in the former (15.21%) than the latter (4.34%), but in both cases, the values were lower as compared to the poor motility Frieswal bulls. This suggests that differential hypermethylation of the CpG islands could possibly influence reproductive parameters in bovines.     

Evaluation and treatment of decreased libido associated with painful lumbar lesions in two bulls

Painful lesions of the vertebral column may cause decreased libido in bulls. Radiographic evaluation of vertebral skeletal problems in mature bulls is limited because of high body mass. Two breeding bulls with signs of decreased libido and spermatozoa production were evaluated. Initial systemic medical treatment for the conditions had not focused on localized lesions and was unsuccessful. Nuclear scintigraphy was performed in both bulls to determine the location of vertebral column lesions and facilitate localized treatment. Localized medical treatment was successful and resulted in decreased signs of pain and increased spermatozoa production in both bulls.     

Scrotal circumference, seminal characteristics, and testicular lesions of yearling Angus bulls

The effect of age and body weight on scrotal circumference (SC), the effect of SC on percentage of sperm abnormalities and seminal characteristics, and the relationship of SC with testicular weight, epididymidal weight, degree of germinal epithelial loss (DGEL), and percentage of tubules graded 4 or greater (G4+) were studied in 37 Angus bulls. All bulls were from one herd and were examined at monthly intervals, during a 140-day weight gain test starting when they were 11 months old. The study was terminated when the bulls were slaughtered at 14 months of age. As age and body weight increased, SC increased (P less than 0.001). The incidence of sperm abnormalities decreased (P less than 0.001) as SC increased; however, seminal characteristics remained poor in bulls with SC less than or equal to 32 cm. Pathologic changes in 600 cross sections of seminiferous tubules from each bull were classified into 9 grades. The DGEL per 100 tubules was calculated by assigning a value to each grade according to the severity of loss of germinal epithelium. Tubules classified as G4+ were devoid of germinal cells and provided an index of irreversible loss of germinal epithelium. The SC was correlated positively with testicular weight (r = 0.91, P less than 0.001) and epididymal weight (r = 0.59, P less than 0.001) and negatively with DGEL (r = -0.48, P less than 0.01) and G4+ (r = -0.44, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)