Effects of dietary gossypol on aspects of semen quality, sperm morphology and sperm production in young Brahman bulls

Eight young reproductively normal Brahman bulls (average age and bodyweight 20 months and 500 kg, respectively) received either cottonseed meal delivering 8.2 g free gossypol/bull/d (treatment group, n=4) or soybean meal (control group, n=4) for 12 wk. After adjustment (1 wk), weekly procedures (11 wk) included blood collection, scrotal circumference measurement and electroejaculation. Semen assessments included sperm motility, percentage of live spermatozoa, general sperm morphology (using brightfield microscopy), and midpiece morphology (using DIC microscopy). After sacrifice (Week 12), sperm production rates (daily and per gram testicular parenchyma) were determined. Treated bulls did not differ from controls in scrotal circumference or the percentage of live spermatozoa. Sperm motility differed at Weeks 9 (P<0.05), 10 and 11 (both P=0.06). Treated bulls had fewer normal spermatozoa at Weeks 5 (P<0.05), 6 (P<0.01) and 7 thru 11 (P<0.001). Beginning from Week 3, treated bulls showed an increased proportion of sperm midpiece abnormalities (P<0.05) which stabilized at 52 to 62.5% between Weeks 5 and 11 (P<0.01 or P<0.001). Treated bulls also had lower sperm production than untreated bulls, both on a daily (P<0.01) and per gram testicular parenchyma (P<0.001) basis. A cottonseed supplement providing 8.2 g of free gossypol per bull per day had adverse effects upon both sperm morphology and spermatogenesis in young Brahman bulls, with the former being first evident within 3 to 4 weeks of feeding of cottonseed meal.     

Characterization of gossypol-induced sperm abnormalities in bulls

To characterize sperm abnormalities induced by gossypol in cattle, young Brahman bulls (n=8) received either cottonseed meal delivering 8.2 g free gossypol/bull/d (treatment, n=4) or isonitrogenous soybean meal (control, n=4) for 11 wk. At slaughter, semen was collected from the following extragonadal sites: mediastinum/rete testis (Site 1), caput (Site 2), corpus (Site 3) and cauda epididymis (Site 4), and ductus deferens (Site 5). At least 200 fixed spermatozoa per site were examined via differential-interference-phase contrast (DIC) microscopy, with electron microscopy (EM) being employed with select samples. Sperm midpiece abnormalities were categorized as aplastic, fragile or asymmetric, with detached sperm heads being tabulated separately. Of these, aplastic defects were considered most likely to occur during spermatogenesis. Bull sperm midpiece lesions induced by gossypol were ultrastructurally similar to those observed in other, nonruminant, species. Combined midpiece abnormalities generally increased with extragonadal passage (EGP) in the treated bulls, as did fragile and asymmetric but not aplastic midpieces, or detached sperm heads. This pattern of EGP changes in bull sperm morphology following gossypol spermatoxicity suggests that structural weakness induced during spermatogenesis leads to secondary spermatozoal changes during EGP, possibly due to the imposition of motility stressors upon prior weakened structures.     

Effects of diets containing gossypol on spermatogenic tissues of young bulls

Eighteen yearling beef bulls were used in a study to determine the effects of diets containing gossypol on spermatogenic tissues, Sertoli cells and Leydig cells. Bulls were randomly assigned to one of three (n = 6) isonitrogenous diet groups formulated from alfalfa hay and corn (gossypol-free control), control plus whole cottonseed and cottonseed hulls, or control plus cottonseed meal and cottonseed hulls as sources of gossypol. Testicular tissues collected were examined histologically, and tissues from bulls fed gossypol-free diets were compared with those fed diets containing cottonseed products. Following a 2-mo period (P(1)) when bulls were fed diets containing gossypol, one-half of the bulls were placed on a gossypol-free diet for an additional 2 mo (P(2)) to determine if gossypol effects were reversible. At the end of P(1), bulls fed whole cottonseed and cottonseed meal had larger (P<0.01) lumens in their seminiferous tubules, decreased (P<0.001) wall thickness in their seminiferous tubules, and a reduced (P<0.0001) number of cell layers in their seminiferous tubles, when compared with bulls fed a gossypol-free diet. These histological changes indicate detrimental effects to the spermatogenic tissues and associated cells. Following the initial two months (P(1)) of receiving feed containing gossypol, herd mates that were fed a gossypol-free diet for 2 mo (P(2)) showed improvement in histological characteristics, indicating that gossypol-induced effects were partially reversible.     

Effects of diets containing gossypol on ovarian histology, function and fertility in prepubertal beef heifers

Forty-five crossbred beef heifers (weight = 268.3 +/- 5.7 kg) were used to determine the effects of dietary gossypol on ovarian morphology, erythrocyte fragility and fertility. Heifers were randomly assigned to 1 of 3 isonitrogenous dietary treatments. The diet consisted of rice mill feed and milo supplemented with soybean meal (n = 13; control), cottonseed meal (n = 16; low supplementation) which supplied 6.1 g free gossypol animal(-1) day(-1), or whole cottonseed (n = 16; high supplementation) which supplied 13.7 g free gossypol animal(-1) day(-1). The heifers were group-fed each diet for 64 days and were maintained on similar but separate fescue pastures overseeded with wheat. After 64 days, 4 heifers from each diet were confined and fed their respective diets. On Day 10 following estrus, each animal was unilaterally ovariectomized, and the ovary containing the corpus luteum was removed. The remaining ovary was removed 6 to 12 hours after detection of estrus in the next cycle. Erythrocyte fragility increased (P < 0.02) in heifers receiving gossypol compared with that of the controls. Cyclicity in the heifers was 81.3, 68.8 and 38.4% for high, low and control diets, respectively, at the end of the 64-day treatment period. First service conception rate, as determined by palpation per rectum, was similar among treatments (58.3, 33.3, 33.3% for high, low and control groups, respectively). Weight gain increased (P < 0.03) in control heifers compared with that of heifers receiving gossypol. Gross ovarian morphology and histology were similar for all heifers. Although gossypol produced mild toxicosis in heifers, no adverse reproductive effects could be detected from gossypol intake.     

Reversibility of the reproductive toxicity of gossypol in peripubertal bulls

Gossypol has been shown to impair sperm production in male ruminants. The purpose of this study was to determine if the adverse effects of gossypol on spermatogenesis in peripubertal bulls were reversible. Twenty-eight crossbred Angus bulls were allocated into treated and control groups at 11 months of age. For 8 weeks, treated bulls were fed a ration containing 8 mg of free gossypol per kilogram of body weight per day while control bulls were fed a soybean meal ration free of gossypol. At 28-days intervals, scrotal circumference was measured and semen collected to assess sperm motility and morphology. Seven control and seven treated animals were castrated 56 days after the start of the experiment and the testes were examined histologically. The remaining bulls were fed a gossypol-free diet for 210 days prior to castration. There were significant increases in primary and secondary sperm abnormalities in treated bulls 28 and 56 days after gossypol feeding. The number of sperm with proximal droplets was significantly higher in gossypol-treated bulls, suggesting testicular degeneration. There was no significant effect on the sperm motility, scrotal circumference, or histopathological characteristics of the testes. Four weeks after the end of gossypol feeding, primary and secondary abnormalities were still increased in gossypol-treated bulls, however in subsequent collection periods the percentage of abnormalities were similar between groups. At 210 days, there was no treatment effect on scrotal circumference, and histological characteristics of the testes were not different between groups. The deleterious effects of gossypol on the morphological characteristics of spermatozoa were reversible. Gossypol (8 mg/kg per day for 56 days) increased sperm abnormalities but the effects were reversible.     

Effects of diets containing gossypol on reproductive capacity of rainbow trout (Oncorhynchus mykiss)

We evaluated five practical diets in which 0%, 25%, 50%, 75%, and 100% (dietary treatments 1-5) of fish meal protein was replaced by solvent-extracted cottonseed meal protein. Adult rainbow trout (initial average weight 247 +/- 8 g) were fed the diets over a period of 131 days during which a general 2-fold body weight increase occurred. The total diet gossypol concentration (free and protein-bound) showed a gradual increase with increased cottonseed meal substitution. Blood samples were collected on Days 0, 64, 112, and 131 for hematological and steroid hormone determination in plasma of males and females. Hemoglobin content was significantly reduced in fish from treatment 5 (7.9 +/- 0.3 g/dl) in comparison to treatments 1-3 (10.3-10.9 g/dl). After 112 and 131 days of feeding, testis weights, concentrations of testosterone, and 11-ketotestosterone were elevated in fish from dietary treatments 2 and 3 in comparison to control and diets 4 and 5. On Day 71, sperm were collected from 6 fish per dietary treatment to assess sperm quality. No significant differences in sperm concentrations (7.2-9.8 x 10(9)/ml), motility (78-89%), and standardized (300 x 10(5) sperm/egg) fertilizing ability (18.9-22.6% hatched embryos) were found. Total gossypol concentrations in blood plasma differed significantly among treatments, and the levels were among the highest ever recorded in animals fed cottonseed-supplemented diets (2.9 +/- 0.2, 11.7 +/- 4.1, 21.7 +/- 1.4, and 29.9 +/- 3.9 microg/ml, for treatments 2-5, respectively). The major portion of gossypol in blood plasma was protein-bound (81-93%). This was in contrast to minute amounts of gossypol present in seminal plasma, mostly in free form (0.02-0.18 microg/ml), which indicates the presence of a barrier between general circulation and the testis with respect to gossypol distribution in lower vertebrates. Thus, the reproductive parameters of male rainbow trout examined in this study were not significantly affected by feeding cottonseed meal for 131 days.     

高效棉酚降解枯草芽孢杆菌M-4菌株的常压室温等离子体诱变及发酵工艺优化

【背景】棉粕中游离棉酚的存在制约了棉粕作为饲料蛋白源的利用,棉酚的微生物降解问题成为研究热点。本实验室前期发现枯草芽孢杆菌(Bacillus subtilis) M-4菌株具有较强的降解棉酚能力,而且已经应用于棉粕脱毒工业。【目的】进一步提高枯草芽孢杆菌M-4菌株降解棉粕中棉酚的能力,扩大棉粕在养殖业的应用领域。【方法】采用常压室温等离子体诱变(atmospheric and room temperature plasma,ARTP)技术对菌株M-4进行诱变,以液体培养条件下的棉酚降解率为初筛指标,筛选获得正向突变株。以棉粕固体发酵条件下的棉酚降解率为复筛指标,测定初筛获得的正向突变株实际降解棉粕中游离棉酚的能力。以棉酚残存量和棉酚降解率为检测指标,采用单因素试验优化固体条件下棉粕发酵条件,获得突变株发酵棉粕的最适工艺参数。【结果】初筛获得正向突变株19株。复筛得到一株高效的突变株MY-4-17,在棉粕固体发酵条件下其棉酚降解率高达97.15%,比菌株M-4的棉酚降解率提高了2.55%。经过5次传代培养,突变株MY-4-17的遗传稳定性良好。突变株MY-4-17发酵棉粕的最适工艺参数为...     

Trypanosomiasis-induced infertility in dromedary (Camelus dromedarius) bulls: changes in plasma steroids concentration and semen characteristics

The effect of Trypanosomiasis on concentrations of plasma steroids and semen characteristics was studied in 24 dromedary bulls. Based upon the parasitological and serological diagnosis, 18 bulls were found infected with Trypanosoma evansi (Group 2) and six were found to be free from infection and served as controls (Group 1). The infected animals exhibited signs of anaemia indicated by the decrease of packed cell volume (PCV) and haemoglobin concentration (Hb), pale mucus membranes, weight loss, lethargy, weakness and dullness. However, five animals (27.8%) of the infected group revealed elevated rectal temperatures and three animals (16.7%) revealed testicular degeneration upon palpation of their scrotal contents. Concentrations of plasma oestradiol-17beta (86.5 +/- 8.6 pg/ml versus 232.5 +/- 74.4 pg/ml) and testosterone (4.8 +/- 0.7 ng/ml versus 2.7 +/- 1.5 ng/ml) were significantly different (P < 0.05) between the control and infected bulls. Evaluation of the semen collected by electroejaculation and evaluated by a computerized cell motion analyzer revealed normal semen characteristics in the control animals compared to deteriorated ones in the infected bulls. There were highly significant (P < 0.01) decreases in sperm count (12.2 +/- 1.3/ml versus 6.5 +/- 4.9 x 10(6)/ml), motility percentage (68.2 +/- 6.7% versus 27.4 +/-15.6%), percentage of live spermatozoa (73.2 +/- 8.3% versus 35.8 +/- 8.2%) and increases in percentage of morphological abnormalities (3.3 +/- 0.6% versus 15.9 +/- 1.0%) in the infected group. An examination of the plasma hormonal profiles and semen characteristics in the infected bulls indicated that altered Sertoli cell function due to formation of immune complexes in four bulls (Group 2A), pituitary dysfunction in six bulls (Group 2B), testicular degeneration in three bulls (Group 2C) and finally trypanotolerancy in five bulls (Group 2D) are possible factors responsible for poor semen characteristics and infertility induced by T. evansi infection in dromedary bulls.     

Gossypol isomers bind specifically to blood plasma proteins and spermatozoa of rainbow trout fed diets containing cottonseed meal

We investigated the role of gossypol isomers binding to blood plasma, seminal plasma and spermatozoa to elucidate gossypol anti-fertility action in the teleost fish, rainbow trout (Oncorhynchus mykiss). Growth and hematological indicators of males were depressed when fish meal protein in diets was completely replaced with cottonseed meal. The cottonseed meal contained equal proportions of (-) (47.8+/-1.6%) and (+) gossypol isomers. Concentrations of spermatozoa were decreased with increasing proportions of gossypol in diets (from 0.22% to 0.95%); however, sperm motility and fertilizing ability were not affected. In contrast to mammals, steroid hormone concentrations were not suppressed in fish given diets with gradual increase of gossypol level. Gossypol concentrations were 100-fold higher in blood plasma than in seminal plasma, confirming a barrier in gossypol transfer between the general circulation and the testis. Spermatozoa accumulated predominantly (+) enantiomer (65-75%) with decreasing proportions as dietary gossypol concentrations increased. Spermatozoa bound most of the gossypol contained in the semen; however, this did not result in impairment of the sperm motility apparatus. Teleost fish sperm rely on ATP stores that accumulate during maturation as a source of energy during activation. In addition, the duration of sperm movement is short in these fish. As such, we hypothesize that the major action of gossypol on mammalian sperm, which is uncoupling of oxidative phosphorylation, does not impair the energy supply required for flagellar beating in fish spermatozoa.     

A potential relationship between the 16;20 and 14;20 Robertsonian translocations and low in vitro embryo development

A possible effect of 16;20 and 14;20 Robertsonian translocations on the development of bovine oocytes matured and fertilized in vitro was assessed on the basis of embryo yield and blastocyst formation. Oocytes fertilized with semen from 2 bulls (A and B), which were heterozygous for these translocations, showed a significantly lower cleavage rate (36.3 +/- 2.25%; 39.8 +/- 3.88%) and percentage of blastocysts (3.7 +/- 1.24%; 3.2 +/- 1.20%) than those fertilized with semen from a bull (C) with a normal karyotype (control, 58.1 +/- 2.14%; 20.1 +/- 1.92%; P < 0.01). There was also a difference in the rate of further blastocyst development between the tested bulls and the control. The rates of expanded blastocysts were 6.6 and 11.1% for Bulls A and B, respectively, and 38.7% for the control bull on Day 7; while on Day 8 these values were 41.7 and 55.5% vs 76.0%. These results demonstrated that in the bulls carrying the 16;20 and 14;20 translocations, in vitro preimplantation embryo development was reduced, probably due to genetically unbalanced spermatozoa.     

The use of in vitro fertilization techniques to investigate the fertilizing ability of bovine sperm with proximal cytoplasmic droplets

The objective of this experiment was to determine the effect of proximal droplets on sperm-oocyte binding, zona penetration, fertilization, and the developmental competence of oocytes fertilized by sperm with proximal droplets (PD) in an in vitro fertilization (IVF) and culture system. Frozen semen from three bulls (PD1, PD2 and PD3) with varying proportions of normal appearing sperm with proximal droplets and semen from a normal control bull (C) were used in this experiment. The mean number of sperm bound to the zona pellucida (26.8 +/- 2.0, n=100; 15.2 +/- 1.1, n=100; 16.2 +/- 1.0, n=100) for bulls PD1, PD2, and PD3, respectively, were significantly lower (P<0.05) than that of the control bull C (47.4+/- 1.9; n=114). No spermatozoa with PD were found bound to the zona pellucida and this finding was consistent among the three bulls. The percentage penetration of zonae for the bulls PD1, PD2 and PD3 (74%, 74/100; 71%, 71/100 and 69%, 69/100, respectively) were not different than that of bull C (72%, 179/245). Similarly, the mean number of sperm penetrating the zona pellucida (1.43+/- 1.2, 1.24 +/- 1.1 and 1.20 +/- 1.1, for bulls PD1, PD2 and PD3, respectively) were not different than that of bull C (1.45 +/- 1.1). However, fertilization rates (8.8%, 8/90; 16.8%, 16/95; and 10.6%, 11/103, for bulls PD1, PD2 and PD3, respectively) were lower (P<0.001) than that of bull C (68.7%; 77/112). Similarly, cleavage rates (5%, 10/200; 8%, 8/100 and 14%, 15/111) for the bulls PD1, PD2 and PD3, respectively, were lower than that of the control bull, C (60.7%; 79/130). Cleaved zygotes resulting from the fertilization of oocytes by apparently normal sperm from bulls with PD did not develop beyond cleavage, whereas, 43.8% (57/130) morulae and 20% (26/130) blastocysts were produced by oocytes fertilized by sperm from bull C. In summary, normal appearing sperm with PD did not bind to the zona pellucida. Apparently normal sperm with out proximal droplets co-existing in the semen along with sperm containing PD were also functionally deficient, resulting in reduced zonae binding and zygotes resulting from insemination with semen with a high percentage of PD did not develop beyond cleavage.     

Platelet activating factor improves the in vitro penetration of zona free hamster eggs by buffalo (Bubalus bubalis) spermatozoa

Twelve buffalo bulls of Murrah breed, selected on the basis of their conception rates, were classified into low-, moderate- and high-fertility groups. Frozen semen was thawed and treated with 200 microM platelet activating factor (PAF) for 15 min at 37 degrees C and 5% CO2. In both treated and control (no PAF) semen samples (five replicates per bull), the following were assessed: motility, acrosome reaction (AR) evaluation (for 10 replicates of each bull), and zona-free hamster oocyte penetration test--to determine aspects of fertilization in vitro, viz., sperm attached per ovum (SA/O), fertilization percent (FP), fertilization index (FI), and polyspermic ova (PO). There was an effect of group (P < 0.01) on all parameters; all except motility were increased by PAF treatment. However, the group X treatment interaction was not significant for any parameter. The overall mean values of motility, AR, SA/O, FP, FI, and PO, for controls, treated spermatozoa and (net change) were: 42.89 +/- 0.85, 36.65 +/- 0.85, (-6.24); 28.94 +/- 0.46, 61.44 +/- 0.58, (32.50); 126 +/- 2, 145 +/- 2, (19); 74.21 +/- 1.59, 89.11 +/- 1.18, (14.90); 0.79 +/- 0.02, 1.10 +/- 0.03, (0.31) and 5.22 +/- 1.22, 21.69 +/- 1.88, (16.47)%, respectively. In conclusion, PAF significantly increased the AR and other aspects of fertilization, despite a small reduction in motility.     

Zootechnical performance of cloned cattle and offspring: preliminary results

This paper presents information on the evolution of sets of cloned heifers of Holstein breed in comparison to that of control heifers derived from artificial insemination (AI) in the same farm, as well as data on a set of cloned bulls and their semen characteristics. Preliminary observations on a group of calves sired by a cloned bull and offspring of cloned females are reported. Mean birth weight in the clone group (50 females) was statistically higher than that of 68 contemporary female controls obtained by AI (49.27 +/- 10.98 vs. 40.57 +/- 5.55 kg, respectively, p < 0.05). Growth rate was within normal values for Holstein heifers (from 0.7 to 0.8 kg/day) and daily gain was not influenced by the high or low birth weight of clones. Within animals of the same clone, variability of daily gain was reduced compared to their control counterparts. Semen production from three cloned bulls was within the parameters expected for young bull of the same age. A direct comparison of morphological analysis was made between the frozen thawed semen of the donor bull and of his three clones collected at the same age. The overall semen picture appeared within acceptable limits and the clones presented similar percentages of sperm abnormalities (80% of morphologically normal spermatozoa) as the donor. These preliminary results suggest no deleterious effect of cloning on the semen picture of cloned sires. Frozen semen from one clone bull was used for an AI trial, resulting in 65% pregnancies, 25 live calves were naturally delivered. Concerning the offspring of both female and male clones, the phenotypical and clinical observation of the calves in the first week of age did not reveal any clinical abnormality, suggesting that the deviations observed in clones are not transmitted to the progeny.     

Effects of administration of ergotamine tartrate on fertility of yearling beef bulls

Sixteen yearling bulls were utilized to investigate administration of ergotamine tartrate on semen parameters, fertilization, and endocrinology. Bulls were allotted to a control diet of cracked corn, corn silage, and soybean meal (CON, n = 8) or a diet supplemented daily with 40 microg/kg body weight of ergotamine tartrate (ET, n = 8). Blood samples, average daily gain, scrotal circumference and rectal temperatures were collected every 14 day. Semen samples were obtained every 60 day and evaluated for motility and morphology. Scrotal temperatures were obtained by thermography immediately before electroejaculation. Semen from a subset of bulls from each treatment was also evaluated for in vitro fertilization. Administration of ET increased rectal temperature and resulted in lower scrotal temperatures compared to CON bulls (P < 0.05). However, prolactin, scrotal circumference, testosterone, and semen motility and morphology did not differ between groups throughout the experimental period (224 day). Cleavage rates of embryos derived from in vitro fertilization (IVF) with semen of bulls, fed with ET, were reduced compared to CON (P < 0.05); however, development of cleaved embryos to blastocyst did not differ between treatments. In conclusion, extended exposure of bulls to ET appeared to reduce fertilization potential of sperm.     

In situ alkaline transesterification of cottonseed oil for production of biodiesel and nontoxic cottonseed meal

The production of fatty acid methyl ester (FAME) by direct in situ alkaline-catalyzed transesterification of the triglycerides (TG) in cottonseeds was examined. The experimental results showed that the amount of cottonseed oil dissolved in methanol was approximately 99% of the total oil and the conversion of this oil could achieve 98% under the following conditions: less than 2% moisture content in cottonseed flours, 0.3-0.335mm particle size, 0.1mol/L NaOH concentration in methanol, 135:1 methanol/oil mole ratio, 40 degrees C reaction temperature and 3h reaction time. Further, the effects of co-solvent petroleum ether and methanol recycling on the cottonseed oil extraction and conversion were also investigated. The use of alkaline methanol as extraction and reaction solvent, which would be useful for extraction oil and gossypol, would reduce the gossypol content in the cottonseed meal. The free and total gossypol contents in the cottonseed meal obtained from in situ alkaline transesterification were far below the FAO standard. And the nontoxic cottonseed meal could be used as animal protein feed resources.     

Efficacy of piperine, an alkaloidal constituent from Piper nigrum on erythrocyte antioxidant status in high fat diet and antithyroid drug induced hyperlipidemic rats

The main aim of this study was to investigate the effect of piperine on erythrocyte antioxidant status in high fat diet (HFD) and antithyroid drug induced hyperlipidemic rats. Male Wistar rats were divided into eight groups. The first four groups were fed a control diet and in addition were given respectively 1% carboxymethyl cellulose (CMC); 10 mg/kg body weight carbimazole (CM); 10 mg CM + 40 mg/kg body weight piperine and 10 mg CM + 2 mg/kg body weight atorvastatin (ATV). A similar pattern was followed for the next four groups except that they were all fed HFD instead of the control diet. Erythrocyte osmotic fragility, total cholesterol, phospholipids, lipid peroxidation products, enzymic and non-enzymic antioxidant status were studied in all experimental groups. Significantly increased osmotic fragility, total cholesterol/phospholipid ratio, thiobarbituric acid reactive substances and lipid hydroperoxides were observed in the plasma and erythrocytes of HFD fed and CM treated rats compared to the control. Superoxide dismutase, catalase, glutathione peroxidase, vitamin E and reduced glutathione in erythrocytes and vitamin C in the plasma were also significantly lowered in HFD fed, antithyroid drug treated rats compared to control animals. Concurrent piperine supplementation along with HFD and antithyroid drug administration normalized erythrocyte osmotic fragility, reduced lipid peroxidation, and improved the enzymic and non-enzymic antioxidant status compared to those rats that did not receive piperine. Thus, our results indicate that piperine supplementation markedly protects erythrocytes from oxidative stress by improving the antioxidant status in HFD fed antithyroid drug treated rats.     

Effects of treatment with GnRH from 4 to 8 weeks of age on the attainment of sexual maturity in bull calves

In bull calves an early transient increase in circulating concentrations of LH occurs between 6 and 20 weeks of age. This has been shown to influence reproductive development and performance later in life. In an attempt to hasten the onset of sexual maturity, bull calves (Hereford x Charolais) were treated (im) with 120 ng/kg of GnRH (n=6) twice every day from 4 to 8 weeks of age; control calves received saline (n=6). Injection of GnRH resulted in an LH pulse in all animals. GnRH treated bulls displayed more rapid testicular growth rates between 22 and 44 weeks of age. Sexual maturity (SC>or=28 cm) was achieved earlier in GnRH treated bulls compared to saline treated bulls (41.7+/-2.22 and 47.0+/-0.45 weeks of age, respectively) and this was confirmed by age of sexual maturity based on ejaculate characteristics (>50 million spermatozoa, >10% motility; 45.0+/-0.86 and 49.0+/-1.13 weeks of age for GnRH and control treated bull calves, respectively; P<0.05). We concluded that treatment with GnRH, twice daily, from 4 to 8 weeks of age, prior to the endogenous early increase in plasma LH concentrations, could increase in plasma LH concentrations, advance testicular development and reduce age at puberty in beef bull calves. This may provide the basis for a simple regimen to hasten sexual development in the bull calf.     

Effect of different levels and sources of zinc supplementation on quantitative and qualitative semen attributes and serum testosterone level in crossbred cattle (Bos indicus x Bos taurus) bulls

An experiment was conducted on 16 crossbred bulls (about 2 years of age, 316.2+/-0.77 kg average body weight), divided into groups I, II, III and IV to study the effect of different levels of Zn supplementation from inorganic and organic sources on semen quality. The animals in the first 3 groups were supplemented with 0, 35 and 70 ppm Zn from Zn sulfate, respectively and the animals in-group IV were supplemented with 35 ppm Zn as Zn propionate. Semen collection and evaluation was done in the first month (to assess semen quality at the start of the experiment) and 7th, 8th and 9th month of experimental feeding to evaluate the effect of supplemental Zn on semen attributes. We gave 6 months for Zn feeding, so that 3 sperm cycles of spermatogenesis had passed and the collected semen reflected the complete effect of Zn supplementation. Six ejaculates from each bull were collected and evaluated for semen quantitative (ejaculate volume, sperm concentration and sperm number per ejaculate) and qualitative characteristics (semen pH, mass motility, individual motility, sperm livability percent and abnormal sperm percent, percent intact acrosome, bovine cervical mucus penetration test, hypo-osmotic sperm swelling test) and activity of seminal plasma enzymes i.e., alkaline phosphatase, acid phosphatase, GOT and GPT. Testosterone level in the blood serum of crossbred bulls was also estimated. Mean values of semen quantitative and qualitative characteristics at the start of the experiment were statistically non significant (P > 0.05) in all the crossbred cattle bulls, however, there were statistically significant differences among the bulls of different groups after 6 months of zinc supplementation. Mean ejaculate volume (mL) was 2.37, 4.70, 5.86 and 6.38, respectively in groups I to IV, indicating a statistically significant (P < 0.05) higher semen volume in Zn-supplemented groups as compared to the control group of bulls. Similarly, sperm concentration (million.mL(-1)), live sperm (%) and motility (%) were significantly (P < 0.01) higher in Zn-supplemented groups as compared to the control group. The results of BCMPT and HOSST revealed a significant improvement in sperm functional ability in all the groups supplemented with Zn as compared to the control group. The activity of alkaline and acid phosphatase in seminal plasma was significantly (P < 0.05) higher in the Zn-supplemented groups, whereas GOT and GPT activities in seminal plasma were significantly (P < 0.05) lower in the Zn propionate supplemented group as compared to the control group. Testosterone concentration (ng.mL(-1)) in blood serum was significantly higher in animals of groups III and IV, as compared to control group. It may be concluded that Zn supplementation either in the inorganic or organic form in the diet of crossbred bulls improved the qualitative and quantitative attributes of semen; however, the number of sperm per ejaculate, mass motility and semen fertility test like bovine cervical mucus penetration was significantly higher in bulls given Zn in an organic form (Zn propionate) as compared to an inorganic form (Zn sulfate).     

Sexual development of dairy bulls in the Mexican tropics

Sexual development and pubertal traits were studied in Holstein Frisian (Ho) and Brown Swiss (BS) bulls born and maintained under tropical conditions. Characteristics evaluated every 2 weeks, from 27 to 63 weeks of age, included live weight, scrotal circumference, testicular diameter, semen quality and sexual behavior. Puberty was defined as the age at which a bull first produced an ejaculate containing at least 50 x 106 spermatozoa, with a minimum of 10% progressive motility. Testicular growth was linear in Ho bulls and quadratic in BS bulls. There was no breed difference in age at puberty (Ho, 333 +/- 15.8 days; BS, 311 +/- 10.5 days). However, at puberty, live weight and scrotal circumference tended to be greater in Ho (276 +/- 16.9 kg and 28.4 +/- 1 cm, respectively) than in BS bulls (233 +/- 11.3 kg and 25.9 +/- 0.7 cm, respectively), and testicular diameter was larger for Ho (5.5 +/- 0.24 cm) than for BS bulls (4.8 +/- 0.16 cm). Pooled data for all bulls for semen characteristics at puberty were: volume, 6.3 +/- 0.6 ml; progressive motility, 26.8 +/- 4.4%; sperm concentration, 58.5 +/- 13.9 x 10(6) spermatozoa/ml, and 351.5 +/- 91.2 x 10(6) spermatozoa/ejaculate. These values improved until at least 18 weeks after puberty. Eighty-five percent of bulls mounted heifers by 206 days of age, but only a few bulls had mounts with ejaculation during the study. It was concluded that reproductive development was similar between Ho and BS bulls, but slower than that reported for dairy bulls in temperate areas. Variation in some characteristics, such as scrotal circumference, was observed among bulls within each breed group, which might be of benefit for genetic selection.     

Effect of Bradykinin on Murrah buffalo (Bubalus bubalis) semen cryopreservation

Keeping in view the poor freezability of bubaline semen in conventionally used extenders, this study was conducted on three Murrah bulls to improve semen cryopreservation with the incorporation of Bradykinin (0.5, 1.0 and 2.0 ng ml(-1)) in routinely used egg yolk tris-glycerol (EYTG) extender. Bradykinin (2.0 ng ml(-1)) had significant (P<0.05) beneficial effect on live sperm % (81.6+/-1.8) and hypo osmotic swelling (HOS) % (63.0+/-1.3) as compared to their respective control values of 73.4+/-2.1 and 56.3+/-2.0 at 0 h post freezing. The post-thaw progressive sperm motility in semen samples diluted with EYTG containing 2.0 ng ml(-1) Bradykinin (65.5+/-1.4) was also significantly (P<0.01) higher than control (60.3+/-1.9) at 0 h post freezing. Thus incorporation of 2 ng ml(-1) Bradykinin in buffalo semen diluted in EYTG extender may be useful in improving the quality of cryopreserved bubaline semen.