Relationship of age to body weight,scrotal circumference,testicular ultrasonograms,and semen quality in Sahiwal bulls

The objective of the present study was to determine the relationship of age to body weight (BW), scrotal circumference (SC), number of pixels of testicular ultrasonograms (NP), and semen quality in Sahiwal bulls. The study was based on 128 Sahiwal bulls of different age groups (from 0 to >100 months of age). Bulls were evaluated for SC, BW, and NP. Semen was evaluated once a week for five consecutive weeks from regularly collected donor bulls (n = 86) ranging in age from 25–30 to >100 months. Ejaculate volume, sperm motility, sperm concentration, sperm morphology, percent live sperms, sperm plasma membrane integrity, and normal acrosome were compared among different age groups. Mean SC and BW increased (P < 0.05) in a curvilinear manner from birth to >100 months of age. Mean NP of testicular ultrasonograms increased (P < 0.05) from 0 to 24 months and then plateaued until >100 months of age. Body weight, SC, and NP were positively correlated with age from birth until >100 months (r = 0.91, 0.87, and 0.40, respectively). Ejaculate volume (5.7 ± 0.2 vs. 4.6 ± 0.09 ml) and sperm concentration (1,281.6 ± 17.7 vs. 1,115.8 ± 55.9 × 10⁶/ml) increased (P < 0.05) in mature bulls compared to younger ones. However, motility (68.6 ± 0.3%), plasma membrane integrity (50.8 ± 1.0%), and normal acrosome (74.8 ± 0.5%) remained insignificant due to age. In six of eight age groups studied, morphological abnormalities were well within the range (18.1 ± 0.3%). In conclusion, the BW, SC, and NP of testicular ultrasonograms, ejaculate volume, and concentration increased with age. Moreover, semen quality is fairly independent of age except volume and concentration in Sahiwal bulls.     

Effect of FMD vaccination on semen quality parameters in Karan Fries and Murrah buffalo bulls

Effect of Foot and Mouth disease (FMD) vaccination was studied on semen quality parameters of 19 Karan Fries (KF) and eight Murrah (MU) breeding bulls during the period 2002 to 2004 at Artificial Breeding Complex, NDRI, Karnal. A total of non-vaccinated 155 KF and 72 MU bulls' ejaculates were taken as control, while 169 KF and 51 MU bulls' ejaculates, collected after vaccination, were used to study the effect of vaccination stress. The results showed that FMD vaccination had no significant (P > 0.05) effect on ejaculate volume and total volume per day of semen in both KF and MU bulls. Volume of semen increased slightly during post-vaccination period in both the breeds. After FMD vaccination, there was significant (P < 0.01) decrease in mass activity (2.27 ± 0.06 vs. 1.67 ± 0.07 and 2.49 ± 0.09. vs. 1.75 ± 0.10, for KF and MU, respectively), initial motility (56.89 ± 0.03% vs. 44.62 ± 0.02% and 62.26 ± 0.04% vs. 47.08 ± 0.05%, for KF and MU, respectively), sperm concentration (754.19 ± 23.96 vs. 554.14 ± 22.95 × 10⁶/ml and 848.61 ± 33.65 vs. 571.57 ± 39.99 × 10⁶/ml, for KF and MU, respectively), and total sperm output per ejaculate (3,685.94 ± 158.40 vs. 2,781.54 ± 151.70 × 10⁶ and 2,218.75 ± 133.14 vs. 1,582.84 ± 158.20 × 10⁶, for KF and MU, respectively). Application of FMD vaccine had significantly (P < 0.05) adverse effect on most of the seminal attributes during post-vaccination in KF and MU buffalo bulls. So, the spermiograms affected following vaccination suggest that in bovines, the semen collection and preservation should be suspended till normal fertility of sperm is restored to avoid the failure of conception from artificial insemination using such semen.     

Seminal Leucocytary Profile in Beef Bulls

Despite evidences that seminal leucocytes could affect semen quality, references for the frequency and concentration of these cells in bulls are not available. The aim of this study was to determine the normal concentration of leucocytes in beef bulls and to correlate this characteristic with semen quality. First, 57 bulls from artificial insemination centres were evaluated to obtain the normal leucocytary profile values. Next, 382 bulls were subjected to breeding soundness evaluation. The average concentration of leucocytes in bovine semen was 4.73 × 10⁶/ml. Unsatisfactory bulls showed a higher number of leucocytes/field than that in the satisfactory ones. Logistic regression analysis revealed that the unsatisfactory bulls showed 6.5‐fold more chances of having higher leucocyte counts than satisfactory ones. Values of up to 1 leucocyte/field in the bull ejaculate are considered physiologically normal, whereas >5 leucocytes/field is associated with poor semen quality.     

Temporal changes in circulating levels of plasma interleukin-8 during peripartum period in Murrah buffaloes (Bubalus bubalis) under subtropical climate

The objective of this study was to elucidate the changes in circulating levels of plasma interleukin-8 (IL-8) during peripartum period in Murrah buffaloes (Bubalus bubalis). IL-8 was estimated in blood plasma of healthy peripartum Murrah buffaloes (n = 6) on days ±30, ±15, ±5, ±3, ±1 and 0 pre- and postpartum with respect to the day of parturition (day 0) in each of the two different seasons (hot–humid and spring). The mean microclimate Temperature–Humidity Index (THI) during spring season was significantly lower (p < 0.01) than the corresponding THI in hot–humid season. In both the seasons, plasma IL-8 remained lower in prepartum period (≤46.56 ± 14.08 pg/ml during spring and ≤ 73.18 ± 18.56 pg/ml during hot–humid season) than in the postpartum period (≥51.41 ± 13.82 pg/ml during spring and ≥ 84.13 ± 16.97 pg/ml in hot humid season). During spring, the IL-8 levels were significantly higher (P < 0.05) on days +5 and +15 postpartum in comparison to the IL-8 levels on days −30, −5, and −3 prepartum. During hot–humid season, IL-8 level was significantly higher (P < 0.05) on day +30 as compared to the IL-8 levels on days −30 and −5 prepartum. The correlation between IL-8 and mean microclimate THI was significant (r = 0.25, P < 0.01). From the results, it is concluded that peripartum period in buffaloes is associated with an inflammatory response leading to significantly higher plasma IL-8 during parturition and postpartum period than in the pre-partum period.     

Effect of semen collection frequency on seasonal variation in sexual behaviour,testosterone, testicular size and semen characteristics of tropical hair rams (<Emphasis Type="Italic">Ovis aries</Emphasis>)

The purpose of this study was to examine the effect of day length on seminal characteristics, testicular size, sexual behaviour and testosterone (T4) concentration in Pelibuey rams subjected to different semen collection frequencies. Eighteen intact males were assigned randomly to one of two semen collection frequencies: in the high rate (HR) treatment, two ejaculations per week were obtained from each ram; one ejaculation every two weeks was collected under the low rate (LR) treatment. All animals were housed individually in contiguous 5 m × 5 m wire mesh pens and evaluated over a 12-month period. At the beginning of the experiment rams were 20 months old and 40–50 kg in weight. All rams ejaculated and produced semen throughout the year. Semen volume, sperm per ejaculation, testicular circumference and testicular volume were significantly (p < 0.05) greater during short days in all rams, regardless of the semen collection frequency, with the exception of sperm concentration, for which no variation was found in HR individuals, and reaction time and T₄ levels, for which no variation was found in LR males. Rams subjected to HR collection were more affected by the short-day photoperiod than rams collected twice per week, exhibiting greater reduction (p < 0.05) in time to achieve their first ejaculation and in sperm per ejaculation, as well as greater increases (p < 0.05) in T₄ concentration than LR rams (14.65 ± 1.22 vs 23.53 ± 5.34 s, (3.37 ± 0.17) × 10⁹ vs (3.52 ± 0.20) × 10⁹ sperm and 8.68 ± 0.44 vs 6.85 ± 0.74 ng/ml, respectively). It was concluded that: (a) the magnitude of the seasonal effects was not sufficient to prevent the rams being used for breeding throughout the year, and (b) seasonal variation within variables was affected differently between semen collection frequencies.     

Crossbred bull selection for bigger scrotum and shorter age at puberty with potentials for better quality semen.

Shortening age at puberty of crossbred breeding bull is an important issue in the tropics. This study aimed at selecting crossbred bulls at earliest possible age with bigger scrotum and potential for donating quality semen. One hundred and 31 pre-joining crossbred bulls of Central Artificial Insemination Laboratory, Saver, Dhaka were examined. The bulls being trained by seeing semen collection from mature bulls were allowed ejaculation into the artificial vagina at homosexual mount during a 20 min time at three occasions, every three months. Eighty one of 131 bulls produced at least one ejaculate during the study and their mean +/- SD age and scrotal circumference (SC) were 20.3 +/- 4.7 months and 28.2 +/-2.7 cm, respectively. Bulls' body weight, body condition score (BCS) and SC influenced the attainment of their puberty (p < 0.05). Bull's body weight had positive effects on scrotal circumference and ejaculate volume (p < 0.05). Scrotal circumference positively influenced the percentages of normal spermatozoa (p < 0.05). Scrotal skin-fold thickness negatively influenced the proportion of spermatozoa with normal head (p < 0.05). Based on age at first ejaculate and SC, 29.6% bulls (n = 24) were selected by cluster analysis. Selected bulls had mean +/- SD age 17.9 +/- 2.2 months, body weight 287.3 +/-48.6 kg, SC 30.5 +/- 1.5 cm, ejaculate volume 3.4 +/- 1.3 ml, sperm motility 50.8 +/- 17.2%, total spermatozoa per ejaculate 2541.9 +/- 1699.2 million and normal spermatozoa 81.5 +/-14.5%. The selected pubertal bull group was different from the unselected pubertal bulls at MANOVA (p < 0.0001). About 30% of pubertal crossbred bulls can be selected with shorter age and larger scrotum at puberty under conditions prevailed in Bangladesh.     

Effect of cattle-specific estrus molecules on libido and semen production of zebu bulls under tropical climate

Zebu bulls are a shy breeder and they exhibit optimum libido in the presence of females with estrus phase. Continuous semen collection with the use of male dummy leads to lack of adequate sexual stimulation. Therefore, the present study was designed to test the effect of estrus-specific molecule(s) for effective sexual preparation of donor bulls. The bulls were divided into normal and poor libido group, five bulls in each group by taking 1-month control study data after collecting the information of individual bull’s sexual behaviour during semen collection by regular semen collector. The bulls were never being exposed to female animals and semen was collected by an artificial vagina. The ten animals were exposed to a glycerol-water solution (50/50 v:v) as control and then exposed to estrus-specific molecules one by one. The estrus-specific molecules like squalene, 1-iodoundecane, acetic acid, coumarin, propionic acid, oleic acid, and 2-butanone were purchased from Sigma-Aldrich Company, USA, and the molecules were solubilised individually in a non-pressurised aerosol dispenser as 1.0% concentration in glycerol-water solution (50/50, v:v). Identical bulls were used as the control and exposed to each molecule one by one by giving a refractory period of 14 days. A nasal spray of acetic acid or 2-butanone significantly (p < 0.05) reduced reaction time (RT) and total time taken to ejaculate (TTTE) in normal libido bull group. Semen volume, sperm concentration, and the total number of sperm per ejaculation obtained did not show significant improvement in the normal libido group of bulls after the application of estrus-specific molecules as compared to the control. In poor libido group, acetic acid, oleic acid, and 2-butanone application showed significant (p < 0.01) improvement in RT and TTTE as compared to the control group, whereas semen production variables like sperm concentration and total sperm output per ejaculation increased significantly (p < 0.05) except semen volume. There was significant (p < 0.01) reduction in RT (%) and TTTE (%) after the application of acetic acid followed by 2-butanone and oleic acid. The sperm concentration and total sperm output per ejaculation were more after the application of each molecule but significant increase (p < 0.05) in sperm concentration was observed with 2-butanone (11.42%), acetic acid (11.42%), and oleic acid (10.13%), whereas total sperm output per ejaculation increased significantly (p < 0.05) only after the application of acetic acid and 2-butanone (24.75% and 26.84%). Hence, it can be concluded that acetic acid, 2-butanone, and oleic acid are effective for better sexual preparation of Sahiwal bulls and total sperm output per ejaculation.

     

Serum sialic acid and oxidative stress parameters changes in cattle with leptospirosis

This study was designed to disclose some indicators of oxidative stress and inflammation in natural cases of bovine leptospirosis. For this purpose, 12 bulls exhibiting clinical signs of leptospirosis and 10 healthy bulls were used. Animals were subjected to thorough clinical examination and the clinical signs were recorded. All animals were blood sampled in order to determine serum total sialic acid (TSA), lipid bound sialic acid (LBSA), malondialdehyde (MDA), reduced glutathione (GSH), nitric oxide (NO), uric acid (UA), total protein (TP), albumin and glucose. Urine samples were collected from each animal and examined under dark-field microscope to observe spirochetes. Diseased animals exhibited clinical signs suggesting leptospirosis and the diagnosis was supported by positive dark-field microscope examination. Mean TSA (mmol/L), LBSA (mmol/L), TP (g/dl), albumin (g/dl), glucose (mg/dl), MDA (μmol/L), GSH (mg/dl), NO (nmol/ml), and UA (mg/L) levels were 1.63 ± 0.02, 0.40 ± 0.10, 7.18 ± 0.24, 3.23 ± 0.5, 64.96 ± 1.88, 5.71 ± 0.11, 78.68 ± 0.72, 7.94 ± 0.34, and 8.75 ± 0.41 in healthy bulls, and 2.50 ± 0.05, 0.70 ± 0.2, 9.27 ± 0.17, 2.55 ± 0.62, 107.93 ± 2.52, 8.82 ± 0.14, 47.85 ± 1.85, 14.57 ± 0.63 and 15.85 ± 0.80 in leptospirosis cases, respectively. The differences between the two groups were statistically significant (P < 0.001). Increased TSA, LBSA, MDA, NO, UA, TP, glucose and decreased GSH and albumin concentrations were suggestive of inflammation and oxidative stress in diseased bulls. The results obtained may suggest that oxidative damage along with other mechanisms might have taken part in the pathogenesis of bovine leptospirosis and further detailed studies are needed to fully understand the mechanism(s) of the disease.     

Exploratory analysis of differences in sperm morphology in Nelore and Gir (Bos indicus) bulls

The aim of this study was to evaluate the effects of breed and season on semen quality parameters of zebu bulls. Data (1,632 registers) of semen production from Gir (n?=?4) and Nelore (n?=?15) bulls were collected between October 2005 and November 2009. The ejaculates were collected twice a week during various seasons (summer, fall, winter, and spring) and evaluated for the following semen parameters: ejaculate volume, sperm concentration, sperm motility, forward progressive motility (FPM), and sperm morphology. Factor analysis was used to determine the relationship among variables. The effect of breed (Gir and Nelore) and season and their cross effect on each parameter and extracted factor were tested using ANOVA. A negative correlation (P?<?0.05) was observed between FPM and proximal droplet, as well as with abnormal loose head, abnormal small head, pouch formation, abnormal mid-peace, and strongly folded tail. Gir bull sperm showed more major defects, detached acrosome, and minor FPM (P?<?0.01), whereas Nelore bulls showed a higher number of sperm with normally loose head.     

Effect of varying dietary energy levels during the last trimester of pregnancy on subsequent first lactation performance in Sahiwal heifers

The aim of the study was to determine optimum dietary energy level during the last trimester of pregnancy for Sahiwal heifers in subtropical Pakistan. Sixteen Sahiwal heifers, 5–6 months pregnant, were assigned to four dietary treatments with four heifers on each treatment. Isonitrogenous (CP = 14.1%) diets having varying energy, namely, ME 88%, ME 100% (Control), ME 112% and ME 124% of NRC recommended level for pregnant heifers, were fed until calving. All were fed a similar diet after calving. Precalving weight gain was highest (P < 0.05) in heifers fed ME 112 and 124% (486 ± 13 and 497 ± 5 g/day, respectively) followed by ME 100% (444 ± 7 g/day), and the lowest weight gain was recorded for ME 88% (397 ± 8 g/day). A similar trend was observed for feed efficiency. Body condition score at calving in groups ME 124% and ME 112% was higher than ME 88% and ME 100%. Nutrient digestibility, birth weight of calves and milk composition except fat content were not influenced by energy levels. The highest daily milk yield was observed in heifers fed ME 100% followed by ME 112, 124, and 88%. We conclude that the NRC recommendation is applicable to the subtropical region.     

Changes in endogenous estrogens and expression of behaviors associated with estrus during the periovulatory period in Heatsynch treated Murrah buffaloes (Bubalus bubalis)

The objective of this study was (1) to establish the duration of behavioral estrus signs and timing of ovulation in Murrah buffaloes (n = 10) and (2) to determine relationship between behavioral estrus signs with change in plasma estrogen concentrations in animals treated with Heatsynch protocol. Estrus and its behavioral signs were detected at hourly intervals by visual observations per rectal examination of genitalia and bull parading four times in a day for 30 min each. Among the behavioral signs of estrus, swollen vulva was the best indicator of estrus followed by excitement and chasing by bull (90%). Among the duration of behavioral estrus signs, the first and longest duration of estrus signs was swollen vulva, which was seen up to 21.6 ± 1.1 h after onset of estrus. The mean total duration of estrus symptoms from appearance to disappearance of all the behavioral estrus symptoms was 40.2 ± 1.8 h. Endocrine profile during the periestrus period showed that the mean peak concentrations of total estrogen 330.9 ± 108.3 pg/ml occurred at 9.6 ± 1.0 h after estradiol benzoate injection. The average number of estrus symptoms observed per animal during Heatsynch treatment was 7.1. Ovulation occurred after 50.0 ± 2.0 h after estradiol benzoate treatment and 26.7 ± 2.0 h after end of total estrogen surge, respectively. In conclusion, our results suggest that all signs of behavioral estrus occurred after the preovulatory rise in estrogens. The first sign of estrus was swollen vulva, and this symptom persisted the longest.     

Environmental factors and interval from the introduction of rams to estrus in postpartum Saint Croix sheep

The objective of this study was to determine whether season and total rainfall during the breeding season, sheep parity, and/or litter size affect the interval from the introduction of rams to estrus (IRE) in hair Saint Croix sheep in northeastern Mexico. An analysis was made of 874 services performed during 9 years, introducing the rams into the sheep flock after an isolation period of 60 days during the postpartum period. Estrus was recorded twice daily during 35 days. Year and season influenced significantly on the interval between ram introduction and estrus length (P < 0.01). Winter IRE length (7.9 ± 0.1 days) was shorter than in the other three seasons (11.1 ± 0.2, 11.1 ± 0.1, and 16.2 ± 0.2 days in summer, autumn, and spring, respectively) (P < 0.01). An interaction was observed between rainfall and season, then by rainfall between 0 and 100 mm, IRE was shorter (P < 0.05) in winter (6.8 ± 0.3 days), and by rainfall between 100 and 199 mm, IRE was shorter (P < 0.05) in autumn (10.2 ± 0.5 days); however, when rainfall was beyond 200 mm, IRE length was shorter (P < 0.01) in summer (4.8 ± 0.5 days) than in autumn (14.5 ± 0.3 days). The IRE length was also longer in first lambing ewes (P < 0.05) and was not affected by litter size. In the present study, several factors, including the breeding season, rainfall and parity, directly influenced the interval between the male introduction and the onset of estrus by Saint Croix hair sheep.     

Variation in sperm cryosurvival is not modified by replacing the cryoprotectant glycerol with ethylene glycol in bulls

Breed and sire differences in sperm cryosurvival have been noted, with negative implications for sperm cryobanking and assisted reproduction programmes. This study hypothesized that these differences could be modified by using lower molecular weight cryoprotectants. Therefore, the effect of replacing glycerol (GLY) with ethylene glycol (EG) on differential cryosurvival of semen from two Sanga cattle breeds (Mashona vs. Tuli) was determined. Three to five ejaculates were collected from each of ten bulls (3-8 years) by electro-ejaculation, diluted in three Tris-egg yolk extenders (Triladyl^®, 7% GLY-based and 7% EG-based) and evaluated for sperm motility, viability and morphology at three time periods (fresh – 0 hr, pre-freeze – 4 hr and post-thaw). Tuli bulls produced larger (11.8 ± 0.31 ml vs. 8.5 ± 0.38 ml) and more concentrated ejaculates of lower fresh semen quality. Breeds differed across time for motility and morphology, but not viability. Mashona bull semen had significantly higher motility and normal morphology values at each sampling time. Bulls classified as poor freezers had lower concentration (0.70 ± 0.09 × 10⁹ sperm/ml vs. 1.37 ± 0.10 × 10⁹ sperm/ml), sperm motility index (SMI, 35.0 ± 3.4 % vs. 67.8 ± 2.1 %) and viability (69.7 ± 1.1 % vs. 75.7 ± 1.0 %) compared to good freezers. Maintenance of semen quality by GLY and EG did not differ between breeds, poor and good freezers, or age groups. The interaction breed by extender across time did not reach statistical significance for all variables. The study revealed that bull and breed variation in sperm quality and cryosurvival is not modified by replacing GLY with EG, suggesting that cryostress tolerance of sperm may be under control of mechanisms other than differential response to GLY cytotoxicity.     

Serum kisspeptin: New possible biomarker for sexual behaviour and sperm concentration in buffalo bulls

The study was designed to decipher the inter-relationship between peripheral hormones (kisspeptin and testosterone), sexual behaviour and seminal variables of Murrah buffalo bulls (n = 134). In this study, we recorded that 13%, 37%, 40%, 6% and 4% Murrah buffalo bulls had reaction time of <30, 31–60, 61–180, 181–300 and >300 s, respectively. Further, it was observed that 4%, 85% and 10% buffalo bulls were sexually aggressive, active and dull, respectively, during semen collection. The courtship behaviour was not found to be desirable for the bulls used for the semen collection. Mean of ejaculate volume, sperm concentration and mass motility (0–5 scale) were 3.57 ml, 977.11 million/ml, 2.7, respectively. Correlation studies revealed that the reaction time was positively correlated with courtship behaviour and body weight, and negatively correlated with sexual aggressiveness and sperm concentration. Serum kisspeptin in buffalo bulls, measured for the first time, was found to 3.8 ± 0.7 ng/ml. Serum kisspeptin and testosterone level are negatively correlated to each other and kisspeptin level influenced the sexual behaviour (reaction time, sexual aggressiveness and penile erection) of study bulls. Serum kisspeptin was higher in the buffalo bulls with higher sperm concentration indicating its role in spermatogenesis. In conclusion, for the first time basic information related to sexual behaviour of Murrah buffalo bulls in large population along with its inter-relationship with peripheral hormones (kisspeptin and testosterone) has been documented.     

A study on the effect of GnRH administration on the ovarian response and laparoscopic intrauterine insemination of Awassi ewes treated with eCG to induce superovulation

The effect of GnRH administration on superovulatory response of ewes treated with equine chorionic gonadotrophin (eCG) in breeding and nonbreeding seasons and the contribution of laparoscopic insemination to the improvement of fertilization and embryo recovery were investigated. Twenty-four nonpregnant Awassi ewes of 3–4 years of age were randomly allocated into two groups (n = 12). Each ewe was treated with a progesterone impregnated intravaginal sponge for 12 days. The following superovulation treatment was used: ewes of group 1 received 1,200 IU of eCG once as an intramuscular injection 48 h prior to sponge withdrawal; ewes of group 2 also received 1,200 IU of eCG once as an intramuscular injection, 48 h prior to sponge withdrawal and after 24 h of sponge removal. Ewes were injected with 80 μg of GnRH. Ewes of groups 1 and 2 were further subdivided into four equal groups (n = 6). Subgroups A and C (superovulated with eCG and eCG plus GnRH, respectively) were mated naturally at least two times with Awassi rams of proven fertility at 8-h intervals. Subgroups B and D (same as A and C) had intrauterine insemination at 44–46 h after sponge removal, under laparoscopic visualization of uterine horns, depositing 1 ml of diluted semen containing 100 × 10⁶ motile sperm in the distal portion of each uterine horn. Ovarian response was assessed by determining the number of corpora lutea by laparoscopy at day 6 after mating. Embryo recovery was performed by using a semi-laparoscopic flushing procedure in both uterine horns. Results of the present study showed that ewes treated in breeding season with eCG plus GnRH has a higher number (P < 0.05) of corpora lutea than eCG alone as 7.33 ± 0.54 and 4.33 ± 0.39, respectively. There was no significant difference in the number of corpora lutea in nonbreeding season when ewes treated with eCG and eCG plus GnRH. The number of unovulated follicles was significantly higher (P < 0.05) in eCG treated ewes than in ewes treated with eCG plus GnRH, both in the breeding and nonbreeding seasons. The number of recovered embryos from ewes treated with eCG plus GnRH and eCG differ significantly (P < 0.05) as 4.32 ± 0.56 and 1.06 ± 0.26, respectively, in the breeding seasons. No significant difference was observed when these hormones used for superovulation in the nonbreeding season. A higher number of unfertilized ova (P < 0.05) was observed in ewes when naturally inseminated than in ewes inseminated using the intrauterine laparoscopic technique. Higher rate of embryo recovery (P < 0.05) was achieved when ewes were inseminated via intrauterine (4.66 ± 0.66) compared with ewes naturally mated (2.16 ± 0.74). The fertilization rate in ewes inseminated intrauterine using laparoscopic techniques and naturally mated were 91.5% and 44.8%, respectively. Fertilization failure in ewes inseminated intrauterine using laparoscopic techniques and naturally mated were 8.4% and 55.2%, respectively. It could be concluded that administration of GnRH 24 h after sponge removal increased ovulation rate of Awassi ewes treated with eCG for superovulation in the breeding season. The use of eCG to induce superovulation in Awassi ewes combined with laparoscopic intrauterine insemination increases the fertilization rate.     

Divergent development of testosterone secretion in male zebu (Bos indicus) and crossbred cattle (Bos indicus x Bos taurus) and buffaloes (Bubalus bubalis) during growth

Delayed pubertal development and low fertility of Bos indicus x Bos taurus crossbred male cattle and domestic buffaloes is hardly understood hence, a sensitive enzymeimmunoassay (EIA) was developed using the second antibody-coating technique and testosterone-3-O-carboxymethyloxime-horseradish peroxidase conjugate as a label for determination of testosterone in blood plasma. The EIA was validated by standard criteria. Blood samples were collected by venipuncture from growing male cattle (Karan Fries and Sahiwal) and buffalo (Murrah) and testosterone was estimated using the EIA procedure. Plasma testosterone concentrations increased significantly (P < 0.05) with advancing age. Testosterone concentrations were significantly (P < 0.01) higher in Sahiwal males in comparison to Karan Fries males. The low testosterone levels in crossbred than Sahiwal could imply that crossbred males have either not stabilized genetically or not adapted well in Indian climatic conditions resulting in poor libido and poor semen quality. The low testosterone levels in Murrah buffalo males may be the possible reason for delayed maturity in this species. The direct, sensitive EIA validated for estimating the plasma testosterone concentration was reliable for studying the testosterone profile in blood plasma of males. The results suggest that there could be a requirement for higher testosterone secretion by males during early stages of growth for attaining early sexual maturity.     

The Breed and Season Effects on Scrotal Circumference and Semen Characteristics of Hair Sheep Rams Under Tropical Conditions

The aim of the present work was to evaluate the breed and season effects on scrotal circumference (SC) and semen characteristics of 28 mature hair sheep rams kept under tropical conditions. SCs, sperm concentration (SPC) and abnormal sperm were significantly affected by breed effect (p < 0.001). The season effect was significant in SPC (p < 0.0001) while ejaculate volume, mass motility and SPC were affected by breed × season interaction effect (p < 0.001). It can be concluded that the magnitude of the breed and season effects were not sufficient to affect the reproductive capacity of hair sheep rams throughout the year.     

Sperm Chromatin Stability During In Vitro Manipulation of Beef Bull Semen

Seven experiments were conducted to study the effect of freezing extenders, antioxidants, motility stimulants, thawing temperature, incubation temperature and time, centrifugation and capacitation on sperm chromatin instability (CI) as well as the influence of sperm CI on pregnancy rates of heifers (n = 360) after AI with frozen semen. Semen was collected once a week from Blonde d’Aquitaine and Limousine bulls (n = 3/breed) via an artificial vagina and only individual ejaculates (n = 300) of >0.3 × 10⁹ sperm/ml and ≥ 70% progressive motility were used. Sperm CI was evaluated by nuclear DNA susceptibility to acid‐induced denaturation using acridine orange fluorescence and by chromatin susceptibility to decondensation using quantitative transmission electron microscopy. Bioxcell extender was better than AndroMed and egg yolk extenders in terms of low incidence of sperm CI in one bull (p < 0.05). Neither antioxidants (EDTA–2Na, Na‐pyruvate and albumin) nor motility stimulants (caffeine and blood serum) had any significant effect on sperm CI. Thawing of frozen semen at 45°C for 30 s decreased (p < 0.025) CI in one bull. Incubation of frozen sperm at 25 and 39°C for 240 min increased sperm CI percentages from 3.47 ± 0.48 and 4.50 ± 0.41% to 6.70 ± 0.36 and 9.71 ± 0.53%, respectively (p < 0.001). Although centrifugation and removal of extracellular milieu increased CI of cooled sperm, it decreased CI of frozen–thawed sperm (p < 0.025). Follicular fluid as a capacitating agent destabilized chromatin structure (p < 0.001). Sperm vulnerability to CI had a negative impact (r² = 0.37–0.77, p < 0.001) on fertility of frozen ejaculates. In conclusion, in vitro manipulation of bovine semen can influence incidence of sperm CI, whereas integrity of sperm chromatin contributes significantly to heifers’ fertility. We would recommend selection of the appropriate extender and thawing temperature for each bull together with careful manipulation of frozen semen to minimize damage of sperm chromatin.     

Milk hygiene and udder health in the periurban area of Hamdallaye, Niger

The prevalence of intra-mammary infections in dairy herds was studied in Hamdallaye, Niger. A total of 956 milk samples were collected in 2007 from 239 lactating cows of four local breeds in eight traditional herds; the first sampling was undertaken in the dry season at morning milking, and the second in the rainy season at evening milking. Staphylococcus aureus, Coagulase-Negative Staphylococci (CNS) and environmental microorganisms were detected in significantly (p < 0.05) more samples in the rainy season, 55.2%, than in the dry season, 27.1%. Statistically significant (P < 0.05) differences in prevalence were observed among herds and according to lactation number. Infections were assigned to four classes, according to the major pathogen, and the respective mean somatic cell counts during the dry season were: S. aureus, 775 × 10³ cells/ml; CNS, 447 × 10³ cells/ml; environmental microorganisms, 407 × 10³ cells/ml; and non-infected, 262 × 10³ cells/ml. Most of the tested strains were sensitive to antibiotics, and selected strains of S. aureus (n = 15) were negative to the multiplex PCR tests for production of enterotoxins.     

Analysis of size and conformation of native Creole goat breeds and crossbreds used in smallholder agrosilvopastoral systems in Puebla,Mexico

Liveweight (LW) of does and bucks of the native Creole goat breed and crosses of Creole does and Nubian bucks, aged 1.5–5 years, were recorded and body traits including: head length (HL), head width (HW), body length (BL), trunk length (TL), chest girth (CG), abdominal perimeter (AP), rump length (RL), and height at withers (HW) were measured to develop equations for predicting LW from the body measurements. Weight, sex, breed and kidding date of 354 kids were recorded at birth, and LW of the kids was measured monthly for one year to determine the effect of kidding season on growth rate. Bucks had higher (p < 0.05) body measurements than the does (HL 15.1 ± 0.1 vs 16.6 ± 0.2 cm; BL 97.6 ± 0.4 vs 104.6 ± 1.2 cm; CG 78.8 ± 0.4 vs 79.9 ± 1.0 cm; AP 82.4 ± 0.5 vs 87.2 ± 1.1 cm; HW 62.7 ± 0.4 vs 70.1 ± 0.8 cm). With the exception of TL, F₂ does had higher (p < 0.05) body measurements and LW (28.8 ± 1.5 vs 27.7 ± 0.5 kg) than Creole does. The body traits of the F₁ does were similar (p > 0.05) to those of Creole does with the exception of HL, BL and HR. The F₂ kids were heavier (p < 0.05) at birth (3.31 ± 0.1 vs 2.60 ± 0.1 kg) and grew faster than the Creole kids. Male kids were heavier (p < 0.05) at birth (3.21 ± 0.10 vs 2.73 ± 0.13 kg), and grew faster than female kids. Season had a significant effect on birth weight. The results showed that LW of Creole goats and Creole × Nubian does could be estimated in the field using body traits. Birth weight and growth rate of kids could be improved by management practices that affect season of kidding.