Evaluation of steroidogenic capacity after follicle stimulating hormone stimulation in bovine granulosa cells of Revalor 200? implanted heifers

Background

Heifers not used as breeding stock are often implanted with steroids to increase growth efficiency thereby altering hormone profiles and potentially changing the environment in which ovarian follicles develop. Because bovine granulosa cell culture is a commonly used technique and often bovine ovaries are collected from abattoirs with no record of implant status, the objective of this study was to determine if the presence of an implant during bovine granulosa cell development impacts follicle stimulating hormone-regulated steroidogenic enzyme expression. Paired ovaries were collected from 16 feedlot heifers subjected to 1 of 3 treatments: non-implanted (n = 5), Revalor 200 for 28 d (n = 5), or Revalor 200 for 84 d (n = 6). Small follicle (1 to 5 mm) granulosa cells were isolated from each pair and incubated with phosphate buffered saline (n = 16) or 100 ng/mL follicle stimulating hormone (n = 16) for 24 h.

Results

Granulosa cells of implanted heifers treated with follicle stimulating hormone produced medium concentrations of progesterone similar (P = 0.22) to non-implanted heifers, while medium estradiol concentrations were increased (P < 0.10) at 28 and 84 d compared to non-implanted heifers indicating efficacy of treatment. Additionally, real-time PCR analysis in response to follicle stimulating hormone treatment demonstrated a decrease in steroidogenic acute regulatory protein (P = 0.05) mRNA expression in heifers implanted for 84 d and an increase in P450 side chain cleavage mRNA in granulosa cells of heifers implanted for 28 (P < 0.10) or 84 d (P < 0.05) compared to non-implanted females. However, no difference in expression of 3-beta-hydroxysteroid dehydrogenase (P = 0.57) and aromatase (P = 0.23) were demonstrated in implanted or non-implanted heifers.

Conclusions

These results indicate follicles which develop in the presence of high concentrations of androgenic and estrogenic steroids via an implant tend to demonstrate an altered capacity to respond to follicle stimulating hormone stimulation. Thus, efforts should be made to avoid the use of implanted heifers to study steroidogenesis in small follicle granulosa cell culture systems.     

Evaluation of steroidogenic capacity after follicle stimulating hormone stimulation in bovine granulosa cells of Revalor 200~ implanted heifers

Background： Heifers not used as breeding stock are often implanted with steroids to increase growth efficiency thereby altering hormone profiles and potentially changing the environment in which ovarian follicles develop. Because bovine granulosa cell culture is a commonly used technique and often bovine ovaries are collected from abattoirs with no record of implant status, the objective of this study was to determine if the presence of an implant during bovine granulosa cell development impacts follicle stimulating hormone-regulated steroidogenic enzyme expression. Paired ovaries were collected from 16 feedlot heifers subjected to 1 of 3 treatments： non-implanted （n = 5）, Revalor 200 for 28 d （n = 5）, or Revalor 200 for 84 d （n = 6）. Small follicle （1 to 5 mm） granulosa cells were isolated from each pair and incubated with phosphate buffered saline （n = 16） or 100 ng/mL follicle stimulating hormone （n = 16） for 24 h. Results： Granulosa cells of implanted heifers treated with follicle stimulating hormone produced medium concentrations of progesterone similar （P = 0.22） to non-implanted heifers, while medium estradiol concentrations were increased （P 〈 0.10） at 28 and 84 d compared to non-implanted heifers indicating efficacy of treatment. Additionally, real-time PCR analysis in response to follicle stimulating hormone treatment demonstrated a decrease in steroidogenic acute regulatory protein （P = 0.05） mRNA expression in heifers implanted for 84 d and an increase in P450 side chain cleavage mRNA in granulosa cells of heifers implanted for 28 （P 〈 0.10） or 84 d （P 〈 0.05） compared to non-implanted females. However, no difference in expression of 3-beta-hydroxysteroid dehydrogenase （P= 0.57） and aromatase （P = 0.23） were demonstrated in implanted or non-implanted heifers. Conclusions： These results indicate follicles which develop in the presence of high concentrations of androgenic and estrogenic steroids via an implant tend to demonstrate an alter     

Effect of feed intake restriction on reproductive performance and pregnancy rate in Egyptian buffalo heifers

The objective of the present experiment is to study the effect of feed intake restriction on the reproductive performance and pregnancy rate in Egyptian buffalo heifers. Thirty anestrus buffalo heifers were randomly divided into two equal groups. The low feed intake (LFI, n?=?15, 50 % restriction) group was fed a diet that consists of 3 kg concentrate, 1 kg wheat straw, and 3 kg fresh alfalfa, while the high feed intake (HFI, n?=?15) group was fed double the amount given to the LFI group for 4 months. All animals were weighed, transrectally examined, and visually checked for the signs of estrus, and blood samples were collected. Heifers in heat were mated with one fertile bull. The number of heifers showing estrus activity was 93.3 % in HFI vs. 20 % in LFI (P?<?0.01). Ovarian activity started earlier (P?=?0.03) in the HFI than LFI group. The weight at breeding, the diameter of the dominant follicle, number of heifers showing ovulations, number of services per conception, pregnancy rate, and overall mean of progesterone and estrogen concentrations were significantly higher (P?<?0.01) in the HFI than in the LFI group. The level of serum total protein, albumin, globulin, glucose, total cholesterol, and calcium were significantly higher (P?<?0.05) in the HFI group. Restriction of the daily feed intake to 50 % from NRC recommendations impair reproductive performance in terms of increasing the age at first service and reducing the pregnancy rate in buffalo heifers. In conclusion, feed intake could be effective in improvement of reproductive performance in buffalo heifers and further studies should be done on large scale of buffaloes in this point.     

Higher feeding diets effects on age and liveweight gain at puberty in crossbred Nelore × Hereford heifers

This study was conducted to determine the age and liveweight at puberty of 120 crossbred beef heifers submitted to four diets to achieve predetermined weight gains (kg/day): 0.5 (G500; n?=?32), 0.75 (G750; n?=?32), 1.0 (G1000; n?=?29), and 1.25 (G1250; n?=?27). Animals were classified depending on their level of crossing between Nelore (N) and Hereford (H): 25%N-75%H, 37.5%N-63.5%H, 43.7%N-56.7%H, 50%N-50%H, and 75%N-25%H. Reproductive evaluation was performed at the beginning and at the end of the experimental period by ultrasonography and hormone analysis. The average age and liveweight at puberty were 388.0?±?1.9 days and 331.4?±?1.3 kg, respectively. Animals from the 25%N-75%H group reached puberty earlier than heifers from other genetic groups supplemented with G1250 diet (P?<?0.05). Heifers with higher degree of Nelore (75%N-25%H) fed with G1000 diet showed estrus 42 days prior to mating, but only 57 % reached puberty at mating (P?<?0.05). Heifers with follicles of higher diameter reached puberty (P?<?0.05) earlier. Higher average daily weight gain showed a positive effect on follicular diameter and IGF-I level at puberty (P?<?0.01). Concentrations of GH were lower in heifers fed G1250 compared to G1000 diet (P?<?0.05). There was a significant interaction between nutritional level and insulin levels at puberty (P?<?0.01). We demonstrated the relationship between IGF-I and average daily gain on the onset of puberty in heifers. In conclusion, heifers submitted to the higher feeding level showed a higher follicular diameter and were younger at puberty.     

Incorporation of estradiol benzoate to CIDR protocol improves the reproductive responses in crossbred dairy heifers

The present study was designed to determine the effect of estradiol benzoate (EB) on reproductive response following a controlled internal drug release (CIDR) protocol in crossbred (Sahiwal × Friesian) dairy heifers. In the first trial, a total of 100 crossbred dairy heifers were treated with CIDR protocol for 7 days and injected with the PGF_2α on day 6. After 24 h of CIDR removal, one group (EB?=?50) was injected with estradiol benzoate whereas the other (control?=?50) remained untreated. Estrus intensity and response were recorded visually and ovulation rate was recorded by ultrasonography. All heifers were artificially inseminated at 48 and 60 h following CIDR removal. Heifers were scanned for pregnancy within days 30–40 of artificial insemination (AI). In the second trial, two subgroups of heifers were included to observe the estrus and ovulatory events. The results of the first trial revealed that estrus response was achieved 100% in both the treatment groups. Estrus intensity (2.9?±?0.1 vs. 2.0?±?0.7) and ovulation rate (100 vs. 88%) differed significantly (P?<?0.05) between the EB and control groups. However, a tendency for higher pregnancy per AI was observed (54 vs. 36%; P?=?0.07) in EB than that in control groups. The results of the second trial revealed that a significantly (P?<?0.05) shorter estrus and earlier ovulatory events were observed in EB-treated heifers. It is concluded that the incorporation of estradiol benzoate to the CIDR protocol is helpful to improve the estrus signs and enhance the ovulation and the pregnancy per AI in crossbred dairy heifers.     

Pre-breeding blood urea nitrogen concentration and reproductive performance of Bonsmara heifers within different management systems

This study investigated the association between pre-breeding blood urea nitrogen (BUN) concentration and reproductive performance of beef heifers within different management systems in South Africa. Bonsmara heifers (n?=?369) from five herds with different estimated levels of nitrogen intake during the month prior to the commencement of the breeding season were sampled in November and December 2010 to determine BUN concentrations. Body mass, age, body condition score (BCS) and reproductive tract score (RTS) were recorded at study enrolment. Trans-rectal ultrasound and/or palpation was performed 4–8 weeks after a 3-month breeding season to estimate the stage of pregnancy. Days to pregnancy (DTP) was defined as the number of days from the start of the breeding season until the estimated conception date. Logistic regression and Cox proportional hazards survival analysis were performed to estimate the association of pre-breeding BUN concentration with subsequent pregnancy and DTP, respectively. After stratifying for herd and adjusting for age, heifers with relatively higher pre-breeding BUN concentration took longer to become pregnant when compared to those with relatively lower BUN concentration (P?=?0.011). In the herd with the highest estimated nitrogen intake (n?=?143), heifers with relatively higher BUN were less likely to become pregnant (P?=?0.013) and if they did, it was only later during the breeding season (P?=?0.017), after adjusting for body mass. These associations were not present in the herd (n?=?106) with the lowest estimated nitrogen intake (P?>?0.500). It is concluded that Bonsmara heifers with relatively higher pre-breeding BUN concentration, might be at a disadvantage because of this negative impact on reproductive performance, particularly when the production system includes high levels of nitrogen intake.     

Effect of duration of dominance of the ovulatory follicle on onset of estrus and fertility in heifers.

In cattle, prolonged progestogen treatments following luteolysis result in persistent dominant follicles (DF) that are associated with precise onset of estrus but marked reductions in pregnancy rate (PR). The aim was to determine whether increasing duration of dominance of the ovulatory follicle in heifers affected 1) precision of onset of estrus and 2) the timing and nature of the decline in PR. In Exp. 1, duration of dominance of the ovulatory follicle was controlled by causing corpus luteum (CL) regression at emergence of the second follicle wave (mean duration of dominance of 2.1+/-.3 d, Dm2, n = 11) or first day of dominance of the second DF of the cycle; the latter was combined with insertion of a 3-mg norgestomet ear implant for 2 to 10 d to maintain the second DF for 4 (Dm4, n = 32), 6 (Dm6, n = 19), 8 (Dm8, n = 49), 10 (Dm10, n = 28), or 12 d (Dm12, n = 20). Heifers detected in estrus were inseminated approximately 12 h later with frozen-thawed semen. Durations of dominance of the ovulatory follicle of up to 8 d did not affect (P>.05) PR (Dm2 8/9, Dm4 19/28, Dm6 14/18, and Dm8 34/48 heifers pregnant), but PR in Dm10 heifers (12/23 heifers pregnant) was reduced (P = .05) compared with Dm2 heifers; PR in Dm12 heifers (2/17 pregnant) was less compared with all other treatments (P<.01). Fitting a logistic regression model to the pooled PR data to examine the trend in PR showed that extending the duration of dominance from 2 to 9 d and from 10 to 12 d resulted in a predicted decline in PR of 10 to 25% and a further decline of 35 to 75%, respectively. Onset of estrus was delayed in heifers assigned to Dm4 treatment relative to all other treatments (P<.001); it was less variable than that for heifers on Dm6, Dm8, and Dm10 treatments (P<.1). In Exp. 2, heifers received a PGF2alpha analogue and a norgestomet implant on d 12 of the cycle for 3 or 7 d to give approximate durations of dominance of the preovulatory follicle of 2 to 4 d (Dm2-4, n = 29) or 6 to 8 d (Dm6-8, n = 24), respectively. The PR did not differ (P>.05) between heifers on Dm2-4 (22/29) and Dm6-8 (15/24) treatments, but the interval to onset of estrus was delayed (P<.05) by 7 h in the Dm2-4 heifers. In conclusion, restricting the duration of dominance of the preovulatory follicle to < or =4 d at estrus, results in a precise onset of estrus and a high PR following a single AI at a detected estrus.     

Progesterone concentration,estradiol pretreatment,and dose of gonadotropin-releasing hormone affect gonadotropin-releasing hormone-mediated luteinizing hormone release in beef heifers

We examined whether progesterone (P₄)-induced suppression of LH release in cattle can be overcome by an increased dose of exogenous gonadotropin-releasing hormone (GnRH) or pretreatment with estradiol (E₂). In Experiment 1, postpubertal Angus-cross heifers (N = 32) had their 2 largest ovarian follicles ablated 5 d after ovulation. Concurrently, these heifers were all given a once-used, intravaginal P₄-releasing insert (CIDR), and they were randomly assigned to be given either prostaglandin F_2α (Low-P₄) or no treatment (High-P₄) at follicle ablation, and 12 h later. Six days after emergence of a new follicular wave, half of the heifers in each group (n = 8) were given either 100 or 200 μg of GnRH i.m. Plasma luteinizing hormone (LH) concentrations were higher in the Low- vs High-P₄ groups, and in heifers given 200 vs 100 μg of GnRH (mean ± SEM 15.4 ± 2.2 vs 9.1 ± 1.2, and 14.8 ± 2.1 vs 9.8 ± 1.4 ng/mL, respectively; P ≤ 0.01). Ovulation rate was higher (P = 0.002) in the Low-P₄ group (15/16) than in the High-P₄ group (6/16), but it was not affected by GnRH dose (P = 0.4). In Experiment 2, heifers (n = 22) were treated similarly, except that 5.5 d after wave emergence, half of the heifers in each group were further allocated to be given either 0.25 mg estradiol benzoate i.m. or no treatment, and 8 h later, all heifers were given 100 μg GnRH i.m. Both groups treated with E₂ (Low- and High-P₄) and the Low-P₄ group without E₂ had higher peak plasma LH concentrations compared to the group with high P₄ without E₂ (12.6 ± 1.8, 10.4 ± 1.8, 8.7 ± 1.3, and 3.9 ± 1.2 ng/mL, respectively; (P < 0.04)). However, E₂ pretreatment did not increase ovulation rates in response to GnRH (P = 0.6). In summary, the hypotheses that higher doses of GnRH will be more efficacious in inducing LH release and that exogenous E₂ will increase LH release following treatment with GnRH were supported, but neither significantly increased ovulation rate.     

Herd and individual animal prevalence of bovine brucellosis with associated risk factors on dairy farms in Haryana and Punjab in India

Herd and individual animal prevalence along with associated risk factors of bovine brucellosis was assessed on dairy farms located in 22 districts in Haryana and Punjab of India. Examination of 4,580 female animals of 119 dairy farms by Rose Bengal test and enzyme-linked immunosorbent assay revealed that an overall herd prevalence was 65.54 % (78/119) and individual animal prevalence was 26.50 % (1,214/4,580). Herd prevalence in Haryana was 62.79 % which was not significantly different (P?=?0.4208) from Punjab (72.72 %). Individual animal prevalence was 34.15 % in Punjab which was significantly higher (P?<?0.0001) than Haryana (22.34 %). Prevalence of brucellosis on dairy farms was detected in 20 of the 22 districts, of which 12 districts were in Haryana and 8 in Punjab. Risk factors such as species of animals, age of animals, herd size, awareness of dairymen for brucellosis, entry of a purchased animals on the farm, abortion on farm, use of calving pens, type of breeding, and type of farming were analyzed. The study indicated that the odds ratio (OR) was significant with risk factors of species (OR?=?1.63; 95 %CI?=?1.40–1.90; P?<?0.0001), age (OR?=?0.22; 95 %CI?=?0.17–0.29; P?<?0.0001), awareness of brucellosis among dairymen (OR?=?21.65; 95 %CI?=?2.63–178.04; P?=?0.0042), entry of purchased animal on the farm (OR?=?9.16; 95 %CI?=?2.38–35.18; P?=?0.0012), abortion in animals (OR?=?5.57; 95 %CI?=?1.92–16.10; P?=?0.0015) and on cow farm (OR?=?3.43; 95 %CI?=?1.33–8.82; P?=?0.0105). While the OR was insignificant (P?>?0.05) with risk factors of herd size, use of calving pen on farms, type of breeding and on buffalo and mixed type of farms.     

The role of thecal androgen production in the regulation of estradiol biosynthesis by dominant bovine follicles during the first follicular wave

The first wave of follicular development following ovulation in cattle is characterized by selection and growth of a large, estrogenic dominant follicle. After the follicle becomes morphologically dominant, concentrations of estradiol in its follicular fluid decrease abruptly. The purpose of this study was to determine whether this decrease in estrogen production is caused by an insufficient supply of androgen from theca interna or decreased aromatization of androgen precursor by granulosa cells. Dominant follicles were collected from Holstein heifers on d 4, 6, or 8 of the first follicular wave (n = 5/d). Amounts of 17alpha-hydroxylase mRNA in theca interna were sevenfold higher (P < 0.01) on d 4 than on d 8. After 3 h in culture, secretion of androstenedione by theca interna collected on d 4 (236 +/- 44 pg/microg of protein) tended to be lower (P = 0.055) compared with d 6 (517 +/- 162 pg/microg protein) and was lower (P < 0.05) compared with d 8 (387 +/- 51 pg/microg of protein). In granulosa cells, amounts of aromatase mRNA decreased (P < 0.05) on d 8 compared with d 6 but not d 4. In vitro secretion of estradiol was higher in granulosa cells collected on d 4 (3.5 +/- 0.8 ng/[10(5) cells x 3 h]) compared with d 6 (1.8 +/- 0.6 ng/[10(5) cells x 3 h]; P < 0.05) and tended to be higher on d 4 than on d 8 (2.2 +/- 0.2 ng/[10(5) cells x 3 h]; P = 0.058). We conclude that the decrease in estradiol production observed during atresia of the dominant follicle is not due to lack of androgen substrate for aromatization or downregulated expression of the aromatase gene, but may be the direct result of decreased activity of the aromatase enzyme within granulosa cells.     

Forage and breed effects on behavior and temperament of pregnant beef heifers

Background

Integration of behavioral observations with traditional selection schemes may lead to enhanced animal well-being and more profitable forage-based cattle production systems. Brahman-influenced (BR; n = 64) and Gelbvieh × Angus (GA; n = 64) heifers consumed either toxic endophyte-infected tall fescue (E+) or one of two nontoxic endophyte-infected tall fescue (NT) cultivars during two yr. Heifers were weighed at midpoint and termination of grazing. Grazing behavior (grazing, resting in the shade, lying, or standing without grazing) was recorded (n = 13 visual observations per yr in June and July) for each pasture. During yr 2, exit velocity (EV) and serum prolactin (PRL) were determined.

Results

Grazing behavior was influenced (P < 0.05) by an interaction between fescue cultivar and breed type. Gelbvieh × Angus heifers assigned to E+ pastures had the lowest percentage of animals grazing and the largest percentage of animals resting in the shade. Brahman-influenced heifers had faster EV (P < 0.001) than GA heifers (0.52 vs. 0.74 ± 0.04 s/m, respectively). Body weight (BW) was affected (P < 0.01) by an interaction of tall fescue cultivar and d, and an interaction of tall fescue cultivar and breed type. Heifers grazing NT pastures were heavier (P < 0.01) than heifers grazing E+ pastures at midpoint and termination. Gelbvieh × Angus heifers grazing NT pastures were heavier (P < 0.01) than GA and BR heifers grazing E+ and BR heifers grazing NT pastures. An interaction of forage cultivar and breed type occurred on serum PRL (P < 0.01).

Conclusion

Collectively fescue cultivar, EV, and concentrations of serum PRL were associated with grazing behavior. Heifers grazing NT pastures were observed to be grazing more than heifers assigned to E+ pastures, regardless of breed type, which may have contributed to changes in BW and average daily gain (ADG) in heifers. Integration of behavioral observations along with traditional selection schemes may lead to enhanced animal well-being and more profitable forage-based cattle production systems.     

Effects of low-dose follicle-stimulating hormone administration on follicular dynamics and preovulatory follicle characteristics in dairy cows during the summer

The well-documented phenomenon of reduced conception rate in dairy cows during the hot season involves impaired functioning of the ovarian follicles and their enclosed oocytes. Three experiments were performed to examine the administration of low doses of follicle-stimulating hormone (FSH) to induce turnover of follicles that are damaged upon summer thermal stress and to examine whether this FSH administration has beneficial effects on preovulatory follicles. In experiment 1, synchronized heifers were treated with 100 mg of Folltropin-V (n = 7) or 4.4 mg of Ovagen (n = 6) on day 3 of the estrous cycle. Treatment with both FSH sources resulted in greater (P < 0.05) numbers of follicles than in control animals (n = 12) on day 6 of the estrous cycle, indicating that low doses of FSH can increase the number of emerging follicles in a follicular wave. In experiment 2, milking cows were assigned to a control group (n = 4) or treated with 2.2 mg (FSH-2.2; n = 6) or 4.4 mg (FSH-4.4; n = 5) Ovagen. Follicle-stimulating hormone was administrated on day 3 or 4 and day 10 or 11 of the estrous cycle, coinciding with emergence of the first and second follicular waves, respectively. The number of follicles emerging during the first wave tended to be higher (P < 0.1) in FSH-4.4-treated cows than in controls. The second-wave dominant follicles emerged 2 d later in the treated cows and were smaller in diameter (P < 0.05) than controls, 2 d before aspiration. Despite being younger, the preovulatory follicles of FSH-4.4 cows expressed a steroidogenic capacity that was similar to controls with a tendency toward greater insulin concentrations (P < 0.09). In experiment 3, milking cows were assigned to a control group (n = 6) or treated with 4.4 mg Ovagen (FSH-4.4; n = 6). Follicle-stimulating hormone was administrated on day 3 and day 12 or 13 of the estrous cycle. The number of emerging follicles was higher (P < 0.05) in the treated vs control cows. However, the features of the preovulatory follicle developed in the subsequent cycle did not differ between groups. In summary, low doses of FSH can efficiently induce follicular turnover accompanied by a modest effect on the preovulatory follicle of the treated cycle. It appears that the administration of low doses of FSH, precisely timed to synchronize with the emergence of follicular waves, might have a beneficial effect on the preovulatory follicle and its enclosed oocyte.     

Ovarian follicular dynamics and hormones throughout the estrous cycle in Thai native (Bos indicus) heifers

Relatively few studies have been reported regarding the reproductive physiology of female Thai native cattle. Therefore, the objective of the present study was to evaluate the follicular dynamics and concentrations of follicle stimulating hormone (FSH), estradiol (E2) and progesterone (P4) during the estrous cycle in Thai native heifers (TNH) and to compare obtained results with those of European and Indian cattle breeds previously reported. For the detection of estrus, ovaries of all 20 heifers were examined twice daily (12 h intervals) by ultrasonography for three consecutive estrous cycles. From data of 60 estrous cycles (n = 60 estrous cycles from 20 heifers), it was found that 14 (70%) and 6 heifers (30%) had two (42 estrous cycles collected from 14 heifers) and three follicular waves (18 estrous cycles collected from 6 heifers), respectively. The days when estrus was detected, interovulatory intervals, life‐spans of corpus lutea (CL), and days for growing and regression of CLs were shorter in the two follicular waves than those in the three follicular waves (P < 0.05). In both two and thre follicular waves, larger maximum diameters and higher growth rates of the dominant follicle (DF) in an ovulatory wave were observed than those of the preceding waves without ovulation (P < 0.05). There was a progressive increase in follicular size and FSH and E2 production during follicular growth in each follicular wave. In addition, the FSH and E2 peak concentrations during the ovulatory wave were higher than those of the anovulation waves (P < 0.05). Moreover, although the ovarian follicular dynamic patterns in Thai native heifers were similar to those previously reported for European and Indian cattle breeds, the diameter of the largest preovulatory follicle (OF), subordinate follicles (SF) and CLs were smaller than those in European and Indian cattle breeds. In conclusion, when compared with European and some breeds of Indian cattle, the length of interovulatory intervals was shorter, and the sizes of dominant SF and CLs were smaller in Thai native heifers.     

Polymorphism,coupling interval and prematurity index in dogs with degenerative mitral valve disease and ventricular arrhythmias

Ventricular arrhythmias (VA) are a recognized concern in dogs with degenerative mitral valve disease (DMVD). The coupling interval (CI) and the prematurity index (PI) have been shown to accurately differentiate between benign and malignant VA in people, where ventricular arrhythmias are known to be associated with an increased risk of development of signs of heart failure or sudden death. In this study, we characterized ventricular arrhythmias in dogs with symptomatic and asymptomatic DMVD. Seventy dogs with naturally-occurring DMVD and ventricular arrhythmias were retrospectively studied. A cross-sectional investigation including dogs with either symptomatic (stages C/D; n?=?41) or asymptomatic (stages B1/B2; n?=?29) DMVD was performed. Electrocardiographic tracings were reviewed to calculate both the CI and PI. In eight dogs these indices were compared with those obtained from both a Holter recording and a standard ECG tracing and no statistical differences were found (CI, p?=?0.97; PI, p?=?0.17). Even though CI and PI were determined in all animals enrolled in the study, VPC characteristics were only compared between symptomatic and asymptomatic dogs when a 24-h Holter recording was available (n?=?49). The PI was different (p?=?0.01) between symptomatic (0.65?±?0.17) and asymptomatic (0.56?±?0.18) dogs, but CI was considered similar (p?=?0.91). Also, the symptomatic dogs had more polymorphic VPC (p?=?0.002) and supraventricular arrhythmias (p?=?0.0002) than the asymptomatic animals. Polymorphism, and repeating patterns of ventricular premature complexes, were characteristics frequently present in overtly symptomatic animals affected by mitral endocardiosis.     

Ovarian evaluation of Girolando (Holstein × Gir) heifers submitted to a GnRH–PGF2α–GnRH protocol in the dry or rainy seasons in the tropical savannah

The Girolando breed is used in pasture-based dairy production systems in Brazil to associate the high production of Bos taurus to the rusticity and thermal adaptation of Bos indicus. This study was designed to evaluate the physiological response to a gonadotropin-releasing hormone (GnRH)–prostaglandin F_2α (PGF_2α)–GnRH protocol to synchronize the ovulation in 40 Girolando heifers of a pasture-based dairy production system and its relationships with the temperature and humidity index (THI) during the dry (DS) and rainy season (RS) in the tropical savannah—Brazil's cerrado biome. Responses were characterized by follicular and corpus luteum number and diameter, ovulation (D9), and pregnancy rates after first AI. Total follicle number (8.1?±?0.3?×?8.8?±?0.3), D9 ovulatory follicle diameter (11.9?±?0.4?×?10.1?±?0.4 mm), corpus luteum diameter (8.6?±?1.3?×?3.9?±?1.5 mm), corpus luteum score (3.7?±?0.8?×?1.8?±?1.0), corpus luteum diameter after AI (9.6?±?1.6?×?3.9?±?1.5 mm), and corpus luteum score after AI (3.2?±?0.4?×?0.9?±?0.6) in DS and RS differed (P?<?0.01). D9 ovulation rate was 40 % (DS) and 20 % (RS), without differences (P?>?0.05). Pregnancy rate was 45 % (DS) and 11 % (RS), with differences (P?<?0.01). THI differed between DS and RS (P?<?0.01). THI may interfere in the follicular and luteal dynamics and in the response of Girolando heifers to the GnRH–PGF_2α protocol in the tropical savannah, thus reducing the chances of pregnancy at the first artificial insemination.     

Effects of month of breeding on reproductive efficiency of Holstein cows and heifers inseminated with sex-sorted or conventional semen in a hot environment

The main objective of this study was to assess the effect of month of breeding on reproduction performance of Holstein heifers and cows inseminated with sex-sorted or conventional semen in a hot environment. Pregnancy per artificial insemination (P/AI; 64,666 services over an 8-year period) both in heifers (n?=?22,313) and cows (n?=?42,353) from a large dairy herd in northern Mexico (26°N) were evaluated with the GENMOD procedure of SAS, with respect to month of AI. Overall, P/AI with sex-sorted semen was greater (P?<?0.01) in heifers (41.6 %) than cows (17.3 %). P/AI for cows serviced with conventional semen was 10 % points higher (P?<?0.01) in January and December (31 vs. 21 %) than cows serviced with sex-sorted semen. While there was no difference in P/AI between the sex-sorted sperm and conventional semen in cows inseminated in July (16 and 18 %, respectively), P/AI plummeted for both groups of cows during the summer and fall (more severe heat stress). P/AI was not different between heifers serviced with sex-sorted or conventional semen during the hottest months of the year (July to October). However, during the coldest month of the year (January and February), P/AI was 10 percentage points greater (P?<?0.01) in heifers serviced with conventional than sex-sorted semen. It was concluded that in this hot climate cow and heifer fertility declined in the summer and fall when inseminated with conventional semen. However, the use of sex-sorted semen during summer and fall did not compromise the breeding success in heifers. Thus, this data suggest that sex-sorted semen promotes some embryonic thermoprotective mechanism, which leads to a marginal summer and fall fertility depression with this type of semen in this particular hot environment.     

Effect of day of the estrous cycle at the initiation of a timed artificial insemination protocol on reproductive responses in dairy heifers

Our objectives were to identify stages of the estrous cycle at which initiation of a timed artificial insemination (Ovsynch/TAI) protocol may reduce pregnancy rates and to monitor ovarian follicle dynamics and corpus luteum development after initiation of the Ovsynch/TAI protocol at different stages of the cycle. Cycling Holstein heifers (n = 24) were injected twice with prostaglandin F2alpha to induce estrus and were scanned by ovarian ultrasonography to determine the day of ovulation (d 0). Heifers were assigned to initiate the Ovsynch/TAI protocol at d 2 (n = 5), 5 (n = 5), 10 (n = 4), 15 (n = 5), or 18 (n = 5) of the cycle. The Ovsynch/TAI was initiated with an injection of gonadotropin-releasing hormone agonist followed 7 d later with an injection of prostaglandin F2alpha. At 36 h after injection of prostaglandin F2alpha, heifers were injected with gonadotropin-releasing hormone agonist and inseminated 16 h later. Heifers were scanned daily during the Ovsynch/TAI protocol and every other day after insemination until 16 d later. Blood samples were collected daily starting at the 1st day heifers were scanned and continued until 16 d after insemination. Initiation of the Ovsynch/TAI protocol at d 15 of the estrous cycle caused heifers to ovulate prior to insemination. A shortened return to estrus (< 16 d) was caused by ovulation failure to the second gonadotropin-releasing hormone injection, by incomplete regression of the corpus luteum, and by short life-span of the induced corpus luteum. Day of the cycle in which the Ovsynch/TAI protocol is initiated affects dynamics of follicular development, plasma progesterone profiles, and occurrence of premature ovulation. Size of the pre-ovulatory follicle was associated positively with subsequent progesterone concentrations following insemination.     

Effects of Lactation and Prenatal Androgenization on the Performance,Carcass Composition,and Longissimus Muscle Sensory Characteristics of Heifers in the Single-Calf Heifer System

Two experiments were conducted to evaluate feedlot performance, lactational characteristics, and carcass composition and quality of heifers and the performance of their calves in a single-calf heifer (SCH) system. In Exp. 1, 13 [10 lactating (L) and 3 nonlactating (NL)] prenatally androgenized (PA) heifers, born to cows implanted with testosterone propionate (TP) and 19 (13 L and 6 NL) control (C) heifers, born to nonimplanted cows, were used. Heifers were calved and the pairs were placed in feedlot pens to evaluate the effects of PA on feedlot performance and lactation. Heifers were fed an 85% concentrate diet and fed to a compositional endpoint of 1.1 cm of subcutaneous fat cover, at which point calves were weaned and heifers slaughtered approximately 12 h later. The NL heifers consumed 17.0% less (P<0.01) dry matter and were 30.8% more (P<0.01) efficient in feed conversion. When calf performance was included, overall feed efficiency of L heifers was 26.9% greater (P<0.05; 0.151 vs 0.119) than that of the NL feedlot heifers. Prenatal androgenization had no effect on heifer performance. Four percent fat-corrected milk yield averaged 7.79 and 5.62 kg/d for PA and C heifers, respectively. The NL heifers had 11.0% greater (P<0.01) marbling score and yield grades were 3.77 and 3.03 (P<0.05) for NL and L heifers, respectively. Livers (P<0.01) and kidneys (P<0.05) as a percentage of shrunk weight were heavier for L heifers than for NL heifers. Two carcasses were classified as hard-boned (C-maturity) and 74% received a USDA Choice grade. The L heifers tended (P<0.10) to have lower taste panel tenderness scores; however, shearforce was similar (P=0.81) for L and NL heifers. In Exp. 2, 24 Angus × Holstein heifers were utilized in the single-calf heifer system, similar to Exp. 1. Calves were weaned from their dam between d 64 and 89 postpartum. Heifers that had their calves early weaned (EW) gained 44.2% faster (P<0.01) and consumed 10.8% less (P<0.05) DM than L heifers. The EW heifers were 60.0% more (P<0.01) efficient than L heifers. However, when calf performance was included with heifer performance, L heifers were 23.7% more (P<0.05) efficient than EW heifers. The EW heifers had 18.9% heavier (P<0.01) hot carcasses than L heifers. Backfat thickness was 1.07 and 0.66 cm (P<0.01) for the EW and L heifers.     

Protein turnover and sensory traits of longissimus muscle from implanted and nonimplanted heifers

Primary bovine muscle cell culture studies were conducted to determine whether implanting heifers had a direct effect on in vitro protein synthesis and degradation and to determine the effect of implanting heifers on longissimus muscle palatability. Feedlot heifers (n = 96) were administered one of six implant regimens to characterize their effect on in vitro amino acid uptake and protein degradation. Treatments consisted of: 1) a nonimplanted control (NI/NI); 2) no implant on d 1 and Revalor-H administered on d 84 of the experiment (NI/Rev); 3) Revalor-H on d 1, but no implant given at d 84 (Rev/NI); 4) Revalor-H administered on d 1 and d 84 (Rev/Rev); 5) Revalor-IH administered on d 1 and Revalor-H at d 84 (RIH/Rev); and 6) Synovex-H given at d 1 and Revalor-H administered at d 84 (Syn/Rev). Blood and longissimus lumborum muscle were collected 20 min postmortem, and serum and muscle extracts were incubated with primary bovine muscle cells. Implant treatments had minimal effects on shear force and sensory traits; however, steaks from Rev/Rev heifers were 0.31 kg more tender (P < 0.05) than steaks from NI/NI heifers. Serum protein synthesis and degradation were not affected (P > 0.10) by any implant treatment. When primary bovine muscle cells were treated with muscle extract, amino acid uptake was greater for heifers implanted with Rev/ Rev than for the average of all other treatments (P < 0.01). The Rev/Rev implant regimen also increased (P < 0.05) amino acid uptake compared with heifers treated with RIH/Rev, Syn/Rev, NI/NI, NI/Rev, or Rev/NI. Cellular protein degradation of the muscle cell culture treated with muscle extract tended (P < 0.10) to be higher in NI/NI-treated cells compared with the average of all implant treatments. In addition, cells treated with muscle extract from heifers implanted with Rev/Rev had lower (P < 0.05) protein degradation than the NI/NI control heifers. These results indicate that anabolic implant strategies can directly affect both muscle protein synthesis and degradation via effects that seem to be more autocrine than paracrine in nature.     

In vitro control of parasitic nematodes of small ruminants using some plant species containing flavonoids

This study determined in vitro anthelmintic efficacy of three plant species: Trema orientalis, Urtica dioica and Zanthozylum capense on nematode larvae of small ruminants. Dried leaf samples (40 g) were extracted in 70% ethanol, in portions of 10 g and concentrated to 100 ml. Half and one quarter of the original crude extract were both made to 100 ml. Rectal faecal material from 10 Merino sheep and 25 Nguni goats was pooled within species and thoroughly hand-mixed. Dung samples, each of 5 g were cultured for 12 days at 27 °C. On day 13, 4 plates were watered and 4 others treated with ethanol to correct for solvent effect on mortality. The design was 2 (animal species)?×?3 (plant species)?×?3 (extract concentrations). In each of three runs, three plates were treated with each crude extract in three incremental concentrations. Surviving L3 larvae were isolated, counted and mortalities became indices of anthelmintic efficacy. Data from nematode larval mortality were analysed to determine the effect of animal species, plant species, concentration and their interactions. Efficacy was affected by concentration (P?=?0.0001), animal species (P?=?0.0046), plant species (P?=?0.0572), the interactions of animal species and concentration (P?=?0.0010), plant species and concentration (P?=?0.0123) and concentration × animal × plant species (P?=?0.0435).