Effect of supplementation on the performance of grazing Belgian Blue double-muscled heifers

Six experiments were conducted to investigate the effect of a feed supplement on the performance of grazing Belgian Blue double-muscled (BBDM) heifers with an initial weight and age of 195 ± 43 kg and 190 ± 52 days. Treatments included were: Exp. 1: supplementation with beet pulp (BP): 2 kg/day per head v. ad libitum intake; Exp. 2: supplementation ad libitum with BP v. a mixture of BP and soybean meal (SBM; BP/SBM ratio of 80/20; FW (fresh weight) basis); Exp. 3: supplementation with 4 kg/day per head of a mixture of BP/SBM (80/20; FW basis) v. BP/formaldehyde-treated SBM (BP/FSBM); Exp. 4: supplementation with 4 kg/day per head of a mixture with a similar protein content (125 g DVE per kg dry matter (DM)), consisting of 80/20 BP/SBM v. 92/8 BP/FSBM; Exp. 5: supplementation with 3 kg/day per head of a mixture of BP/SBM (80/20; FW basis) v. BP/DDGS (dried distillers grains and solubles; 70/30, FW basis); and Exp. 6: supplementation with 3 kg/day per head of 80/20 BP/SBM v. maize silage (MS) and SBM, on the basis of a similar protein concentration in the DM as the 80/20 BP/SBM supplement, and fed at a similar amount of DM as in the BP/SBM group. Supplementing BP ad libitum did not affect daily gain (0.54 v. 0.48 kg) and partial feed conversion (3.62 kg on average) compared with 2 kg/day. Supplying SBM besides BP increased growth rate compared with BP (0.87 v. 0.62 kg/day; P < 0.001), but partial feed conversion was similar. Supplying FSBM did not affect growth rate and partial feed conversion (P > 0.10), but blood urea levels were reduced by FSBM (P < 0.05). DDGS tended to increase growth rate (0.77 v. 0.59 kg/day; P < 0.10) compared with BP/SBM, without effect on partial feed conversion. Replacing BP by MS did not affect daily gain, but partial feed conversion tended to be higher (3.21 v. 3.60 kg/kg body weight (BW) gain; P = 0.062). Increasing the supplement (80/20 BP/SBM) level from 3 to 4 kg daily, corresponding to 1.02% and 1.18% of the mean BW, respectively, resulted in a tendency (P = 0.121) for an increased growth rate. Grazing BBDM heifers of <1 year of age necessitate extra protein besides an energy supplement to improve their performance. DDGS can replace SBM and BP can be replaced by MS.     

Embryo production in superovulated Angus cows inseminated four times with sexed-sorted or conventional, frozen-thawed semen

This study tested the hypothesis that four inseminations of commercially frozen sexed semen (≥2.1 × 10⁶ sperm per 0.25-mL straw) in superstimulated embryo donors would yield a percentage and quantity of transferable embryos similar to that achieved with conventional frozen semen. Bos taurus, angus cows (n = 32), stratified by age and body condition, were randomly allocated to receive four inseminations of frozen-thawed semen, either conventional semen (≥15 × 10⁶ sperm/straw; Conventional) or sexed semen (≥2.1 × 10⁶ sperm/straw; Sexed) from one of two AI sires. From 10 to 13 d after estrus, follicle-stimulating hormone (FSH) was given twice-daily, with prostaglandin F_2α given twice on the last day. Cows were inseminated once (1×) at first detected estrus and twice (2×) and once (1×) at 12 and 24 h later, respectively, with nonsurgical embryo recovery 7 d after first detected estrus. The study was repeated 30 d later (switch-back experimental design). The total number of ova per flush was similar between Conventional and Sexed treatments (10.9 ± 1.8 vs. 10.5 ± 1.6), but the number of Grade 1 embryos was greater (P < 0.01) for Conventional (4.3 ± 0.8 vs. 2.3 ± 0.7). Conversely, the mean number of unfertilized ova was greater (P < 0.05) for Sexed (5.6 ± 1.0 vs. 3.0 ± 1.2). There was no significant difference between treatments for numbers of degenerate, Grades 2 or 3, and transferable embryos and no significant differences between bulls in percentage of transferable embryos (44.4% and 46.7%). However, fertilization rates and percentage of transferable embryos were affected (P < 0.05) by period and donor. In conclusion, superstimulated donor cows inseminated four times had fewer Grade 1 embryos and more unfertilized ova with sexed versus conventional semen.     

Effect of prepartum somatotropin injection in late-pregnant Holstein heifers on metabolism, milk production and postpartum resumption of ovulation

The aim of this study was to determine the effect of prepartum somatotropin injection in late-pregnant Holstein heifers on metabolism, milk production and resumption of postpartum ovulation. For this study, 31 late-pregnant Holstein heifers were used. The heifers were assigned randomly into two treatments: (1) 500 mg sc injections of somatotropin (somatotropin treatment, n = 15) at -35 and -21 days, and, if pertinent, at -7 days from expected calving date and (2) no treatment (control group, n = 16). Blood samples were collected weekly from -5 to 7 weeks after calving. Heifers with progesterone concentrations in plasma above 1 ng/ml in two consecutive postpartum samples were considered as having resumed ovarian activity. A higher proportion (P = 0.04) of heifers treated with somatotropin resumed ovarian activity in the first 7 weeks post partum (73.3%; 11/15) compared with the control group (37.5%; 6/16). A higher number (P = 0.02) of heifers in the somatotropin treatment group also ovulated during the first postpartum follicular wave (53.3%; 8/15) compared with the control group (12.5%; 2/16), as indicated by the number of heifers ovulating in the first 3 weeks post partum. Pregnancy rate was not affected by treatments (P > 0.10) and averaged 40.0% (6/15) in somatotropin-treated and 25.0% (4/16) in control heifers when evaluated up to 150 days in milk. Somatotropin treatment increased the average daily milk production by 2.8 kg/cow per day (P < 0.0001) and reduced the somatic cell count (P = 0.009). Plasma IGF-I was higher (P < 0.05) for somatotropin-treated heifers in the prepartum period. Insulin and body condition score were higher (P < 0.05) and non-esterified fatty acids were lower (P < 0.05) for somatotropin-treated cows in the early postpartum period. In conclusion, somatotropin injection during the prepartum period in late-pregnant Holstein heifers was able to increase the proportion of heifers resuming ovarian activity early post partum, inspite of higher milk production.     

Effects of exogenous progesterone and cloprostenol on ovarian follicular development and first ovulation in prepubertal heifers

The objective of this study was to determine the effects of progesterone and cloprostenol (a PGF_2α analogue) on ovarian follicular development and ovulation in prepubertal heifers. In Experiment 1, crossbred Hereford heifers (Bos taurus; 10 to 12 mo old, 255 to 320 kg) were assigned randomly to three groups and given (1) an intravaginal progesterone-releasing insert (CIDR; P group, n = 13); (2) a CIDR plus 500 μg cloprostenol im (PGF_2α analogue) at CIDR removal (PPG group, n = 11); or (3) no treatment (control group, n = 14). The CIDR inserts were removed 5 d after follicular wave emergence. Progesterone-treated heifers (P and PPG groups) had a larger dominant follicle than that of the control group (P = 0.01). The percentage ovulating was highest in the PPG group (8 of 11, 73%), intermediate in the P group (4 of 13, 31%), and lowest in the control group (1 of 14, 7%; P < 0.02). In Experiment 2, 16 heifers (14 to 16 mo old, 300 to 330 kg) were designated to have follicular wave emergence synchronized with either a CIDR and 1 mg estradiol benzoate im (EP group, n = 8) on Day 0 (beginning of experiment) or by transvaginal ultrasound-guided ablation of all follicles ≥5 mm on Day 3 (FA group, n = 8). On Day 7, CIDRs were removed in the EP group, and all heifers received 500 μg cloprostenol im. Ovulation was detected in 6 of 8 heifers (75%) in both groups. In summary, the use of PGF_2α with or without exogenous progesterone treatment increased the percentage ovulating in heifers close to spontaneous puberty.     

Effect of follicular wave synchronization on in vitro embryo production in heifers

Aiming to achieve the ideal time of ovum pick-up (OPU) for in vitro embryo production (IVP) in crossbred heifers, two Latin square design studies investigated the effect of ovarian follicular wave synchronization with estradiol benzoate (EB) and progestins. For each experiment, crossbred heifers stage of estrous cycle was synchronized either with a norgestomet ear implant (Experiment 1) or a progesterone intravaginal device (Experiment 2) for 7 d, followed by the administration of 150 μg d-cloprostenol. On Day 7, all follicles >3 mm in diameter were aspirated and implants/devices were replaced by new ones. Afterwards, implant/device replacement was conducted every 14 d. Each experiment had three treatment groups. In Experiment 1 (n = 12), heifers in Group 2X had their follicles aspirated twice a week and those in Groups 1X and 1X-EB were submitted to OPU once a week for a period of 28 d. Heifers from Group 1X-EB also received 2 mg EB i.m. immediately after each OPU session. In Experiment 2 (n = 11), animals from Group 0EB did not receive EB while heifers in Groups 2EB and 5EB received 2 and 5 mg of EB respectively, immediately after OPU. The OPU sessions were performed once weekly for 28 d. Therefore, in both experiments, four OPU sessions were performed in heifers aspirated once a week and in Experiment 1, eight OPU sessions were done in heifers aspirated twice a week. Additionally, during the 7-d period following follicular aspiration, ovarian ultrasonography examinations were conducted to measure diameter of the largest follicle and blood samples were collected for FSH quantification by RIA. In Experiment 1, all viable oocytes recovered were in vitro matured and fertilized. Results indicated that while progestin and EB altered follicular wave patterns, this treatment did not prevent establishment of follicular dominance on the ovaries of heifers during OPU at 7-d intervals. Furthermore, the proposed stage of follicular wave synchronization strategies did not improve the number and quality of the recovered oocytes, or the number of in vitro produced embryos.     

Effects of repetitive norgestomet treatments on pregnancy rates in cyclic and anestrous beef heifers

Sixty-eight 12- to 14-month-old crossbred beef heifers averaging 285 kg were assigned at random to treated (n = 35) and control (n = 33) groups to evaluate the use of repetitive norgestomet treatments. Treated heifers received an ear implant containing 6 mg norgestomet on two occasions 16 days apart. Injections of 3 mg norgestomet and 5 mg estradiol valerate (EV) were given intramuscularly the same day as first implantation (Syncro-Mate-B). Implants were removed after eight days. Four bulls were then placed in each of two pastures containing half of the treated and half of the control heifers for 24 days after the time of the first implant removal. Progesterone concentrations from blood samples collected prior to the first treatment were used to determine reproductive status. The overall pregnancy rate 64 days after first implant removal for treated anestrous heifers (61%; 14 23 ) was similar (p > 0.25) to untreated (73%; 11 15 ) and treated (75%; 9 12 ) cyclic heifers, but higher (p < 0.1) than for untreated anestrous heifers (33%; 6 18 ). This treatment advantage resulted from an increased (p < 0.01) pregnancy rate after the second implant removal. In summary, repetitive norgestomet treatments enhanced pregnancy rate in anestrous heifers within a 24-day breeding season.     

Effect of organic zinc supplementation on growth, nutrient utilization and mineral profile in lambs

To study the efficacy of organic zinc (Zn) supplementation on growth, nutrient utilization and mineral profile as compared to inorganic source [zinc sulphate (ZnSO₄)], 18 Muzaffarnagari male lambs of 11.30 ± 0.45 kg mean body weight (4–5 months of age) were divided into three groups of six animals in each in a randomized block design. Lambs in the control group were fed a standard total mixed ration (TMR) consisted of 60 kg/100 kg of concentrate mixture (CM) and 40 kg/100 kg of wheat straw. CM was consisted of 300 g/kg crushed maize grain, 270 g/kg soybean meal, 400 g/kg wheat bran, 20 g/kg mineral mixture (without Zn) and 10 g/kg common salt. Animals in the experimental groups were additionally supplemented with 20 mg Zn/kg of diet either through inorganic (ZnSO₄) or organic [Zn-methionine AA complex (Zn-meth)] sources. Experimental feeding was done for a period of 150 days including a 6 days metabolism trial. The intake of dry matter (DM), organic matter (OM), crude protein (CP), digestible CP and total digestible nutrients and digestibility of DM, OM, CP, ether extract, neutral detergent fibre and hemicellulose were comparable (P>0.05) among the three groups. However, digestibility of cellulose and acid detergent fibre was significantly (P<0.05) higher in Zn-meth group as compared to control group. Though the balance of calcium was adversely affected (P<0.01) in both the Zn supplemented groups, but it was significantly higher in Zn-meth group compared to ZnSO₄ group. While apparent absorption and retention of nitrogen, phosphorus, copper, iron and manganese were similar (P>0.05) among different groups, retention of Zn (P<0.05) as well as its concentration in the serum (P<0.01) were highest in Zn-meth group, followed by ZnSO₄ group and lowest in the control group, suggesting higher bioavailability of Zn from Zn-meth as compared to ZnSO₄. Average daily gain of the lambs and feed conversion efficiency were also significantly (P<0.05) higher in Zn-meth group as compared to control and ZnSO₄ groups, suggesting a positive role of organic zinc supplementation on the performance of lambs.     

Effect of dietary protein on embryo recovery rate and quality in superovulated heifers

For almost 3 decades, superovulation and embryo transfer have been used in cattle breeding to increase the number of offspring from genetically superior female animals. Several factors including nutrition affect the number of transferable embryos recovered. We compared the effects of two different dietary protein levels easily achieved in practical conditions on embryo number and quality in superovulated heifers. Finnish Ayrshire heifers (n = 37) were allocated to isoenergic diets containing either 14% (D14) or 18% (D18) crude protein (CP). Estruses were synchronized, and the heifers were subsequently superovulated and inseminated using a standard FSH-protocol. Embryos were collected 7 days after inseminations (71-72 days after the beginning of the treatment period) by uterine flushing. The number of corpora lutea, and the number and quality of embryos were determined. Protein feeding did not affect superovulatory response, the number of embryos or the number of transferable embryos recovered. Proportionally more poor-quality embryos were found in group D14 than in group D18 (20.2% versus 13.2%, respectively, P = 0.053). It is concluded that a long-term moderate increase in the content of crude protein fed to energy-adequate heifers does not seem to affect superovulatory response and the number of embryos recovered, but it may be advantageous to the quality of embryos.     

The influence of ovulation number and ovarian dimensions on embryo production in superovulated cattle

Twenty-one cycling Angus heifers and five Holstein cows received a subcutaneous (SC) injection of 50 mg of progesterone (P) in oil for 14 consecutive days. On day 6 of (P) treatment, animals were injected intramuscularly (IM) with 6 mg of estradiol valerate, and on day 13, received an IM injection of 2,000 IU of Pregnant Mare Serum Gonadotropin. Three additional Angus heifers were used as non-hormone treated controls. Seventeen of 21 heifers and 4 of 5 cows (81%) exhibited estrus within 48 to 132 hr following P treatment. Two of the five animals in which estrus was not observed were palpated as pregnant and discarded from the study. Treatment animals showing estrus were randomly assigned either to Group I, animals bred by natural service, or Group II, animals artificially inseminated with two straws of frozen semen at 12-hr intervals for a total of four breedings. Twenty-one animals were slaughtered 2 to 6 days after the onset of estrus, and those animals in which estrus was not detected were slaughtered 10 days after the last P injection. Two of the 24 treated animals had no ovulations. A total of 397 ovulation points ($\text{397}\text{22}$) were counted for a mean ovulation rate of 18 ovulations per animal. One hundred and fifty-six ova were recovered ($\text{156}\text{397}$) for a collection rate of 39%. Group I animals had 44 of 66 (67%) of their ova fertilized while 23 of 71 (32%) of the ova in Group II were fertilized. Nineteen unfertilized eggs were collected from the three animals not observed in estrus. No differences in fertilization rates between the Group I and Group II animals were found. Mean ovarian width, length and weight in the treated animals was measured and found to be 3.5 ± 1.1 cm, 4.8 ± 1.4 cm, and 21.7 ± 21.2 gm, respectively. Ovarian width, length and weight were all positively correlated with the number of ovulations per ovary r=.74, r=.74, and r=.55, respectively. No significant correlation existed between ovarian width (r=.16), lenght (r=.21), or weight (r=.13) when compared to ova recovery rate. This result suggests that ovarian size or weight may not be the limiting factor involved in embryo recovery.     

应用矿物盐改良池塘水质的研究

为了研究矿物盐对淡水养殖池塘水质的改良效果及应用前景,在12口土质池塘中对淡水养殖斑点叉尾鲴(Ictalurus punctatus Rafinesque,1818)施用三组矿物盐:NaNO3、KCl+MgCl2、NaNO3+KCl+MgCl3的对照实验,对照组池塘不施用任何矿物盐类;在182d的养殖期间,对所有处理组和对照组池塘的17项水质和5项底质因子进行了定期监测.结果表明,各处理组均显著降低了池塘水中的蓝藻相对密度;KCl+MgCl2的施用可促进水中硝化作用的进行;NaNO3+KCl+MgCl2的施用,显著提高了养殖池塘底泥表层的氧化还原电位;NaNO3+KCl+MgCl2组的池塘鱼产量比对照组显著提高6.6%,而饲料系数显著降低6.2%;NaNO3与KCl+MgCl2的共同施用起到了协同改良池塘水质和底质的作用.因此,NaNO3+KCl+MgCl2的应用可为淡水池塘水质的改良开辟一个新的途径,具有一定的应用前景.     

Effect of dominant follicle removal before superstimulation on follicular growth, ovulation and embryo production in Holstein cows

This study was to investigate whether removing the dominant follicle 48 h before superstimulation influences follicular growth, ovulation and embryo production in Holstein cows. After synchronization, ovaries were scanned to assess the presence of a dominant follicle by ultrasonography with a real-time linear scanning ultrasound system on Days 4, 6 and 8 of the estrus cycle (Day 0 = day of estrus). Twenty-six Holstein cows with a dominant follicle were divided into 2 groups in which the dominant follicle was either removed (DFR group, n=13) by ultrasound-guided follicular aspiration or left intact (control group, n=13) on Day 8 of the estrus cycle. Superovulation treatment was initiated on Day 10. All donors were superovulated with injections of porcine FSH (Folltropin) twice daily with constant doses (total: 400 mg) over 4 d. On the 6th and 7th injections of Folltropin, 30 mg and 15 mg of PGF2alpha (Lutalyse) were given. Donors were inseminated twice at 12 h and 24 h after the onset of estrus. Embryos were recovered on Day 6 or 7 after AI. During superstimulation, the number of follicles 2 to 5 mm (small), 6 to 9 mm (medium) and > or = 10 mm (large) was determined by ultrasonography on a daily basis. At embryo recovery, the number of corpora lutea (CL) was also determined by ultrasonography and blood samples were collected for analysis of progesterone concentration. Follicular growth during superstimulation was earlier in the DFR group than in the control group. The number of medium and large follicles was greater (P < 0.01) in the DFR group than in the control group on Days 1 to 2 and Days 3 to 4 of superstimulation, respectively. The numbers of CL (9.6+/-1.1 vs 6.1+/-0.9) and progesterone concentration (30.9+/-5.4 vs 18.6+/-3.5 ng/mL) were greater (P < 0.05) in the DFR group than in the control group, respectively. The numbers of total ova (7.7+/-1.3 vs 3.9+/-1.0) and transferable embryos (4.6+/-0.9 vs 2.3+/-0.8) were also greater (P < 0.05) in the DFR group than in the control group, respectively. It is concluded that the removal of the dominant follicle 48 h before superstimulation promoted follicular growth, and increased ovulation and embryo production in Holstein cows.     

Effect of GnRH antagonist-induced prolonged follicular phase on follicular atresia and oocyte developmental competence in vitro in superovulated heifers

A GnRH antagonist (Antarelix) was used to suppress endogenous pulsatile secretion of LH and delay the preovulatory LH surge in superovulated heifers to study the effect of a prolonged follicular phase on both follicle and oocyte quality. Oestrous cycles were synchronized in 12 heifers with progestagen (norgestomet) implants for 10 days. On day 4 (day 0 = day of oestrus), heifers were stimulated with 24 mg pFSH for 4 days and luteolysis was induced at day 6 with PGF2 alpha (2 ml Estrumate). Animals in the control group (n = 4) were killed 24 h after the last FSH injection. At this time, heifers in group A36h (n = 4) and group A60h (n = 4) were treated with 1.6 mg of Antarelix every 12 h for 36 and 60 h, respectively, and then killed. After dissection of ovarian follicles, oocytes were collected for individual in vitro maturation, fertilization and culture; follicular fluid was collected for determination of steroid concentrations, and granulosa cells were smeared, fixed and stained for evaluation of pycnosis rates. Granulosa cell smears showed that 90% of follicles were healthy in the control group. In contrast, 36 and 58% of the follicles in group A36h showed signs of early or advanced atresia, respectively, while 90% of the follicles in group A60h showed signs of late atresia. Intrafollicular concentrations of oestradiol decreased (P < 0.0001) from healthy follicles (799.14 +/- 40.65 ng ml-1) to late atretic follicles (3.96 +/- 0.59 ng ml-1). Progesterone concentrations were higher (P < 0.0001) in healthy follicles compared with atretic follicles, irrespective of degree of atresia. Oestradiol:progesterone ratios decreased (P < 0.0001) from healthy (4.58 +/- 0.25) to late atretic follicles (0.07 +/- 0.009). The intrafollicular concentrations of oestradiol and progesterone were significantly higher (P < 0.0001) in the control than in the treated groups. The oestradiol:progesterone ratio was higher (P < 0.0001) in the control (4.55 +/- 0.25) than in the A36h (0.40 +/- 0.05) and A60h (0.07 +/- 0.009) groups. Unexpectedly, the cleavage rate of fertilized oocytes, blastocyst rate and number of cells per blastocyst were not significantly different among control (85%, 41% and 95 +/- 8), A36h (86%, 56% and 93 +/- 5) and A60h (88%, 58% and 79 +/- 4) groups. In addition, there were no significant differences in the blastocyst rates from oocytes derived from healthy (45%), early atretic (54%), advanced atretic (57%) and late atretic follicles (53%). In conclusion, the maintenance of the preovulatory follicles in superovulated heifers with a GnRH antagonist induced more atresia and a decrease in oestradiol and progesterone concentrations. However, the developmental potential in vitro to day 8 of the oocytes recovered from these atretic follicles was not affected.     

Effects of one versus two doses of prostaglandin F2alpha on AI pregnancy rates in a 5-day, progesterone-based, CO-Synch protocol in crossbred beef heifers

The present study determined whether a 5-d progesterone-based CO-Synch protocol with a single dose of prostaglandin F_2α (PGF) at progesterone withdrawal on Day 5, would yield a timed AI pregnancy rate similar to two doses of PGF given 6 h apart on Day 5. Angus cross beef heifers (N = 562) at six locations were used. All heifers received 100 µg of gonadorelin hydrochloride (GnRH) and a controlled internal drug release (CIDR) insert on Day 0. Within farm, heifers were randomly allocated to receive one dose of 25 mg dinoprost (PGF) at CIDR removal on Day 5 (1 PGF; N = 264), or two doses of 25 mg PGF, with the first dose given on Day 5 at CIDR removal, and the second dose 6 h later (2 PGF; N = 298). Most heifers (N = 415) received a heat detector patch at CIDR removal. After CIDR removal, heifers were observed twice daily through Day 7 for estrus and heat detector aid status was recorded. On Day 8, heifers were given 100 µg of GnRH, heat detector aid status was recorded, and heifers were inseminated approximately 72 h after CIDR removal. Accounting for significant variables such as location (P < 0.01), heifers in estrus at or prior to AI (P < 0.001), and a treatment by location interaction (P < 0.01), two doses of PGF on Day 5 tended to have higher pregnancy rates to timed AI compared to those that received one dose of PGF (P = 0.06). In conclusion, heifers given two doses of PGF at CIDR removal on Day 5, in a 5-d CIDR-CO-Synch protocol, tended to have a higher pregnancy rate than those that received only one dose of PGF.     

The effect of a depot injection of recombinant bovine somatotropin on follicular development and embryo yield in superovulated Holstein heifers

Superovulated Holstein heifers (n = 32) were given a depot injection of 500 mg recombinant bovine somatotropin (rBST) or vehicle at Day 4 of the estrous cycle (7 days before the first FSH injection); at Day 11, coincidentally with the first FSH injection; or at Day 15, the time of artificial insemination. Embryos were collected nonsurgically, and the number of corpora lutea was counted by ultrasonography at Day 7 after insemination. Blood samples were taken every second day, from Day 2 of the superovulatory cycle until the day of embryo collection, and were analyzed for progesterone, somatotropin and insulin-like growth factor-1 (IGF-1). Somatotropin-treated heifers at Day 11 had a significantly higher mean number of corpora lutea than the controls (18.1 vs 13.4; P 0.63), but it was negatively correlated with progesterone (P 相似文献   

Response to biostimulation in peri-puberal beef heifers: influence of male-female proximity and heifer's initial body weight

The objectives were to determine if exposure of 12 mo old peri-puberal beef heifers to androgenized steers for 35 d hastened puberty, and if the response was related to the physical proximity between males and females and to heifer's initial body weight. Hereford x Aberdeen Angus heifers (n = 131), 12 mo old, were assigned to two treatments: 1) Exposed group, exposed to androgenized steers from Day 0 to Day 35 (E, n = 66); or 2) Control group, isolated from the steers and other males (C, n = 65). Cyclic activity was determined through estrous behavior detection (twice daily) and weekly ultrasound imaging to detect a CL. For each Exposed heifer, an association index (with males) was determined thrice weekly, based on the distance to androgenized steers every 10 min for 4 h (until cyclic activity began). Data were analyzed according to heifer's initial body weight, which was categorized into three ranges (low, medium, and high, designated LW, MW, and HW, respectively). The cumulative proportion of cyclic heifers was greater for Exposed than Control heifers as of Day 21. By the end of the exposure period, more Exposed than Control heifers had attained puberty (16/66 vs. 2/65; P < 0.001). Within the HW classification, more Exposed than Control heifers became puberal (11/20 vs. 2/21; P = 0.002). However, there were no differences between MW and LW in the proportions of heifers that reached puberty. Association index in Exposed heifers was greater in HW than in MW and LW (0.10 ± 0.09 vs. 0.06 ± 0.03 and 0.06 ± 0.04; P < 0.05), and in heifers that began cyclic activity compared to those that did not in the MW heifers (0.09 ± 0.05 vs. 0.05 ± 0.02; P = 0.01) and tended to be different in the HW treatment (0.12 ± 0.10 vs. 0.06 ± 0.02; P = 0.09). In conclusion, exposure of peri-puberal beef heifers to androgenized steers for 35 d advanced puberty in heavier heifers; an earlier response occurred in heifers with greater proximity to androgenized steers.     

Ovarian response,embryo production and hormonal profile in superovulated goats treated with insulin

The influence of insulin on ovarian response and embryo production was investigated in 30 mixed breed goats, divided randomly into three equal (n=10) groups. Goats in Group 1 (control) were superovulated using 20 IU FSH i.m. in six divided descending doses, i.e. 4/4, 3/3 and 3/3 IU at 12 h interval for three consecutive days and were not given insulin treatment. Goats in Group 2 (insulin pretreatment) were pretreated with long acting purified bovine insulin 0.2 IU/kg body weight per day s.c. on Days 7, 8 and 9 of the estrous cycle prior to initiation of superovulatory treatment as in Group 1. Animals in Group 3 (insulin cotreatment) were treated as in Group I, but in addition received long acting purified bovine insulin 0.2 IU/kg body weight per day s.c. as a cotreatment along with the first, third and fifth FSH treatments on three consecutive days. Total ovarian response (corpus luteum and unovulated large follicle (UOLF)) was significantly (P<0.05) higher in insulin pretreatment (17.90+/-3.08) than in the cotreatment (11.50+/-2.34) and control (11.90+/-1.87) groups. The number of UOLF was significantly higher (P<0.05) in the insulin pretreatment (10.2+/-1.67) than the cotreatment (4.9+/-1.14) and control (3.6+/-1.09) groups. The mean transferable quality of embryos did not differ significantly among treatments. Progesterone concentration on the day of PGF(2)alpha treatment was not different (P>0.05) between the insulin treatment groups (5.28+/-0.79; 5.30+/-0.66 ng/ml). Estradiol-17beta concentration was significantly (P<0.05) higher on the day of PGF(2)alpha treatment in both the insulin treatment groups (36.67+/-6.40; 34.33+/-4.33 pg/ml) as compared to the control group (20.00+/-2.73 pg/ml). There is ample evidence to indicate beneficial effect of insulin on folliculogenesis and steroidogenesis in superovulated goats.     

Effect of the luteinizing hormone on embryo production in superovulated rabbit does

For most domestic animals, the responses to superovulation treatments are not controlled as a consequence of the lack of knowledge on exogenous gonadotrophins effects on the ovarian function. The role of luteinizing hormone (LH) on the number and quality of embryos produced was evaluated on rabbit does superovulated with porcine FSH (pFSH). Parameters of embryos recovery, in vitro and in vivo embryo development rates after freezing/thawing were compared. We used three experimental groups: (1) control group without superovulation treatment, (2) "pFSH+pLH" and (3) "pFSH" groups where females were treated with pFSH, respectively, with (20%) or without (0%) porcine LH supplementation. The number of corpora lutea and the number of embryos produced were significantly higher (p<0.001) in superovulated does than in control group (27.1, 26.7 versus 11.9 corpora lutea and 20.3, 21.2 versus 9.6 embryos produced for pFSH+pLH, pFSH and control group, respectively). However, both gonadotrophins administrations (groups 2 and 3) led to defaults of ovulation when compared with untreated does. No significant difference was observed between the number and quality of the embryos produced by does treated with pFSH+pLH or with pFSH alone. Moreover, we observed no significant difference between results of in vivo and in vitro viability assays after thawing. We concluded that pFSH alone seems to be sufficient to stimulate the follicles growth and that exogenous pLH administrated has no effect on the quantity and quality of embryos. Further studies are needed to evaluate the hormonal patterns before and after the gonadotrophins injections in the rabbit species.     

Effects of propylene glycol drenching before and after luteolysis on blood glucose, ovarian steroids and follicular dynamics in heifers

The effect of propylene glycol drenching on ovarian and hormonal dynamics was studied in heifers. Five cycling heifers were used twice (as control and treatment) with crossover design. After the confirmation of ovulation (day 0), the heifers in the treatment group received propylene glycol on days 6, 7 and 8 as an oral drench (250 ml of 90% propylene glycol). On day 10, prostaglandin F2α (PGF2α), 15 mg per head of dinoprost, was administered intramuscularly to induce luteal regression followed by the follicular phase and then propylene glycol was again administered twice daily (500 ml/day) on days 10, 11 and 12. Palpation per rectum and ovarian ultrasonography were performed every other day from days 0 to 10, and daily after PGF2α administration until the subsequent ovulation (second ovulation) for analysis of follicular and luteal dynamics. Blood samples were also collected every other day from days 0 to 10, and then at 6 h intervals after PGF2α administration until the second ovulation. For the samples taken at 6-h intervals after PGF2α administration, the concentrations of glucose showed clear daily fluctuations in both groups. Changes in the plasma concentration of glucose in the treatment group were significantly (P < 0.05) higher than those of the control groups during the period between 0 and 72 h after PGF2α administration. No significant difference was detected in the growth of dominant follicles, maximum diameter of the ovulatory follicles and the changes in oestradiol and progesterone during the follicular phase between treatment and control groups. This study showed the clear daily fluctuations and stimulatory changes in the blood glucose concentrations at 24-h intervals during the short-term treatment of propylene glycol drenching in heifers. However, no significant changes in ovarian and hormonal dynamics were found under such metabolic conditions.     

Dose of FSH-P as a source of variation in embryo production from superovulated cows

Various superovulation treatments were evaluated retrospectively in a commercial embryo transfer program. When it appeared that embryo production was dependent on the dose of FSH-P, a dose response curve to FSH-P was developed and embryo production compared using several treatment regimes. There was a significant effect of dose of FSH-P on embryo production in superovulated cows. At doses in excess of 28 mg, embryo production declined from 5.9 transferable embryos per collection (28 mg) to 2.7 (60 mg). Total embryos collected declined from 14.9 to 6.8 and the percent transferable from 57% to 40%. There was no advantage in using a five-day treatment over a four-day treatment regimen or in using a level over a declining dose regimen. There was a large individual variation in cow response rendering decisions on treatment changes based on single records unreliable. The percentage of zero collections increased with dose rate. Adoption of a 28-mg dose rate in commercial donors resulted in the embryo production forecast by these studies.     

Effects of oxytocin on cloprostenol-induced luteolysis, follicular growth, ovulation and corpus luteum function in heifers

Twenty-five normally cyclic Holstein heifers were used to examine the effects of oxytocin on cloprostenol-induced luteolysis, subsequent ovulation, and early luteal and follicular development. The heifers were randomly assigned to 1 of 4 treatments: Group SC-SC (n=6), Group SC-OT (n=6), Group OT-SC (n=6) and Group OT-OT (n=7). The SC-SC and SC-OT groups received continuous saline infusion, while Groups OT-SC and OT-OT received continuous oxytocin infusion (1:9 mg/d) on Days 14 to 26 after estrus. All animals received 500 microg, i.m. cloprostenol 2 d after initiation of infusion (Day 16) to induce luteolysis. Groups SC-OT and OT-OT received oxytocin twice daily (12 h apart) (0.33 USP units/kg body weight, s.c.) on Days 3 to 6 of the estrous cycle following cloprostenol-induced luteolysis, while Groups SC-SC and OT-SC received an equivalent volume of saline. Daily plasma progesterone (P4) concentrations prior to cloprostenol-induced luteolysis and rates of decline in P4 following the induced luteolysis did not differ between oxytocin-infused (OT-OT and OT-SC) and saline-infused (SC-SC and SC-OT) groups (P >0.1). Duration of the estrous cycle was shortened in saline-infused heifers receiving oxytocin daily during the first week of the estrous cycle. In contrast, oxytocin injections did not result in premature inhibition of luteal function and return to estrus in heifers that received oxytocin infusion (OT-OT). Day of ovulation, size of ovulating follicle and time of peak LH after cloprostenol administration for oxytocin and saline-treated control heifers did not differ (P >0.1). During the first 3 d of the estrous cycle following luteal regression, fewer (P <0.01) follicles of all classes were observed in the oxytocin-infused animals. Day of emergence of the first follicular wave in heifers treated with oxytocin was delayed (P <0.05). The results show that continuous infusion of oxytocin during the mid-luteal stage of the estrous cycle has no effect on cloprostenol-induced luteal regression, timing of preovulatory LH peak or ovulation. Further, the finding support that an episodic rather than continuous administration of oxytocin during the first week of the estrous cycle results in premature loss of luteal function. The data suggest minor inhibitory effects of oxytocin on follicular growth during the first 3 d of the estrous cycle following cloprostenol-induced luteolysis.