Temporary Weaning Research Articles

Plant-animal relationship, metabolic and behavioral adaptations, and their association with production levels in primiparous cows in response to changes in herbage allowance in Basaltic native grasslands

Based on a two-level of herbage allowance (OF) with seasonal variations experiment, two experiments were conducted in spring-calving primiparous cows on basalt campos. Experiment 1 (Exp1) assessed high OF (AOF) and low OF (BOF) in cows undergoing temporary weaning and flushing (DTF) at the beginning of the breeding season, while Experiment 2 (Exp2) investigated the interaction between AOF and BOF levels pre and postpartum without DTF. Herbage quantity and height were generally below recommended values and they were higher in AOF during autumn and summer compared to BOF, explained by a lower stocking rate (~30%). In Exp1, AOF increased concentrations of IGF-I and insulin, and BCS in autumn, explained by higher herbage intake. These changes had a positive impact on IGF-I concentrations during winter and after the start of DTF in AOF compared to BOF, attributed to a carryover effect or metabolic memory, explaining the higher probability of ovulation and pregnancy. After DTF, AOF cows exhibited greater behavioral plasticity: a lower proportion of daytime spent grazing and more on rumination and walking, staying closer to their calves compared to BOF. The calves’ weight after 120 days was higher in AOF compared to BOF, associated with increased calves’ herbage intake and cow-calf proximity. In Exp2, BCS levels would have been sufficient to mitigate the negative energy balance in winter, explaining the absence of a prepartum OF effect. Postpartum AOF increased herbage intake compared to BOF and recorded higher concentrations of IGF-I, milk production, calf weight from 90 days, and the proportion of cows that ovulated. The OF affected the nutritional plane at different times between experiments; however, AOF in both experiments increased meat production per cow, biological efficiency and production per area associated with higher herbage intake, and metabolic and behavioral plasticity. The results contribute to the design of more productive, resilient and environmentally friendly systems.

Simulation of the financial impact caused by different pregnancy rate in a beef cattle system

The objective of this study was to develop a simulation model for a beef cattle system, in order to carry out an economic analysis of the variable costs influenced by the use of technologies that aim to increase the pregnancy rate of this system and thus, to show whether the Pregnancy rates resulting from a greater intensification of the system coincide with the best economic responses, among the evaluated scenarios. The results were obtained through the elaboration of herd evolutions with different pregnancy rates and cost/animal analysis of each technology used in the system (early weaning, temporary weaning and improved native pasture), aiming at obtaining the enjoyment and variable costs in different scenarios, in order to compare and describe the data. The variation in the pregnancy rate indicated different values for the enjoyment of the system, from 65 to 85%, corresponding to 100 and 116 kg/ha/year, respectively, while the pregnancy rates of 90 and 95% reflected approximate values of 113 and 112 kg/ha/year, respectively. It is concluded that the highest pregnancy rates did not coincide with the highest economic result.

Effect of creep feeding with rice bran and temporary weaning on cow-calf performance.

This study was conducted to investigate if calvessupplemented with rice bran in a creep feeding (CF)system associated with temporary weaning (TW) affects the performance of the cow-calf pair grazing natural grasslands during summer. Two experiments were performedusing 275 cow-calf pairs of British breeds and their crosses of different parities (primiparous [n = 188]in Experiment 1 and multiparous [n = 87] in Experiment 2). In both experiments, the factors evaluated were: (1) supplementation of calves with rice bran using CF: yes (+CF) or no (-CF); (2) TW for 14 days using nose plates: yes (+TW) or no (-TW). Four experimental groups were formed in both experiments: -CF - TW, -CF + TW,+CF - TWand +CF + TW. TW decreased the average daily weight gain and live weight of calves independently of the age of their mothers. The use of CF decreased both of these parameters in calves born to primiparous cows, and there was no response in the case of calves born to multiparous cows. A greater proportion of primiparous cows that received +CF conceived in the first 21 days of mating (+CF - TW = 63.5% and +CF + TW = 50%) than the other groups. The final pregnancy rate was similar among groups in both experiments. In conclusion, TW decreased the average daily weight gain and weaning weight of calves. Supplementation of calves born to primiparous cows with rice bran decreased their daily weight gain during the period of TW and their weaning weight, but their dams were conceived earlier.

Effect of temporary weaning and creep feeding on calf growth and the reproductive efficiency of their Hereford dams.

ObjectiveThe objective was to test if creep feeding (CF) improves the average daily gain (ADG) and weaning weight of calves submitted to temporary weaning (TW) and if the combination of CF and TW improves conception and pregnancy rates of cows.MethodsPrimiparous (n = 74) and primiparous and multiparous (n = 104) cows grazing native grasslands were used in experiment 1 and 2; respectively. The experimental design was in plots divided into complete random blocks with two replications. The CF was the big plot and TW the small plot, thus four experimental groups were formed: i) −CF−TW (n = 21 and 27); ii) −CF+TW (n = 16 and 24); iii) +CF−TW (n = 20 and 26); iv) +CF+TW (n = 17 and 27) with cow-calf pairs for experiments 1 and 2; respectively. Nose plate application for TW had a duration of 14 and 15 days for experiment 1 and 2: respectively. In experiment 1, calves were fed at 1% of live weight for 112 days using a commercial supplement with 18.4% crude protein. In experiment 2, the supplementation lasted 98 days, and was carried out with corn dried distillers grains with soluble (DDGS) at 40% of the potential intake on a daily basis.ResultsThe TW reduced ADG during the TW period and the following 14 days, but the negative effect of TW was maintained until the final weaning only in experiment 2. The CF increased ADG during TW period in both experiments. The TW promoted an earlier conception of the dams (12 days in −CF treatment and 19 days in +CF treatment, p<0.01) and CF increased pregnancy rate in experiment 1, being the effects not consistent between experiments.ConclusionThe CF consistently promoted an increase in ADG during the period of TW and increased final weaning weight of calves, therefore it is economically viable.

COMPARAÇÃO ENTRE PROTOCOLOS COM DESMAME TEMPORÁRIO VERSUS GONADOTROFINA CORIÔNICA EQUINA APÓS TRATAMENTO COM PROGESTERONA INTRAVAGINAL VISANDO A INSEMINAÇÃO ARTIFICIAL EM TEMPO FIXO EM VACAS BOS TAURUS INDICUS

The aim of the study was to compare the reproductive efficiency of two protocols with temporary weaning (TW) of calves and one using equine chorionic gonadotropin (eCG), the synchronization of estrus and ovulation in timed artificial insemination (TAI) protocol. A total of 534 multiparous cows were distributed into three groups: temporary weaning on day 8 of the protocol group (TW8G; n = 225); temporary weaning on day 9 group (TW9G; n = 139) and equine chorionic gonadotropin group (eCGG, n = 170). TW8G received on day zero (d0) an intravaginal device with progesterone (P4; 0.558g) + estradiol benzoate (EB; 2mg, im). On d8, the device was removed with P4 + PGF (0.075mg, im) + estradiol cypionate (EC 0.5 mg, im) + removal of the calf for 48 hours. On d10, TAI was performed, and the calves returned to their mothers. The TW9G was subjected to the same protocol as the TW8G, except for the removal of the device with the P4, which occurred on the 9th, and on the d11, TAI was performed, and the calves returned to their mothers. eCGG was subjected to the same protocol as TW8G, except that on d8 it received eCG (300IU, im), on d9 estradiol benzoate and TAI on d10. The pregnancy diagnosis was made change for done at d45. The non-pregnant cows (post TAI) were re-inseminated under the observation for estrus observation (conventional AI). The remaining empty cows from conventional AI remained with the bull for another 45 days. PR after TAI was 47.1 (TW8G), 40.2 (TW9G) and 51.7% (GeCG), while PR after conventional AI was 19.3%; 31.3% and 26.8%. PR at the end of the breeding season resulted in 95.1, 90.6, and 92.3% respectively for TW8G, TW9G and eCGG. It was concluded that there was no difference in reproductive efficiency in the timed artificial insemination between the applied protocols; the use of TW or eCG can be implemented in the breeding season of beef cows.

Intramyocardial Injection of Mesenchymal Precursor Cells and Successful Temporary Weaning From Left Ventricular Assist Device Support in Patients With Advanced Heart Failure

Left ventricular assist device (LVAD) therapy improves myocardial function, but few patients recover sufficiently for explant, which has focused attention on stem cells to augment cardiac recovery. To assess efficacy and adverse effects of intramyocardial injections of mesenchymal precursor cells (MPCs) during LVAD implant. A randomized phase 2 clinical trial involving patients with advanced heart failure, undergoing LVAD implant, at 19 North American centers (July 2015-August 2017). The 1-year follow-up ended August 2018. Intramyocardial injections of 150 million allogeneic MPCs or cryoprotective medium as a sham treatment in a 2:1 ratio (n = 106 vs n = 53). The primary efficacy end point was the proportion of successful temporary weans (of 3 planned assessments) from LVAD support within 6 months of randomization. This end point was assessed using a Bayesian analysis with a predefined threshold of a posterior probability of 80% to indicate success. The 1-year primary safety end point was the incidence of intervention-related adverse events (myocarditis, myocardial rupture, neoplasm, hypersensitivity reactions, and immune sensitization). Secondary end points included readmissions and adverse events at 6 months and 1-year survival. Of 159 patients (mean age, 56 years; 11.3% women), 155 (97.5%) completed 1-year of follow-up. The posterior probability that MPCs increased the likelihood of successful weaning was 69%; below the predefined threshold for success. The mean proportion of successful temporary weaning from LVAD support over 6 months was 61% in the MPC group and 58% in the control group (rate ratio [RR], 1.08; 95% CI, 0.83-1.41; P = .55). No patient experienced a primary safety end point. Of 10 prespecified secondary end points reported, 9 did not reach statistical significance. One-year mortality was not significantly different between the MPC group and the control group (14.2% vs 15.1%; hazard ratio [HR], 0.89; 95%, CI, 0.38-2.11; P = .80). The rate of serious adverse events was not significantly different between groups (70.9 vs 78.7 per 100 patient-months; difference, -7.89; 95% CI, -39.95 to 24.17; P = .63) nor was the rate of readmissions (0.68 vs 0.75 per 100 patient-months; difference, -0.07; 95% CI, -0.41 to 0.27; P = .68). Among patients with advanced heart failure, intramyocardial injections of mesenchymal precursor cells, compared with injections of a cryoprotective medium as sham treatment, did not improve successful temporary weaning from left ventricular assist device support at 6 months. The findings do not support the use of intramyocardial mesenchymal stem cells to promote cardiac recovery as measured by temporary weaning from device support. clinicaltrials.gov Identifier: NCT02362646.

Follicular size, luteinizing hormone (LH), and progesterone (P4) levels in postpartum Santa Inês ewes subjected to ram effect combined with suckling interruption

The objective was to evaluate the role of ram effect combined with temporary weaning on P4, LH, follicular size and reproductive performance of hair ewes during postpartum. Pluriparous Santa Inês ewes (n = 99) during 15 to 30 days postpartum were selected and isolated from rams for an additional period of 30 days. Before exposure to rams, ewes were allocated to experimental groups, where on SI0, no suckling interruption was performed, and in SI24 and SI48, suckling interruption was performed for 24 and 48 hours, respectively. Mean P4 was according to anestrus condition before the introduction of rams, and it reached cyclicity levels after contact between genders. Ewes displaying a single estrus were more frequent in SI24 than SI48 (P 〈 0.05). The LH pre-ovulatory peaks were detected within 44 hours and 60 hours after introduction of rams, irrespectively of the group. Ovulatory follicles reached a more significant size in SI24 than SI0 and SI48 (P < 0.05). Pregnancy rates differed at first service since SI24 was higher than SI48. Moreover, prolificacy was similar among groups (P 〉 0.05). Ram effect combined with temporary weaning for 24 hours is more efficient for Santa Inês reproduction, since it leads to larger ovulatory follicle size, increased the P4 level and higher pregnancy rate at first service.

Calf presence and estrous response, ovarian follicular activity and the pattern of luteinizing hormone in postpartum Bos indicus cows.

The main objective of the present experiment was to assess the effect of temporary weaning on the onset of estrus, ovarian follicular activity and secretion of luteinizing hormone in Bos indicus cows. Forty six mature cows were divided into three groups 1) calves were weaned for 72 h allowing auditory, olfactory and visual contact with their dams (VISUAL, n = 17), 2) calves without contact with their dams for 72 h (NC, n = 17) and 3) calves not weaned and in constant contact with their dams (CTRL, n = 12). Estrus was synchronized in all cows using CIDR for 9 days plus 2 mg of estradiol benzoate given at CIDR insertion. The VISUAL group had a greater (P < 0.05) proportion of cows in estrus (76.5%) compared to the CTRL group (16.7%), but no differences were found when compared to the NC group (58.8%). The VISUAL group had a greater proportion of animal that ovulated (76.5%) compared to CTRL (33.3%) and NC groups (64.7%; P = 0.059). Duration of estrus was shorter (P = 0.04) in the VISUAL (8.4 ± 4.4 hours) than in the NC (12.9 ± 13.4 hours) however, CTRL treatment (11 ± 1.4 hours) was not different from either of these two groups. LH concentration after implant removal was similar among treatments and started to increase at 36 h post CIDR removal. Only in the CTRL group was there an obvious increase by 54 h after implant removal. Follicular size increased in diameter from 36 h and were evident in treatments and control groups by 60 h (P < 0.05). The VISUAL treatment increased the number of cows ovulating and shortened the length of estrus. VISUAL and NC groups showed a similar response in follicular growth and pattern of circulating LH because of treatment.

Effects of separation time on behavioral and physiological characteristics of Brahman cows and their calves

The aim of this study was to investigate the effects of separation time on behavioral and physiological characteristics of Brahman cows and their calves. Thirty Brahman cow-calf pairs raised under extensive conditions were randomly assigned to one of three temporary weaning duration: (n=10/group): (1) 24h, (2) 48h, (3) 72h. Treatment was applied at 25 and 45days postpartum (dpp), with the same cow-calf pairs allocated to the same weaning duration treatment at both ages. Behaviors recorded include the proximity of cows and calves to the fence separating them, and animals vocalizing and/or lying down. Serum cortisol concentration in cows and calves, and calves weight loss and milk intake were calculated as physiological and productivity measures. At 25dpp the percentage of cows at <10m from the fence-line separating them from their calf, decreased as increasing duration of the separation period increased (Z=6.2, p<0.05). At 45dpp this pattern was not observed. The number of cows vocalizing decreased as the separation period increased (37–10% and 13–0%, from 24 to 72h at 25 and 45dpp, respectively (Z=6.6, p<0.05). More calves vocalized (Z=3.6, p<0.05) at 24 and 48h in comparison to 72h, regardless of their age. In cows, increases in cortisol with respect to pre-treatment concentration were only significant (F 2/57=6.6 p<0.05) when subjected to 72h separation at 25dpp, while in calves, increases in cortisol were inversely proportional to the duration of cow-calf separation (10.3±2.9, 5.3±2.2 and 2.0±1.1 (F 2/57=6.6, p<0.05) vs. 6.2±2.8, 2.1±1.4 and 0.8±0.7ng/ml (F 2/57=4.6, p<0.05), at 24, 48 and 72h of separation of 25 vs. 45day old calves, respectively). A similar relation was observed in weight losses (5.4±1.3, 2.7±0.9 and 0.2±0.1 (t=8.13, p<0.05) vs. 2.2±0.9, 0.6±0.5 and 0.7±0.6kg (t=4.15, p<0.05), at 24, 48 and 72h of separation for 25 vs. 45day old calves, respectively). In conclusion, most stress indicators in cows and calves decreased after 48h of separation, cows were less affected than their young, and older calves displayed less signs of stress than younger animals.

Impact of Equine Chorionic Gonadotropin Associated with Temporary Weaning, Estradiol Benzoate, or Estradiol Cypionate on Timed Artificial Insemination in Primiparous Bos Indicus Cows

The study aimed to determine the impact of equine chorionic gonadotropin (eCG) associated with different timed artificial insemination (TAI) protocols on the pregnancy rate (PR) in Bos indicus cows previously treated with progesterone. Five hundred and fifty-seven primiparous cows were subjected to the following treatments: on day 0 (d0), GeCGTW (group equine Chorionic Gonadotropin+Temporary Weaning;n=178) received 0,558 g intravaginal progesterone (P4)+1.0 mg of estradiol benzoate (EB) (IM); on d8 (P4 removal+0,075 mg D-cloprostenol + 400 IU eCG + TW for 48 h); on d10, TAI + calves return to dam; GeCGEB (group equine Chorionic Gonadotropin+Estradiol benzoate; n=176) the same as GeCGTW without TW + application of 1.0 mg of EB on d9; GeCGEC (group equine Chorionic Gonadotropin+Estradiol Cypionate; n=203), the same as GeCGTW without TW+1.5 mg EC (IM). On d35, post TAI, pregnancy diagnosis (PD) was performed. Non-pregnant animals remained under clean-up bulls for 90 days. After this period, the animals were subjected to PD using ultrasound. The PR of TAI was 51.1%, 47.1%, and 47.8% for GeCGTW, GeCGEB24, and GeCGEC (P>0.05) respectively. The PR under clean-up bulls was 88.3%, 47.3%, and 31.1% (P<0.05). The final PR (TAI+clean-up bulls) of the groups was 94.4%, 72.1%, and 64.0%, respectively (P<0.05). It was concluded that no differences in PR among the protocols related to TAI were detected; PR in the GeCGTW protocol under clean-up bulls was higher compared to others (P<0.05); the overall PR of cows subjected to TAI+clean-up bulls was significantly higher in GeCGTW than in the other groups.

PREGNANCY RATES AND BODY MORPHOMETRY IN NELLORE COWS SUBMITTED TO PROGESTERONE AND TEMPORARY WEANING OF CALVES

Body morphometry and temporary weaning (TW) associated to two protocols of fixed-time artificial insemination (FTAI) with intravaginal progesterone releasing device (IPRD) upon pregnancy rates were evaluated. Cows, at 45-59 days post-partum, were randomly divided into group 1 (n=147) and group 2 (n=197). Group 1: received 1g progesterone (IPRD) and 2mg estradiol benzoate on day 0 (EB-D0); 150μg D-cloprostenol on day 7 (PGF-2α-D7); 0,5mg estradiol cypionate and (TW-48 hours) on day 9 (EC+TW-D9); FTAI on day 11 (D11); group 2: IPRD+EB (D0); PGF-2α+EC+TW (72 hours) on D8; FTAI (D11). The pregnancy rate was higher in cows submitted to TW (72 hours) than in cows with TW (48 hours), or rather, 49.74% vs 30.60% (p&lt;0.05). There was a statistical difference (p&lt;0.05) in groups 1 and 2 between pregnant or non-pregnant cows with regard to body weight (412kg vs 400kg and 419kg vs 390kg) and body condition score (BCS) (3.33 vs 3.08 and 3.53 vs 3/32) respectively. Further, 72-hour weaning associated to the applied protocol improved the pregnancy rate. The evaluation of BCS during post-partum may adjust the start of the breeding season.

Influence of biostimulation and temporary weaning on follicular dynamics and pregnancy rates in Nelore cows (Bos taurus indicus).

The objective of this study was to evaluate the effect of biostimulation and temporary weaning on the follicular dynamics and pregnancy rates in Nelore cows. We used three groups of 75 cows: a control group without biostimulation and suckling calves (WB), a group that was biostimulated and had suckling calves (BE) and a group that was biostimulated and subjected to temporary weaning for 56 h (BETW). Ovarian dynamics were examined using ultrasonography. All groups showed follicular atresia. The interval between beginning of the treatment and wave emergence was 3.25 ± 0.30 days for BE, 3.40 ± 0.27 days for BETW and 3.37 ± 0.50 days for WB. The time between implant removal and ovulation was 64.50 ± 1.88 h for BE, 66.75 ± 1.35 h for BETW and 60.85 ± 3.10 h for WB. Eight cows were submitted to ultrasound analysis, and the percentages of cows that had ovulatory follicles of the new follicular wave with maximum diameters greater than 0.80 cm were 100 % (8/8) in BE (1.28 ± 0.12 cm), 100 % (8/8) in BETW (1.52 ± 0.07 cm) and 87.5 % (7/8) in WB (1.21 ± 0.10 cm). The pregnancy rate was 52 % (39/75) in BE, 69.3 % (52/75) in BETW and 37.3 % (28/75) in WB. The association of biostimulation and temporary weaning increased follicular development, ovulation synchronisation and, consequently, the pregnancy rate in beef cows.

A pre-synchronization program at early postpartum might increase the chances of Bos indicus cows cycling prior to 50 days regardless of the length of calf separation.

The aim of this study was to establish if pre-synchronization would enhance the number of animals cycling prior to conventional breeding at 45 days irrespective of the length of calf separation. Multiparous Bos indicus cows were allotted in four groups (n = 10). Control group (C) dams remained with their calves; groups G24, G48 and G72, which were partially weaned for 24, 48 and 72 h, respectively, were estrus synchronized using a controlled internal drug. These procedures were performed at 25 days and again at 45 days postpartum. The number of follicles, presence of a corpus luteum and back fat thickness (BFT) were determined by ultrasound. The proportion of cows with estrus and ovulation at day 25 postpartum was statistically different between the control and treated groups, with the values being 20, 60, 50 and 70 for the control, G24, G48 and G72 groups respectively (P < 0.05). At days 45 postpartum, the proportion of cows with estrus and ovulation was different in group G48 compared with the other groups (P <0.05). The average BFT and body condition score for the four experimental groups in the two periods were similar (P >0.05). Animals with a higher proportion of follicles from 17 to 21 mm, BFT values above 3.5 mm and a regular body condition were significantly different regardless of whether the dams remained with their calves or were separated, regardless of the length of this event. It can be concluded that (1) a pre-synchronization program at day 25 could trigger the onset of ovarian activity and facilitate a breeding program at day 50 and (2) temporary weaning enhances the effect of a pre-synchronization program.

Behaviour response to two-step weaning is diminished in beef calves previously submitted to temporary weaning with nose flaps

Temporary weaning (TW) of beef calves for 5–14 days is a husbandry practice that is frequently used to help advance rebreeding in postpartum cows. The aim of this study was to compare the behaviour response to two-step weaning with the use of nose flaps, in beef calves that had or not been submitted to TW with nose flaps during the breeding period. Thirteen calves that had been fitted with nose-flap anti-suckling devices from 71 to 84 days of age (TW group), and 11 calves that had not received nose flaps during breeding of their dams (C group) were weaned with a two-step procedure. At 189 days of age, they were fitted with nose flaps and remained with the dams (nose flap period, NF); 14 days later all calves were separated from the dams (permanent separation period, PS). Behaviour was observed from 186 to 193 days of age (NF) and from 200 to 209 days of age (PS). Behaviour data for the NF and PS periods were analysed with mixed models for repeated measures. Before weaning, TW calves had greater proportion of observations suckling and grazing, lower proportion of playing, and remained closer to the dam compared to C calves. During the NF period, C calves had lower frequencies of observations standing, grazing, and drinking water, indicating that calves that had nose flaps during their dams' breeding period adapted faster to the anti-suckling device and the cessation of suckling. During the PS period, C calves had a lower frequency of observations grazing and a greater rate of vocalisations, and TW calves displayed an overall earlier, but shorter behaviour response than C calves. We conclude that the benefits of two-step weaning with nose flaps are greater for calves that have worn nose flaps for temporary weaning during the breeding of their dams.

Resumption of postpartum ovarian cyclicity after different suckling manipulation treatments in primiparous beef cows

The aims of this experiment were to study suckling manipulation strategies, such as early weaning, suckling inhibition with nose plates or temporary weaning for 5 days, on resumption of ovarian cyclicity in anoestrous beef cows. Seventy-four primiparous Aberdeen Angus and Hereford cows with a mean body condition score of 3.8 ± 0.1 (mean ± s.e.m, 1–8 scale) grazing together on rangeland were used. At 71 days postpartum (Day 0) animals were assigned to one of four groups as follows: (1) suckling group (S, n = 14): cows were suckled throughout all the experiment; (2) nose plates group (NP, n = 20): nose plates were placed to calves for 14 days; (3) temporary weaning group (TW5d, n = 20): calves were isolated from their dams for 5 days; (4) early weaning group (EW, n = 20): calves were definitely weaned. After treatments, weekly serum progesterone concentrations were measured for 9 weeks. EW and NP cows had shorter intervals between treatments and resumption of ovarian cyclicity (19.6 ± 1.7 and 24.5 ± 3.3 days versus 40.6 ± 3.5 and 37.5 ± 4.0 days for EW, NP, TW5d and S, respectively, P &lt; 0.01). A higher proportion of the EW group showed luteal progesterone concentrations the first week after treatments (20 versus 5, 0 and 0% for EW, NP, TW5d and S, respectively, P &lt; 0.05), then proportions of EW and NP cows resuming postpartum cyclicity were similar throughout the remainder of the study. Temporary weaning for 5 days showed no effects on ovarian cyclicity resumption. When body condition score is not very limiting, restricting suckling over 14 days with nose plates is a useful strategy to induce postpartum cyclicity in range cow herds with effects similar to early weaning.

Treatments to Optimize the Use of Artificial Insemination and Reproductive Efficiency in Beef Cattle under Tropical Environments

Bos indicus cattle, the preferred genetic group in tropical climates, are characterized by having a lower reproductive efficiency than Bos taurus. The reasons for the poorer reproductive efficiency of the Bos indicus cows include longer lengths of gestation and postpartum anestrus, a short length of estrous behavior with a high incidence of estrus occurring during the dark hours, and puberty at older age and at a higher percentage of body weight relative to mature body weight. Moreover, geography, environment, economics, and social traditions are factors contributing for a lower use of reproductive biotechnologies in tropical environments. Hormonal protocols have been developed to resolve some of the reproductive challenges of the Bos indicus cattle and allow artificial insemination, which is the main strategy to hasten genetic improvement in commercial beef ranches. Most of these treatments use exogenous sources of progesterone associated with strategies to improve the final maturation of the dominant follicle, such as temporary weaning and exogenous gonadotropins. These treatments have caused large impacts on reproductive performance of beef cattle reared under tropical areas.

The use of insulin to improve fertility of timed-inseminated postpartum suckled beef cows

The objective of this work was to evaluate the effect of insulin alone or in association with equine chorionic gonadotropin (eCG) on the fertility of postpartum beef cows subjected to synchronization. A total of 340 cows was subjected to fixed time artificial insemination. In the trial 1, the cows were subjected to temporary weaning (TW), while in the trial 2 the same protocol was tested without TW. The addition of an insulin injection to a progesterone/eCG-based protocol without TW increased the pregnancy rate of beef cows with body condition score (BCS) equal to or lower than 2.5. Insulin had no effect on cows submitted to TW or with BCS equal to or higher than 3.0.

Ram-induced oestrus and ovulation in lactating and weaned Corriedale ewes

Two experiments were conducted in consecutive years in which recently (Experiment 1) or temporarily (Experiment 2) weaned ewes and matched post-partum non-lactating flockmates (DRY) were exposed to a stimulus group of rams and oestrous ewes (10 and 20 in Experiment 1, 20 and 20 in Experiment 2) for 28 days in spring. Lactating ewes (n = 130) in Experiment 1 were isolated from their lambs 4 (W-4), 2 (W-2), 1 (W-1) or 0 (W-0) days in advance and exposed along with a group of 32 DRY flockmates. Lactating ewes in Experiment 2 (n = 230) were allocated to an unreplicated factorial of two levels of temporary weaning before stimulation (B0: control; B24: lambs removed 24 h before stimulation) by four levels of ewe-lamb contact imposed at the start of the stimulation (A0: control; A12, A24 and A36: lamb-ewe separation during the initial 12, 24 or 36 h of exposure); DRY ewes (n = 54) acted as an augmented factorial control. Oestrus (rump marks) and ovulation (laparoscopy on day 5 and on day 28 (Experiment 1) or day 32 (Experiment 2)) were recorded. Ovulation and oestrous responses in Experiment 1 were similar for DRY (90.6% and 55.2%, respectively) and recently weaned ewes (83.8% and 53.7%, respectively). Amongst recently weaned ewes, the immediate ovulation response to the rams and the proportion of ewes still cycling by day 28 tended to be lower (P = 0.065 and P = 0.011) in ewes weaned on the day of ram exposure (71.9% and 54.8% v. 87.8% and 80.0%, respectively). Ovulation rate was lower (P < 0.003) in W-2 ewes (1.3 ± 0.10) than in the other recently weaned groups. In Experiment 2, ovulation (83.3%) and oestrous (68.9%) responses in DRY ewes were higher (P = 0.022 and P = 0.053, respectively) than in lactating ewes (66.2% and 51.0%, respectively). More ewes ovulated (P = 0.036) in B24 (70.5%) than in B0 (61.8%). Ewes having their lambs returned 12 h after the onset of stimulation (A12) had poorer ovulation responses (54.9%) than control ewes (A0, 72.9%, P < 0.05); this was probably associated to lamb restitution after the sunset. Main conclusions were that (i) the presence of the lambs is a depressing factor of both ovulation and oestrous responses to the ram effect in lactating ewes, (ii) the ovulation response of lactating ewes will probably benefit from removing lambs for a period of 24 h before the onset of stimulation, (iii) until additional information becomes available, temporary weaning protocols should be designed avoiding lamb restitution during the night.

Progesterone-based estrous synchronization protocols in non-suckled and suckled primiparous Bos indicus beef cows

In Experiment 1, effects of an intravaginal progesterone insert (CIDR) for synchronization of estrus in non-suckled cycling primiparous Bos indicus beef cows were evaluated. Cows received either no treatment (Control), prostaglandin F 2α (PGF), or CIDR (6 d) + prostaglandin F 2α (CIDR + PGF). There were greater ( P < 0.05) percentages of cows inseminated and pregnant in 4 d of breeding season in CIDR + PGF (81.6%; 48.7%) than in PGF (53.8%; 32.5%) and Control cows (14.6%; 8.5%). In Experiment 2, efficacy of a treatment with CIDR (6 d) + prostaglandin F 2α + 48 h temporary weaning (CIDR + PGF + TW) associated or not with equine chorionic gonadotropin (eCG) for synchronization of estrus in suckled primiparous B. indicus beef cows was evaluated. Cows were assigned to receive either no treatment (Control), CIDR + PGF + TW, CIDR + PGF + TW + 200 IU of eCG, or CIDR + PGF + TW + 400 IU of eCG. There were greater ( P < 0.05) percentages of insemination and pregnancy in 4 d of breeding season in treatment groups (47.0%; 27.5%) than in Control cows (4.5%; 3.0%) and in cows treated with eCG (50.9%; 29.4%) than in cows treated only with CIDR + PGF + TW (39.4%; 23.7%). No effects of eCG dosage were detected. The percentage of cows inseminated and pregnant in a 30 d breeding season were greater ( P < 0.05) in cows assigned to synchronization treatments (53.3%; 37.2%) than in Control cows (35.3%; 21.4%). In the beginning of the BS, non-suckled primiparous cows treated with CIDR + PGF with estrous cycles having been initiated following calving had greater estrous detection and pregnancy rates than PGF and Control cows, and suckled primiparous cows had improved estrous detection and pregnancy rates when eCG was associated with CIDR + PGF + TW.

SINCRONIZAÇÃO DE ESTROS PARA IATF ASSOCIADA AO DESMAME TEMPORÁRIO OU ANTECIPADO EM VACAS DE CORTE

The objective of this experiment was to determine the reproductive performance of suckled beef cows in programs of artificial insemination (AI) submitted to definitive early or temporary weaning (EW or TW) and estrous synchronization protocol to fixed-time artificial insemination (FTAI). Two-hundred and five Angus x Nelore cows body with condition score 2.6±0.4 and post-partum period between 54 and 122 days were used in the trial. After EW, one-hundred, fifty three cows were separated three groups according to the AI or FTAI protocol. A group of cows was artificial inseminated according estrous detection after 10 days of definitive weaning during a period of 30 days (EW-AI, n= 53). Estrous synchronization programs to FTAI were carried out in two groups in different moments after EW. In the group EW-FTAI (n= 50), cows were treated at the moment calves were removed while in EW-FTAI 10 (n= 50) the hormonal treatment began 10 days later. The hormonal treatment consisted of an intravaginal implant containing 1,9g of Progesterone, for 8 days, and an injection of Estradiol benzoate (EB), 2mg, im. When the dispositives were removed, 75mcg of Cloprostenol were injected, im, and after 24 hours, 1mg of EB, im. Cows were fixed-time artificial inseminated 52 to 56 hours after implants removal. In TW-FTAI group (n= 52), cows were treated with the same hormonal therapy, but a temporary weaning of 60 hours was done after the implant removal and the FTAI moment. The breeding season was 60 days in EW-FTAI and TW-FTAI groups, 50 days in EW-FTAI10 group and 30 days in EW-AI group. In a sample of 20% of cows ovaries were scanned by ultrasound and it was determined that 55% of the cows were in anestrous. Follicular diameters were determined at beginning of hormonal treatment and at FTAI moment in cows submitted to estrous synchronization (EW-FTAI= 10, EW-FTAI10= 10 and TW-FTAI= 10) by ultrasound. The means of follicular diameters were not different (P>0.05) between groups at Day 0 (7.0±3.1mm; 8.1±1.9mm e 6.5±1.7mm) and at Day 10 (9.8±1.4mm; 12.5±1.2mm e 11.8±2.8mm). The pregnancy rates at AI were 57, 48, 48 and 46% and at the end of the breeding season were 77, 88, 68 and 78%, EW-AI, EW-FTAI, EW-FTAI10 and TW-FTAI respectively, without significance (P>0.05). According to the this study, EW didn’t improve reproductive performance compared to TW associated to estrous synchronization programs to FTAI and 10 days of interval from EW and hormonal therapy didn’t increase fertility in FTAI. Key words: Beef cows, early weaning, fixed-time artificial insemination.