Backfat Thickness Does Affect the Restoration of Ovarian Activity Postpartum in Different Breeding Programs in Zebu Cattle.

The backfat thickness (BFT) was used to forecast the onset of ovarian activity and predict the calf growth. Eighty Brahman cows with their calves were allocated in two groups of 40 distributed in 4 months according to the month of calving, starting in March and finishing in June. One was synchronized and inseminated at fixed time following by natural mating (TAI+NM); whilst the other only by natural mating (NM). The programs started at 60 ± 5 days postpartum and ended 60 days later. From day 30 postpartum, serial ultrasound examinations and progesterone samples were used to monitor the onset of ovarian activity. The BFT in the rump area was measured by ultrasound from 30 days postpartum and every 15 days thereafter. The weight of the calves was recorded at birth and at weaning on 160 days. The adjusted effect of BFT on ovarian activity and the calves' development was assessed by binomial logistic regression at 30, 60, 75, and 120 days postpartum. The cycling cows averaged higher BFT irrespective of breeding program (P < 0.001). Also, slower changes in BFT were recorded during the follow-up at each time for all cows. However, the former had the higher BFT values from calving to the end of the study (P < 0.001). At 60, 75, and 120 days, the BFT measured, at the preceding time, was the only factor predicting the commencement of cyclicity (P < 0.001). The accumulative pregnancy through time was higher in TAI+NM (P = 0.003). Daily weight gain and weaning weight of the calves born in March was significantly heavier (P < 0.001) than peers born in April, May, or June. The most critical element to forecast the onset of ovarian activity is the monitoring of BFT around calving regardless of the breeding program. BFT to estimate the development of the calves until weaning was unpredictable.

Resumption of ovarian function, the metabolic profile and body condition in Brahman cows (Bos indicus) is not affected by the combination of calf separation and progestogen treatment.

To evaluate the effect of different calf separation procedures after a progestogen treatment on the resumption of ovarian function, body condition and metabolic profile, 59 multiparous Brahman cows grazing on a mixed grass pasture were studied. No supplementation was given at any time. Body condition score (BCS), fat thickness (FAT) and blood metabolites were measured fortnightly from the beginning of the last trimester of gestation until 96days postpartum. At 30days postpartum all animals received a progesterone (P4)-releasing device (CIDR) which was withdrawn 9days later when prostaglandin F2α was applied. At this time, treatments TW (n=28), where calves were separated from their dams for 48h; RS (n=21), calves were allowed to suckle once a day for 1h; and continuous suckling (CS; n=10). Ovarian function was assessed by blood concentrations of progesterone on days -14, -9, 10, 13, 30 and 33 after CIDR removal. At the end of the experimental period, an average of 20% of the cows had not initiated estrous cycles. There were no changes of FAT or BCS during the last trimester of pregnancy in all cows (P>0.05). During the postpartum period cows of all groups lost (P<0.05) BCS and FAT with a nadir at 60-80days postpartum, regardless of treatment. At 10days after CIDR withdrawal the percentage of cows having ovulations was 75, 61 and 80 (P>0.05) for TW, RS and CS groups. Blood metabolites follow a similar pattern in the three groups. With the conditions of the present study, the method of calf separation after a progestogen treatment, does not affect the resumption of ovarian function or metabolic profile.

Effect of restricted suckling on the onset of follicular dynamics and body condition score in Brahman cattle raised under tropical conditions.

With the aim of evaluating the effect of restricted suckling on the onset of follicular dynamics and body condition, multiparous Bos indicus cows were distributed in two groups. One group (RS=36) was subjected to a scheme of restricted suckling starting at 21 days postpartum. Calves were allowed to suckle once per day for a period of two h whilst the control group (C=18) remained with their dams at all times. At calving, body condition score, back fat thickness and body weight had similar values (p>0.05) for both groups. By day 85 postpartum both groups had recorded losses in body weight. The cows in the continuous group formed a greater (p<0.05) number of follicles of class size <6mm in both periods before and after synchronization. The proportion of cows showing estrus and ovulation before 45 days, was not different (p>0.05). The number of cows that exhibited estrus after 45 days, was greater (p<0.05) in RS than C group, 72.2% and 55.5%, respectively. Same situation (p<0.05) occurred in cows that ovulated, 88.8 and 66.7%, for groups RS and C, respectively. The subset in the intensive observations showed that the size of the bigger follicle was larger (p<0.05) for RS cows than C cows from 36 h after CIDR withdrawal. At 57 h, the size of the biggest follicle recorded was not different between groups (p>0.05). A regime of restricted suckling favors the earlier growth of follicles and the prompt restoration of ovarian activity.

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.

Embryo transfer, a useful technique to be applied in small community farms?

The objective of this study was to determine if the technique of embryo transfer in cattle can be commercially feasible in a region situated in the humid tropics of Mexico. Twenty-six Bos taurus and twenty-six Bos indicus cows were estrous synchronized and superovulated to obtain a total of 80 embryos of both sub-species. Embryos were classified using stereoscopic microscopy based on established criteria. Nine dual-purpose farms situated in the tropics of Mexico were chosen to provide ten recipient cows each to transfer one embryo per cow. The females were transferred using a fixed-time protocol after verifying the presence of a corpus luteum on the seventh day after the end of hormonal treatment. Pregnancy diagnosis was carried out 28 days after embryo transfer by ultrasonography. Estimation of the cost was determined by calculating the expenses for preparation of the donor and embryo recovery, which were US $633 and US $589 for B. taurus and B. indicus, respectively. The cost of each embryo was determined considering the number of transferable embryos recovered, which was 3.8 on mean. The cost of each conception was calculated taking into account the percentage of pregnant animals (27% on mean), and the cost for preparing donor and recipient cows, for transferring embryo. The overall cost per gestation was US $1,447. Considering a 50:50 ratio of male to female born, the cost for a replacement heifer calf was US $2,894, which surpassed by far the commercial cost of a crossbred ready-to-bred heifer normally used as replacement (approximately US $900).