Comparison of CellRox green fluorescence upon thawing on in vitro Bos taurus and Bos indicus embryos cryopreserved by slow freezing or vitrification.

The aim of this study was to compare the levels of reactive oxygen species (ROS) in Bos taurus and Bos indicus in vitro embryos cryopreserved using either slow freezing or vitrification. Embryos were divided into four groups based on subspecies and freezing method: Bos indicus slow freezing (BiSF; n = 8), Bos indicus vitrification (BiVT; n = 10), Bos taurus slow freezing (BtSF; n = 9), and Bos taurus vitrification (BtVT; n = 6). After thawing, the embryos were incubated with CellRox Green and images were obtained using a confocal microscope. The fluorescence intensity of each cell was measured and expressed as arbitrary units of fluorescence (auf) and compared using a multiple regression and unpaired t-test with α = 0.05. Results showed that subspecies and the freezing method significantly affected auf (P < 0.001; R2 = 0.1213). Bos indicus embryos had higher auf than Bos taurus embryos, whether frozen by slow freezing (67.05 ± 23.18 vs 51.30 ± 16.84, P < 0.001) or vitrification (64.44 ± 23.32 vs 47.86 ± 17.53, P < 0.001). Slow freezing induced higher auf than vitrification in both Bos taurus (51.30 ± 16.84 vs 47.86 ± 17.53, P < 0.001) and Bos indicus (67.05 ± 23.18 vs 64.44 ± 23.32, P < 0.014). In conclusion, Bos taurus embryos had lower ROS levels when frozen using vitrification, while Bos indicus embryos had consistent ROS patterns regardless of the freezing method. However, Bos indicus embryos frozen by slow freezing tended to have a higher number of cells with elevated ROS levels.

Dual-Purpose Cattle Raised in Tropical Conditions: What Are Their Shortcomings in Sound Productive and Reproductive Function?

Dual-purpose husbandry might well be the most commonly employed cattle management system in tropical regions worldwide. The advantages of producing both meat and milk, although in reduced quantities, gives an edge to the farmer in coping with the volatile economic conditions that prevail in the region. Herein, we discuss the different methods of cattle management under tropical conditions based on the financial and social structure of this system. An account of the sanitary and nutritional conditions available to the farmers and how these factors affect the profitability of the enterprise will also be given. Finally, we will discuss how these systems can take advantage of several biotechnological procedures, and how these tools (such as controlled natural mating, artificial insemination, and embryo transfer) affect reproductive outcomes. The present review will mainly concentrate on production systems located less than 1000 m above sea level, as the problems and shortcomings of cattle raised above this arbitrary landmark are quite different.

Effects of Season on Donor and Recipient Cows and Calf Performance from Birth to Weaning in Embryo Transfer Programs in the Tropics.

The aim of this study was to assess the seasonal effect of an embryo transfer program in the tropics on the donor response, recipient reproductive performance and calf growth from birth to weaning. This study included five-year records from 145 donors, 1149 embryo transfers (ET) and 609 in calves. The effect of the season (dry or wet) was evaluated at the time of embryo flushing, embryo transfer and birth of the calves. There was a seasonal effect on the yield and quality of the embryos. The number of nonfertilized and transferable good quality embryos increased in the wet season. For the recipients, the probability of pregnancy after an ET decreased by 6% for each year of the dam's age. However, no seasonal effect was found when comparing ET calves with their control group (natural mating-NM), nevertheless, weaning weight was associated with birth body weight, treatment, sex of the calf, season at birth, year of treatment, and dam's age. Calves born by NM had lower average daily gain (ADG), and male calves registered higher gains than females. Likewise, calves born during the rainy season had lower ADG compared with calves born during the dry season. In conclusion, this study shows that seasonal effect is more apparent in donor and calf performance than in the recipients.

Effect of temperature - humidity index on the onset of post- partum ovarian activity and reproductive behavior in Bos indicus cows.

The effect of climatic factors on ovarian activity and reproductive behavior (RB) was evaluated in 46 Bos indicus cows kept under grazing conditions. Temperature-humidity index (THI) was used as an indicator of stress and divided in alert, damage and emergency levels. Fat thickness (FAT) was taken during the last trimester of gestation (LTG) to approximately 90d postpartum (PP). At 30d PP animals received a progesterone (P4)-releasing device (CIDR) which was withdrawn 9d later. Ovarian activity was assessed by blood progesterone on days 21, 24, 27, 30, 49, 51, and 54 PP. Animals were divided into three groups, higher, and moderate RB and non-behavior. Sixty percent presented a THI >74 increasing dramatically from June to September up to >78. During LTG, animals lost 27% of their body reserves contrasting to PP where an increase of 2.6% (P=0.002) was observed. The percentages of cyclic and non-cyclic animals were 57 and 43%, respectively (P> 0.05). Seventy-two percent displayed RB and 28% were non-behavior (P<0.05). A negative correlation (r = -0.307; P = 0.038) between THI and RB, and a positive correlation (r = 0.427; P = 0.003) between the onset of ovarian activity and RB were observed. Differences in THI during the LTG (P<0.01) were observed between cyclic and non-cyclic animals. Non-behavior cows in the LTG had a higher THI (P <0.05). High levels of THI have a negative effect on the resumption of ovarian activity and RB in Bos indicus especially if high THI occurs during the last trimester of gestation.

The Use of Computer Records: A Tool to Increase Productivity in Dairy Herds.

The level of adoption of herd management information system veterinary automated management and production control program (VAMPP) Bovine and its impact on productivity of 912 specialized dairy systems with at least 5 years of information recorded was studied. Herds were classified as low (n = 389), medium (n = 343), or high (n = 180) adoption level on the basis of extent and consistency of record keeping for variables related to production, reproduction, and health. For each herd, within-year averages were obtained for six performance traits: age at first calving (AFC), days open (DO), daily milk yield (DMY), productive life (PL), incidence of clinical mastitis (MAST), and incidence of lameness (LAM). These variables were investigated with a generalized linear mixed model that included the fixed effects of the adoption level, follow-up year, and their interaction, adjusted by the fixed effects of herd size, agroecological zone, calendar period, breed group, and the random effects of variation between/within herds. A significant effect of the adoption level over all the variables was observed, except DMY and PL. The follow-up year was significant for all the variables except LAM. There were marked reductions for AFC and DO in the first 4 years of follow-up. AFC was higher and DO shorter in the low compared to medium and high level of adoption herds (p < 0.001). DMY showed a significant increasing trend (p < 0.001), regardless of the adoption level. There was higher MAST and LAM incidence in the higher adoption level (p < 0.05). The economic benefit was estimated through a stochastic simulation model using an approach based in partial budget analysis. For a herd with a medium level of adoption, the change in gross margin (GMMIS $USD) and marginal return rate (MRRMIS %) for the first 5 years of use of the system was estimated. Under these conditions, there was a GMMIS of $6890 and MRRMIS of 163%. Variation of ±10% in DMY and DO caused changes in the GMMIS of ±$1000 and ±$110, respectively, and in MRRMIS ±24% and ±4%, respectively. The trends suggest a positive influence of VAMPP in productive and reproductive traits during the first years of implementation, with less benefit for the low adoption levels.

Lipid droplets in clusters negatively affect Bos indicus embryos during cryopreservation.

Embryo transfer using cryopreserved B. indicus embryos results in low pregnancy rates. The low viability of B. indicus embryos is likely a result of their low freezability relative to embryos from other species, notably B. taurus. Freezability is probably related to the quantity of lipid droplets in the embryonic cells. However, the mechanism underlying this association is unknown. Using multiphoton and transmission electron microscopy, the proportion, volume, morphology and composition of lipid droplets in fresh and cryopreserved B. indicus and B. taurus embryos were studied. B. indicus embryos have more droplets than B. taurus and a greater percentage of lipid droplets in clusters (34% vs. 24%; p < 0.05). Also, B. indicus individual droplets are of greater volume than those of B. taurus (47 µm3 vs. 34 µm3 ; p < 0.05). After freezing, the percentage of clusters decreased in B. indicus (11% vs. 5%; p < 0.05), while in B. taurus they increased (2% vs. 7%; p < 0.05). Freezing influenced the lipid droplet morphology, increasing the number of cracked droplets in B. indicus embryos (33% fresh vs. 62% frozen; p < 0.05), but not in B. taurus embryos (35% fresh vs. 34% frozen; ns). Regarding composition, saturated lipid droplets prevail in B. indicus embryos, contrary to B. taurus embryos. We observed differences in lipid droplet organization, proportion, volume, morphology and composition between B. indicus and B. taurus embryos which are altered in opposite directions following freezing.

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.