The essence of fertilization: oocyte meets sperm

The problem of reduced fertility in high yielding dairy cattle is a very complicated one, and the relationship between various measures of fertility and level of milk production remains controversial. In this brief review the essence of the problem is considered: what is the oocyte's and the sperm's contribution, and what is the importance of the resulting embryo in the declining fertility of the Holstein Friesian cow

Circadian rhythm of metabolic changes associated with summer heat stress in high-producing dairy cattle

The current study aimed to investigate the circadian rhythm of blood metabolic parameters associated with summer heat stress (HS) in dairy cows. Ten healthy lactating Holstein Friesian cows were followed during HS for three successive days at six different time points. Blood was sampled from each cow starting from 07:00AM; at 4-h intervals. Ambient air temperature and relative humidity were recorded, and temperature-humidity index (THI) was calculated as well. Respiration rate (RR) and rectal temperature (RT) were recorded for each cow at the time of blood sampling. Concentrations of glucose, non-esterified fatty acids (NEFA), total cholesterol (TC) and urea were measured in each blood sample. The THI values were >68 at all times of the day, and the highest values were recorded at 11:00AM, 03:00PM and 07:00PM (80.9, 83.7, and 80.8, respectively). All the cows showed a significantly higher RR and RT coinciding with higher THI values (93±4 and 39.6±0.1; 90.2±3.4, and 40.1±0.1; 87.6±4.1, and 39.8±0.1, respectively, P<0.05). The concentrations of glucose were the lowest at 11:00AM and 03:00PM (3.75±0.1 and 3.44±0.1 mmol/L, respectively, P<0.05). Decreased glucose concentrations coincided with increased NEFA concentrations, (0.43±0.01 and 0.56±0.02 mmol/L, respectively, P<0.05), and were highly negatively correlated (r=−0.50, P<0.001). The highest urea and TC concentrations were registered at 11:00AM (6.11±0.15 mmol/L and 109.9±2.2 mg/dl, respectively) whereas the lowest urea and TC values were recorded at 03:00AM (4.97±0.18 mmol/L and 99.5± 1.7 mg/dl, respectively, P<0.05). The results of the present study indicate that there was a circadian variation in glucose, NEFA, urea, and TC resulting in the most unfavorable metabolic condition during the hottest moment of the day in dairy cattle. Earlier work revealed that HS-metabolic changes are reflected in the follicular fluid. The circadian changes observed in the present study associated with HS may imply that also the microenvironment of the oocyte is affected

Effects of Extenders Supplementation with Gum Arabic and Antioxidants on Ram Spermatozoa Quality after Cryopreservation

Semen cryopreservation is very important in animal agriculture to maximize the number of daughters of genetically superior males and to distribute the cryopreserved semen of good males all over the world. However, the freezing process generates some damage to sperm that reduce their fertilizing ability after thawing. Moreover, egg yolk, which is the most common animal-origin cryoprotectant used in semen dilution, is considered a source of biosecurity risk. In the current study, we aimed to compare the replacement of egg yolk in the extender by gum arabic (5%) along with supplementation with antioxidant cysteine or ascorbic acid on semen quality and freezability in Noemi rams in vitro. Semen from six rams were collected with an artificial vagina two times per week. Semen evaluation parameters such as color, volume, pH, general motility, percentage motility, concentration and cell viability ratio were assessed. Spermatozoa motility and concentration were estimated with the computer-assisted semen analysis system. The semen samples were frozen using a Tris extender containing either 15% egg yolk or 5% gum arabic. For antioxidant-supplemented extenders, cysteine or ascorbic acid was dissolved at concentrations of 0.10, 0.50 or 1.0 mM in egg yolk or gum arabic extender. The semen from each ejaculate of each ram were resuspended with a specific extender with glycerol (5%); the final volume after dilution was 1 mL semen to 4 mL extender. The samples were then cooled to 4 °C for 120 min, loaded into 0.5 mL straws and frozen in liquid nitrogen for 7 days. Supplementation of gum arabic or egg yolk extenders for ram semen with antioxidants such as cysteine or ascorbic acid has beneficial effects on semen quality after cold storage or cryopreservation. However, supplementation of a 5% gum arabic extender with cysteine at 0.5 or 1 mM concentration or ascorbic acid at 0.5 mM concentration improved the quality of spermatozoa postcryopreservation. It could be concluded that gum arabic is a good alternative for egg yolk in Noemi ram semen extenders. Antioxidants are necessary to support the addition of gum arabic to the extender to help the ram spermatozoa to survive freezing–thawing and oxidative stresses

Consequences of twinning induction to Noemi ewes by a recombinant human follicle-stimulating hormone compared with pituitary-derived porcine follicle-stimulating hormone on follicular dynamics, maternal biochemical attributes, and neonatal traits

Aim: The aim of this study was to investigate the effectiveness of using recombinant human follicle-stimulating hormone (FSH) compared with pituitary-derived porcine FSH given as one dose or multiple doses on the neonatal traits, follicular dynamics, and maternal blood biochemical constituents in Noemi ewes. Materials and Methods: A 3×2 factorial arrangement was designed utilizing 60 adults Noemi ewes to test the effects of using two sources of FSH (human vs. porcine) in addition to control, either given as a single total dose or six descending doses to provoke twinning. Six treatments (T) were tested (n=10 ewes/T). C1 and C6 served as control ewes given saline as one dose and six doses, respectively; H1 and H6 ewes were given human FSH as one and six doses; and P1 and P6 ewes were given porcine FSH similar to the above treatments. Saline and/or FSH administration were administered at days 8, 9, and 10 of the 10-day controlled internal drug release (CIDR) implant. At CIDR removal, fertile rams were used for natural mating. Blood samples for the assessment of serum metabolites were collected. Results: Twinning increased in FSH-treated ewes than control. However, giving FSH of either source as a single dose resulted in a higher incidence of stillbirths. Pregnancy rates were 30, 40, 50, 60, 70, and 80% in C1, C6, P1, P6, H1, and H6, respectively. Respective percent of ewes delivering twins/multiple birth was 0, 0, 80, 66.7, 71.4, and 87.5%. FSH of human source was more efficient for folliculogenesis than porcine FSH. Administration of FSH increased blood cholesterol, decreased high-density lipoprotein; however, low-density lipoprotein levels were not different than control. Moreover, an interaction (p<0.05) exists between source and type of FSH administration on blood glucose. Six doses of FSH elevated blood protein. Blood albumin decreased by porcine-FSH but not affected by human-FSH. Blood globulins were not different due to source of FSH, whereas giving FSH as six doses increased globulins than in single-dose protocol. Contrariwise, an interaction was found between source and type of FSH administration on elevating the activity of alanine aminotransferase and reducing the activity of aspartate aminotransferase. Conclusion: Administration of human FSH at 180 IU in six descending doses resulted in the best neonatal outcomes and maternal health in Noemi ewes

Cryotolerance of bovine blastocysts is affected by oocyte maturation in media containing palmitic or stearic acid

In this study, non-esterified fatty acids (NEFAs) were added during in vitro maturation at concentrations measured previously in follicular fluid (FF) of high-producing dairy cows in a negative energy status to evaluate their subsequent effect on the embryos cryotolerance. Oocytes were matured for 24 h in serum-free media with or without (negative control) the addition of NEFAs dissolved in ethanol or ethanol alone (positive control). Matured oocytes were fertilized and cultured for 7 days in synthetic oviduct fluid medium supplemented with 5% FCS. Embryos that had at least reached the blastocyst stage were vitrified by open pulled straw (OPS) vitrification. Addition of palmitic (C16 : 0) or stearic acid (C18 : 0) during oocyte maturation had significant negative effects on embryo cryotolerance, whereas ethanol or oleic acid (C18 : 1) had no effect. These in vitro results suggest that high NEFA concentrations in FF during a period of negative energy balance in high-yielding dairy cows can have carry-over effects on embryo quality