Estimation of maximum thermo-hygrometric index thresholds affecting milk production in Italian Brown Swiss cattle.

It is known that heat stress affects dairy cow performance in multiple ways: physiological, behavioral, reproductive, and productive. The aim of the present study was to determine if a threshold of temperature-humidity index (THI) exists for multiple milk production traits (milk yield, fat-corrected milk, protein and fat yield and percentage, energy-corrected milk, cheese production, and cheese yield) in Italian Brown Swiss dairy cows from the period 15 d before the day of the Italian Breeders Association test-day sampling. A 10-yr data set (2009-2018) containing 202,776 test-day records of 23,296 Brown Swiss cows was matched with the maximum THI. In all parities considered, no THI thresholds were observed for milk yield in Brown Swiss. In contrast, a THI threshold of 75 was identified for fat-corrected milk. No THI threshold was found for fat percentage, but fat yield showed the highest THI thresholds in cows of first and second parity. Protein yield and cheese production were affected by heat stress with average THI threshold of 74. The THI thresholds identified indicate that the Brown Swiss breed has higher thermal tolerance versus literature values reported for Holstein cows. As THI rises, Brown Swiss cows tend to produce the same volume of milk, but with a decreasing quality with regard to components. Further study is necessary to estimate the genetic component of heat tolerance, in Brown Swiss cattle, considering that the correct estimation of THI thresholds represents the first step to identify components that could be included in selection procedures.

In vitro effect of isotocin on ovarian tunica albuginea contractility of gilthead seabream (Sparus aurata L.) in different reproductive conditions.

Contractions of ovarian tunica albuginea, the teleostean cystovary wall layer containing smooth muscle fibres, facilitate oocytes and fluids movements within the ovary, oocytes ovulation and spawning. Fish isotocin, the homologue hormone of mammalian oxytocin, plays a significant role in ovulation, oviduct contraction and spawning. In the present study, ovarian wall spontaneous contraction, as well as isotocin in vitro effect on tunica albuginea contractility, was analysed in female seabream in different reproductive conditions: vitellogenesis, regressing (post-spawning) and extensive atresia. Tunica albuginea spontaneous contractility was recorded using ovary wall strips mounted in an organ bath containing modified Ringer's solution. The strips were then exposed to cumulative doses of isotocin (6, 30, 60 µg/ml). Female seabream in regressing condition exhibited the highest level of tunica albuginea spontaneous contraction amplitude compared with the other two groups. Only fish in vitellogenesis state showed a significant increase in contraction amplitude after isotocin administration at the dose of 30 µg/ml. The same group exhibited also a significant isotocin dose-dependent decrease in the contractile frequency. These results confirm the involvement of isotocin in stimulating tunica albuginea contractile activity during the oestrogen-regulated phase of vitellogenesis, whereas the absence of significant effects of isotocin on ovarian contractility in fish at the regressing state might be ascribed to the occurrence of a contractile activity autonomously regulated by the internal pacemaker system. The absence of exposed isotocin receptors could explain the lack of effects of the isotocin administration in seabream showed extensive atresia of the follicular cells.

Ovarian contractility in reared gilthead seabream (Sparus aurata L.) in different phases of the reproductive cycle.

Spontaneous ovarian tunica albuginea contractility was evaluated in gilthead seabream (Sparus aurata L.) at different phases of the reproductive cycle. Fourteen adult females were sampled from February to November 2012 in a commercial fish farm, and ovaries were removed and processed for histological and contractility analyses. Fish reproductive stages were evaluated on haematoxylin-eosin-stained ovary sections or by simple macroscopic observation of hydrated oocytes in spawning individuals. Tunica albuginea spontaneous contractility was recorded by using ovary wall strips mounted in an organ bath containing modified Ringer's solution. Ovary macro- and microscopic analyses allowed the identification of three different reproductive conditions: vitellogenesis, spawning and regressing. The gilthead seabream tunica albuginea was capable to contract spontaneously, and significant differences were found in mean contraction amplitude among the three reproductive states, with the highest value recorded in individuals in regressing condition and the lowest in individuals at spawning stage. No differences in mean contractility frequency among the three different groups were found. Possible involvement of spontaneous contractility in facilitating developing follicle advancement towards the ovarian lumen within the ovary and in supporting recovery of regressing ovaries may be hypothesized. The low contractility observed during the final oocyte maturation and spawning phases does not seem to support a role of tunica albuginea during ovulation, which could conversely involve theca cell contraction. Alternatively, possible single instantaneous contractions of tunica albuginea muscle fibres, not detected in the present study, could occur during ovulation in response to neuro-hormonal stimulations; a role of abdominal wall musculature in ovary "squeezing" and consequent release of ovulated eggs cannot be excluded.

Effects of lycopene on in vitro quality and lipid peroxidation in refrigerated and cryopreserved turkey spermatozoa.

1. The effects of lycopene-enriched extenders on the in vitro quality of turkey semen including lipid peroxidation were examined after chilled and frozen storage. 2. Five pools of semen diluted in extenders containing 0, 0·05 or 0·1 mg/ml of lycopene were stored at 5°C for 48 h or cryopreserved as pellets and the following variables determined in fresh samples and samples stored chilled or frozen: sperm motility, viability, osmotic resistance, DNA integrity and lipid peroxidation (as malonaldehyde production). 3. Semen quality was generally compromised after storage, especially post-freezing. However, in the presence of the highest dose of lycopene, both the viability and osmotic-resistance of chilled spermatozoa and the DNA integrity of frozen spermatozoa were similar to those of fresh spermatozoa. 4. Greater lipid peroxidation was detected in refrigerated compared to fresh or cryopreserved spermatozoa. However, spermatozoa chilled in lycopene-enriched extenders showed significantly lower malonaldehyde levels than those chilled without lycopene, while the addition of lycopene to the freezing medium served to maintain the lipid peroxidation levels observed in fresh semen. 5. In conclusion, the presence of lycopene in the extender improved the survival of turkey spermatozoa after liquid-storage and protected DNA integrity against cryodamage. The beneficial effects of lycopene observed could be related to its capacity to diminish sperm lipid peroxidation during refrigeration or cryopreservation.