Short communication: Heat treatment and souring do not affect milk estrone and 17ß-estradiol concentrations.

The aim of our study was to establish whether heat treatment and souring of milk affect its estrone (E1) and 17ß-estradiol (E2) concentrations. Milk samples were collected from 10 Holstein cows in late pregnancy. Concentrations of E1 and E2 were measured in milk samples that were previously heated to 70 and 95°C for 5 min. Additionally, E1 and E2 concentrations were determined in the same milk samples after 2 d of spontaneous souring at room temperature, and these samples were compared with E1 and E2 levels in raw, unprocessed milk. Concentrations of both hormones were determined by commercial ELISA kits. Concentrations of E1 in unprocessed and processed milk (milk heated to 70 and 95°C and soured milk) were (mean ± SE) 47.25 ± 4.16, 44.84 ± 3.47, 41.00 ± 4.55, and 44.92 ± 3.91 pg/mL, respectively. Concentrations of E2 in the same milk samples were 36.11 ± 10.01, 32.46 ± 9.88, 31.78 ± 9.56, and 31.43 ± 8.00 pg/mL, respectively. Concentrations of E1 and E2 in heat-treated milk did not differ significantly from those in unprocessed milk. Similarly, E1 and E2 concentrations in soured milk did not differ significantly from those in unprocessed milk samples. These results indicate that E1 and E2 are stable in milk and that milk processing (heating and souring) does not influence their degradation. Therefore, E1 and E2 concentrations are expected to be similar between commercial full-fat milk and the raw milk from which it was produced.

Effect of dietary estrogens from bovine milk on blood hormone levels and reproductive organs in mice.

Cows are often milked until 60 d before their next expected calving. Milk from cows in the third trimester of pregnancy contains up to 20 times more estrogens than milk from nonpregnant cows. The aim of this study was to evaluate whether exposure to known doses of estrogens from bovine milk could affect blood hormone levels in mice and influence their reproductive organs. This study was performed with 30 intact male and 30 ovariectomized female mice. Mice of each sex were randomly divided into 3 experimental groups, each with 6 animals of each sex, and a control group with 12 animals of each sex. The first experimental group received 4mL of milk each day from a pregnant cow with natural estrone (E1) and 17ß-estradiol (E2) in concentrations 0.093 and 0.065ng/mL, respectively. The second experimental group received 4mL of the same milk each day, with an added 10ng/mL of both E1 and E2. The third experimental group received 4mL of the same milk each day, with an added 100ng/mL of both E1 and E2. The control group received no milk. After 8 d of treatment, mice were euthanized, blood was collected, and the uteruses, testes, and seminal vesicles were weighed. The results of our study demonstrated that consumption of native milk from a pregnant cow did not affect plasma E1 and E2 levels in either sex; uterine weight in females; or testosterone levels and testes and seminal vesicle weights in males. Similarly, we found no changes in the group that received the milk with an added 10ng/mL of E1 and E2. We did observe elevated plasma estrogens in both sexes, increased uterus weight in females, and decreased plasma testosterone levels in males from the group that received milk with an added 100ng/mL of E1 and E2. However, concentrations in the third group exceeded the physiological concentration of milk estrogens by 1,000 times, so it would be extremely unlikely to find such concentrations in native cow milk.

Does closantel in therapeutic doses display thyroid hormone-like activity in sheep?

The aim of this study was to define the thyroid hormone-like activity of closantel in sheep by measuring some blood parameters that are known to be influenced by thyroid hormones triiodothyronine (T3) and thyroxine (T4). Our hypothesis was that, if closantel possesses thyroid hormone-like activity, its use under in vivo conditions will result in changes similar to those in hyperthyroidism. The study was conducted in 20 Jezersko-Solchava breed sheep. Blood sampling was performed before and 10 days after routine anthelmintic treatment with closantel. Complete blood count, plasma cholesterol, triglycerides, protein, and albumin levels, as well as those of serum T3 and T4, were compared before and 10 days after closantel administration. This routine anthelmintic treatment of sheep with closantel did not significantly influence hematological parameters, thyroid hormone levels, or most of the biochemical parameters. No evidence was found for thyroid hormone-like activity of closantel in sheep. However, significantly (P < 0.01) elevated levels of plasma triglycerides were present 10 days after closantel administration.

Effects of season, age, and breed on semen characteristics in different Bos taurus breeds in a 31-year retrospective study.

Besides genetic factors, the season of semen collection could have an important effect on ejaculate characteristics, although results from previously published studies are somewhat variable. To determine seasonal effects on semen characteristics, we have analyzed 71,983 ejaculates collected from bulls of four different breeds over a 31-year period. Ejaculate volume, semen concentration, and total sperm output were analyzed with the respect to season and age of bull. Results revealed that semen concentration did not vary significantly during seasons, and ejaculate volume and total sperm output are influenced by season in all breeds. The highest ejaculate volume and total number of sperm in ejaculates were observed during the summer, followed by spring, autumn, and winter. Results suggest that the gradual increase in the day length in the spring is most likely responsible for the highest sperm output during the summer months, suggesting that seasonal effects are also present in cattle, which is not normally considered a seasonal species.

Higher thyroid hormone levels in neonatal life result in reduced testis volume in postpubertal bulls.

Thyroid hormones appear to determine adult testis size in rodents by regulating the period of Sertoli cell proliferation in the neonatal period. In the present study, the correlation between neonatal thyroid hormone levels (T3 and thyroxin, T4) and postpubertal testis size in Simental bulls was examined. T3 and T4 levels were measured in blood plasma from 35 calves immediately after their arrival at the AI centre at age 3-6 months. Testis size (height and width) was measured at 12 months of age in the same live animals. A significant negative correlation (r = -0.55; p < or = 0.001) was found between T4 and calculated testicular volume using either the Pearson correlation test or linear regression analysis, while the levels of T3 and testis volume showed a negative correlation, although this did not reach statistical significance (r = -0.20, p < or = 0.05). The results of this study suggest, therefore, that neonatal thyroid hormone levels might have the same effect on testicular size in cattle as they do in rodents.