Mutations induced in Tradescantia by small doses of x-rays and neutrons: analysis of dose-Response curves

Dose-response curves for pink somatic mutations in Tradescantia stamen hairs were analyzed after neutron and x-ray irradiation with doses ranging from a fraction of a rad to the region of saturation. The dose-effect relation for neutrons indicates a linear dependence from 0.01 to 8 rads; between 0.25 and 5 rads a linear dependence is indicated for x-rays also. As a consequence the relative biological effectiveness reaches a constant value (about 50) at low doses. The observations are in good agreement with the predictions of the theory of dual radiation action and support its interpretation of the effects of radiation on higher organisms. The doubling dose of x-rays was found to be nearly I rad.     

Reproductive performance of immobilized cryopreserved bovine semen used for timed artificial insemination

The SpermVital^® technology comprises embedding of spermatozoa within an alginate gel to facilitate release of sperm cells over a prolonged period in utero after AI. The aim of this study was to examine whether the survival time of spermatozoa is extended when applying this immobilization technology in combination with cryopreservation. Sperm cell survival (acrosome and plasma membrane integrity) was studied in vitro for 48 hr at physiological temperature. One dose of SpermVital^® (SV) semen was compared with single doses of Biladyl^® (B) processed semen as well as double doses of B (B double). B double was obtained by adding a second B dose the following day, thereby mimicking double AI. Furthermore, reproductive performance applying single early timed AI (TAI) with SV following oestrus synchronization was studied in a field trial. Double insemination (TAI on two consecutive days) with B semen served as control. Number of acrosome‐intact live sperm cells decreased over time in vitro for all treatments (p < .05). There was no difference between SV sperm cell survival and B double after 24 hr (p > .05). However, after 48 hr, SV sperm cell survival was higher than B double (p < .05). Moreover, multivariate analysis showed that the outcome of single early TAI with SV was not significantly different from B double (p > .05). Likelihood of pregnancy and calving in the heifer group was higher than in the cow group (p < .05). These results imply that spermatozoa immobilized in alginate gel have prolonged survival.     

Metabolic blood profile of beef heifers during oestrous and non‐oestrous states

Haematological metabolic profiles in heifers could contribute to the development of proxies for oestrous detection and provide clues to further characterize biological changes during oestrus. One hundred and seven beef heifers were observed for oestrous behaviour twice daily for 124 days. Feed intake and productive performance (body weight and composition) traits were measured, and feed efficiency was determined using residual feed intake (kg DM/day). Blood plasma samples were collected when signs of oestrus were observed and every 30 ± 2 days. Heifers were considered in oestrus (n = 71) when plasma progesterone concentrations were <0.6 ng/ml. Least square means of blood metabolic parameters were compared between oestrous and non‐oestrous states and within oestrous groups according to performance traits and age. Heifers in oestrus exhibited higher concentrations of alkaline phosphatase, aspartate aminotransferase (AST), beta‐hydroxybutyric acid, creatine kinase (CK) and triiodothyronine (T3) than heifers in non‐oestrus. Heifers in oestrus revealed lower osmolality and concentrations of calcium, sodium and total protein than during non‐oestrus. Younger (and smaller) heifers had greater concentrations of CK, gamma‐glutamyl transferase (GGT), glucose and sodium than the older heifers. Heifers with lower fatness had increased osmolality and concentrations of cholesterol, CK, phosphorus, sodium and reduced T3 levels. Feed efficient heifers had greater levels of AST, cholesterol and GGT than inefficient heifers. Blood plasma parameters may be complementary to oestrous detection upon further validation; effects of age, feed efficiency, body size and body composition should be considered to optimize this haematological assessment.