Reproductive response to insulin in the ruminant

Abstract

Moisture content of snow-free, unfrozen soil is inferred using passive microwave brightness temperatures from the Scanning Multichannel Microwave Radiometer (SMMR) on Nimbus-7. Investigation is restricted to the two polarizations of the 1.66 cm wavelength sensor. Passive microwave estimates of soil moisture are of two basic categories; those based upon soil emissivity and those based upon the polarization of soil emission. The two methods are compared and contrasted through the investigation of 54 potential functions of polarized brightness temperatures and, in some cases, ground-based temperature measurements. Of these indices, three are selected for the estimated emissivity, the difference between polarized brightness temperatures, and the normalized polarization difference. Each of these indices is about equally effective for monitoring soil moisture. Using an antecedent precipitation index (API) as ground central data, temporal and spatial analyses show that emissivity data consistently give slightly better soil moisture estimates than depolarization data. The difference, however, is not statistically significant. It is concluded that polarization data alone can provide estimates of soil moisture in areas where the emissivity cannot be inferred due to nonavailability of surface temperature data. Two studies were conducted to determine what effect exogenous insulin or feed intake would have on pituitary secretion of luteinizing hormone (LH) or ovulation rate and steroid production in the female bovine. Ovariectomized crossbred heifers were used in the first study to remove the influence of ovarian feedback on the pituitary. After a 24 h fast, blood samples were obtained at 15 min intervals on three separate occasions. At the first collection period, heifers were presented with a corn/cottonseed meal concentrate; at the second, infused with saline or one of three insulin dosages; and at the third, infused with insulin plus gonadotrophin releasing hormone (GnRH). All samples were analyzed for LH and insulin concentration. Neither feeding nor insulin infusion altered LH release, nor was there a synergistic effect between insulin and GnRH to increase LH release. Acute presentation of feed did not significantly raise serum insulin concentrations. The lowest insulin dosage administered did not increase mean concentrations of insulin over control heifers. The highest insulin dosage induced serum insulin concentrations 10 to 20 times endogenous levels and caused insulin shock in some heifers. A second study utilized intact Brangus heifers individually fed a low energy (LE) or high energy (HE) diet. ...