No abstract

Prediction of the exact time of calving would be highly important especially in small farms where there are no assistants working in day and night shifts. It has been known for a long time that precalving decrease in body temperature can be used for prediction of calving (Ewbank, 1963; Graf & Petersen, 1953; Porterfield & Olson, 1957). Since then, several reports have confirmed the precalving decrease in vaginal temperature by using sensors inserted into the vagina after attaching to a modified controlled internal drug release device without progesterone at least 6 days before the expected time of calving retrospectively as temperature data could be downloaded only after calving (Burfeind, Suthar,

Transabdominal ultrasonography has been shown to be a useful and reliable method for assessing fetal well-being in horses and cattle. To test the applicability of fetal aortic diameter measurement in cattle, 44 late-term pregnant cows and heifers were examined 21 to 0 days prior to calving. Mean fetal aortic diameter was 2.07 ± 0.14 cm and mean fetal heart rate (FHR) was 109 ± 17 bpm. Three dead calves were dissected and their aortic diameter was measured in a water bath. The mean birth weight (n = 44) was 39.9 ± 5.8 kg. There was a significant negative correlation between FHR and fetal aortic diameter. However, although some studies have shown that fetal aortic diameter strongly correlates with birth weight in near-term horses and cattle, in this study there was no correlation between fetal aortic diameter and birth weight in Holstein-Friesian cows and heifers irrespective of whether the fetus was born alive or dead.Key words: Fetal well-being, ultrasonography, aortic diameter, cattle Despite the availability of improved techniques in the dairy industry, perinatal mortality and morbidity is still high in cattle, and the need for techniques suitable for monitoring fetal well-being is still growing (Kornmatitsuk et al., 2002). To investigate and decrease perinatal losses, the first step is to develop techniques suitable for evaluating fetal well-being under farm conditions. In human obstetrics, non-invasive transabdominal ultrasonography has been used for assessing fetal health status for almost forty years. From the 1980s, there were also attempts to develop antepartum assessment methods in veterinary medicine (Adams-Brendemuehl and Pipers, 1987;Reef et al., 1995Reef et al., , 1996. Reef's methodology has been used as a gold standard for late-term ultrasonographic examinations in horses and other species of domestic animals (Reef et al., 1995(Reef et al., , 1996.

The study was carried out in a Hungarian large-scale dairy farm during a 5-day period in hot August weather. Altogether 16 preweaning calves were chosen for the study. An agricultural mesh with 80% shielding was stretched over eight calf cages at 2 m from the ground to shield the cages in their entirety, while eight others were left unshaded. Ambient temperature and relative humidity were measured in 10 min intervals inside and outside one of the hutches in the shaded and unshaded groups during the total length of the study. The rectal temperature of the calves was measured by a digital thermometer every 4 h. Surface temperatures were measured on body parts, in the same intervals as rectal temperature with an infrared thermometer. Measuring sites included: the leg (metacarpus), muzzle, eye bulb, scapula, and ear. Statistical analyses were performed to assess the effects of shading on environmental and body temperatures and to also assess the strength of the association between core, skin and ambient temperatures; to estimate the temperature gradient between body shell and core; to compare the changes in heat dissipation capacity of the different body regions (as represented by temperatures of various sites) with increasing ambient temperature controlling for shaded or unshaded conditions; and to predict the risk of hyperthermia (rectal temperature not lower than 39.5°C) with the CART classification method. The average rectal temperatures suggest that the temperature conditions both in shaded and unshaded groups imposed a severe heat load on the calves. The temperature of the body shell, as represented by skin temperatures, shows a much more significant variation, similar to ambient temperature. As expected, areas that are closer to the core of the body (ear and eye) show less difference from rectal temperature and show a narrower range (lower variance), as more distal regions (leg, scapula) have a wider range. Body surface temperatures are more related to ambient temperature in calves than rectal temperature. The predictive value of infrared body surface temperatures for predicting heat stress or rectal temperature is low.

Parallel with the successful genetic selection for higher milk production in Holstein-Friesian cows, a dramatic decline in fertility rates has been observed around the world. Therefore, to achieve an optimum herd reproductive performance, we must focus on the first 100 days postpartum. During and after calving, a cow overcomes a series of physiological hurdles before becoming pregnant. By selecting accurate diagnostic devices and/or methods, such as predicting the onset of calving, monitoring activity and rumination time to determine cows for early treatment of clinical metritis and/or metabolic diseases, long-term measurement of reticuloruminal pH to monitor subclinical acidosis, perform metabolic profile tests to diagnose subclinical metabolic diseases at the herd level, estrous detectors and/or detection aids, on-farm/in-line P4 test to monitor specific events in the postpartum periods, diagnosis of early pregnancy and pregnancy loss using ultrasonography to correctly identify problems and their potential causes to enable these issues are to be rectified. Despite higher milk production, acceptable fertility results can be achieved, even on large-scale dairy farms, if the impacts of the above factors that contribute to reduced fertility can be moderated. The advantages and disadvantages of the different diagnostic methods are discussed to help the dairy select the most accurate method.