Responses of the reproductive vascular system during the egg‐formation cycle of unanaesthetised laying hens

1. Vascular adjustments to the process of egg formation were examined in the unanaesthetised laying hen, by the radioactive microspheres method.

2. Three‐ to four‐fold increases in blood flow were found in segments surrounding the egg during its passage along the oviduct, possibly due to an enhanced metabolic activity in the muscle layer of the oviduct.

3. Shell‐gland blood flow was minimal in the absence of an egg and increased gradually to a maximum (5‐fold) about 5 h after entrance of the egg into the shell gland. This parallels the rate of calcification of the egg shell.

4. Changes in blood flow in the ovarian follicles and other parts of the oviduct were small while the egg was in the shell gland. This might be typical for the reproductive system of the fowl, which undergoes little structural alteration during egg formation.     

The thermoneutral temperature zone and seasonal acclimatisation in the hen

1. Oxygen consumption, body temperature, respiratory frequency and respiratory water loss of White Leghorn x Rhode Island hens were measured for short periods at six air temperatures between 2 and 32 °C. The hens were kept between tests in an open shed. The experiments were carried out over 3 years.

2. The upper critical temperature (Tcu) was estimated by the air temperature at which: 1, respiratory frequency increased above 60 respirations/min and 2, body temperature increased by 0.3 °C above that at the lower critical temperature. These responses to the test temperatures were examined as a function of the. acclimatisation temperature (Ta) represented by the mean daily temperature during experimental periods.

3. A seasonal change in Tcu was observed, which correlated with Ta(r = 0.836). The seasonal 10 °C change in the Ta brought about a 3 °C change in Tcu, compared with an 8.5 °C change in the lower critical temperature.

4. Thermoneutral temperature zone decreased with increasing Ta; the two critical temperatures tended to merge at a Ta of 32 °C. The latter probably represents an upper limit for acclimatisation to heat.     

Development of a robotic detection system for greenhouse pepper plant diseases

Automation of disease detection and monitoring can facilitate targeted and timely disease control, which can lead to increased yield, improved crop quality and reduction in the quantity of applied pesticides. Further advantages are reduced production costs, reduced exposure to pesticides for farm workers and inspectors and increased sustainability. Symptoms are unique for each disease and crop, and each plant may suffer from multiple threats. Thus, a dedicated integrated disease-detection system and algorithms are required. The development of such a robotic detection system for two major threats of bell pepper plants: powdery mildew (PM) and Tomato spotted wilt virus (TSWV), is presented. Detection algorithms were developed based on principal component analysis using RGB and multispectral NIR-R-G sensors. High accuracy was obtained for pixel classification as diseased or healthy, for both diseases, using RGB imagery (PM: 95%, TSWV: 90%). NIR-R-G multispectral imagery yielded low classification accuracy (PM: 80%, TSWV: 61%). Accordingly, the final sensing apparatus was composed of a RGB sensor and a single-laser-beam distance sensor. A relatively fast cycle time (average 26.7 s per plant) operation cycle for detection of the two diseases was developed and tested. The cycle time was mainly influenced by sub-tasks requiring motion of the manipulator. Among these tasks, the most demanding were the determination of the required detection position and orientation. The time for task completion may be reduced by increasing the robotic work volume and by improving the algorithm for determining position and orientation.     

Angiotensin Converting Enzyme in Bovine Ovarian Follicular Fluid and its Relationship with Oestradiol and Progesterone

The purpose of the present study was to identify angiotensin converting enzyme (ACE) in bovine ovarian follicular fluid and to relate the ACE activity to the phase of the oestrous cycle, pregnancy, and the follicular fluid concentrations of oestradiol and progesterone. The ACE activity was similar to that found in bovine serum and was completely inhibited by the specific ACE inhibitor captopril. The 50% inhibitory concentration (IC₅₀) was 1.4 × 10^?8 mol/l (range 0.8 × 10^?8 to 5.0 × 10^?8 mol/l; n=6), which is similar to that found in bovine and human serum. The ACE activity did not differ in the pre‐ovulatory and luteal phase, pregnancy or cystic follicles. It correlated with the follicular fluid concentration of progesterone in cycling cows (ρ=0.476; p < 0.005; n=36), but did not correlate with the diameter of the follicles, the follicular fluid concentration of oestradiol or the ratio between the oestradiol and progesterone concentrations. The demonstration of ACE in bovine ovarian follicular fluid provides further evidence for the presence of a local renin–angiotensin system in the bovine ovary.     

Homoeothermy and growth rate in the fowl

Observations on growth rates and diurnal changes in colonic temperatures were made on seven groups of 30 to 50 White Plymouth Rock x Cornish chicks aged between 6 and 8 weeks. Ambient air temperature ranged from 22 °C to 35 °C.

Colonic temperatures in the morning (08.00 to 09.00 h) and growth rates were within the normal range. A slight hyperthermia was evident from 13.00 to 14.00 h.

Morning colonic temperatures were not correlated with the later increments in body temperatures. This suggests that the set‐point temperature for thermo‐regulatory control differs between individuals.

Growth rates were not correlated with the morning colonic temperature, except in one group; they were, however, significantly correlated with the diurnal fluctuation in colonic temperature in all groups. These results suggest that the maintenance of a constant body temperature is essential for a normal growth rate.

The variation in thermoregulatory ability accounted for 31 to 71% of the total variation in growth rate.     

Estimates of heat stress relief needs for Holstein dairy cows

Estimates of environmental heat stress are required for heat stress relief measures in cattle. Heat stress is commonly assessed by the temperature-humidity index (THI), the sum of dry and wet bulb temperatures. The THI does not include an interaction between temperature and humidity, although evaporative heat loss increases with rising air temperature. Coat, air velocity, and radiation effects also are not accounted for in the THI. The Holstein dairy cow is the primary target of heat stress relief, followed by feedlot cattle. Heat stress may be estimated for a variety of conditions by thermal balance models. The models consist of animal-specific data (BW, metabolic heat production, tissue and coat insulation, skin water loss, coat depth, and minimal and maximal tidal volumes) and of general heat exchange equations. A thermal balance simulation model was modified to adapt it for Holstein cows by using Holstein data for the animal characteristics in the model, and was validated by comparing its outputs to experimental data. Model outputs include radiant, convective, skin evaporative, respiratory heat loss and rate of change of body temperature. Effects of milk production (35 and 45 kg/d), hair coat depth (3 and 6 mm), air temperature (20 to 45 degrees C), air velocity (0.2 to 2.0 m/s), air humidity (0.8 to 3.9 kPa), and exposed body surface (100, 75, and 50%) on thermal balance outputs were examined. Environmental conditions at which respiratory heat loss attained approximately 50% of its maximal value were defined as thresholds for intermediate heat stress. Air velocity increased and humidity significantly decreased threshold temperatures, particularly at higher coat depth. The effect of air velocity was amplified at high humidity. Increasing milk production from 35 to 45 kg/d decreased threshold temperature by 5 degrees C. In the lying cow, the lower air velocity in the proximity of body surface and the smaller exposed surface markedly decrease threshold temperature. The large variation in thresholds due to environmental and animal factors justifies the use of thermal balance-based indices for estimating heat stress. Such an approach may make possible estimates of threshold temperatures at which heat stress relief is required for widely different cattle types and environmental situations.     

Epizootiologic Studies Of Shipping Fever: II. Exposure Of Calves To Pasteurellae and Para-lnfluenza 3 Virus

In four trials, the exposure of six calves to various stressors and an aerosol of pasteurellae did not evoke significant responses. In ten trials, 20 calves were exposed by aerosol or intratracheal injection to myxovirus para-influenza 3 (PI3) alone or combined with pasteurellae. A respiratory syndrome similar to that observed in mild cases of shipping fever was regularly reproduced in calves which had low serum hemagglutination titers to PI3. One calf developed a severe bronchopneumonia, was killed and the virus was reisolated from its lungs. Exposure to P13 plus pasteurellae usually resulted in an increased nasal discharge. The stressors employed in a few trials did not significantly alter the response.