Sadaki Yamamoto

Diurnal patterns of heat production and heart rate under thermoneutral conditions in Holstein Friesian cows differing in milk production

SUMMARY Ten dairy cows were allocated into three groups according to milk productivity (four high, four intermediate and two dry cows, respectively). Heat production and heart rate, but not rectal temperature, were significantly different (P < 005) between groups. Heat production increased during feeding in the morning and in the afternoon and reached a peak 3 h later. Minimum heat production was observed in the early morning before feeding. The diurnal pattern for heart rate reflected that of heat production. These results suggest that cooling dairy cows during hot summer days is most effective at feeding time and 3 h afterwards.

Effects of environmental temperature on heat production associated with food intake and on abdominal temperature in laying hens

An experiment was carried out to verify the relationship between the heat production associated with food intake and environmental temperature. Four laying hens were trained to eat two meals per day and were kept under artificial illumination with dark, dim and light periods. 2. Metabolic heat production was measured using two open-circuit respiratory chambers. Abdominal temperatures were measured, using thermocouples, at environmental temperatures of 12, 16, 20, 24, 28, 32 and 36 degrees C and at food intakes of 90, 60, 30 and 0 g/d. 3. The rate of heat production was dependent on both environmental temperature and food intake. Increasing environmental temperature resulted in a decrease in total metabolic rate at any food intake, indicating that heat production associated with food intake was not directly linked with thermoregulation at low environmental temperatures. 4. Abdominal temperature varied little with either food intake or environmental temperature below 28 degrees C. Above 28 degrees C, abdominal temperature increased with both environmental temperature and quantity of food, indicating that the heat production associated with food intake adds to the heat load at high environmental temperatures. 5. Both heat production and abdominal temperature declined with decreasing light intensity and increased before feeding time. These effects were considered to result from changes in physical activity.

Effects of environmental temperature and heat production due to food intake on abdominal temperature, shank skin temperature and respiration rate of broilers

1. Eight broilers were used to determine the effects of environmental temperature and the increased heat production attributable to food intake on thermoregulatory physiological responses. Heat production, abdominal temperature, shank skin temperature and respiration rate were measured. 2. Heat production rose with increase in food intake and environmental temperature. Abdominal temperature, shank skin temperature and respiration rate also increased but, at 36 degrees C, there was no difference in respiration rate between the different rates of food intake after exposure for 1 h. Also, heat production decreased with exposure time when the birds were exposed to 28 degrees C and 32 degrees C, but increased at 36 degrees C ambient temperature. 3. Although the effect of the increased heat production on thermoregulatory physiological responses was not greater than that of environmental temperature, the increase in heat production enhanced the effect of ambient temperature on thermoregulatory physiological responses. However, with increasing heat production, the greatest response in shank skin temperature was at 28 degrees C, in respiration rate at 32 degrees C and in abdominal temperature at 36 degrees C. 4. These results suggest that, at high environmental temperatures, arranging feeding management to restrict the increase in heat production may alleviate the effect of environmental temperature.

Diurnal variation in heat production related to some physical activities in laying hens

1. Heat production, standing and eating activities, and hourly food intake of 4 laying hens were observed simultaneously and the effects of activity and food intake on heat production were studied. 2. Average heat production during the dark period (20.00 to 06.00 h) was 18.9 kJ/kgW0.75 h which was 33% lower than that during the light period. About 76% of the light-dark difference in the rate of heat production was probably associated with activity and posture. 3. Standing time, which included a range of behavioural activities, occupied 90% of the light period and the increased rate of heat production associated with standing was estimated to be about 18% of daily heat production. 4. Eating time occupied 40% of the light period; the heat production associated with eating activity represented about 5% of daily heat production or 3% of ME intake. 5. Because the regression of heat production on time spent eating agreed with the regression of heat production on hourly food intake, it is suggested that the energy expenditure associated with ad libitum feeding can be estimated for hens from the regression of heat production on hourly food intake.

Thermoregulatory responses and blood viscosity in dehydrated heat-exposed broilers (Gallus domesticus)

Abstract This study was to elucidate thermoregulation in dehydrated heat-exposed broilers. When broilers were dehydrated, heat production (HP), comb surface temperature (Tcs) and respiration rate (RR) decreased significantly. Conversely, rectal (Tr) and back skin (Tbs) temperatures, whole blood viscosity (WBV), haematocrit (HCT), plasma protein concentration (PPC) and plasma osmolality (PO) increased. During heat exposure, HP, WBV, HCT and PPC decreased significantly, while Tr, Tcs, Tbs and RR increased. The onset of panting against rectal temperature was delayed in dehydrated birds. These results suggest that dehydration leads to a lower blood volume, resulting in a decrease in blood flow to heat exchange organs and surfaces in broilers. This induces a lower sensible heat loss from extremities, a lower evaporative heat loss and a higher sensible heat loss from trunk, subsequent to regulate their body temperature at a higher level of deep body temperature.

Distribution of body fluid and change of blood viscosity in broilers (Gallus domesticus) under high temperature exposure

Abstract This study was to observe the distribution of body fluid by measuring blood volume, extracellular and intracellular fluid volumes and total body water under heat exposure, in order to clarify the mechanism of decrease in whole blood viscosity of the heat-exposed broilers. Whole blood viscosity, haematocrit, plasma protein concentration, plasma osmolality and extracellular fluid volume decreased during high temperature exposure, while plasma and blood volumes increased. No significant changes were found in both intracellular fluid volume and total body water between thermoneutral and high temperature exposure. These results indicate the decreased whole blood viscosity is induced by a plasma volume expansion, in which water may come from the interstitial space and alimentary tract, under heat exposure.

Use of limited daily access to food in measuring the heat production associated with food intake in laying hens.

1. Two experiments were carried out to determine the heat production associated with food intake in laying hens allowed access to food for one (experiment 2) or two hours (experiment 1) daily. 2. In experiment 1, heat production in the fed state was measured for two successive days after 46 h of food deprivation. The rate of heat production in the fasting state was measured from 47 to 69 h after feeding. 3. In experiment 2, heat production was measured at 4 fixed food intakes: 100, 70, 40 and 0 g/bird. Heat production associated with food intake, eating activity, net availability of ME and maintenance ME requirement was estimated. 4. Heat production after 46 h of food deprivation did not differ from that after 22 h of deprivation. In the hens receiving 100 g of food, heat production reached the pre-feeding level by 20 h after eating; the hens with lower food intakes reached the pre-feeding level more rapidly. It is suggested that the heat production associated with feeding had been eliminated by 22 h after eating. 5. Heat production associated with feeding was 16% of ME intake. Because the total energy cost of eating activity was only 0.8% of ME intake, the heat production associated with food intake in the limited-access hens came mainly from the effects of digestion, absorption and metabolism of the ingesta. 6. The net availability of ME was estimated to be 0.84. The estimated maintenance ME requirement was 569.6 kJ/kgW0.75 d.

Effects of heat production attributable to forced walking on thermoregulatory physiological responses of chickens in a warm environment.

1. To determine the effects of heat production on thermoregulatory physiological responses, 5 chickens were forced to walk to increase heat production. The study consisted of two experiments. One involved 3 walking speeds (8, 16 and 24 m/min) at 25 degrees C ambient temperature. The other involved a single walking speed of 16 m/min at 3 ambient temperatures (20, 25 and 30 degrees C). Heat production, heart rate, abdominal temperature, shank skin temperature and respiration rate were measured before, during and after walking. 2. Heat production, heart rate and respiration rate increased abruptly after the start of walking and with increase in walking speed. At the start of walking, an abrupt increase in abdominal temperature occurred independently of walking speed and environmental temperature; then, as walking continued, abdominal temperature increased further with increasing walking speed and increasing environmental temperature. Shank skin temperature declined at the initiation of walking, then increased. 3. Heat production and heart rate recovered rapidly after walking, while shank skin temperature and respiration rate increased and then recovered, except at 30 degrees C. 4. A proportion, 17% to 35%, of the increased heat production was stored, increasing body temperature during walking. After walking, the stored heat was lost by means of panting until abdominal temperature recovered to 41 degrees C or shank skin temperature recovered to 37 degrees C. 5. These results suggest that the greatly-increased heat production attributable to forced walking leads to abrupt thermoregulatory physiological responses, and the heat stored in the body is actively dissipated by panting until abdominal temperature recovers to the pre-walking level. The chief mode of heat loss of birds changes with deep body temperature.

産卵鶏の体温,呼吸数,心拍数ならびに血漿中の脂質,蛋白質およびグルコース濃度に及ぼす短期暑熱感作の影響

Feed intake levels, physiological response and plasma substrate concentration were measured to assess the effect of heat on substrate metabolism during physiological acclimation for heat balance over a three-day period of heat exposure and/or feed reduction in laying hens. 1) Decreased daily feed intake on the 1st day of heat exposure assumed a definite level on the 3rd day of heat exposure. 2) Body temperature and respiration rate attained maximum levels on the 1st day of heat exposure, and then steadily declined during heat exposure. Heart rate was slightly low during heat exposure. 3) Plasma concentrations of uric acid, cholesterol ester, phospholipid and β-lipoprotein showed low levels during heat exposure and/or even following heat exposure. The decrease in these concentrations appeared higher during heat exposure than feed reduction. Thus possibly, changes in plasma lipid and/or protein metabolism due to heat, regardless of reduction in feed intake, may accompany physiological acclimation for heat balance during a period of heat exposure. Jpn. J. Zootech. Sci., 61 (8): 707-713, 1990

Effects of Environmental Temperature on Egg Production, Food Intake and Water Consumption in Laying White Leghorns

白レグ産卵鶏15羽(1年鶏10羽,2年鶏5羽)を供試し,産卵鶏の産卵,採食,飲水におよぼす環境温度(25～35℃,2.5℃間隔,各温度感作10～15日)の影響を,環境調節室内で実験し,次の知見を得た. 1) 採食量は温度上昇と共に減少し,25～35℃において,温度1℃あたりの減少率は1.6%であった.飲水量は温度上昇と共に増加し,摂取飼料1gあたりの飯水量も急激に増加し,30℃で25℃の1.5倍,32.5℃で2倍,35℃で3倍に達した. 2) 産卵率は35℃において73%と最低で,一日あたりの卵生産量も最低であったが,飼料消費あたりの産卵効率は61%と最高であった. 3) 破卵,軟卵をのぞいた正常卵の生産効率は,32.5℃において53%と最高で,一方35℃においては42%であった.35℃では,破卵,軟卵の出現率が31%にも達した.32.5℃では25℃を基準にした場合,15%の卵生産効率の増加がみられ,この点について考察した.