Dik-dik Antelope Research Articles

Nitrogen metabolism and renal function in the dik-dik antelope ( Rhynchotragus kirkii)

Nitrogen metabolism and kidney function of the dik-dik antelope ( Rhynchotragus kirkii) were studied under a range of controlled, experimental conditions and diets. Dik-dik antelope remained in nitrogen balance even when fed a diet low in protein and high in fibre. When fed a diet high in protein (20%) and water ad-libitum, 55.3% of the urea filtered by the kidney was reabsorbed. Limiting water intake increased urea reabsorption to 77.2%. The U/P urea concentrations were maintained at similar ratios on all diets, as well as during dehydration and solute loading. Minimum endogenous nitrogen excreted was 74 mg/kg 0.75/day. Dehydration (water deprivation) and solute loading (intraruminal infusion of 0.25 M NaCl) had varying effects on nitrogen metabolism. It is concluded that the metabolic nitrogen economy of the dik-dik antelope is qualitatively similar to that of other domestic and wild ruminants.

Digestive efficiency in two small, wild ruminants: the dik-dik and suni antelopes

A comparative study, using six dik-dik and eight suni antelope, was undertaken to identify similarities and differences that may exist in the digestive process of these two small, East African ruminant browsers. The suni antelope was the more select feeder, preferring the native, Grewia sinilis leaves over that of lucerne hay. Daily forage consumption rate, per unity body weight, was greater in the dik-dik (40.4 g/kg) than for the suni (30.6 g/kg), while daily fluid intake was considerably less (i.e. dik-dik, 68 ml/kg versus suni, 106 ml/kg body weight). Rumen fermentation studies suggested that the suni antelope attained the more rapid rumen and caecal fermentation activities, when compared to the dik-dik antelope. The difference in ruminal and caecal digestive process of the two antelope is suggested to be partly the result of the dik-dik’s arid-adaptation strategies of less fluid intake and a more diverse (less selective) browse consumption, relative to the suni antelope.

The entrainment of breathing rhythm to stride frequency in the dik-dik antelope ( Rhynchotragus kirki) with observations on the thermoregulatory consequences

1. 1. Three adult dik-dik antelopes with an average weight of 4.5 kg were used to investigate the rate of oxygen consumption (V̇O 2) during exercise and the entrainment of respiratory rate with stride frequencies at running velocities between 2–11 km/hr. 2. 2. The results of V̇O 2 and the metabolic cost of horizontal locomotion were found to agree with what would be expected of an animal of this size. 3. 3. Respiratory frequencies recorded during the most strenuous exercise were approximately 50% below the value observed when dik-diks are exposed to an ambient temperature ( T a ) of 42°C. 4. 4. Respiratory evaporative heat loss was estimated to account for only 4% of the total heat production during exercise. 5. 5. Respiratory frequencies were found to be entrained quite strongly to stride frequencies. The thermoregulatory consequences of this entrainment is discussed.

Physiology of the dik-dik antelope

1. 1. The East African dik-dik antelope represents a miniature model ruminant for comparative studies. 2. 2. Dik-diks are browsers, consuming a diet consistently high in fermentable and digestable plant material. 3. 3. Their foregut structure is designed for a relatively rapid passage of food and effective absorption of fermentative products. 4. 4. Dik-dik antelopes are very economical in their use of water, having a low daily water exchange and excreting a highly concentrated urine. 5. 5. Dik-diks have been observed to employ three thermoregulatory mechanisms; thermopanting, active sweating and a labile body temperature. 6. 6. Their reproductive cycle is polyestrous with peak breeding in June and December, having a gestation period of between 170 and 174 days.

Studies on renal excretion of potassium in the dik-dik antelope

1. 1. In a study on the renal handling of potassium by the dik-dik antelope, plasma and urine samples were analysed for potassium, sodium and creatinine concentrations and osmolality during dehydration and intra-ruminal loading of potassium solutions. 2. 2. The fractional excretion of potassium was 0.64 during the control period and rose up to as high as 3. 2.3 during potassium loading. Urinary osmolality and potassium concentration decreased as the urine volume increased but the total amounts of potassium excreted were independent of urine volume. 4. 3. Potassium loading led to a steady increase in its urinary excretion but a decrease in plasma potassium concentration was observed. This observation casts doubt on the hypothesis that alterations in potassium intake produce parallel alterations in plasma potassium concentration (which supposedly stimulates or depresses potassium excretion) and thereby maintain potassium homeostasis. 5. 4. A possible alternative signal for increased potassium excretion following increased intake is discussed.

Renal excretion of urea in a small east african antelope, the dik-dik ( Rhynchotragus kirkii)

1. 1. A study on the renal handling of urea by the dik-dik antelope ( Rhynchotragus kirkii) was conducted. 2. 2. Plasma and urine samples were analysed for osmolality, urea and creatinine concentrations during dehydration and intra-ruminal loading of potassium and sodium solutions. 3. 3. The glomerular nitration rate (GFR) of the dik-dik was found to be 182.6 ± 11.7 ml/min/100 kg body mass. 4. 4. Dehydration was observed to increase tubular urea reabsorption and increase plasma and urine osmolalities, but had no effect on the amount of urea filtered at the glomerulus. 5. 5. Potassium loading increased both GFR and urine flow rate.

Metabolism and evaporative heat loss in the dik-dik antelope ( Rhynchotragus kirki)

1. 1. Under controlled conditions, the rate of oxygen consumption ( V ̇ O 2 ) respiratory frequency, evaporative water loss, heat balance, rectal ( T rec ) and surface temperatures were determined in the dik-dik antelopes at ambient temperatures ( T a ) ranging from 1 to 44°C. 2. 2. The thermal neutral zone was found to be between 24 and 35°C. 3. 3. Respiratory frequency ranged between 27 and 630 breaths/min. 4. 4. At a T a of 44°C, 95% of the heat produced by the dik-dik was lost via respiratory evaporation. Despite an increase in T rec , cutaneous evaporation did not increase. 5. 5. During panting, V ̇ O 2 increased in accordance with the expected Q 10 effect, contrary to earlier findings. 6. 6. Measurements of circadian rhythm [LD 12:12 (7–19) CT26°C] in V ̇ O 2 showed that the minimum .VO 2 (0.42ml O 2/g/hr) occurred at midnight while the maximum (0.78ml O 2/g/hr) occurred at midday. The 24 hr mean V ̇ O 2 was 0.61 ml O 2/g/hr. 7. 7. These measurements suggest that in nature, determinants other than light may be responsible for triggering the variations observed in V ̇ O 2 .

Salt excretion and saline drinking in the dik-dik antelope ( Rhynchotragus kirkii)

1. 1. The ability of the dik-dik antelope to survive while drinking saline solutions was tested in controlled laboratory experiments by providing drinking water containing up to 0.5 M NaCl. 2. 2. Fluid intake increased from 230.5 ml/day when fresh water was offered to a maximum of 373.9 ml/day when 0.3 M NaCl solution was offered. 3. 3. At concentrations higher than 0.3 M animals lost weight, were anorexic and developed diarrhoea. 4. 4. It is concluded that the dik-dik antelope will probably tolerate drinking water containing 0.24 M NaCl.

Thermoregulation and heat balance in the dik-dik antelope Rhynchotragus kirki: A field and laboratory study

1. 1. Experiments were conducted in the field to study the physiological responses of dik-dik antelope to direct solar radiation and shade. The results were compared to those obtained in the laboratory. 2. 2. The rates of metabolic heat production when the animals were exposed either to the sun or the shade were identical. 3. 3. Dik-dik antelopes lost about 50% more heat evaporatively when exposed to the sun compared to the shade at an ambient temperature ( T a,) of 28°C or a 7, of 40°C in a climatic chamber. 4. 4. Heat storage in the laboratory at 7, 40°C or at 7, 28°C in the shade accounted for between 30 and 35% of the total heat production. The corresponding value in the sun was 55%. 5. 5. The net rate of heat gain under the sun was four times greater than under shade at 28°C or in the laboratory at 40°C. 6. 6. Behavioural mechanisms for avoidance of high insolation must constitute important adaptations that the dik-dik uses to avoid dehydration and dependence on drinking water in their natural environment.

The design and the role of the nasal passages in temperature regulation in the dik-dik antilope ( Rhynchotragus kirki) with observations on the carotid rete

Exhaled air temperatures (Tex) and rectal temperatures (Trec) were measured in five dik-dik antelopes under controlled environmental temperatures (Ta)_between 15 and 40 °C. In addition morphometric analysis of the nasal passages, gross and histological identification of the carotid rete were carried out in an attempt to illustrate a possible brain cooling system in this small ungulate. Below Ta of 30 °C, Tex decreased with decreasing Ta leading to the establishment of a temperature gradient of about 20 °C between Ta and Trec at a Ta of around 15 °C. At Ta of 30 °C Tex was approximately half a degree lower than the Trec. Gross and histological studies revealed the presence of carotid rete and profuse vascularisation of the nasal turbinates. Morphometric analysis established a mean volume density of the nasal passages (np) in the splanchnocranium (sp) (V V(np,sp)), surface density (S V(np,sp)) and harmonic mean width of the nasal passages (W) of 9.5%, 2.15 cm 2/cm 3 and 1.23 mm, respectively. Combined physiological and anatomical measurements suggest that the dik-dik possess an efficinet brain cooling and water conserving system. The design of the upper respiratory system in these antelopes may help these animals to tolerate the extremes of temperatures and insolation encountered in their habitat.

Changes in thyroxine, triiodothyronine and metabolic rate in the dik-dik antelope (Rhynchotragus kirkii): effects of temperature and dehydration

1. Changes in plasma total thyroxine, triiodothyronine (T3) and metabolic rate were investigated in both hydrated and dehydrated dik-diks after prolonged exposure to ambient temperatures (Ta) of 25°C, 35°C and 15°C. 2. AtTa of 25°C, metabolic rate, T3 and T4 were 2.58 W·kg−1, 56.3 ng ml−1 and 0.93 ng ml−1 for the hydrated group, and 1.95 W·kg−1, 70.0 ng ml−1 and 0.85 ng ml−1 for the dehydrated group, respectively. 3. Exposure to 15°C increased metabolic rate and total hormonal concentrations in both groups. 4. Following dehydration and exposure toTa of 35°C a significant decrease in metabolic rate occurred in the presence of a significant increase in both T3 and T4 concentrations. 5. Levels of total plasma T3 and T4 alone are unlikely to be responsible for the decrease in metabolic rate observed in the dehydrated dik-dik antelopes.

The relationship between rate of oxygen consumption, heart rate and thermal conductance of the dik-dik antelope ( Rhynchotragus kirkii) at various ambient temperatures

1. 1. The extent of cardiovascular adjustments to heat and cold were investigated between ambient temperatures of 5 and 45°C by measuring conductance and the rates of oxygen consumption and heart beats. 2. 2. Minimum heart rate was observed at 25°C (114 ± 9 beats/min). In the heat at 45°C heart rate was observed to increase only slightly (127 ± 12 beats/min) but in the cold − 5°C heart rate nearly doubled that at 25°C. 3. 3. Thermal conductance was on average 0.031 mlO 2 (g.hr.°C) −1 below 25°C but increased by more than 20 times at 40°C. 4. 4. A positive correlation between heart rate and rate of oxygen consumption was demonstrated below 25°C and the relation may be of practical use.

The effects of dehydration on electrolyte concentrations and water content along the large intestine of a small ruminant: The Dik-dik antelope

1. The concentrations of Na, K, and Cl and the water content in the large intestine and rectum of an East African ruminant, the Dik-dik antelope, was investigated in hydrated and dehydrated animals. 2. Intestinal contents were removed at six sites along the large intestine and rectum, and the water fraction and the amounts of Na, K, and Cl were measured per g dry matter. An impermeant water marker showed that the dry matter amount was nearly constant along the lower gut. Local electrolyte absorption rates were determined in the terminal colon by a dialysis bag method. 3. Approximately 4/5 of the absorption of NaCl and H2O took place in the upper large intestine. Throughout the lower gut the Na concentration of the absorbate was close to that of plasma. The Na and Cl concentrations of the digesta decreased aborally while the K concentration rose, but K was still absorbed. 4. Dehydration resulted in a reduction of 35% of the water lost per gram dry faeces. The water content was reduced from the start of the large intestine (by 13%), but the fractional absorption of salt and water in the large intestine and rectum was not significantly changed. The local electrolyte absorption rates and the electrical potential difference were slightly reduced. The Na and K concentrations of the absorbate remained nearly constant. The water saving during dehydration thus seems to proceed without specific adjustments of the transport parameters of the lower gut. The concentrations of Na and Cl in faeces approach those which in dialysis bag experiments result in zero absorption rates. This explains the constant fractional absorption of NaCl and water in the lower gut at different flow rates of dry matter. 5. Animals shot in the field were not dehydrated, but more Na-depleted than those studied in captivity. They had a pronounced net K absorption in the lower gut.

Some aspects of salt and water balance of feral goats from arid islands.

ARTICLESSome aspects of salt and water balance of feral goats from arid islandsWA DunsonWA DunsonPublished Online:01 Mar 1974https://doi.org/10.1152/ajplegacy.1974.226.3.662MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByPreference and discrimination behaviour of llamas to saline drinking waterSmall Ruminant Research, Vol. 207Boer goats physiology adaptation to saline drinking waterResearch in Veterinary Science, Vol. 129Rumen function in goats, an example of adaptive capacity17 February 2020 | Journal of Dairy Research, Vol. 38Oxygen isotopes in bioarchaeology: Principles and applications, challenges and opportunitiesEarth-Science Reviews, Vol. 188Adaptation capacity of Boer goats to saline drinking waterAnimal, Vol. 13, No. 10Effects of drinking saline water on food and water intake, blood and urine electrolytes and biochemical and haematological parameters in goats: a preliminary studyAnimal Production Science, Vol. 58, No. 10Oxygen (δ18O) and carbon (δ13C) isotopic distinction in sequentially sampled tooth enamel of co-localized wild and domesticated caprines: Complications to establishing seasonality and mobility in herbivoresPalaeogeography, Palaeoclimatology, Palaeoecology, Vol. 485Effects of level of brackish water on feed intake, digestion, heat energy, and blood constituents of growing Boer and Spanish goat wethers1Journal of Animal Science, Vol. 94, No. 9Metabolic rates of three gazelle species (Nanger soemmerringii, Gazella gazella, Gazella spekei) adapted to arid habitatsMammalian Biology, Vol. 80, No. 5Biology and Impacts of Pacific Island Invasive Species. 9. Capra hircus , the Feral Goat (Mammalia: Bovidae)Pacific Science, Vol. 67, No. 2Evolutionary adaptations of ruminants and their potential relevance for modern production systemsAnimal, Vol. 4, No. 7Renal structural flexibility in response to environmental water stress in feral hogsJournal of Experimental Zoology, Vol. 247, No. 3Salt excretion and saline drinking in the dik-dik antelope (Rhynchotragus kirkii)Comparative Biochemistry and Physiology Part A: Physiology, Vol. 88, No. 2Urinary concentrating capacity of Rattus rattus and other mammals from the lower florida keysComparative Biochemistry and Physiology Part A: Physiology, Vol. 71, No. 1Untersuchungen an den Nieren von Wild- und Hausschweinen26 April 2010 | Zeitschrift für Tierzüchtung und Züchtungsbiologie, Vol. 93, No. 1-4 More from this issue > Volume 226Issue 3March 1974Pages 662-669 Copyright & PermissionsCopyright © 1974 by American Physiological Societyhttps://doi.org/10.1152/ajplegacy.1974.226.3.662PubMed4817419History Published online 1 March 1974 Published in print 1 March 1974 Metrics

Thermoregulation and heat balance of the East African eland and hartebeest.

Thermoregulation and heat balance of the East African eland and hartebeest.

Metabolic rate of camels: effect of body temperature and dehydration.

Metabolic rate of camels: effect of body temperature and dehydration.

Description of a new Dik‐dik Antelope (Madoqua) discovered in N.E. Africa by Mr. H. S. H. Cavendish.

Description of a new Dik‐dik Antelope (Madoqua) discovered in N.E. Africa by Mr. H. S. H. Cavendish.