Effects of training on Na, K-ATPase contents in skeletal muscle and K homeostasis of African draught bulls and cows.

In semiarid parts of Africa animal traction is still one of the most reliable sources for rural work power. However, draught animals have to produce most of their work power at an unfavourable moment of the year that is at the end of the dry season when feedlot is scare. To improve their condition prior to the planting season, a short training could help. The effect of training can be expressed by the changes in contents of Na(+), K(+)-pumps in the muscle cell membrane. After a training period of 15 days all cattle showed a mean increase in Na(+), K(+)-ATPase of 24% (P < 0.01) in the semitendinosus muscle of the hind leg, whereas the control group showed no change. Bulls demonstrated already after 8 days of training an increase of 20% (P < 0.05). The principal factor responsible for this up-regulation of the Na(+), K(+)-pumps is most probably the excitation of muscles during exercise. In the course of the 15 days training period, the surge of plasma K(+) in during exercise showed a tendency to decrease, but this was not significant. Nevertheless, the reduced elevations of plasma [K(+)] may delay the moment of fatigue and so improve endurance. In conclusion, a training period of 8-15 days improves the contents of Na(+), K(+)-pumps and so the possible work output of draught cattle.

Preliminary studies on the concentration of Na+,K(+)-ATPase in skeletal muscle of draught cattle in Mozambique: effect of sex, age and training.

The effect of training on the potential for work in draught cattle was assessed by measuring the Na+,K(+)-ATPase in the muscle cell membrane and the elevation in the concentration of K+ in plasma during exercise. Biopsies of the semitendinosus muscle and venous blood samples were taken from the cattle used for draught work in Mozambique. No differences were found in the plasma ion or Na+,K(+)-ATPase concentrations in samples taken from Nguni, Africander and Angoni breeds. There were no significant differences in plasma ions (Na+,K+ and Cl-) or muscle Na+,K(+)-ATPase concentrations between the Angoni males and females, although the males showed an increase in Na+,K(+)-ATPase with age, while the females showed a decrease. The increase in males might be attributed to their higher level of activity in the herds than that of females. After a training period of 15 days, a significant increase in Na+,K(+)-ATPase concentration in semitendinosus muscle was found in Angoni cattle. In females, this was significant after 8 days of training (about 30%); in males after 15 days of training (about 16%). On day 15, there was a reduction in the elevation of plasma K+ during the 2 h of draught work, indicating an increased capacity of the Na+,K+ pumps to maintain the extracellular K+ concentration in working muscles and a possible delay in the moment of fatigue.

Artificial incubation of Muscovy duck eggs: why some eggs hatch and others do not.

This study was designed to gain insight into the influence of spraying and cooling, during artificial incubation, on the embryo metabolic rate and hatching ability of Muscovy duck eggs. Three times a week 93 incubated eggs were sprayed and cooled for 0.5 h at room temperature. Daily embryo metabolic rate was measured in 30 eggs with a water vapor conductance ranging from 1.15 to 2.07 mg/day-kPa. Egg weight ranged from 63.73 to 84.52 g; length and breadth ranged from 59.6 to 66.4 mm and 43.2 to 48.2 mm, respectively. According to observed hatching ability, eggs were classified by three categories: eggs that hatched normally; eggs that were assisted during hatching, and nonhatched eggs. Five ducklings were assisted during hatching. Four ducklings died on Day 31, two on Day 32, and two on Day 34. Two functions were derived by discriminant analysis and accounted for 100% of the variation among the three categories of hatching ability. Collectively, these functions were able to classify 93.3% of the eggs in the correct hatching category. Egg length and metabolic rate at Days 21 and 28 of incubation were the most important predictor variables of the two functions. The results obtained in the present study indicate that an incubation temperature of 37.5 C with spraying and cooling seems to be beneficial for larger eggs.

Breeding biology of Muscovy duck Cairina moschata in natural incubation: the effect of nesting behavior on hatchability.

A breeding biology study of a genetically unselected variety of Muscovy duck Cairina moschata was conducted in an experimental duck unit in Maputo, Mozambique (25 degrees 58' S, 32 degrees 35' E), to gain insight into factors affecting hatchability during natural incubation. Nesting and incubation behaviors were recorded by daily nest visits. Of 1,338 nests investigated, 70% were incubated until hatching. In 23% of the incubated nests, eggs were laid by more than one duck in the same nest, indicated as dump nests. Artificial dump nests (15% of the incubated nests) were created by adding eggs (690 eggs) from nests abandoned by the duck before incubation had started. A total of 37% of the incubated nests contained eggs that were laid after the onset of incubation (nonterm eggs). Similar hatching rate was found between ducks raised in parks with or without access to swimming water. No significant difference was found in hatchability between normal (0.76) and dump nests (0.77). Artificial dump nests showed higher hatching rates than nests containing nonterm eggs. Dump nesting appears to be a reproductive strategy used by the Muscovy duck to enhance duckling production. Hatching rate was strongly influenced by the length of laying period (period between the ovoposition of the first egg until the onset of incubation) and reproduction cycle (laying period and incubation period). Hatchability was higher for clutches with a shorter reproduction cycle. It is concluded that nesting behavior of the domesticated Muscovy duck is similar to that of its wild ancestor.

Food restriction and development of thermoregulation in Muscovy ducklings (Cairina moschata).

1. The interaction between the effects of food restriction and cold stress on the development of body temperature, homeothermy index, metabolic rate and body weight were studied in Muscovy ducklings from hatching to 21 d of age. 2. The control group (ad libitum fed) and the food restricted group (fed to zero growth rate for 9 d) both became homeothermic when they were 2 d old with moderate (10 degrees C) cold stress. At severe cold stress (0 degrees C) the control group was homeothermic 5 days after hatching. However the food restricted group did not reach homeothermy at 0 degrees C and showed a large decrease (to hatching level) in homeothermy index at 10 degrees C and 0 degrees C after 9 d of food restriction. 3. Body temperature was lower in the food-restricted group during restriction and increased by 1 degree C after 24 h of ad libitum feeding. During food restriction, resting metabolic rate did not increase with age and was lower than the basal and existence metabolic rate predicted by Aschoff and Pohl (1970) and Kendeigh (1970) respectively. 4. The ratio of metabolisable energy (ME) intake to resting metabolic rate was 3 times lower in the food-restricted group than in the control group (0.09 and 0.27 respectively) on day 9. The availability of ME was more important than age for the development of thermoregulation in Muscovy ducklings. It is concluded that small improvements in the feeding regimen of young ducklings enhance the endurance and consequently reduce mortality from to environmental cold stress in a scavenger poultry system.

Predictions of normal forced vital capacity and forced expired volume in one second in Tanzanian children.

Data on ventilatory function with particular reference to forced vital capacity (FVC), forced expired volume in one second (FEV1), and FEV1 expressed as percentage of FVC (FEV1%FVC) were obtained in 1413 healthy Tanzanian school children aged between 8 and 18 years. All subjects were nonsmokers and had neither symptoms nor history of cardiopulmonary diseases. Subjects in this study were significantly smaller in stature (P less than 0.05) and had smaller FVC and FEV1 (P less than 0.001) compared to values reported in children of comparable age and stature in the west. Lung volumes could best be described as a power function of standing height (y = a.Hb). The power derived from ln FVC on ln H were 3.39 and 3.24 for boys and girls respectively, while the power derived from ln FEV1 on ln H were 3.11 and 3.03 for boys and girls respectively. Constructed prediction formulae gave FEV1 and FVC which showed good agreement with FEV1 and FVC computed from prediction equations based on a similar mathematical model for black children in the Caribbean.