M. Van Kampen

Energy relationships in growing chickens given daily injections of corticosterone

The energetic efficiency of growing chickens given daily injections of corticosterone was investigated by measuring metabolic activity and energy balance. Water consumption increased significantly within the first day of treatment; food consumption increased by the third day of treatment. Growth rate, which was suppressed during the first two days, returned to normal by the third day of treatment. Excreted water, dry matter and uric acid increased within the first day of treatment. Heat production was not changed by treatment; however, the CO2:O2 respiratory ratio (RQ) was increased by the third day and exceeded 1.0 on days 4 and 5 of treatment. Leg muscle weight was decreased and abdominal fat and liver weight were increased by corticosterone treatment. Balance data indicated that energy absorption efficiency was decreased and energy retention efficiency was increased by corticosterone treatment, confirming the RQ and carcase findings that greater amounts of energy were stored as fat.

The phospholipase activity of Staphylococcus hyicus lipase strongly depends on a single Ser to Val mutation.

Site-directed mutagenesis and domain exchange were used to investigate the role of the C-terminal domains of Staphylococcus hyicus lipase (SHL) and S. aureus lipase (SAL) in substrate selectivity. The introduction of a single point mutation coding for the substitution of Val for Ser356 in SHL yields an enzyme which has retained full lipase activity, but with more than 12-fold lower phospholipase activity. Starting with this S356V variant of SHL the C-terminal 40 amino acids were replaced by the corresponding SAL sequence. Although 23 amino acid changes were introduced simultaneously the impact on the phospholipase/lipase activity ratio was only 4-fold. We therefore conclude that in the C-terminal domain it is Ser356 which mainly determines phospholipase activity. The introduction of a Val357 to Ser substitution in SAL did not turn SAL into a phospholipase, showing that residues from other domains contribute to this activity as well. The results are discussed in view of the sequence homology of lipases and (lyso)phospholipases.

Daily energy budgets of avian embryos: The paradox of the plateau phase in egg metabolic rate

The metabolic rate of precocial bird eggs reaches a plateau when about 80% of the incubation period has passed. This is unexpected, as in many species the embryo continues to grow and maintenance costs must therefore increase. To investigate this paradox, daily energy budgets were constructed for embryos of four galliform species according to two models that used empirical data on egg metabolic rate and embryo growth. In the first model, embryonic synthesis costs were estimated, with an assumed synthesis efficiency, before calculating the maintenance costs. In the second model, embryonic maintenance was calculated first, and no assumptions were made on the synthesis efficiency. The calculations show that assumptions of the synthesis efficiency had a major impact on the energy budget calculations, because embryonic growth rate was high. During the plateau phase, a galliform embryo allocated energy in favor of its maintenance costs in three ways: by decreasing growth rate, by increasing synthesis efficiency, and by depressing the formation of glycogen. Our study suggests that a reduction in growth rate plays a minor role. An increase of synthesis efficiency is more likely to explain the plateau in energy expenditure, since small increases in synthesis efficiency can lead to great savings on synthesis costs.

Cloning, purification and characterisation of Staphylococcus warneri lipase 2.

A gene encoding an extracellular lipase was identified in Staphylococcus warneri 863. The deduced lipase is organised as a prepro-protein and has significant similarity to other staphylococcal lipases. The mature part of the lipase was expressed with an N-terminal histidine tag in Escherichia coli, purified and biochemically characterised. The results show that the purified lipase (named SWL2) combines the properties of the staphylococcal lipases characterised so far. It has both a high preference for short chain substrates and surprisingly, it also displays phospholipase activity. Homology alignment was used to analyse sequence-function relationships of the staphylococcal lipase family with the aim to identify the structural basis underlying the different properties of the staphylococcal lipases.

Water balance of Colostomised and non‐Colostomised hens at different ambient temperatures

1. The quantities of water gained and lost, and hence the total water balance, were determined in normal and colostomised White Leghorn laying hens at ambient temperatures of 5, 20 and 35 °G. 2. In both groups the water intake and water loss at all temperatures were well balanced. 3. Water to food ratios and water content of excreta of normal hens increased with increasing temperature. 4. The wetter excreta at 35 °C are caused by an increased urine production and not by an increased water passage through the alimentary tract.

Occurrence and effects of PCBs, PCDDs and PCDFs in hatchlings of the common tern (Sterna hirundo)

Abstract From eight common tern (Sterna hirundo) colonies eggs were collected for laboratory incubation. Significant differences between colonies were found for yolk sac concentrations of polychlorinated biphenyls (PCBs), polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzo-p-dioxins (PCDDs). Corresponding differences were observed for hepatic EROD and PROD activities. No differences between the colonies were observed regarding embryonic O 2 CO 2 exchange, egg weight, eggshell thickness, hatchling weight or liver weight/body weight ratio. It is concluded that hepatic EROD activity is usable as a relative sensitive biochemical indicator for early exposure to planar halogenated polyaromatics in the early life stage of the common tern.

Effect of water : Food intake ratios in laying hens on food metabolisable energy

1. It has been hypothesised that a relatively high water intake results in a lower food digestibility. 2. The influence of water: food ratios on the metabolisability of a diet was investigated. 3. With ad libitum water and food the water :food ratios varied between 1.17 and 2.47 and showed a positive relationship with metabolisable energy. 4. In groups of hens receiving 40 g food and water sufficient to provide water: food ratios of 1, 2, 3 and 4, the results showed a non‐significant negative regression of apparent metabolisable energy with water:food ratios.

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.

The development of thermoregulation in turkey and guinea fowl hatchlings: similarities and differences

The development of thermoregulation was studied in turkeys (Meleagris gallopavo, 60.5 g) and guinea fowl (Numida meleagris, 33.5 g) from 2 to 24 h after hatching. Thermoregulation was measured at different ages during 1 h of cold exposure (20°C). Final body temperature rose linearly with age in turkeys, but reached a plateau in guinea fowl between 12 and 16 h. At 2 h after hatch final body temperature was highest in guinea fowl, while at 24 h after hatch there was no difference between the species. The development of mass-specific metabolic rate with age resembled the pattern of final body temperature. At 2 h post-hatch mass-specific metabolic rate was highest in guinea fowl; however, at 24 h post-hatch there was no difference between the species. since mass-specific metabolic rate reached a plateau in guinea fowl at 16 h. In turkeys mass-specific dry thermal conductance decreased with age initially, while in guinea fowl it remained stable. Nevertheless, at both 2 and 24 h after hatch mass-specific wet conductance did not differ significantly between the species. In turkeys mass-specific wet conductance increased initially. This increase in mass-specific wet conductance may be due to the rapid onset of feather growth in turkeys. The O2 consumption per breath doubled during the first 24 h in turkeys but remained stable in guine fowl. This suggests that at least two different developmental patterns of O2 intake exist within Galliformes. The results show that 2 h post-hatch the thermoregulatory ability was lowest in turkeys, despite their larger body mass. However, at 24 h post-hatch the difference between the species was not significant, because the thermoregulatory ability had increased more in turkeys.