The effects of laying cycle upon the blood pH, blood gases and other
Transkript
The effects of laying cycle upon the blood pH, blood gases and other
The effects of laying cycle upon the blood pH, blood gases and other related parameters in geese B. KARADEMIR1*, I. KAYA2, O. UCAR3 and G. KARADEMIR4 1 Department of Internal Medicine, Faculty of Veterinary Medicine, Kafkas University, Kars-Turkey Department of Animal Nutrition and Nutritional Diseases, Faculty of Veterinary Medicine, Kafkas University, Kars-Turkey Department of Reproduction and Artificial Insemination, Faculty of Veterinary Medicine, Kafkas University, Kars-Turkey 4 Department of Animal Nutrition and Nutritional Diseases, Institute of Health Sciences, Kafkas University, Kars-Turkey 2 3 * Corresponding author : E-mail: <basaran_k@hotmail.com> or <basaran@kafkas.edu.tr> SUMMARY RÉSUMÉ This study was carried out to determine the changes in venous blood pH, HCO3- concentration, BE-ecf, BE-b, pCO2, ct-CO2, pO2 and O2sat every 6 h during the laying cycle of the goose. Seven geese (2 year-old, weighing 4.26 kg at average) with a laying cycle of 42 h were used. Diets were formulated to cover their nutrient requirements. After 15 days of adaptation period, blood samples were collected every 6 h during the laying cycle. A first decrease of HCO3- concentrations, base excess in extracellular fluid (BE-ecf) or in blood (BE-b), pCO2 and ct-CO2 was observed at the 6th h, following by a more marked reduction at the 30th h of the laying cycle. Highly significant correlations were obtained between HCO3- concentrations, base excess, pCO2 and ct-CO2 (p < 0.001, correlation coefficients were comprised between 0.946 and 1.000). Although blood pH values remained within normal ranges, close to the inferior limit, multiple regression analyses evidenced links between blood pH, alkaline reserve and CO2 related parameters. By contrast, pO2 and the percentage of O2 saturation (O2sat) fluctuated in an opposite way with the occurrence of 3 spikes at the 6th, 18th and the 30th h, and were highly positively correlated (p < 0.001, r = 0.942). These results indicate that buffering systems (HCO3-, base excess) and functional adaptive responses of lungs and probably kidneys are involved for blood pH regulation during the laying cycle in goose. Therefore, it is suggested that decreased blood HCO3-, BE-ecf, BE-b, pCO2 and ct-CO2 should be corrected in geese, especially at the 30th h of laying cycle for animal’s health and productivity. Effets du cycle de ponte sur le pH sanguin, les gaz du sang et les autres paramètres associés chez l’oie. Par B. KARADEMIR, I. KAYA, O. UCAR et G. KARADEMIR. Keywords : Goose - laying cycle - blood pH - blood gas bicarbonate. Les objectifs de cette étude sont d’analyser les variations dans le sang veineux du pH, des concentrations de HCO3- et du CO2 total (ct-CO2), des excès de bases dans le liquide extracellulaire (BE-ecf) et dans le sang (BEb), des pressions partielles de CO2 et de O2, et du pourcentage de saturation de O2 (O2sat) durant le cycle de ponte chez l’oie. Sept oies âgées de 2 ans, pesant 4.26 kg en moyenne et présentant un cycle de 42 heures ont été utilisées. Les rations alimentaires ont été adaptées pour que les besoins en nutriments soient couverts. Après 15 jours d’adaptation, des échantillons sanguins ont été prélevés toutes les 6 heures au cours du cycle de ponte. Une première faible diminution des concentrations de HCO3-, des excès de bases, de pCO2 et de ct-CO2 a été observée à la 6ème heure du cycle, suivie d’une autre réduction, plus marquée à la 30ème heure. De très fortes corrélations positives ont été obtenues entre ces paramètres (p < 0.001, les coefficients de corrélations étant compris entre 0.946 et 1.000). Bien que les valeurs du pH sanguin soient restées comprises dans les valeurs normales, proches de la limite inférieure, l’analyse en régression multiple a mis en évidence des liens significatifs entre le pH sanguin, les réserves alcalines et les paramètres associés au CO2. En revanche, pO2 et O2sat, très positivement corrélés (p < 0.001, r = 0.942), ont montré des variations opposées caractérisées par 3 pics obtenus à la 6ème, 18ème et 30ème heures. Ces résultats indiquent que des systèmes tampons (HCO3-, excès de bases), et des réponses fonctionnelles adaptatives des poumons et probablement des reins sont impliqués dans la régulation du pH sanguin durant le cycle de ponte chez l’oie. De ce fait, il est suggéré que les variations des concentrations de HCO3-, du CO2 total, des pressions partielles de CO2 et des excès de base dans le secteur extracellulaire et dans le sang devraient être corrigées afin de préserver la santé et la productivité des animaux. Mots-clés : Oie - cycle de ponte - pH sanguin - gaz sanguin - bicarbonate. Introduction For optimum productivity, the animals have to be in healthy conditions. Particularly, the pH of body fluids is maintained within narrow limits (7.35-7.45) [6]. It is also needed for the maintenance of protein structure and function, which represent essential conditions for normal progression of metabolic events [4]. These pH ranges have been also validated for geese, as with other animals [22]. The blood pH, HCO3- concentration (mmol/L), base excess of extracellular fluid (BE-ecf, mmol/L), base excess of blood (BE-b, mmol/L),CO2 pressure (pCO2, mmHg), Revue Méd. Vét., 2005, 156, 5, 275-280 total CO2 (ct- CO2, mmol/L) O2 pressure (pO2, mmHg) and O2 saturation (O2sat, %) are related parameters to each other [6, 19]. Changes in one of them immediately affect others and thus can impair all body functions. In healthy individuals, approximately 60% of CO2 is transported within the blood stream in the form of bicarbonate. Carbonic acid (H2CO3) is formed when dissolved CO2 combines with water in the erythrocytes with the aid of Carbonic anhydrase enzyme. H2CO3 spontaneously ionises to H+ and HCO3-. The oxygen affinity of haemoglobin (Hb) is influenced by H+ status so-called as to the Bohr effect [12]. Alveolar macrophages have a crucial role in defence system of the lungs [10], as they are capable of destroying microorganisms 276 (such as bacteria and viruses) by phagocytosis. For this, these cells need a high content of pO2 and a correct pH. Undoubtedly, a low pO2 and acidosis reduce pulmonary macrophage functions [23]. CaCO3 was the mainly constituent of the eggshell. The necessary Ca2+ is provided from either the bone or nutrients, while CO32- is obtained from the blood HCO3-. HCO3concentrations and pH decline to their minimum values in blood at the 22nd h during the laying cycle in hens [14]. At this time, the pH was reported to be 7.34 in hens [11]. Additionally, the changes in CO2 contents in blood can affect both the pH and eggshell quality [14]. It was also reported that low blood pH and HCO3- concentrations impair the eggshell thickness [24]. Thus, several experimental protocols have been proposed in laying hens to restore blood pH and HCO3- concentrations and consequently to improve the eggshell quality [2, 5, 9]. The values of blood pH, pCO2 and pO2 in geese and in chickens were reported to be numerically similar to each other [21, 22]. Additionally, it was also reported that no significant changes of these parameters were observed in different races, seasons or genders in geese [22]. Little information about the effects of laying cycle upon blood pH, gases and other related parameters is available in geese. Therefore, the aim of the present study was to determine the influence of laying cycle on venous blood pH, HCO3- concentration, BE-ecf, BE-b, pCO2, ct-CO2, pO2 and O2sat in geese. Materials and methods KARADEMIR (B.) AND COLLABORATORS TABLE I. — Ingredients and chemical composition of geese diet. a For per kg : vitamin A 4 800 000 IU, vitamin D 96 000 IU, vitamin E 3 12 000 mg, vitamin K3 1 000 mg, vitamin B1 1 200 mg, vitamin B2 2 800 mg, vitamin B6 1 600 mg, vitamin B12 6 mg, nicotinamide 16 000 mg, calcium-D-pantothenate 3200 mg, folic acid 400 mg, D-biotin 18 mg, vitamin C 20 000 mg, chlorine 50 000 mg, manganese 32 000 mg, iron 16 000 mg, zinc 24 000 mg, copper 2 000 mg, iodine 160 mg, cobalt 40 mg, selenium 60 mg, antioxidant 4 000 mg. b Calculated from the tabular values [18]. ANIMALS Seven out of 98 native (local, cross-bred), 2 year-old geese (from Kars district) were used in their second laying period for this study. Selection of these animals was made as follows : It was observed that the laying cycles of these 98 geese lasted from 38 h to 52 h and each goose laid an average of 10 to 15 eggs within the laying period. Then, observations during a couple of laying cycle of individuals also showed that most animals with regular cycle had about 42 h laying interval and the total number of them was only seven. The average weight of these animals was 4.26 kg and they were kept in individual cages with a self-feeder and water ad libitum. Since the room where the animals were kept had presented irregular light supply, a continuous (24 h) lighting scheme were applied for standardisation of this condition during the study, as also routinely used in laying hens. The animals were fed by a basal diet formulated to cover their nutrient requirements [18] (the composition is given in table I). BLOOD COLLECTIONS After 15 days of adaptation period, a total of one ml of blood samples was collected from the vein, V. cutanea ulnaris (in plastic syringes containing 500 IU/ml heparin) within the first hour of laying. Then, the collections were continued at every 6 h during the whole laying cycle until the 36th h. Since all the 7 geese used have not laid promptly at the 42nd h (some laid just before, while others just after), it was considered that blood samples to be collected at that time would lead inconsistency in the results. Therefore, sample collections at the 42nd h were neglected. Following the collections, the anaerobic condition of blood samples was obtained by closing the syringes with glass putty and blood samples were then kept at 0-5°C until the analyses made within 30 minutes after collections [3]. LABORATORY ANALYSES Chemical Analysis : The parameters of dry matter (DM), organic matter (OM), crude protein (CP), ether extract (EE), crude fibre (CF), nitrogen-free extract (NFE) of diet were determined by AOAC [1]. The values of metabolisable energy (ME), calcium (Ca) and phosphorus (P) were also calculated from the tabular values [18]. Biochemical Analyses : For analyses of the blood pH, HCO3- concentration (mmol/L), base excess of extracellular fluid (BE-ecf) (mmol/L), base excess of blood (BE-b) (mmol/L), pCO2 (mmHg), total CO2 (ct-CO2) (mmol/L), pO2 (mmHg) and O2 saturation (O2sat) (%) a Rapid Lab 248 pH/Blood Gas Analyzer (Chiron Diagnostics, USA) was used. Control of accuracy was performed using a commercial quality control solution (Complete®, Bayer, East Walpole, USA). Control values were within the normal ranges as described by the manufacturer. To determine techRevue Méd. Vét., 2005, 156, 5, 275-280 BLOOD PH, BLOOD GASES AND LAYING CYCLE IN GEESE nical precision of all the parameters, blood samples collected from 7 geese were analysed five times each. Coefficients of intra-assay and inter-assay variations of these parameters were as follows : pH : 0.02 - 0.52% ; HCO3- : 0.04 - 3.78% ; BE-ecf : 0.26 - 20.46% ; BE-b : 0.30 - 27.02% ; pCO2 : 1.58 - 3.61% ; ct-CO2 : 0.21 - 3.67% ; pO2 : 0.24 - 5.91% and O2sat : 0.02 - 5.37% , respectively. STATISTICAL ANALYSIS Data collected from the 7 geese whom the laying cycle has lasted about 42 h were used for statistical analysis. Firstly, data were analyzed by paired t test: comparisons between each time points for each of the parameters were made by considering paired individual data [15] and differences were considered to be statistically significant at P<0.05. Secondly, Pearson’s correlation test was used to have an idea about the relationships between the blood parameters. Then, simple regression analyses was used for the analyses of parameters that have presented statistically significant correlation (P<0.05) to give more detailed results, and parameters (blood pH, HCO3-, BE-ecf, BE-b, pCO2 and ct-CO2) suspected to be related closely [6, 19] were finally analysed by multiple regression analyses. Minitab statistical software programme [17] was used for all the analysis methods. Results The mean values of blood pH, HCO3- concentration, BEecf, BE-b, pCO2, ct-CO2, pO2 and O2sat according to time intervals during the goose laying cycle are summarised in table II. During the laying cycle, pH values decreased at the 12th 18th h, slightly increased at the 24th h, then decreased again at the 30th h, but not significantly, before roughly reaching initial values at the 36th h (table II). Some positive significant correlations were obtained between blood pH values and BE-ecf or BE-b or O2sat (table III). The correlation coefficients of simple regression were 0.306 (p < 0.05), 0.434 (p < 0.01) and 0.424 (p < 0.01), respectively. Multiple regression analysis showed that pH, HCO3- concentrations, BE- 277 ecf, BE-b, pCO2 and ct-CO2 were closely related (p < 0.001, table IV). HCO3- concentrations, BE-ecf, or BE-b globally tended to decrease during all the duration of laying cycle (1st h vs. 36th h: p < 0.05). Moreover, the 3 parameters have presented simultaneous variations with first slight drops at the 6th h (1 h vs. 6 h and 6 h vs. 12 h: p < 0.05) and more marked declines at the 30th h (24 h vs. 30 h and 30 h vs. 36 h: p < 0.05) (table II). HCO3- concentration, BE-ecf and BE-b were highly positively correlated together (p < 0.001) (figure 1). The correlation coefficients were 0.982, 0.946 and 0.990 for HCO3- concentrations and BE-ecf, HCO3- concentrations and BE-b and for BE-ecf and BE-b, respectively. Similar fluctuations of pCO2 and ct-CO2 were also noticed throughout the laying cycle : these 2 parameters showed a first slight decline at the 6th h (1 h vs. 6 h and 6 h vs. 12 h: p < 0.05), then they markedly decreased again at the 30th h (24 h vs. 30 h and 30 h vs. 36 h: p < 0.05) (table II). A strong positive correlation was obtained between pCO2 and ct-CO2 The regression equation was pCO2 = 1.57 ct-CO2 , r = 1, p < 0.001. Furthermore, pCO2. was positively correlated with HCO3- concentrations (r = 1, equation : pCO2 = 1.65 HCO3-, p < 0.001), BE-ecf (r = 0.982, equation: pCO2 = 42.5 + 1.55 BE-ecf, p < 0.001) and BE-b (r = 0.946, equation: pCO2 = 43.8 + 1.80 BE-b, p < 0.001) (table III, figure 2a,b). In the same way, ct-CO2, HCO3- concentrations, BE-ecf and BE-b were significantly closely related (p < 0.001). The respective correlation coefficients and regression equations were: - for HCO3- concentrations and ct-CO2: r = 1, HCO3- = 0.952 ct-CO2 - for BE-ecf and ct-CO2: r = 0.982, BE-ecf = 0.974 ct-CO2 - 26.3 - for BE-b and ct-CO2: r = 0.946, BE-b = 0.784 ct-CO2 21.7. Although pO2 and the percentage of O2sat were also diminished during all the laying cycle like pCO2, HCO3- concentrations, BE-ecf and BE-b, opposite variations (spikes whom the magnitude gradually decreased) were noticed at the 6th, 18th and 30th h (1 h vs. 6 h and 6 h vs. 12 h: p < 0.05; 12 h vs. 18 h and 18 h vs. 24 h: p < 0.05; 24 h vs. 30 h and 30 h vs. 36 h: p < 0.05) (table II). A highly significant correlation was obtained between pO2 and O2sat (r = 0.942, equation: pO2 = 0.921 O2sat - 15.5, p < 0.001) (table III, figure 3). TABLE II. — Variations of blood pH, gases and other releated parameters during the goose laying cycle (Mean ± SEM) The values with different superscripts within the same column are statistically significant (P<0.05). Revue Méd. Vét., 2005, 156, 5, 275-280 278 KARADEMIR (B.) AND COLLABORATORS TABLE III. — Correlation coefficients (r) of simple regression between blood pH, gases (pCO2, pO2) and other related parameters measured in laying geese. BE-ecf: base excess of extracellular fluid, BE-b: base excess of blood, O2sat: percentage of O2 saturation, ct-CO2: total CO2. * P<0.05; **P<0.01; ***P<0.001. TABLE IV. — Multiple regression analyses between blood pH, gases (pCO2) and other related parameters in laying geese. BE-ecf: base excess of extracellular fluid, BE-b: base excess of blood, ct-CO2: total CO2. * The parameters are highly correlated with other X variables (predictors) and have been removed from the equation. Discussion In the present study, we describe the effect of laying cycle in geese upon the parameters of venous blood: pH, HCO3-, BE-ecf, BE-b, pCO2, ct-CO2, pO2 and O2sat. Decreases of blood pH were observed in hens during eggshell formation [14]. In goose, blood pH values remained close to the physiological inferior limits (7.33-7.36 vs. 7.257.33 for geese [22] and 7.20-7.60 for the chicken [21]) and differences between time points were not statistically significant. CO2 + H2O ⇔ H2CO2 ⇔ H+ + HCO3⇑ Carbonic Anhydrase According to equation given, HCO3- used for the formation of eggshell leads to an increase of H+ concentration in blood. Similarly, an additional free H+ will be available while CO32- is provided from HCO3- [14]. These elevations of H+ concentrations would decrease the blood pH. However, blood pH may also be influenced by other buffering systems (haemoglobin, hydrogeno-phosphates, proteinates, etc.) and by the functional adaptive responses of lungs and kidneys (not directly explored in this study). Indeed, although blood pH value may vary, more or less, in parallel to fluctuations of related parameters (HCO3- concentration, BE-ecf, BE-b, pCO2 and ct-CO2) studied during the laying cycle, it remained at around physiological limits in laying geese. In a first attempt, the tendency to acidosis will be compensated by the conversion of HCO3- into H2CO3. Base excess in extracellular fluid (BE-ecf) and in blood (BE-b) are involved in the acid-base equilibrium and are highly correlated together. The BE-ecf and BE-b have to be comprised between -4 and 4 mmol/L for compensations of acid-base fluctuations [13], otherwise blood pH and other relevant biochemical and physiological cellular functions would be inevitably impaired [4]. Consequently, blood HCO3- concentrations and BE-ecf or BE-b decreased. These variations have been observed firstly at the 6th h and finally at the 30th h during the laying cycle. As pH values were only moderately correlated with HCO3- concentrations, BE-ecf and BE-b, other buffer systems probably occurred for pH regulation or lungs and kidneys would develop adaptive responses. Moreover, the buffering capacity of blood HCO3- would be reduced during laying cycle because CO32-, which are obtained from HCO3- are required for eggshell formation. Consequently, blood HCO3- concentrations gradually decline during egg formation. It was previously reported that HCO3- concentrations were minimal at the 22nd h of the hen laying cycle [14]. In our study, this minimal value was obtained at the 30th h in laying geese. In this study, the values of pCO2 ranged from 35.27 to 52.27 mmHg that were similar to those reported previously in geese (33 to 43.5 mmHg) [22] and in the chicken (17 to 56 mmHg) [21]. The H+ fixation by haemoglobin (Bohr effect) would spare blood HCO3- concentrations and amplify H+ Revue Méd. Vét., 2005, 156, 5, 275-280 BLOOD PH, BLOOD GASES AND LAYING CYCLE IN GEESE 279 FIGURE 1. — Positive correlation between HCO3- concentrations and base excess in extracellular fluid (BE-ecf) (●) or in blood (BE-b) (❍) obtained in geese during the laying cycle. The regression equations were HCO3- = 25.8 + 0.942 BE-ecf and HCO3- = 26.5 + 1.09 BE-b respectively. The regression equation between BE-ecf and BE-b was : BE-ecf = 0.761 + 1.19 BE-b. FIGURE 2a. — Positive correlation between pCO2 and base excess in extracellular fluid (BE-ecf) (●) or in blood (BE-b) (❍) obtained in geese during the laying cycle. The regression equations were pCO2 = 42.5 + 1.55 BE-ecf and pCO2 = 43.8 + 1.80 BE-b respectively. FIGURE 2b. — Positive correlation between pCO2 and HCO3- concentrations (■) or ct-CO2 ( ) obtained in geese during the laying cycle. The regression equations were pCO2 = 1.65 HCO3- and pCO2 = 1.57 ct-CO2 respectively. pulmonary elimination via formation of H2CO3 into pneumocytes and dissociation into CO2 and H2O after Carbonic Anhydrase action [8]. Indeed, pCO2 and ct-CO2 also decreased at the 6th and the 30th h and were strongly correlated with HCO3- concentrations. Multiple regression were obtained Revue Méd. Vét., 2005, 156, 5, 275-280 for pH, HCO3-, BE-ecf, BE-b, pCO2 and ct-CO2, indicating that fluctuations of these parameters were linked to each other [6, 19]. Simultaneously, pO2 and O2sat showed opposite variations with significant increases at the 6th, 18th and 30th h during the laying cycle. It is well known that the H+ 280 KARADEMIR (B.) AND COLLABORATORS FIGURE 3. — Positive correlation between pO2 and percentage of O2 saturation (O2sat) obtained in geese during the laying cycle. The regression equations was pO2 = 0.921O2sat - 15.5. fixation on haemoglobin decreases its affinity to O2 [12], leading to increases of pO2 into blood. Nevertheless, pO2 and O2sat remained within normal ranges (pO2: 43.6- 62.7 vs. 41.5-56.6 mmHg for geese [22] and 25 to 68 mmHg for the chicken [21]) throughout the laying cycle. Although no precise O2sat values could not be found in literature for geese, the present values observed (from 64.66 to 82.62%) were very close to those (70%) reported to be ‘normal’ in human [10]. These findings suggest that O2 equilibrium was weakly affected by laying process. 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