Influence of environmental temperature and energy intake on skeletal muscle respiratory enzymes and morphology

Comparative Analysis of Broiler Housing Systems: Implications for Production and Wellbeing

This study compares the effects of modern colony cage systems and traditional floor systems on the production and welfare of broiler chickens. Through two trials spanning 35 days each, we evaluated various physiological parameters, including growth performance, bone health, stress responses, and meat quality. Colony cages demonstrated superior thermal regulation and growth performance compared to traditional floor systems, but also exhibited higher frequencies of leg deformity and reduced standing ability. Conversely, the broilers in traditional floor systems experienced heat stress-related challenges, impacting the meat quality. Our findings underscore the need to balance productivity with animal welfare in broiler farming practices. By understanding the distinct impacts of different housing systems, we can work towards improving broiler rearing methods to ensure optimal welfare and production outcomes.

Effects of heat stress on animal physiology, metabolism, and meat quality: A review

Heat stress is one of the most stressful events in the life of livestock with harmful consequences for animal health, productivity and product quality. Ruminants, pigs and poultry are susceptible to heat stress due to their rapid metabolic rate and growth, high level of production, and species-specific characteristics such as rumen fermentation, sweating impairment, and skin insulation. Acute heat stress immediately before slaughter stimulates muscle glycogenolysis and can result in pale, soft and exudative (PSE) meat characterized by low water holding capacity (WHC). By contrast, animals subjected to chronic heat stress, have reduced muscle glycogen stores resulting in dark, firm and dry (DFD) meat with high ultimate pH and high WHC. Furthermore, heat stress leads to oxidative stress, lipid and protein oxidation, and reduced shelf life and food safety due to bacterial growth and shedding. This review discusses the scientific evidence regarding the effects of heat stress on livestock physiology and metabolism, and their consequences for meat quality and safety.

Postnatal regulation of myosin heavy chain isoform expression and metabolic enzyme activity by nutrition

Development of muscle is critically dependent on several hormones which in turn are regulated by nutritional status. We therefore determined the impact of mild postnatal undernutrition on key markers of myofibre function: type I slow myosin heavy chain (MyHC) isoform, myosin ATPase, succinate dehydrogenase and α-glycerophosphate dehydrogenase. In situ hybridization, immunocytochemistry and enzyme histochemistry were used to assess functionally distinct muscles from 6-week-old pigs which had been fed an optimal (6 % (60 g food/kg body weight per d)) or low (2 % (20 g food/kg per d)) intake for 3 weeks, and kept at 26°C. Nutritional status had striking muscle-specific influences on contractile and metabolic properties of myofibres, and especially on myosin isoform expression. A low food intake upregulated slow MyHC mRNA and protein levels in rhomboideus by 53 % (P < 0·01) and 18 % (P < 0·05) respectively; effects in longissimus dorsi, soleus and diaphragm were not significant. The oxidative capacity of all muscles increased on the low intake, albeit to varying extents: longissimus dorsi (55 %), rhomboideus (30 %), soleus (21 %), diaphragm (7 %). Proportions of slow oxidative fibres increased at the expense of fast glycolytic fibres. These novel findings suggest a critical role for postnatal nutrition in regulating myosin gene expression and muscle phenotype. They have important implications for optimal development of human infants: on a low intake, energetic efficiency will increase and the integrated response to many metabolic and growth hormones will alter, since both are dependent on myofibre type. Mechanisms underlying these changes probably involve complex interactions between hormones acting as nutritional signals and differential effects on their cell membrane receptors or nuclear receptors.

Influence of early postnatal cold exposure on myofiber maturation in pig skeletal muscle

Early after birth, piglets rely almost exclusively on muscular shivering thermogenesis to produce heat in the cold and this can possibly modulate skeletal muscle development. An experiment involving 10 individually housed piglets was conducted to determine the influence of cold (24-15 degrees C, D5C group) vs. thermoneutrality (34-30 degrees C, D5TN group) between birth and 5 days on myosin heavy chain (MyHC) polymorphism and metabolic characteristics of longissimus lumborum (LL) and rhomboideus (RH) muscles. Five additional piglets were sacrificed at birth. Piglets exposed to cold received 43% more artificial milk on a liveweight basis in order to achieve similar growth rates. D5C piglets produced 93% more heat and exhibited intense shivering during the whole experiment. Contractile and metabolic characteristics of muscles were determined by immunocytochemistry, electrophoresis and enzyme activities. At least eight MyHC isoforms were detected, including atypical expressions of the alpha-cardiac and extraocular isoforms. Dramatic changes in MyHC composition, myofiber cross-sectional area (CSA) and energy metabolism occurred between birth and 5 days. Cold exposure did not affect either the total number of fibers or the CSA, but it did influence muscle maturation. In particular, it increased the expression of alpha-cardiac and type I MyHC, and decreased that of fetal MyHC, confirming an acceleration in the rate of postnatal maturation. An increase in oxidative enzyme activities was observed in both muscles in the cold, whereas the activity of a glycolytic enzyme, lactate dehydrogenase, remained unchanged. Cold exposure also induced an increase in T3 plasma levels. The extent to which these changes are the result of sustained shivering or are due to the action of hormonal factors, such as thyroid hormones, are discussed.

Effects of chronic cold exposure on the activities of cytochrome c oxidase, glutathione peroxidase and glutathione reductase in rat tissues (Rattus norvegicus)

The effects of cold acclimation on the activity levels of cytochrome c oxidase, glutathione peroxidase and glutathione reductase in various tissues of the rat (Rattus norvegicus) were investigated. One group was individually housed at 4 +/- 1 degrees C and the other at 24 +/- 1 degrees C for 6 months. Chronic cold acclimation resulted in significantly (P < 0.05) increased cytochrome c oxidase activity levels in liver, kidney, heart, interscapular brown adipose tissue and gastrocnemius muscle. The activity of glutathione peroxidase was significantly (P < 0.05) elevated in liver, interscapular brown adipose tissue, lung and muscle, whereas glutathione reductase was only significantly (P < 0.05) elevated in interscapular brown adipose tissue as a result of chronic cold exposure. The results obtained are possibly indicative of a positive compensatory response against the increased production of oxygen derived radicals as a result of chronic cold exposure.

Role of thyroid hormones in early postnatal development of skeletal muscle and its implications for undernutrition

Energy intake profoundly influences many endocrine axes which in turn play a central role in development. The specific influence of a short period of mild hypothyroidism, similar to that induced by undernutrition, in regulating muscle development has been assessed in a large mammal during early postnatal life. Hypothyroidism was induced by providing methimazole and iopanoic acid in the feed of piglets between 4 and 14 d of age, and controls were pair-fed to the energy intake of their hypothyroid littermates. Thyroid status was evaluated, and myofibre differentiation and cation pump concentrations were then assessed in the following functionally distinct muscles: longissimus dorsi (l. dorsi), soleus and rhomboideus. Reductions in plasma concentrations of thyroxine (T4; 32%, P < 0.01), triiodothyronine (T3; 48%, P < 0.001), free T3 (58%, P < 0.001) and hepatic 5'-monodeiodinase (EC 1.11.1.8) activity (74%, P < 0.001) occurred with treatment. Small, although significant, increases in the proportion of type I slow-twitch oxidative fibres occurred with mild hypothyroidism, in l. dorsi (2%, P < 0.01) and soleus (7%, P < 0.01). Nuclear T3-receptor concentration in l. dorsi of hypothyroid animals compared with controls increased by 46% (P < 0.001), a response that may represent a homeostatic mechanism making muscle more sensitive to low levels of circulating thyroid hormones. Nevertheless, Na+, K(+)-ATPase (EC 3.6.1.37) concentration was reduced by 15-16% in all muscles (l. dorsi P < 0.05, soleus P < 0.001, rhomboideus P < 0.05), and Ca(2+)-ATPase (EC 3.6.1.38) concentration was significantly reduced in the two slow-twitch muscles: by 22% in rhomboideus (P < 0.001) and 23% in soleus (P < 0.05). It is concluded that during early postnatal development of large mammals a period of mild hypothyroidism, comparable with that found during undernutrition, induces changes in myofibre differentiation and a down-regulation of cation pumps in skeletal muscle. Such changes would result in slowness of movement and muscle weakness, and also reduce ATP hydrolysis with a concomitant improvement in energetic efficiency.

Metabolic changes associated with sustained 48-hr shivering thermogenesis in the newborn pig

Metabolic changes associated with sustained 48-hr shivering thermogenesis were studied in piglets maintained at 34 (thermoneutrality) or 25 degrees C (cold) between 6 and 54 hr of life. Despite their high shivering activity and elevated heat production, cold-exposed piglets exhibited a slightly lower rectal temperature than thermoneutral animals (-1.1 degrees C; P < 0.01) at the end of the treatment. The enhancement of heat production and shivering activity were associated with a decrease in muscle glycogen (-47%; P < 0.05) and total lipid content (-23%; P < 0.05), a reduction of blood lactate levels (P < 0.05) and an enhancement of muscle cytochrome oxidase activity (+20%; P < 0.05) which suggests that muscle oxidative potential was increased by cold exposure. Potential for capturing lipids (lipoprotein lipase activity) was also higher in the red rhomboideus muscle (+71%; P < 0.01) and lower in adipose tissue (-58%; P < 0.01) of the cold-exposed piglets. Measurements performed at the mitochondrial level show no changes in rhomboideus muscle, but respiratory capacities (state IV and FCCP-stimulated respiration) and intermyofibrillar mitochondria oxidative and phosphorylative (creatine kinase activity) capacities were enhanced in longissimus dorsi muscle (P < 0.05). These changes may contribute to provide muscles with nonlimiting amount of readily oxidable substrates and ATP necessary for shivering thermogenesis. A rise in plasma norepinephrine levels was also observed during the second day of cold exposure (P < 0.05).

Histochemical arguments for muscular non-shivering thermogenesis in muscovy ducklings

1. The histochemical characteristics of gastrocnemius muscle were investigated in 6-week-old cold-acclimated (5 weeks, 4 degrees C) and glucagon-treated (5 weeks, 25 degrees C, 103 nmol/kg I.P. twice daily) muscovy ducklings, two groups able to develop non-shivering thermogenesis in vivo. A comparison was made with thermoneutral controls (25 degrees C) of the same age. All animals were fed ad libitum. Fibre type, fibre area and capillary supply have been studied. Further, a quantitative histochemical method for mitochondrial Mg(2+)-ATPase activity was developed to characterize the mitochondrial coupling state in situ. 2. White gastrocnemius was composed of fast glycolytic (FG) and fast oxidative glycolytic (FOG) fibres, while red gastrocnemius contained FOG and slow oxidative (SO) fibres. In white gastrocnemius, the proportion of FG fibres was higher in glucagon-treated than in control or cold-acclimated ducklings. In red gastrocnemius, the proportion of SO fibres was higher in both cold-acclimated and glucagon-treated ducklings than in controls. The area of all fibres was generally lower in glucagon-treated than in other ducklings. 3. The capillary density was higher in both red and white components of the gastrocnemius muscle in cold-acclimated and glucagon-treated than in control ducklings, as a result of an increased number of capillaries around each fibre. 4. In all fibres, except the FG type in cold-acclimated ducklings, the staining intensity of the Mg(2+)-ATPase reaction was higher in cold-acclimated and glucagon-treated than in control ducklings whereas the staining intensity with maximal decoupling of oxidative phosphorylation by dinitrophenol was unchanged. This indicated a more loose-coupled state of mitochondria in situ in all fibres of cold-acclimated ducklings, and in FOG fibres of white gastrocnemius and SO fibres of red gastrocnemius in glucagon-treated ducklings. 5. These results indicated a higher oxidative metabolism of skeletal muscle in both cold-acclimated and glucagon-treated than in control ducklings, and for most of the parameters studied, a similarity between cold acclimation and glucagon treatment. Because of the higher loose-coupled state of muscle mitochondria in cold-acclimated and glucagon-treated than in control ducklings, the higher oxidative capacity of skeletal muscle in these ducklings could be used for heat production rather than ATP synthesis and account for muscular non-shivering thermogenesis.

Effects of warm exposure on adipose tissue and muscle metabolism in growing pigs

1. Forty-eight pigs weaned at 3 weeks old and acclimated to the experimental temperatures for 2 weeks before the start of the experiment, were fed ad lib and used between 9 and 33 kg live weight to determine the effects of warm exposure (31.5 vs 18.5 degrees C) on adipose tissue and muscle metabolism. 2. Warm exposure induced a decline in the lipid content (P less than 0.01) of backfat whereas degree of saturation (P less than 0.05) and adipocytes size were increased (P less than 0.05). 3. At 31.5 degrees C, as compared to 18.5 degrees C, activities of malic enzyme and glucose-6-phosphate dehydrogenase were depressed by an average 33% in backfat (P less than 0.01) and 23% in leaf fat (P less than 0.05) while lipoprotein-lipase activity was stimulated by 60% (P less than 0.01) in leaf fat. 4. In warm conditions, the activities of the enzymes indicative of oxidative and glycolytic metabolism in muscle, i.e. lactate dehydrogenase, beta-hydroxyacyl coenzyme-A dehydrogenase, citrate synthase and cytochrome oxidase, were reduced in the longissimus dorsi muscle (P less than 0.05) and to a lesser extent in the trapezius muscle. 5. At 31.5 degrees C, pigs exhibit lower average plasma levels of insulin, T3 and T4 than those maintained at 18.5 degrees C.

3H-ouabain binding sites in porcine skeletal muscle as influenced by environmental temperature and energy intake

The influence of environmental temperature and energy intake on 3H-ouabain binding sites in skeletal muscle has been investigated in young growing pigs at 8 weeks of age. Animals lived for several weeks at 35 or 10 degrees C on a high (H) or low (L) level of energy intake. The four treatment groups were thus: 35H, 35L, 10H and 10L. The total number of 3H-ouabain binding sites (Bmax) in longissimus dorsi muscle (mean values +/- SEM) were 221 +/- 66, 214 +/- 61, 350 +/- 76 and 486 +/- 114 pmol/g wet weight for the 35H, 35L, 10H and 10L groups respectively. Bmax was significantly greater in those living in the cold than the warm (P less than 0.001). Moreover, at 10 degrees C energy intake had a significant effect, with Bmax being greater in the 10L than the 10H group (P less than 0.005). Level of energy intake had no influence on Bmax at 35 degrees C. The apparent dissociation constant was not affected by either temperature or intake. The elevated Bmax and hence the increase in number of Na+,K+-pumping sites in the cold is probably related to increased muscular activity associated with shivering. However, thyroid status also influences the number of Na+,K+-pumping sites and this may have been a contributory factor in the present study. In addition, the elevated Bmax suggests a greater potential for non-shivering thermogenesis associated with increased Na+,K+-ATPase concentration in the cold. Differences in relative stage of development between the four groups may help to explain the results for Bmax in relation to level of energy intake.