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Early-lactating dairy cows mobilize body protein to provide amino acids that are directed toward gluconeogenesis and milk protein synthesis. Propylene glycol (PG) is a precursor of ruminal propionate, and feeding PG has been reported to improve energy supply by increasing blood glucose. Our hypothesis was that feeding PG could spare body protein by providing an alternative source of carbon for gluconeogenesis. The major objectives of this study were 1) to delineate the effects of pre- and postpartum PG supplementation in transition dairy cows on whole-body nitrogen balance, urinary 3-methylhistidine (3-MH) excretion, body composition, and gene expression profiles for the major protein degradation pathways in skeletal muscle; and 2) to characterize the changes in body protein metabolism during the periparturient period. Sixteen pregnant cows (7 primiparous and 9 multiparous) were paired based on expected calving dates and then randomly assigned within each pair to either a basal diet (control) or basal diet plus 600 mL/d of PG. Diets were fed twice daily for ad libitum intake, and PG was fed in equal amounts as a top dress from d -7 to d 45. All measurements were conducted at 3 time intervals starting at d -14 +/- 5, d 15, and d 38 relative to calving. Propylene glycol had no effect on whole-body N balance, urinary 3-MH excretion, or body composition. However, N balance was lower at d 15 and 38, compared with d -14. Urinary excretion of 3-MH was lower at d -14 than at d 15 and 38. Supplemental PG had no effect on body weight (BW) and all components of empty BW. On average, cows fed both diets mobilized 19 kg of body fat and 14 kg of body protein between d -14 and d 38. Supplemental PG had no effect on mRNA abundance in skeletal muscle for m-calpain, and the 14-kDa ubiquitin-carrier protein E2 (14-kDa E2) and proteasome 26S subunit-ATPase components of the ubiquitin-mediated proteolytic pathway; however, PG supplementation downregulated mRNA expression for mu-calpain at d 15, and tended to downregulate mRNA expression for ubiquitin at d 15 and 38. Relative to calving, mRNA abundance for m- and mu-calpain, ubiquitin, and 14-kDa E2 were greater at d 15 compared with d -14 and d 38. In summary, these results indicate that transitional effects on whole-body metabolism and gene expression for the Ca(2+)-dependent and ubiquitin-mediated proteolytic pathways in skeletal muscle were more pronounced than those elicited by PG supplementation.

Modern strains of fast-growing meat type poultry are highly susceptible to heart failure. Heart-related mortalities are observed predominantly in fast-growing broiler chickens, with ascites and sudden death syndrome being the most common heart-related conditions in modern broiler flocks. This paper examines the role of structural, molecular, and biochemical factors pertinent to the pathophysiology of heart failure in fast-growing broilers. Evidence explaining the pathogenesis of acute and chronic heart failure, in the context of the underlying molecular and biochemical changes in the cardiomyocytes, contractile apparatus, and extracellular matrix in the ventricular myocardium are critically evaluated and discussed with reference to the clinical signs associated with deterioration of heart pump function. The secondary pathophysiological effects on the cardiovascular system, resulting from hemodynamic changes associated with the failing heart pump, are also reviewed and critically discussed.

. 2010. Temperature gradients in trailers and changes in broiler rectal and core body temperature during winter transportation in Saskatchewan. Can. J. Anim. Sci. 90: 321Á330. Temperature conditions inside commercial trailers transporting market-age broilers during four winter journeys were measured, and changes in the rectal and core body temperature of birds were quantified. Pre-selected modules were equipped with data loggers recording temperature every 72 s. Rectal temperatures were taken from eight birds in each of four modules immediately before and after each trip, and two or three birds, with temperature recording implants, were placed in each of two selected modules. Temperature heterogeneity was found among modules on all loads with average crate temperatures ranging from 10.9 to 30.7, 8.9 to 28.1, 2.5 to 26.1 and (0.7 to 16.58C for transportation times of 191, 193, 178 and 18 min and ambient temperatures of (7.1, (27.1, (28.2 and (18.48C, respectively. Wet birds, condensation and frost provided evidence for moisture accumulation during transportation. Body temperature recordings indicated the potential for the development of both hypothermia and hyperthermia, showing that cold stress can occur near air inlets and heat stress in poorly ventilated areas. Passive ventilation inside trailers resulted in crate temperatures 17.7 to 55.28C above outside temperature. Mortality ranged from 0.7 to 1.4% but several deaths occurred during lairage, prior to processing. A heterogeneous distribution of airflow resulted in undesirable temperate and humidity conditions for some birds.

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A study was completed to characterize the electrocardiographic (ECG) patterns of male broiler chickens. Data were collected from 300 commercial broilers. ECG readings were collected from all birds between 12 and 15 days of age and then twice more at 10-day intervals. The measurements. included heart rate and rhythm, QRS complex duration, amplitude and mean electrical axis (MEA), incidence of ascites and incidence of sudden death syndrome (SDS). Eight birds died from SDS and 4 birds died from ascites. Twelve birds were condemned for ascites at the processing plant. The overall population heart rate declined with age. Birds that died of SDS had a higher heart rate, whereas those that developed ascites had a lower heart rate than the remainder of the population. The normal MEA was found to be between 0 degree and 180 degrees. On average 30% of birds showed left or right QRS axis deviation, and this pattern was observed in 14 of the 16 birds that developed ascites. Several types of cardiac arrhythmias were observed, the most common being premature ventricular contractions (PVC). The incidence of PVC increased with age, ranging from 1% at 12-15 days of age to 8.9% at 32-35 days of age. QRS axis deviation was present in 5 SDS birds. It is concluded that some 30% of the broiler flock tested was at risk of developing heart failure or heart-related disease.

The present study exam ines the differences in blood gas param eters, cardiac output, cardiac index, oxygen delivery and tissue oxygen extraction in slow growing chickens (leghorn and feed restricted broilers), fast growing chickens (broilers fed ad libitu m) and chickens with fulm inant heart failure and ascites. In com parison to leghorns, broiler chickens had lower pO2 and O2 saturation levels in venous blood (P , 0.001) . At the age of 35 days, broilers had arterial and venous pO2 signi® cantly lower than 7-day-old broilers (P , 0.05). Overall, blood pO 2 and O2 saturation tended to decline, and CO 2 content tended to increase with age. Chickens developing ascites had lower blood pO2 and O2 saturation levels, and higher blood CO 2 content in com parison to normal chickens (P , 0.05). In com parison to other chickens, ascitic chickens had the lowest pO2 and O2 saturation, and highest CO 2 content in both venous and arterial blood (all P , 0.001) . Broilers at 35 days of age had higher arterial O2 content than leghorn chicks, and there were only m inor differences between norm al and ascitic chickens. However, ascitic chickens had the lowest venous O2 content (P , 0.001) , but the highest tissue O2 extraction index (P , 0.001) . Cardiac index was higher in leghorn chicks than in broilers (P , 0.001) . Ascitic birds had the lowest cardiac index (P , 0.001). Oxygen delivery was higher in leghorns than in broilers (P , 0.001) . Ascitic birds had the lowest oxygen delivery index. The present study has identi® ed signi® cant differences in previously unexamined performance indicators of the cardiovascular system between slow growing chickens, fast growing chickens and chickens with heart failure. Low cardiac index in broiler chickens appears to be the key haem odynam ic problem leading to hypoxaem ia and ultim ately cardiovascular failure in fast growing broilers. IntroductionAscites is the excessive accumulation of¯uid in body coelomic cavities. This condition is the cause of signi® cant econom ic losses in the comm ercial broiler industry throug hout the world. In clinical terms, ascites is a non-spe ci® c sign and m ay have several causes. In broiler chickens, ascites is most often associated with heart failure, but the aetiology of ascites is poorly understood. A m arked decline in heart rate (HR) is a consistent pathophysiological feature in fast growing broiler chickens prone to ascites (Olkowski & Classen, 1998). In normal chickens, an increase in HR begins shortly after hatching, but HR plateaus around 4 weeks of age, and then slowly declines until m aturity (Ringer et al., 1957;Flick, 1967; Tazawa et al., 1992) . Since the increase in HR is an important component of physiological adjustm ent of cardiac output (CO) during the intensive growth phase in normal young chickens, adequacy of systemic oxygen ation becom es an important issue in individuals unable to adjust HR during growth. The adequacy of systemic oxygen ation ultim ately depends on the relationship between oxygen demand and oxygen supply. In t...