Checking billy barr’s snow log…
Congestive heart failure, secondary to pulmonary hypertension, has historically been considered a disease associated with high altitude exposure. The disease was first reported to occur at altitudes over 2,440 m (8,000 ft.) and so became known as "high altitude disease". One common clinical sign due to congestive heart failure in cattle is swelling of the brisket. Consequently, the disease also became known as "brisket disease". In more recent years, congestive heart failure has been reported to occur in both beef and dairy cattle at a more moderate altitude of 1,600 m. Anecdotal reports from cattle producers in Nebraska, Colorado and Texas suggest that the incidence of congestive heart failure may be increasing. This suggests that bovine congestive heart failure is not strictly a disease of high altitude exposure. Anatomical studies of cattle indicate that cattle have a smaller lung volume and alveolar surface area available for gas exchange than mammals with similar body masses and oxygen requirements. This may be because selection for increased growth rate, and other traits of high production, increases metabolic oxygen demand. The overarching hypothesis of this doctoral dissertation was that congestive heart failure secondary to pulmonary hypertension is not strictly a disease of high altitude but, a multifactorial disease, that is also associated with physiological traits that increase metabolic oxygen demand relative to oxygen supply via the cardiopulmonary system. The goal of this doctoral dissertation was to identify epidemiological, physiological and genetic risk factors associated with congestive heart failure and increased mean pulmonary arterial pressure in cattle. The results of this dissertation indicate that pulmonary arterial pressures of cattle are substantially higher than other mammalian species. Among pre-weaned calves, mean pulmonary arterial pressures increased significantly with age even at the moderate altitude of 1,470 m. As hypothesized, high oxygen demand relative to supply was positively associated with mean pulmonary arterial pressure in both pre-weaned calves at high altitude (2,170 m) and feedlot cattle at moderate altitudes (1,300 m). A study of 10 Canadian feedlots indicated that the risk of congestive heart failure increased from the year 2000 to the year 2012. The risk of congestive heart failure increased more than the underlying change in the risk of digestive disorders. Death from congestive heart failure occurred throughout the feeding period but typically occurred late in the feeding period, which makes this disease particularly costly to the feedlot industry. Treatment for respiratory disease was a significant risk factor for CHF. Increased growth rate and increased feed efficiency were risk factors for increased mean pulmonary arterial pressure in cattle. Mean pulmonary arterial pressures were significantly higher at the end of the confined feeding period at moderate altitude (1,300 m) than in pre-weaned calves at high altitude (2,170 m). Growth promotion through a steroid implant containing estradiol and trenbolone acetate did not significantly increase mean pulmonary arterial pressure as hypothesized. However, diastolic pulmonary arterial pressure was significantly lower than non-implanted controls, which suggests that one or both of these steroid hormones has cardio-pulmonary protective effects. Genome-wide association analyses of mean pulmonary arterial pressure and traits physiologically associated with mean pulmonary arterial pressures among calves at 4 and 6 months of age did not identify any concordant single nucleotide polymorphisms (SNPs). However, multiple SNPs were identified to be associated with mean and systolic pulmonary arterial pressures that have been associated with pulmonary hypertension in humans or have a plausible biological role in the development of pulmonary hypertension. In conclusion, the results of these investigations provide evidence to suggest that congestive heart failure of cattle is a multifactorial disease that is exacerbated by high altitude exposure.
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