Ventricular Septal Defect in Eight Holstein Calves in a Large Dairy Herd Septal Defect in Eight Holstein Calves in a Large Dairy Herd.

Ventricular We aimed to present clinical findings on congenital ventricular septal defect (VSD) in a commercial dairy herd in Iran and to distinguish between VSD and respiratory diseases in Holstein young calves. Eight cases of VSD were diagnosed and reported in the present study in a large commercial dairy herd in Tehran, Iran. The VSD is a common heart abnormality leading to culling or death of young calves. Hyperpnea, lethargy, and poor growth are its most common symptoms, but they should be differentiated from the similar symptoms of respiratory diseases. It has been reported that maternal lifestyle as well as excessive body mass possess potential roles in increasing congenital heart defects in babies. Suboptimal calf welfare may occur when dams are exposed to stresses and diseases during pregnancy Consequently, preventing calf culling or death will benefit commercial dairy herds’ sustainability and economy.


Introduction
In this clinical case series report, we aimed to present clinical findings concerning congenital ventricular septal defect (VSD) in a commercial dairy herd in Iran (Behroozi Dairy Complex, approximately 3000 dairy cattle, Tehran, Iran) and to differentiate between VSD and respiratory diseases in Holstein calves. The VSD is an abnormality in both human and animal hearts in which the heart wall (septum) that divides the heart into two separate parts (left and right ventricles) is not fully developed during embryogenesis [1]. As a result, a hole is formed between heart ventricles leading to disturbed and abnormal blood flow into the heart that cause heart failure. Genetic background has been proposed as a main cause of VSD in humans. However, in a recent study [2], it was concluded that maternal stressful life had a significant role in the development of heart disorders especially VSD in offspring.

Case Presentation and Discussion
In previous reports concerning VSD in Holstein calves, only one calf has been identified with VSD [3,4]. However, according to our observations in a large dairy herd, we suggest that VSD occurs more frequently and that it could be confused with respiratory diseases at least in some cases. In the current case report, eight Holstein calves occurs in different young ages. As the VSD is a congenital disorder, its severity can be affected by the hole diameters. This implies that calves with a smaller hole in the septum might live without any problem unless the hole becomes large enough to seriously compromise the heart function as calf ages. Therefore, disorder detection and calf culling, or death may occur in a variety of ages.
Like the age, the VSD was not sex-dependent either and it occurred in both female and male calves. Moreover, exploring parity in the incidence of VSD revealed no differences between cows or heifers.  As a result, the useless antibiotics therapy should be avoided. Finally, the right calf culling time can be decided upon. As noted above, mothers exposed to stressful life during pregnancy had higher risks of VSD development in offspring. It has been reported that maternal lifestyle as well as excessive body mass possess potential roles in increasing congenital heart defects in babies [5]. Suboptimal calf welfare may occur when dams are exposed to stresses and diseases during pregnancy [6]. Overall, it is suggested that gestation is a critical phase for both dam and fetus and that all pressures must be minimized during this period. Overcrowding, hyperthermia, and nutritional deficiency are the most common stressors in ruminant farms worldwide.
As a result, optimizing the pregnant and dry cow environment by reducing stress might reasonably decrease congenital disorders, and hence, improve the productivity and sustainability of commercial dairy herds.

Conclusion
Eight cases of the Ventricular Septal Defect (VSD) were diagnosed and reported in the present study in a large dairy herd in Iran. The VSD is a common heart abnormality leading to culling or death of young calves. Hyperpnea, lethargy, and poor growth are its most common symptoms, but they should be differentiated from the similar symptoms in respiratory diseases. Palpation of the right side of thorax would be useful for the early diagnosis of VSD. Controlling stress in late gestation and attention to herd genetics programs could be helpful in minimizing congenital heart problems. Consequently, preventing calf culling or death will benefit the commercial dairy herds' economy.