Since model that I’ll build is about decision either to keep or to sell/cull a calf, we made a decision that growth will affect the time to breed the heifer. The most important thing now is to determine which disease are important in reducing the growth.
First, I have to find all the diseases which is important in my model. This depends on the time I wanted to make the decision of keeping the calf and also the relevence of the disease based on that time. We are going to do the decision after calf is succesfully born, healthy; I guess in 2-3 days after parturition. I think it is because the farmer will make decision for replacement after seeing the healthy calf in first few days. So, diseases more of postnatal until before first calving.
I found 2 books; Radostis wrote Vet Med and Smith (LA internal medicine). Chapter neonates disease describes disease in calf age 1-4 weeks of age. After that age, I have to find another chapter. I am also doing my transition matrix. In order to find the most relevent disease and the cure rate, I have to consult Ruud. I had sent him my questions (rather simple one), and also continues to search now for the cure rate to put in my model. Anyway, I am making summary of diseases I’m interested. I had read both book in 2 days at Veterinary library.
In Radostis book, I only look at 2 topics, neonatal infections and perinatal diseases. For perinatal diseases; it is divided into 3 subtopics; fetal diseases, parturient diseases and postnatal diseases. Postnatal diseases is divided into early, delayed or late. Fetal diseases includes prolonged gestation, intra-uterine infections, abortion, fetal death with reabsorption or mummification and goiter. Parturient diseases include dystocia, causing cerebral anoxia or fetal hypoxemia, injury to skeleton or soft tissues.
I am more interested at postnatal diseases especially delayed (2-7 days) and late (1-4 weeks). It was mentioned that fetal diseases and postnatal diseases are the most common cause of loss. Early death in calf is associated with non infectious cause while in delayed and late is usually due to infectious cause. First week (delayed) have higher risk of death due to septicaemia and enteritis while in 2nd week, respiratory disease commonly occur. In delayed postnatal diseases, colibacillosis, joint ill, septicaemic disease, most of the viral enteric infections in young animal eg rotavirus and coronavirus occur.
Since I am interested with infectious diseases, I look at the topic neonatal infection. The etiology are bacteremia and septicaemia, and enteritis. Bacteremia and septicaemia are commonly caused by Escherechia Coli, Listeria Monocytogens, Pasteurella Spp, Streptococci, or Salmonella Spp. While enteritis is usually caused by enterotoxigenic E.Coli, Salmonella Spp, rotavirus, coronavirus, Cryptosporidium parvum, Clostridium prefringes type A, B, and C; and occasionally by the virus of infectious bovine rhinotracheitis, and bovine viral diarrhoea. So the infectious agents are mostly opportunistic bacteria. This is due to the fact that neonates are naive to this agents, failure for passive transfer will worsen the effect of those infections. Treatment is antibiotic and fluid therapy. It was also mentioned about navel ill and the pathogenesis. It is a septicaemia and infection of navel–> mixed bacterial flora–> iE.coli, Proteus, Staphylococcus, Actinomyces–> bacteremia–> joints, bones, meninges, eyes, nedocardium, end arteries of the feet, ear and tail. Control is by good sanitation and hygiene, disinfectant application at navel.
The LA internal medicine also have a special chapter of neonatal infection. In the book, it was mentioned that the etiology are opportunistic bacteria at the genital tract, skin and environment that usually cause the infection. Portal of entry for infection are respiratory tract, gastrointestinal tract, placenta(which I am not interested of) and umbilicus. The chapter also mentioned the other causal factors of neonates diseases such as late gestation, abnormality, perinatal stress, unsanitary environment, immune status of calf, adverse management, environment condition and mincronutrient deficiency. It was also mentioned that in first 10 days of life, calf have eleveted cortisol which depress neutrophil function, thus depress bacteria killing.
The book also mention about the pathogenesis of septic shock. It was mentioned that the enterotoxigenic of the agents cause septic shock in the calf. Septic shock usually cause respiratory failure with the clinical signs of hypoxemia, pulmonary hypertension, pulmonary edema and respiratory failure. Usually in ruminants, respiratory and gastrointestinal tract are most affected by septic shock. Other complication associated with septicaemia are pneumonia (common),; pleuritis (less common), osteomyelitis, septic arthritis, septic physitis, enteritis, peritonitis, gastrointestinal ulceration (often asymptomatic), meningitis, brain or spinal cord hemorrhage, corneal ulceration, patent urachus, omphalophleibitis, resistant bacterial infection, anemia, progressive debilitation, uroperitoneum.
Treatment that was mentioned in the book are antibiotic treatment, circulatory support, immunologic support and other supportive therapy (nutritional, respiratory support and nursing care).
The book also wrote that prognosis in calf with failure of passive transfer + septicaemia + multiple organ involvement as guarded. If blood culture is negative + localization infection (enteritis, pneumonia) is present, the outcome is positive with aggressive therapy.
Next task is to find the cure rate, bovine viral diarrhoea and to put the most important diseases in the model. I also need to read up about heifer reproduction, fertility and infertility to get a clear picture of the state arrangement. I also need to read about how to produce the transition matrix.