In livestock production, it is difficult to quantify possible risk factors affecting productivity, because production-related problems typically involve several interacting factors. Reproductive epidemiology is an essential tool for assessing production problems. It identifies the incidence rate, relative frequency and risk factors related to the problems using a large database obtained through livestock production. Livestock producers are undergoing changes in their standard operation procedures to improve production efficiency and to accommodate an increasing number of animals per farm. These changes include construction of a large database that contains records of animals, animal processing and other production-related events. However, the application of the database to livestock operation remains underutilized, because farmers or advisers have limited knowledge or time to perform epidemiological analysis. In order to identify problem areas and improve productivity, understanding production epidemiology is vital. This review provides the concepts of production epidemiology and explains how we can apply this tool to improve production efficiency using production data acquired from commercial livestock operations.

View full abstract

Recent global warming has had a significant impact on productivity in the livestock industries. The effect of summer heat stress, especially, is becoming severer and more serious year after year. According to the global warming scenario created by the Intergovernmental Panel on Climate Change, the projected increase in average ambient temperature in Japan is from 2.5 to 3℃ by the end of the 21st century compared with the year 2001. The number of days with a maximum temperature of higher than 35℃ will also increase. Under these climate scenarios, reduction in productivity and reproductive performance during summer months is inevitable not only in dairy cattle but also in all kinds of livestock.High temperature and humidity in summer increase the body temperature of livestock. It is thought that this elevation of body temperature lowers productivity and reproduction efficiency by directly decreasing dry matter intake and by negatively affecting the metabolism and other physiological functions through increased oxidative stress levels. For farmers, these adverse effects manifest as economic losses. In this review, the effects of heat stress on livestock production are addressed with a focus on body temperature. The latest technologies in heat stress management and future perspectives are also discussed.

View full abstract

The occurrence of dermatosis in Japanese Black calves before marketing influences the calf price and has recently increased in Oita Prefecture. An epidemiological survey of infection with Demodex bovis was performed in 2,106 calves from 2011 to 2014 by palpation of the skin at the time of vaccination （254 days old on average）, and parasitological examination was performed in 131 infected calves. The prophylaxis and treatment records were also obtained from each farm. The mean sizes （length × width） of female and male adult mites were, respectively, 234.6 × 66.7μm（n=28） and 264.5× 67.6μm （n=24） in the hair follicles and 218.8 × 63.4μm （n=30） and 219.0 × 57.5μm （n=19） in the crusts. Two female adult mites were also found on the skin surface （135.8 × 53.8μm）. The skin lesions （nodules） were most often found in the cervical region （67%）. No sex predilection was observed in the incidence rate, and the onset of demodicosis found after 4 months old and increased after 7 months old. The rate of transmission from dam to calf after next parturition was 49% （30/61）. Ivermectin injection and flumethrin pour-on given twice two weeks apart were effective for prevention and treatment, respectively. Although the occurrence of demodicosis tends to increase in high-temperature months, differential diagnosis between demodicosis and insect bites is needed from June to August when insect bites are most common. Since various skin lesions may appear in demodicosis, examination of skin scrapings is important in a complicated case with secondary infection.

View full abstract

The objective of this study was to identify the factors affecting the conception rate （CR） following embryo transfer in dairy cattle. Reproduction history, season, days postpartum （cow） or age （heifers）, number of artificial inseminations （AI） and diameter and luteal tissue area of the corpus luteum （CL size） at embryo transfer （ET） were evaluated in Holstein-Friesian recipient cattle. In Experiment 1, total of 36 animals （21 cows and 15 heifers） were examined for CL size on Day 7 after estrus by ultrasonography. Embryo transfer was performed on Day 7 after estrus in animals having a CL diameter of more than 20 mm. Animals were divided into two groups according to the CL diameter, that is, animals having CL of 20 ~ 30 mm and those having CL of more than 30 mm in diameter. Although there was no difference in luteal tissue area between pregnant and non-pregnant cows, the luteal tissue area in pregnant heifers tended to be smaller than that in non-pregnant heifers （357.6±60.1 mm² vs. 401.2±40.6 mm², p<0.1）. In regard to the CL diameter, there was no difference between pregnant and non-pregnant animals for both cows and heifers. In Experiment 2, the CR was compared for factors other than CL size in 301 recipient animals （210 cows and 91 heifers）. The CR was significantly higher in heifers than in cows （56/91, 61.5% vs. 103/210, 49.1%, p<0.05）. There was no significant difference in CR among seasons. The CR was not affected by the number of days postpartum or by the number of AI. It was concluded that an average conception rate could be expected if a recipient heifer had a CL of 20 mm or greater in diameter and that ET was an effective means of breeding in order to mitigate negative impacts of heat stress and repeated breeding on reproductive performance in dairy cattle.

View full abstract

A 4-year-old Holstein cow presented with anorexia, jugular venous distention and dewlap edema. Traumatic pericarditis was diagnosed based on these clinical signs, muffled heart sounds and cardiac ultrasound images, which showed fibrin-like structures on the epicardium. The cow died one month after the first presentation in spite of the treatment. The postmortem examination revealed a neoplastic growth on the epicardium and lymphoma cell infiltration in the myocardium. Pathological diagnosis was concurrent pericardial mesothelioma and endemic bovine leukemia in the heart.

View full abstract