In modern cattle, pregnancy rates after artificial insemination are decreasing year after year, causing a substantial economic loss to farmers. The quality of embryos from superovulated donor cows, which can be affected by many factors including nutrition conditions, management techniques and the quality of roughage, is another source of inconsistent reproductive performance.

　Among various forms of fatty acids that are present in the body, linoleic acid and other polyunsaturated fatty acids （PUFAs） have significant benefits in bovine fertility. Many studies have documented the nutritionally and physiologically important roles of PUFAs and their favorable effects on superovulation and reproductive performance.

　One of the proposed mechanisms of action of PUFAs in bovine reproduction is increased biosynthesis of cholesterol and thus sex steroid hormones, which stimulate follicular growth and ovulation. PUFAs may also improve the quality and freezing tolerance of ova and embryos by modifying the lipid composition and structure of the plasma membrane. In addition, linoleic acid functions as a precursor of prostaglandin F_2α, a physiologically active substance that is essential for the reproductive function of cattle.

　In summary, the available evidence suggests that while fatty acid supplementation alone may not improve the energy balance, strategic supplementation of rumen-protected PUFAs is likely the current best solution to promote follicular growth, to improve the quality and freezing resistance of ova and embryos, and to stimulate the production of reproductive steroid hormones and eicosanoids.

　Vitamin C（VC）is a potent antioxidant. Although VC is synthesized in the body of livestock, it has been reported that the plasma VC concentration decreases in Japanese Black cattle during the late fattening stage, suggesting that VC may be deficient. In humans, VC deficiency is associated with liver diseases such as cirrhosis, and VC is administered as a treatment. In this study, we investigated the effect of a rumen-protected VC preparation containing 70% of VC in Japanese Black fattening cattle on elevated liver enzymes that was likely caused by decreased levels of other antioxidant vitamins such as vitamin A（VA）. Ten Japanese Black fattening cattle aged 19 to 20 months with elevated liver enzyme values received 30 g/day of VC for 7 days in addition to their regular feed. Blood samples were taken before and 1, 3, 7 and 14 days after the start of VC treatment. The plasma VC concentration significantly increased at Day 3 and Day 7 compared with that before administration. The serum VA concentration was lower than the reference range at the baseline and significantly decreased at Day 7 and Day 14 from the baseline value. The serum AST activity significantly decreased at Day 7 in comparison with the baseline. The serum GGT activity significantly decreased at Day 3 and Day 7 in comparison with that before administration. The increased plasma VC concentration and decreased serum AST and GGT activities following VC administration suggest that VC may have hepatoprotective effects in cattle.

　In cattle, the conception rate declines as air temperatures rise, because the higher body temperature can affect the quality of the ovum and embryo and result in embryonic degeneration. The aim of this study was to analyze correlations between the calving rate and the mean daily air temperature data obtained from the Japan Meteorological Agency.

　We obtained consent from 42 Holstein farms, which were using the same non-governmental cattle management software, for anonymous use of their reproductive data of 7,174 cows recorded between 2012 and 2014. Another reproduction dataset of one Japanese Black cattle farm in Aomori Prefecture recorded between 2003 and 2009 was also used. These data were used to calculate calving rates relative to the number of artificial inseminations（AI） and embryo transfers（ET）conducted in 2012 and 2013. Local mean daily air temperatures were obtained from the Japan Meteorological Agency. Correlations among calving rate, temperature and geographic area were examined.

　In Holstein cows, the calving rate decreased significantly above the mean daily air temperature of 20℃ at the time of AI. The calving rates in the embryo-transferred Holstein cows, AI or ET Holstein heifers and Japanese Black cattle did not decrease. These results suggest that AI during the time of lactation stress and at high air temperature negatively affected the conception rate and thus resulted in a lower calving rate. However, no association between the conception rate and air temperature was consistently found across the evaluated regions indicating that location and/or other farm-level factors should also be taken into consideration.

　There are several treatment options for humeral fracture in cattle, such as intramedullary pinning, external fixation, plating, spica splinting and stall rest. The best treatment recommendations, however, have not been established. We performed internal fixation with a dynamic compression plate（DCP）for humeral fracture in two calves. Case 1 was a 6-month-old, 140-kg Japanese Black calf with an oblique fracture in the distal diaphysis of the left humerus. Case 2 was a 1-dayold, 40-kg Japanese Black with a long oblique fracture in the distal diaphysis of the left humerus. In both cases, surgery was performed on right lateral recumbency under triple-drip anesthesia with xylazine, guaifenesin and butorphanol. A cutaneous incision was made from the greater tubercle to the lateral epicondyle of the humerus. The brachialis muscle was divided to approach the bone. After fracture reduction, a contoured DCP（Case 1, 12-mm wide and 87-mm long; Case 2, 12-mm wide and 103-mm long）was positioned on the craniolateral side of the humerus and fixed with 4.5-mm cortical screws. The postsurgical outcome was favorable in both. In Case 1, despite a broken screw, lameness resolved 68 days after surgery. The calf grew steadily and was used for breeding. In Case 2, lameness disappeared after 29 days postoperatively, and the calf grew steadily. We speculate that insufficient length and bending of the plate caused the screw breakage in Case 1. In Case 2, fixation seemed well maintained by the use of a bending press to achieve better plate fitting to the humerus. These outcomes suggest that internal fixation using a DCP is a good option for humerus fracture reduction in calves and that appropriate plate selection and contouring are important.

　A 51-month-old Holstein cow was presented for anorexia（Day 1）. Jugular vein distension and auscultation difficulty were noted on examination, and pericarditis was suspected. Lymphadenopathy was not detected by both surface and rectal palpations. Hematological examination revealed marked lymphocytosis（80,436/μℓ）with atypical lymphocytes. An ELISA test for bovine leukemia virus antibody was positive. Increased activities of total LDH and LDH isozymes 2 and 3 were 15,640, 3,909 and 3,128 U/l, respectively. Serum thymidine kinase activity was also remarkably increased to 1,920U/l. On Day 10, the patient showed brisket edema and dyspnea and died. At necropsy, multiple masses were found in the pericardial cavity with bloody pericardial fluid. Several masses were also detected in the anterior mediastinum, around the gall bladder and pancreas, in the mesenteric, and around the abomasum. Histopathological analysis revealed that the masses were B-cell lymphoma which led to a diagnosis of enzootic bovine leucosis.