12 INTRAUTERINE CHITOSAN INJECTION ADVANCES THE OESTROUS RETURN DATE AFTER DELIVERY IN JAPANESE BLACK COWS

Abstract

Shortened parturition interval is very profitable for beef cattle production. Chitosan is made by treating shrimp and other crustacean shells with alkali sodium hydroxide, a linear polysaccharide composed of randomly distributed β-(1–4)-linked D-glucosamine and N-acetyl-D-glucosamine, and has been utilised as an antibacterial agent. Intrauterine injection of chitosan, as an antibacterial agent, is expected to stimulate immune functions and to improve uterine recovery. The aim of the present study was to evaluate whether intrauterine chitosan injection shortened oestrous return after parturition in Japanese black cows. Chitosan powder was dissolved in water (5 g L^–1), sterilized, and stored in a freezer at –20°C until use. At 30 days after delivery, chitosan solution was injected (50 mL/head) into the uterine body from the vagina via the cervix of cows. Heat detection was performed daily with a pedometer wirelessly connected to a computer. When heat-specific increased steps and standing heat were observed, we considered the cow to be in heat. In total, 9 cows were injected chitosan from December 2012 to June 2013, and those data were compared by ANOVA with control data collected from 42 cows from December 2011 and November 2012. Mean durations when oestrus was first returned after parturition shortened significantly in the chitosan-injected group (45.3 ± 4.9 days) than in controls (62.4 ± 2.7 days). Six females that showed oestrus after treatment with chitosan became pregnant following AI at the oestrus or the next cycle, and three others were waiting to be checked for pregnancy after AI. These preliminary data indicate that chitosan injection after parturition may shorten the oestrous return and improves reproductive efficiency. However, a large number of observations are necessary to reach further conclusions.