| There is great potential of long-term development for the buffalo industry in China, especially in southern where milk production capacity is very poor. Furthermore, milk yield and fertility of buffaloes are so low that seriously restrict the development of buffalo industry. Reproductive performance of buffalo has effects on its milk production and breeding efficiency, which is one of the important conditions for produce sustainable development. Recovery of reproductive function directly affects the reproductive performance in postpartum buffalo. Postpartum uterine involution and ovarian function recovery are very important to ensure the buffalo pregnant again and shorten the calving interval. Introduction of excellent buffalo varieties from overseas to crossbreeding local buffaloes is a very useful way to improve buffalo milk yield. In order to successfully establish buffalo industry, we must clarify and improve the reproduction function of hybird buffalo, and develop new reproductive technologies. Moreover, because of the difference of the chromosome number between the abroad-introduced river buffaloes (2n=50) and the local swamp buffaloes (2n=48), the Chromosome number (2n) of the offsprings varies among 48,49 and 50, which leads to an even lower fertility due to the aneuploidy of chromosome. Currently, many abroad studies focused on recovery of reproductive function in river buffalo, and domestic researches were interested in swamp buffalo. However, research in the hybrid buffalo is very few. Attempt to provide a theoretical basis for improve fertility and economic benefits of dairy buffaloes, this study is investigating the law of uterine involution and ovarian function resumption of hybrid buffaloes by B-mode ultrasound during postpartum. The results are as follows:1. Study of uterine involution and factors influencing in postpartum hybrid dairy buffaloes.(1) The involution interval of postpartum female buffalo's uterine cervix, pregnant horn, un-pregnant horn are 33.5±4.1 days (n=31),34.4±6.1 days (n=31),31.5±5.3 days (n=31). respectively. Involution speed of un-pregnant horn is fastest, and uterine cervix is second, involution interval of pregnant horn is longest.(2) Compared to the uterine involution interval (32.8±3.2 days, n=26) of normal female buffalo, the uterine involution intervalof female buffalo with placenta retention and endometritis (45.0±7.3 days,n=5) is significantly delayed (P< 0.05).The uterine involution interval (38.4±4.0 days,n=5) of female buffalo which calving in the summer is significantly longer than other seasons. There was no significant difference of the uterine involution interval between high-(34.9±3.2 days, n=12) and low-(32.8±4.5 days, n=19) milk production group (P>0.05).The uterine involution interval of Nili-Ravi×Jianghan Buffalo, Murrah×Jianghan Buffalo and triple cross Buffalo are 34.0±4.7 days (n=21), 32.7±3.0 days (n=7) and 33.3±2.5 days (n=3) respectively, there's no significant difference (P> 0.05). The uterine involution interval of body condition score (2.5,3.0,3.5 and 4.0) in postpartum female Buffaloes is 33.0±2.0 days (n=3),34.5±45.1 days (n=12), 33.2±3.8 days (n=14),32.5±2.1 days (n=2) respectively, there's no significant difference (P>0.05). The uterine involution interval of body weight less than 500 kg,500-700 kg, more than 700 kg in female Buffaloes is 34.8±5.9 days (n=6),33.1±3.5 days (n=17), 34.0±4.1 days (n=8) respectively, there's no significant difference (P> 0.05).These results indicate that obstetric diseases, such as endometritis, placenta retention and others, and calving saeson significantly affect the rate of uterine involution in postpartum dairy Buffaloes (P< 0.05). Howerever, milk yield, hybrid varieties, BCS and body weight have no significant effect on postpartum uterine involution of dairy Buffaloes (P> 0.05).2. Study of resumption of ovarian activities and ovulation in postpartum hybrid dairy buffaloes.(1) Follicular activity started earlier in the ovaries contralateral to the gravid horn compared to the ipsilateral ovaries and most of ovulation in the same ovaries during the first 25 postpartum days. And the fisrt time ovulation after calving occurs in the ipsilateral ovaries accounted for 77.3%(17/22).(2) The average interval of the fisrt ovulation time after calving is 40.6±11.0 days (n=22), and the second ovulation time is Day 57.3±10.0 (n=22). The average interval of estrus cycle is 16.6±4.5 days. The fisrt ovulation time of the most water buffaloes (81.8%, 18/22) without show estrus. The maximum average diameter of the dominant follicle before the second ovulation time (18.3±2.6 mm) is larger compared wtih the first ovulation time (16.7±2.4 mm). These results indicate that postpartum delayed resumption of ovarian activity and the high proportion of silent estrus is the main reason of buffalo calving interval for a long time. (3) 2 (54.5%,12/22) or 3 (22.7%,5/22) follicular waves were discovered in one estrous cycle in the most hybrid female buffaloes and the former was dominant. Follicular wave 1 and 2 emerged on day 1.7±0.6,10.3±1.9 in hybrid female buffaloes for 2 follicular wave model. Follicular wave 1,2 and 3 emerged on day 1.6±0.6,9.6±1.1 and 16.2±1.3 for 3 follicular wave model, respectively.(4) After the first ovulation time of postpartum female buffaloes, the formation ol" persistent corpus luteum accounted for 36.6%(6/16), while 18.8%(3/16) corpus luteum of female buffaloes were maintain a very short time. In other words,56%(9/16) corpus luteum of female buffaloes development abnormally which are produced after the first ovulation time. These results suggest that the high proportion of the abnormal corpus luteum which is produced after the first time ovulation in buffaloes, is one of the reasons caused Buffalo's fertility lower and estrus and breeding less effective than Holstein. |
