純種豬場流死產原因調查

Abstract

每頭母豬每年離乳仔豬頭數為評估豬場生產效能最重要的指標，其所生產的離乳仔豬數主要受產仔數和離乳前死亡率影響。流產、死產及離乳前死亡率是造成商業豬場仔豬損失的重要因素。造成豬流死產原因可分成兩大類 : 第一類為原發性生殖道感染導致30-40 % 的流產、木乃伊胎及死產；第二類包括毒素、環境因子、緊迫及母豬全身性感染等因子佔了剩下的60-70 % 。本研究以豬場為基準調查豬隻傳染性和非傳染性流死產的原因。實驗期間針對台灣北部兩個商業種豬場進行流死產胎兒臟器及胎盤的收集，共收集未足月流產胎13頭、足月死產胎63頭、木乃伊胎26頭及57個胎盤樣材。A場約有25.6 % 的窩數有死產發生，死產率為4.7 %；B場約有43 % 的窩數可見死產，死產率為6.3 %。以即時定量聚合酶連鎖反應 (real-time PCR) 調查九種猪隻傳染性繁殖障礙病原，其中包含猪小病毒 (PPV)、猪第二型環狀病毒 (PCV2)、假性狂犬病病毒 (PRV)、猪瘟 (CSFV)、猪繁殖與呼吸道綜合症病毒 (PRRSV)、日本腦炎病毒 (JEV)、布氏桿菌 (Brucella suis)、鉤端螺旋體 (Leptospira sp.)、弓蟲 (Toxoplasma gondii) 等九種病原。檢出率為JEV 2例陽性，佔1.2% (2/159)；PCV2 80例陽性，佔50.3% (80/159)；PPV 19例陽性，佔11.9% (19/159)；B. suis 3例陽性，佔1.9% (3/159)；及T. gondii 6例陽性，佔3.8% (6/159)，其他病原檢測則呈陰性結果。此外，單一病原的陽性檢出率為 77/159 (48.4 %)；兩種病原混合感染的檢出率為 15/159 (9.4 %)；三種病原混和感染的檢出率為 1/159 (0.6 %)；而皆未檢出病原的比率為 66/159 (41.5 %)。由A、B兩豬場收集323胎母豬生產資料，分析非傳染性風險的因子包括: 母豬品種、胎次、窩仔數、母豬分娩時間、母豬體態評分、是否在分娩過程進行陰道觸診、一窩中是否有木乃伊胎及是否使用oxytocin 。風險因子分析結果發現：杜洛克品種母豬、窩仔數大於12頭、分娩時間大於3小時及分娩時有進行助產等因子，皆會增加死產的風險，且有顯著差異 (p<0.05)。文獻中一般猪場胎兒損失，死產和木乃伊胎的比率約為 5-15％，死產率約為5-8 %，木乃伊胎率約為3-5%。經由上述的分析A、B兩場的死產率似乎皆在可接受範圍，唯由分析因子的改善將可協助提升生產效能。

The number of piglets weaned per sow per year, is considered as the most important indicator in evaluating the productive efficacy of commercial swine herds. The number, however, is mainly influenced by the litter size and pre-weaning mortality. Abortion and stillbirth as well as pre-weaning mortality are among the most important causes of losses in commercial swine herds. Diagnosis of the cause of abortion in swine is seldom straightforward and is frequently unsuccessful. There are two major classes of causes involved in the abortion. The first class are the agents that cause primary infection of the reproductive tract that are probably responsible for 30~40% of abortions, mummies, and stillbirth. The second class, including toxins, environmental and nutritional stresses, and systemic diseases in the sow is responsible for the other 60~70%. This study was a herd-based investigation on the infectious and non-infectious causes of swine abortion and stillbirth. Samples of abortion, stillborns and mummified foetus were collected in two commercial breeding farms in northern Taiwan. Sixty three stillbirths, 26 mummified fetus, 13 middle term abortions and 57 placenta were collected. Stillborn piglets were observed in 25.6% of the litters and the stillborn rate was 4.7% in herd A. Stillborn piglets were observed in 43% of the litters and the stillborn rate was 6.3% in herd B. Nine reproductive pathogens including porcine parvovirus (PPV), porcine circovirus 2 (PCV2), pseudorabies virus (PRV), porcine respiratory and reproductive syndrome virus (PRRS), Japanese encephalitis virus (JEV), classical swine fever virus (CSFV), Brucella suis, Leptospira sp., and Toxoplasma gondii were examined by real-time PCR in this study. The molecular screeing results showed that the positive rate for JEV was 1.2% (2/159)、PCV2 was 50.3% (80/159)、PPV was 11.9% (19/159)、B. suis was 1.9% (3/159) and T. gondii were 3.8% (6/159), and the detection of other pathogens was negative. In the samples examined, the rate of single pathogen infection was 48.4 % (77/159); two pathogens co-infection was 9.4 % (15/159); three pathogens co-infection was 0.6% (1/159)；and 41.5 % (66/159) was negative for all 9 pathogens screened. In total, the delivery information of 323 sows from two pig herds was included in the study. The non-infectious risk factors analyzed included breed, parity, litter size, duration of parturition, body condition score, vaginal palpation during parturition, mummified foetus in the litter and the use of oxytoxin. The results showed that the risk factors well as: Duroc breed sow with litter size more than 12, the duration of parturition more than 3 hours and vaginal palpation during parturition were statistically significantly associated with stillbirth (p< 0.05). Generally, fetal losses (mummified fetuses and stillborns) can vary from about 5 to 15%; stillbirth rate was 5-8 %, mummified rate was 3-5%. Based on these results, appropriate recommendations for improving the performance of sows in each herd would be provided.