Modifikasi keragaman mikroba dan fermentasi rumen sapi dengan pemberian saponin lerak (Sapindus rarak)

Abstract

Peternakan sapi potong rakyat di Indonesia masih mengandalkan ransum hijauan yang kurang berkualitas dalam jumlah tinggi (70-100%). Hal ini dapat menyebabkan kecernaan pakan rendah dan terjadinya defisiensi nutrien terutama nitrogen (N). Selain itu, pada ekosistem rumen seringkali populasi dan aktivitas bakteri terganggu dengan adanya protozoa karena protozoa sering memangsa bakteri untuk mencukupi kebutuhan proteinnya. Akibatnya efisiensi pemanfaatan energi pakan rendah, produksi gas metan tinggi dan pertambahan bobot badan sapi rendah. Strategi untuk mengatasi permasalahan tersebut dapat dilakukan dengan memodifikasi mikroba rumen yang dapat menekan pertumbuhan protozoa dan mengoptimalkan pertumbuhan bakteri rumen. Populasi bakteri rumen yang tinggi dapat meningkatkan aktivitas fermentasi pakan, aliran N dalam rumen serta sintesis protein mikroba. Populasi protozoa dalam rumen dapat ditekan secara parsial (defaunasi parsial) dengan pemberian senyawa saponin asal tanaman. Defaunasi parsial memungkinkan beberapa bakteri rumen dapat berkembang namun populasi protozoa tidak seluruhnya mati. Hal ini akan menguntungkan proses fermentasi karena protozoa juga mempunyai peran dalam degradasi serat dan mempertahankan pH rumen. Salah satu tanaman tropika yang banyak mengandung saponin adalah buah lerak. Potensi saponin ekstrak buah lerak sudah dikaji pemanfaatannya pada ternak domba sebagai suplemen defaunasi. Namun demikian penelitian yang menganalisis pengaruh saponin ekstrak lerak terhadap keragaman komunitas bakteri rumen, dinamika populasi bakteri spesifik, aktivitas fermentasi pada berbagai rasio hijauan dan pemanfaatannya pada sapi potong belum banyak dikaji. Penelitian ini bertujuan untuk menganalisis pemanfaatan ekstrak keseluruhan buah lerak untuk memperbaiki fermentasi, keragaman dan populasi mikroba rumen serta performa sapi potong lokal yang mendapat ransum hijauan tinggi.

The aim of this research was to investigate the utilization of whole lerak extract to improve the in vitro fermentation, microbe diversity and performance of beef cattle fed with high forage based ration. There were four experiments i.e. 2 in vitro and 2 in vivo experiment. The first in vitro experiment evaluated the effect of whole fruit lerak extract with different levels (0;0.001; 0.01; 0.1 and 1 mg/ml) on ruminal fermentation and microbial diversity using native grass and concentrate (50:50, w/w) as a substrate. The second in vitro was aimed to investigate the effect of different level of lerak extract (0, 0.6, 0.8 mg/ml) on fermentation, population of rumen microbes and enzyme activity in the in vitro fermentation of diets composed of different ratios of forage and concentrate (90:10, 80:20, 70:30, w/w). The first in vivo study was conducted using 12 local beef cattle which received 3 different treatments of 0, 500 and 1000 mg lerak meal/kg body weight (BW). Daily gain, nutrient digestibility and blood profile were measured. Thus, the second in vivo study was conducted using 12 local beef cattle with three diets containing lerak extract of 0, 100 and 200 mg/kg body weight. Parameters measured were nutrient digestibility, fermentation products, feed intake and daily gain of beef cattle during 90 days treatment. In vitro experiment showed that 1 mg/ml of lerak extract reduced (P<0.01) protozoa population. The gas production tended to increase while methane production/ml gas was reduced but total methane production was same among treatments. Although lerak extract did not affect concentration of total VFA, it decreased molar proportion of acetic and butyric acid but increased that of propionic acid significantly (P<0.01) and improved the ratio of acetate: propionate. The population of some bacteria spesies most closely related to Prevotella ruminicola increased. The second in vitro experiment showed that there was no interaction between ratio of forage and level of lerak extract for all parameters. The addition of lerak extract did not affect dry matter digestibility, but reduced organic matter digestibility. In contrast, total VFA and propionate production increased (P<0.05) with 0.8 mg/ml lerak extract addition. Total numbers of Ruminococcus albus and Prevotella ruminicola were enhanced by increasing level of lerak extract in all diets, but numbers of Fibrobacter succinogenes tended to decrease. In vivo experiment showed that the addition of lerak meal 500 mg/kg BW in the beef cattle ration did not affect nutrient intake and digestibility. In contrast, lerak meal at higher level (1000 mg/kg BW) increased fibre intake and decreased nutrient digestibility (P<0.05) and white blood cells (P<0.01). There was no difference on average daily gain among treatments. The addition of lerak extract up to 200 mg/kg BW did not affect on nutrients digestibility. Total VFA and propionate proportion increased (P<0.05) and ratio of acetate:propionate decreased (P<0.05) with lerak extract addition. The used of lerak extract decreased NH3 concentration while nitrogen balanced and microbial crude protein synthesis similar among treatments