Urea lepas-lamban dalam ransum berbasis jerami padi untuk meningkatkan efisiensi produksi sapi bali

Abstract

Urea is the most frequently used for substituting natural feed protein in ruminant rations. However, because it is hydrolyzed to ammonia and absorbed into circulatory system, urea may contribute negative impact on ruminant animals. Any effort to optimize urea usage as NPN source for ruminant must consider its negative effect. In this study, the effort was accomplished by characterizing and examining slow-release urea (SLU) products used in vitro and in vivo techniques. The in vitro study was intended to reveal SLU characteristics of zinc-urea (US), zeolites-urea (UZ), and zeolites-zinc-urea (USZ) under different molasses levels in relation to the ruminal fermentative changes observed in different incubation time. The experimental design was randomized block design with a 4 x 3 factorial arrangement plus a control treatment, and conducted in two replications. The factors were urea (U), US, UZ, and USZ and molasses concentrations (0%, 6%, and 12%). The control treatment was the rice straw based diets containing neither urea nor molasses (TU). Diets consisted of 45% rice straw and 55% concentrates (DM basis) were formulated to have similar N and TDN levels. The in vitro diet showed the best ruminal fermentative response was applied in the in vivo study. Under the in vivo study, SLU characteristics of US, UZ, and USZ were examined using 20 Bali bulls (145.3 ± 2.5 kg of BW) allocated to five treatments and four replications in a completely randomized design to evaluate the effects on Bali bull performances. Treatments consisted of diets contained no urea (TU), U, US, UZ, and USZ. Results of solubility study showed that N solubility of US (61.96%), UZ (39.71%), or USZ (40.12%) was lower (P<0.05) than the N solubility of U (91.02%) in two hours of incubation period. The results of the in vitro study revealed that the best impact of the in vitro SLU characteristics of US, UZ, and USZ on the ruminal fermentative changes (NH3, VFA, pH, DMD, OMD, microbial biomass, microbial protein, and efficiency of microbial protein synthesis) was well attributed to the diets contained 6% molasses. The results of the in vivo study revealed that US or UZ might effectively substitute for U in increasing (P<0.05) feed intake. SLU characteristics of US or USZ decreased rumen ammonia concentrations whereas UZ increased total VFA and acetate concentrations (P<0.05) without affecting other fermentative products. US, UZ, or USZ increase crude protein total tract apparent digestibility and nitrogen retention whereas US or UZ increased fiber total tract apparent digestibility when substituted for U (P<0.05). Efficiency of rumen microbial protein synthesis and the microbial protein inflow to post rumen tracts increased with UZ when substituted for U (P<0.05). Finally, UZ increased live weight gain and feed efficiency when substituted for U or TU diets (P<0.05). In conclusion, ureazeolite showed a slow-release urea characteristic that had a positive impact on feed intake, ruminal fermentative system, digestibility traits and in turn, increased efficiency of Bali bull production.

Urea merupakan sumber nitrogen bukan protein (NPN) yang paling sering digunakan untuk menggantikan sebagian dari protein ransum pada ruminansia. Namun karena urea bersifat mudah terhidrolisis menjadi amoniak di dalam rumen dan dengan cepat pula diserap memasuki sistem darah, maka dalam praktiknya penggunaan urea dapat berdampak negatif bagi ternak, mulai dari penurunan konsumsi dan performa ternak sampai kematian akibat keracunan urea. Upaya untuk mengoptimalkan nilai guna dari urea sebagai sumber NPN yang ekonomis bagi ruminansia harus mempertimbangkan dampak negatif dari sifat urea tersebut. Pada penelitian ini, upaya tersebut diwujudkan dengan menguji tiga macam produk urea lepas-lamban, yakni: urea-seng sulfat (US), urea-zeolit (UZ), dan urea-seng sulfat-zeolit (USZ) yang diuji dalam tiga tahap (preparasi dan penentuan sifat produk, in vitro, dan in vivo). Penelitian tahap pertama bertujuan mempelajari kelarutan preparat US, UZ, dan USZ sebagai suplemen sumber NPN lepas-lamban pada ruminansia. Pada tahap ini, zeolit dipanaskan pada suhu 100 0C lalu kerapatan ruah dan keporiannya diukur untuk menentukan daya serapnya. Selanjutnya, urea dicampurkan dengan zeolit, seng sulfat, atau zeolit dan seng sulfat dengan metode pelelehan urea pada suhu 80 – 110 0C. Rasio urea:zeolit ditetapkan berdasarkan daya serap zeolit, sedangkan rasio urea:seng sulfat ditetapkan berdasarkan reaksi pembentukan kompleks urea-seng sulfat. Produk yang dihasilkan lalu dipindai dengan scanning electron microscopy untuk mengetahui tingkat ketercampuran antara zeolit dan urea. Produk tersebut dilarutkan dalam larutan McDougall dan kelarutan nitrogennya diukur pada rentang waktu: 0, 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 10, 12, 24, dan 48 jam. Rancangan percobaan yang digunakan untuk uji kelarutan ini adalah Rancangan Acak Lengkap dan setiap perlakuan terdiri atas 2 ulangan.