This review paper is aimed at presenting and discussing the effects of rumen digesta (RD) as an alternative protein source on nutrient utilization, rumen fermentation characteristics, growth performances, and milk production in ruminants. RD is a by-product of abattoir; it is a partially digested feed that mainly originates from rumen of ruminants. RD consisted of 13.5-46.1% crude protein and some essential nutrients (microbial cells, amino acids, minerals, and volatile fatty acids [VFAs]), which beneficially affect the ruminant production. Recent studies have shown that transfer of RD from buffalo to cattle improved nutrient digestibility. Ensiling RD with agro-industrial by-products improved the nutritional value of agro-industrial by-products, such as by improving protein contents and increasing their digestibility. In addition, dried RD could enhance ruminal fermentation, diet utilization, and rumen microorganisms in in vitro, beef cattle and buffalo, which has no adverse effect on production performance. Therefore, utilization of RD is suggested because it improves nutrient utilization, reduces feed costs, and controls waste disposal to the environment.
Keywords: Environmental pollution; Nitrogen source; Rumen; Slaughterhouse waste.