Effect of Urea-Molasses Block Enriched with Monensin on Performance and Some Blood and Rumen Parameters of Mehraban Male Lambs

Introduction Feed supplements can improve nutritional value of ruminant’s diet. According to many studies, urea molasses-mineral block (UMMB) is a good source of easily available nitrogen and fermentable energy and its usage causes nitrogen and energy available for rumen microorganisms simultaneously and improves feed efficiency especially in low quality feeds. Increased dry matter intake is reported when UMMB was included in the diet of buffalo. It was observed that increasing digestibility of dry matter, crude protein, NDF and ADF in cows by using UMMB. Also better availability of fermentable energy for rumen microorganisms was seen. Monensin, as a feed additive through the manipulation of rumen fermentation, increases feed efficiency in ruminants. This substance selectively inhibits gram-positive bacteria, thereby impacting ruminant metabolism by increasing efficiency of energy metabolism, improving nitrogen metabolism, and reducing bloat and lactic acidosis risk. Monensin may provide an additional energetic benefit from enhanced forage digestibility. In order to evaluate the effect of UMMB enriched with monensin on performance, digestibility, and some blood and rumen parameters in male lambs, two experiments were conducted in a factorial arrangement as a completely randomized design.
Materials and Methods Ingredients used to manufacture UMMB were cotton seed meal (21%), wheat bran (19.7%), urea (2.5%), molasses (43.3%), calcite (3.4%), mineral supplement (4.2%) and common salt (5.9%). In the first experiment, 24 male lambs with 7-8 month age were randomly divided into 4 groups including 1) concentrate mixture and forage, 2) concentrate mixture and forage 30 ppm monensin, 3) concentrate mixture and forage (85%) and UMMB without monensin (15%), and 4) concentrate mixture and forage (85%) and UMMB enriched with monensin (15%). During the experimental period (70 days), dry matter intake and body weight gain were measured daily and fourth nightly, respectively. Blood and rumen fluid samples were taken on days 68 and 69, respectively, 3 hours after the morning feeding. For the second experiment, 4 lambs from each treatment were randomly selected and transferred to metabolic cages to determine the effects of UMMB and monensin on nutrients digestibility and nitrogen retention. Data were analyzed as a 2×2 factorial experiment based on a completely randomized design using the GLM procedure of SAS (1999).
Results and Discussion The results showed that UMMB increased dry matter intake, daily weight gain and decreased feed conversion ratio (PConclusion Overall results showed that UMMB improves efficiency of fermentable energy and nitrogen, dry matter and crude protein digestibility and nitrogen retention in lambs. So it can be concluded that UMMB may be used to improve performance of growing male lambs.