Nutritional Evaluation of Two Promising Varieties of Forage Sorghum in Sheep Fed as Silage

Abstract

Two promising varieties of forage sorghum viz. HD-15 and J. Sel-10 were identified for their higher forage yield (350- 400 quintals per hectare) compared to traditional/existing variety, HC-136 at Indian Grassland and Fodder Research Institute, Jhansi. Silage of these three forage sorghum varieties viz., HD-15, J.Sel-10 and HC-136 were prepared in three concrete silos for their nutritional evaluation in sheep. Twelve adult Muzaffarnagari Ewes, divided into three equal groups of 4 each, were offered a particular variety of sorghum silage ad libitum over a period of 30 days followed by a 6 day metabolism trial and a collection of rumen liquor and blood samples. The HD-15 variety of forage sorghum silage contained higher crude protein (CP) than both the J.Sel-10 and HC-136. Average daily dry matter (DM) intake (% of live weight) differed significantly (p<0.05) in sheep that were fed the different varieties of silage, with the maximum amount in HD-15 (2.55) followed by J.Sel-10 (2.49) and HC-136 (1.84). The average apparent digestibility of all the nutrients was low in the sheep that were fed the HC-136 variety of sorghum silage when compared to both HD-15 and J.Sel-10. However, digestibility of organic matter (p<0.05) and crude protein (p<0.01) was significantly low in the HC-136 variety. The average daily nitrogen retention was-0.19, 2.15 and 0.42 g in HC-136, HD-15 and J.Sel-10, respectively which differed significantly (p<0.01). The average digestible crude protein and total digestible nutrient (TDN) contents (%) of the silage varieties were higher in HD-15 (3.14 and 55.3) than HC-136 (0.25 and 58.6) and J.Sel-10 (1.58 and 55.3) varieties. On comparing to the maintenance requirements (ICAR, 1985) for dry matter, crude protein and total digestible nutrients, both the improved varieties (HD-15 and J.Sel-10) almost met the requirements except crude protein, which met only 73.3% of the requirement by J.Sel-10, while the HC-136 variety was unable to meet the requirements. The average rumen pH and total volatile fatty acids concentrations were comparable among the groups. However, concentrations of nitrogen metabolites were higher in the animals fed the HD-15 variety of silage. Varieties of sorghum silage also did not have any influence on the concentration of the blood metabolites. It was concluded that the HD-15 variety of sorghum silage was nutritionally superior to both J.Sel-10 and HC-136 silage. (Asian-Aust. J. Anim. Sci. 2005. Vol 18, No. 12 : 1715-1720)