Effect of Dietary Protected Fat and Roughage Level on Digestion, Rumen Metabolism and Plasma Lipids of Growing-Finishing Lambs

Abstract

Sixty male Barki lambs, 8 month old and 27.5 kg average body weight , were randomly divided into six similar groups. Lambs were fed ration at level of 3.5% of body weight for 70 days. Rations were iso nitrogenous containing 10 % or 30 % berseem hay each with 0, 4 or 8% Ca-Soap. At the end of growth trail, twenty-four metabolism trials were conducted to evaluate nutrient digestibilities, nutritive value of the experimental rations, nitrogen balance and water intakes. Ruminal fluid samples were collected at 0 and 4 hrs post feeding to determine pH, ammonia-nitrogen, total VFA'S concentrations and molar proportions of fatty acids, total nitrogen and non-protein nitrogen. Blood plasma total lipids, triglycerides and cholesterol were also determined. Results indicated feeding 4% calcium soap rations (P<0.05) improved nutrient digestibilities but this effect was not evident by feeding with 8% calcium soap supplement. Increasing roughage from 10% to 30% had no significant effect on nutrient digestibility. Cell wall constituents digestibilities were higher for 30% roughage rations and positively affected by fat supplement. Higher energetic values (DE and TDN) was associated with fat supplement and low roughage levels. The DCP values were not affect by the dietary treatments. Calcium soap supplement significantly improved DE and TDN intakes specially with high roughage level but had no significant effect on DCP intake. Water intake (P<0.05) increased by increasing fat supplement to 8% and roughage level to 30%. Nitrogen balance was not affected by the dietary treatments. Fat Supplement had no significant effect on ruminal parameters. However, increasing roughage level increased (P<0.05) ruminal pH, acetate concentration and acetate: propionate ratio but decreased propionate, iso butyrate and valerate. Ruminal total VFA's concentrations, butyrate and iso valerate were not affected by dietary roughage level. Lower pH and higher total VFA's concentrations, acetate, butyrate, iso butyrate, valerate and iso valerate were found at 4 hrs post-feeding, but propionate and acetate: propionate ratio were not affected by sampling time. Increasing calcium soap level in sheep diet had no significant effect on rumen nitrogen metabolism. However, increasing roughage level (P<0.05) decreased ruminal total nitrogen, non protein nitrogen ammonia nitrogen and true protein nitrogen. All forms of ruminal nitrogen were (P<0.05) lower at 4 hrs post feeding than those before feeding Increasing protected fat level to 4% or 8% of ration dry matter significantly increased plasma total lipids and (P<0.05) triglycerides. Total cholesterol was El-Bedawy et al. 220 (P<0.05) higher for 8% fat group than the control and 4% fat group but increasing roughage level (P<0.05) increased total plasma lipids and total cholesterol but had no significant effect on triglycerides. Total cholesterol (P<0.05), total lipids and triglycerides (P>0.05) were higher at 4 hrs post feeding than those before feeding. Inclusion of 4% calcium soap improved the nutrient utilizati...