Extruded urea-corn product can partially replace true protein sources in the diet for lactating Jersey cows

ABSTRACT Non-protein nitrogen is a source of ammonia for rumen microorganisms to produce microbial protein, provided energy and required carbon skeletons are available. Extrusion of urea with corn plus Sulphur results in a slower ammonia release product (starea), which, associated with the energy source, would allow an increase in rumen microbial protein synthesis and could improve the efficiency of nitrogen utilization. Thus, the objective of this study was to evaluate the effect of replacement of true soybean meal protein by non-protein nitrogen source of extruded urea-corn-sulphur product (starea) on nutrient intake and apparent digestibility, lactation performance and blood parameters of lactating cows. Twenty Jersey cows in the middle third of lactation (initial milk yield = 11.98 ± 0.75 kg/day, and initial body weight = 409.10 ± 17.13 kg) were assigned according to milk yield to five treatments by randomized complete block design. The diet consisted of concentrate, corn silage and Tifton-grass. The concentrates were formulated so that the animals consumed 1.013 kg/day of crude protein from the concentrate, replacing soybean meal with starea at 0, 125, 250, 375 and 500 g/kg. Increasing starea in concentrate reduced daily dry matter intake (P=0.003) without affecting milk yield and 4% fat-corrected milk yield. Total apparent digestibility of organic matter was improved by replacing soybean meal with starea (P=0.022) and there was a tendency for improvement in dry matter digestibility. The components fat, protein, lactose and total milk solids were not changed by replacing soybean meal with starea. Milk urea nitrogen concentrations (P=0.046) and plasma urea nitrogen before (P = 0.049) and after feeding (P=0.001) increased linearly with the replacement of soybean meal by starea, but did not exceed the recommended levels. These results demonstrate that replacing soybean meal with starea can reduce dry matter intake, without altering TDN intake, because there was increasing linearly on organic matter digestibility, indicating starea effects in improving fiber degradation, without affecting milk production, milk components and blood parameters. Therefore, replacement of soybean meal with starea can be practiced up to 500 g/kg in concentrate for mid-lactation Jersey cow diets.