The objective of this study was to evaluate the effect of concentrate supplementation strategies on the nutritional characteristics of beef cattle in intensive management of tropical pasture. Twenty-four Nellore steer at 250 kg body weight (BW) were used, divided into two plots, with 12 animals in each plot. The experimental area consisted of 32 paddocks with 0.25 ha of Panicum maximum cv. Mombaça. The experiment consisted of 96-day experimental periods, with three periods of 32 days. The strategies studied were P = exclusively on pasture and without concentrate supplementation (control), ES = pasture and supplemented with a concentrate low in protein, PS = pasture and supplemented with high protein content, and PES = pasture and supplementation with balanced protein-energy. There was reduced intake of DM in animals of the treatment P in relation to supplemented pasture, regardless of supplementation. Animals fed on ES showed an intake of more nutrients than the animals on PS. The CP and TDN were also lower in P than in pastures where animals received the additional types of concentrate, and the PS animals showed greater digestibility of CP and TDN than the ES animals. However, the animals exhibited similar weight gains. Animals on P ingested smaller amounts of N and had lower fecal excretion compared to the supplemented animals, but there was no difference between treatments in nitrogen balance. Urea nitrogen and urea from the blood were higher in the supplemented animals than in animals fed on pasture; these levels were also higher in PS animals compared to animals receiving ES. Both the purines absorbed and microbial protein production were similar between treatments. However, the animals fed with concentrate supplementation, independent of the strategy involved, showed higher microbial efficiency compared to animals fed exclusively on pasture.

-The objective of this study was to evaluate the nutritive value of passion fruit by-product for cattle, contrasting the results with those found with sorghum silage. Four treatments were then constituted, comprising the combinations of the two roughages and the two levels of supplementation (with or without), in a completely randomized design with four animals per treatment. The considered variables included: feed intake, digestibility coefficients of the diets, and live weight gain of the animals. The experimental period lasted 70 days, preceded by a standardization period of 30 days. Chromium oxide was utilized to estimate the fecal output, in the digestibility trial. Treatments were compared by means of three orthogonal contrasts: between the two roughages and between the two concentrate levels within each roughage. Animals fed passion fruit by-product showed higher feed intake (total, per 100 kg of live weight (TLW), and per unit metabolic size) and had higher TLW gain than those fed sorghum silage (1.304 kg vs. 0.134 kg). The coefficients of apparent digestibility of dry matter (DM), organic matter (OM), and crude protein (CP) and the digestibility coefficient of neutral detergent fiber from passion fruit by-product were high, and much higher than those from sorghum silage. The concentrate supplement did not improve the TLW gain of animals fed passion fruit by-product and had a limiting effect on the digestibility coefficients of the diet. The concentrate supplement had a positive associative effect on intake and digestibility coefficients of DM, OM, and CP from sorghum silage. The by-product of fresh passion fruit is an excellent food for growing cattle as it provides high intake levels and weight gains, even when supplied as the only feed.

-The objective of this study was to evaluate the intake and digestibility of silages containing pineapple pulp and coast-cross hay, with or without addition of urea, and the recovery of the markers chromium oxide (Cr 2 O 3 ), indigestible neutral detergent fiber (iNDF), indigestible acid detergent fiber (iADF), and indigestible dry matter (iDM), in a digestibility assay, in sheep. Treatments were as follows: two levels of pineapple pulp (818 and 758 g kg −1 ) and two levels of urea (with and without urea), in a completely randomized design. Twelve sheep (three per treatment) were used, kept in metabolic cages. Fecal excreta were determined by total collection or estimated by using the markers. Marker samples were obtained in morning and afternoon collections, with mean concentrations obtained for both daily activities. The level of silage pulp did not affect intake, while addition of urea increased the intake of crude protein (CP), but did not influence the intakes of dry matter, organic matter, neutral detergent fiber, or acid detergent fiber. The digestibility coefficients of all afore-mentioned fractions increased with the increase in pulp, the same happening with the addition of urea. The internal marker with lowest variability among the internal markers was iADF, with mean values near 100%. Mean recovery of Cr 2 O 3 was approximately 107%, but with lower variability among treatments. Inclusion of pineapple pulp in silage does not influence intake, while addition of urea only increases the intake of CP. The levels of pineapple pulp in silage with or without urea increase the digestibility of the silage. Indigestible acid detergent fiber is the marker with lowest variability of recovery, with mean recovery for the four silages used very close to 100%.

No abstract

-Eight rumen-cannulated steers were assigned to two 4 × 4 balanced Latin squares to evaluate degradability and kinetics of fiber particles from diets based on corn silage and supplements with or without addition of lipids. Dietary treatments were: only corn silage (T1), corn silage plus concentrate with no added lipids (T2), corn silage plus concentrate with added soybean oil (T3), and corn silage plus concentrate containing ground soybean seeds (T4). Kinetics of gastrointestinal transit of fibrous particles was evaluated based on chromium-mordanted fiber. Events of rumen degradation dynamics of fibrous carbohydrates were quantified using the in situ incubation procedure. The mixed models methodology from SAS was used to fit models and the Tukey test was used to compare means. The ruminal digestibility of fiber was lower in treatments T3 and T4 and, consequently, lower proportions of potentially digestible fraction of standardized fiber and higher proportions of indigestible fraction of standardized fiber for treatments T3 and T4 compared with T1 and T2 were observed. However, there were no differences in mean retention time of the rumen, total mean retention time, mean digestion time, and rumen fill among diets. Animals from T2, T3, and T4 showed higher dry matter intake, organic matter intake, and crude protein intake rates than animals receiving T1 diet, but there was no effect of the addition of lipid. Treatments did not differ regarding neutral detergent fiber intake. Animals from T1 had lower crude fat intake than animals from T2, which showed lower crude fat intake than those from T3 and T4. The addition of lipid to concentrate has no effect on passage rate, digestion rate, and intake, when a good quality roughage is used.

No abstract

This study investigated the influence of energy supplementation with or without the addition of lipids on microbial production, microbial synthesis efficiency and nitrogen balance. Eight fistulated steers were used with accessible rumens and kept in individual stalls. Their diets consisted of corn silage; corn silage + concentrate; corn silage + concentrate with addition of lipids in the form of soybean oil; and corn silage + concentrate with addition of lipids in the form of soybean grains. Estimates of microbial protein synthesis were obtained based on the urinary excretion of purine derivatives. The concentrations of ammonia in the rumen were determined immediately at 2, 4, 6 and 8 hours after feeding. The diets with concentrate increased (P<0.05) the microbial protein synthesis and the efficiency of the synthesis and nitrogen balance without a difference between the lipid sources (P>0.05). Concentrated diets presented higher concentrations of urea nitrogen in the serum and urinary urea excretion (P<0.05), but there was no difference between the lipid sources (P>0.05). Energy supplementation, with or without lipid addition, can be used as a strategy to increase the synthesis of the microbial protein in the cattle fed corn silage.

This study investigated the effectiveness of the urine sample collection method in predicting the volume urinary and synthesis of microbial nitrogen. Eight fistulated steers were used with accessible rumens and kept in individual stalls. Their diets consisted of corn silage; corn silage + concentrate; corn silage + concentrate with addition of lipids in the form of soybean oil; and corn silage + concentrate with addition of lipids in the form of soybean grains. Estimates of microbial protein synthesis were obtained based on the urinary excretion of purine derivatives. There was no effect of diets on daily creatinine excretion (P>0.05). There were differences (P<0.05) between the urinary volume and microbial synthesis values determined by the total urine collection and those estimated from the urine spot samples and equations proposed by different authors. The estimation of microbial synthesis based on the urine excretion of purine derivatives should be performed from the total collection of the urine for a period of 24 hours.