Nicole Stephane Abreu Lima

This study aimed to evaluate the effects of sequential supplementation with different crude protein levels and periods on performance, nutritional and metabolic characteristics, and efficiency of nitrogenous compounds use in grazing male Nellore calves at pre-weaning. Fifty male Nellore calves during pre-weaning were distributed in a completely randomized design in a 2 × 2 factorial arrangement. The strategies were as follows: Supplementation period in the initial pre-weaning was 1–78th experimental day and in the final pre-weaning was 79–156th experimental day. The Low and high protein levels in the supplement were 150 g CP/kg) and 300 g CP/kg, respectively. All animals received 6 g/kg BW of supplement. Protein levels in the supplement did not affect intake of forage DM, and neutral detergent fiber in the animals. However, a higher CP intake and the CP to DOM ratio (p-value < 0.05) was evidence for the high calves compared with low calves. Supplementation strategies did not affect the blood concentrations of IGF-1, glucose, and total protein. Likewise, protein levels in the supplement did not affect the ADG and number and diameter of muscle fibers. In conclusion, the decrease in protein levels in the supplement from 300 to 150 g CP/kg DM does not detrimentally affect performance and nutritional and metabolic characteristics in male beef calves under a grazing system at pre-weaning.

Nitrogen (N) is one of the most important components of feeds and its quantification allows estimating protein equivalents, an important characteristic for diet formulation in ruminant nutrition. We aimed to evaluate N recovery in tropical forages using the Kjeldahl method with modifications involving a pre‐digestion step with salicylic acid and, or a partial replacement of copper sulfate by titanium dioxide as a catalyst. Forty‐eight study materials (i.e., tropical forages) were evaluated. Kjeldahl standard procedure was based on acid digestion with sodium sulfate and copper sulfate (20:1), followed by steam distillation in sodium hydroxide and titration with hydrochloric acid. The Kjeldahl variations were: salicylic acid as pre‐treatment before digestion, titanium dioxide replacing 50% of copper sulfate as catalyst in the digestion mixture, and salicylic acid and titanium as described above. The Dumas method was used as standard method to verify N recovery through Kjeldahl procedures. The N concentrations of the study materials (Dumas method) ranged from 1.9 to 28.3 g/kg as‐is. We found that all the methods were strongly and positively associated with each other (p < .01). All Kjeldahl methods produced N concentrations different from those obtained by the Dumas method (p < .01). The N recovery ranged from 0.971 to 0.980 for the different Kjeldahl methods. However, we did not find any difference between the different Kjeldahl methods regarding N concentrations (p≥ .89). The N recovery of the Kjeldahl method is not influenced by a pre‐digestion with salicylic acid or by the partial replacement of copper sulfate with titanium dioxide as a catalyst.

Background: Dry matter (DM) is a routine test for all animal feeds, facilitating feed comparisons and diet formulation. It is the most frequent test, yet the most challenging with respect to precision and accuracy.Objective: Our objective was to evaluate the accuracy, repeatability, and physicochemical impacts of oven-drying times on LDM test results in animal feeds obtained by loss on drying (LoD) at 105°C.Methods: Eighteen primary samples collected from different feed sources were grouped into high-moisture (HM) and low-moisture (LM) content materials. The tested methods were based on LoD at 105°C and Karl Fischer titration was adopted as the reference method. Test portions were oven dried at 105°C for 3, 6, 12, 16, and 24 h, and test results were compared to the reference method. Test portions were also subjected to a color evaluation using a colorimetric technique.Results: The method based on 3 h of drying provided the closest estimates to those obtained by Karl Fischer titration. Extending heating time (i.e., above 3 h) increased the bias, especially for HM feeds, which was attributed to a higher occurrence of non-enzymatic reactions. This was corroborated by the color of the residues, which became darker with increased heating time. The repeatability of LoD methods was considered adequate, ranging from 0.32 to 0.73%.Conclusion: The LoD method based on the binomial 105°C × 3 h minimizes the bias in the water recovery and causes less non-enzymatic browning in the test portions.Highlights: The loss-on-drying method recommended for laboratory DM in animal feeds is drying the test portions at 105°C for 3 h.

The aim of this study was to evaluate the effect of adding virginiamycin to either mineral mixture or multiple supplement on intake, digestion, ruminal fermentation profile, rumen microbial production, blood metabolites, and liver metabolism of zebu heifers fed a high-quality tropical forage. Eight Brahman heifers were assigned to a replicated 4 × 4 Latin Square design. The treatments were: mineral mixture, mineral mixture with virginiamycin, multiple supplement, and multiple supplement with virginiamycin. The basal diet consisted of a high-quality Tifton 85 hay (Cynodom sp.) chopped at 10-cm particle size and fed twice daily. The mineral mixture was provided daily at 120 g/animal. The multiple supplement was formulated to provide 300 g of crude protein (CP)/kg as fed, contained mineral mixture, corn grain, and urea: ammonium sulfate, and was daily provided at 200 g/animal. The mineral mixture and multiple supplement provided the same daily amount of minerals. The amount of supplemental virginiamycin was based on a maximum theoretical response on animal performance (50 mg/100 kg body weight) and daily mixed to the supplements types. The treatments were compared according to a 2 × 2 factorial arrangement (mineral mixture and multiple supplement, with or without virginiamycin). The virginiamycin supplementation did not alter either voluntary intake or digestibility (P≥0.44). Using the multiple supplement decreased forage (P<0.05) and digested organic matter (DOM, P<0.10) intake, but increased dietary CP : DOM ratio (P<0.01). The multiple supplement increased the ruminal ammonia concentration (P<0.04) and the acetate-to-propionate ratio (P<0.06). Virginiamycin increased urinary nitrogen (N) when provided along with multiple supplement (P<0.05). Fecal N was decreased by multiple supplement (P<0.06). Despite these effects, no effect was verified on either body N accretion (P≥0.48) or microbial N production in the rumen (P≥0.27). Virginiamycin decreased the blood IGF-1 (P<0.07). The hepatic gene expression for propionyl-CoA carboxylase was increased by virginiamycin (P<0.01). Virginiamycin increased the hepatic gene expression of both citrate synthase and pyrivate carboxylase when mineral mixture was provided (P<0.01), but decreased it when animals were fed multiple supplement (P<0.04). Using a low-intake multiple supplement with a high CP content for cattle fed high-quality forage causes a substitutive effect on forage intake, but keeps nitrogen accretion unchanged. That pattern indicates an improvement in feed efficiency. On the other hand, virginiamycin supplementation seems to cause some post-prandial influences, which may vary according to the type of supplement. Those influences apparently improve animal efficiency.