Can the post-ruminal urea release impact liver metabolism, and nutritional status of beef cows at late gestation?

We aimed to evaluate the effects of post-ruminal supply of urea (PRU) on nutritional status, and liver metabolism of pregnant beef cows during late gestation. Twenty-four Brahman dams, pregnant from a single sire, and weighing 545 kg ± 23 kg were confined into individual pens at 174 ± 23 d of gestation, and randomly assigned into one of two dietary treatments up to 270 d of gestation: Control (CON, n = 12), consisting of a basal diet supplemented with conventional urea, where the cows were fed with diets containing 13.5 g conventional urea per kg dry matter; and PRU (PRU, n = 12), consisting of a basal diet supplemented with a urea coated to extensively prevent ruminal degradation while being intestinally digestible, where the cows were fed with diets containing 14,8 g urea protected from ruminal degradation per kg dry matter. Post-ruminal supply of urea reduced the urine levels of 3-methylhistidine (P = 0.02). There were no differences between treatments for dry matter intake (DMI; P = 0.76), total digestible nutrient (TDN) intake (P = 0.30), and in the body composition variables, such as, subcutaneous fat thickness (SFT; P = 0.72), and rib eye area (REA; P = 0.85). In addition, there were no differences between treatments for serum levels of glucose (P = 0.87), and serum levels of glucogenic (P = 0.28), ketogenic (P = 0.72), glucogenic, and ketogenic (P = 0.45) amino acids, neither for urea in urine (P = 0.51) as well as urea serum (P = 0.30). One the other hand, enriched pathways were differentiated related to carbohydrate digestion, and absorption, glycolysis, pyruvate metabolism, oxidative phosphorylation, pentose phosphate pathway, and biosynthesis of amino acids of the exclusively expressed proteins in PRU cows. Shifting urea supply from the rumen to post-ruminal compartments decreases muscle catabolism in cows during late gestation. Our findings indicate that post-ruminal urea supplementation for beef cows at late gestation may improve the energy metabolism to support maternal demands. In addition, the post-ruminal urea release seems to be able to trigger pathways to counterbalance the oxidative stress associated to the increase liver metabolic rate.

Mineral and glycerol concentrations in drinking water on body weight loss and acid-base balance in feed-deprived Holstein bulls.

Situations in which cattle are feed-deprived over extensive periods of time are common in the context of transport and is an animal welfare concern which may also compromise growth and carcass yield grade. This study investigated how the main components of an oral rehydration solution would affect BW loss and blood parameters in feed-deprived bulls. Three dose-response experiments were performed with 24 bulls each (n = 6 per treatment) to study the effect of mineral concentration in Study I (0, 100, 200 and 300 mOsm/kg), the K+ to Na+ ratio in Study II (25:75, 40:60, 60:40 and 75:25), and glycerol concentration in Study III (0%, 1%, 2% and 4% of the final solution). The blocking factor was initial BW and treatments were randomly assigned within each block. Measurements included fluid intakes, BW, and blood parameters at 0, 24 and 48 h relative to the start of feed deprivation. In Study I, increasing mineral concentration in solution linearly decreased BW losses at 48 h. At 24 and 48 h, serum urea linearly decreased with increasing mineral concentration. At 48 h, blood K+ and Na+ linearly increased, resulting in increased blood osmolarity. Additionally, at 24 h feed deprivation, blood pH linearly increased with increasing osmolality. In Study II, BW losses decreased with increasing K+ to Na+ ratio at 24 h, but not at 48 h. No effect of the K+ to Na+ ratio was found on blood parameters, apart from a trend for a linear decrease of blood osmolarity at 48 h. In Study III, serum urea tended to linearly decrease with increasing glycerol inclusion at 24 h, while blood glucose linearly increased with glycerol inclusion at 24 and 48 h. These combined results indicated that a solution with an osmolality of 200 mOsm/kg and a high K+ to Na+ ratio would effectively mitigate BW losses and maintain blood acid-base balance, whereas high glycerol inclusion sustained blood glucose in feed-deprived bulls.

Urea supplementation in rumen and post-rumen for cattle fed a low-quality tropical forage.

We evaluated the differences between the supplementation of urea in rumen and/or abomasum on forage digestion, N metabolism and urea kinetics in cattle fed a low-quality tropical forage. Five Nellore heifers were fitted with rumen and abomasum fistulas and assigned to a Latin square design. The treatments were control, continuous infusion of urea in the abomasum (AC), continuous infusion of urea in the rumen, a pulse dose of urea in the rumen every 12 h (PR) and a combination of PR and AC. The control exhibited the lowest (P < 0·10) faecal and urinary N losses, which were, overall, increased by supplementation. The highest urinary N losses (P < 0·10) were observed when urea was either totally or partially supplied as a ruminal pulse dose. The rumen N balance was negative for the control and when urea was totally supplied in the abomasum. The greatest microbial N production (P < 0·10) was obtained when urea was partially or totally supplied in the abomasum. Urea supplementation increased (P < 0·10) the amount of urea recycled to the gastrointestinal tract and the amount of urea-N returned to the ornithine cycle. The greatest (P < 0·10) amounts of urea-N used for anabolism were observed when urea was totally and continuously infused in the abomasum. The continuous abomasal infusion also resulted in the highest (P < 0·10) assimilation of microbial N from recycling. The continuous releasing of urea throughout day either in the rumen or abomasum is able to improve N accretion in the animal body, despite mechanism responsible for that being different.

Effect of Lipid Sources with Different Fatty Acid Profiles on Intake, Nutrient Digestion and Ruminal Fermentation of Feedlot Nellore Steers.

The present study was conducted to determine the effect of lipid sources with different fatty acid profiles on nutrient digestion and ruminal fermentation. Ten rumen and duodenal fistulated Nellore steers (268 body weight±27 kg) were distributed in a duplicated 5×5 Latin square. Dietary treatments were as follows: without fat (WF), palm oil (PO), linseed oil (LO), protected fat (PF; Lactoplus), and whole soybeans (WS). The roughage feed was corn silage (600 g/kg on a dry matter [DM] basis) plus concentrate (400 g/kg on a DM basis). The higher intake of DM and organic matter (OM) (p<0.001) was found in animals on the diet with PF and WF (around 4.38 and 4.20 kg/d, respectively). Treatments with PO and LO decreased by around 10% the total digestibility of DM and OM (p<0.05). The addition of LO decreased by around 22.3% the neutral detergent fiber digestibility (p = 0.047) compared with other diets. The higher microbial protein synthesis was found in animals on the diet with LO and WS (33 g N/kg OM apparently digested in the rumen; p = 0.040). The highest C18:0 and linolenic acid intakes occurred in animals fed LO (p<0.001), and the highest intake of oleic (p = 0.002) and C16 acids (p = 0.022) occurred with the diets with LO and PF. Diet with PF decreased biohydrogenation extent (p = 0.05) of C18:1 n9,c, C18:2 n6,c, and total unsaturated fatty acids (UFA; around 20%, 7%, and 13%, respectively). The diet with PF and WF increased the concentration of NH3-N (p<0.001); however, the diet did not change volatile fatty acids (p>0.05), such as the molar percentage of acetate, propionate, butyrate and the acetate:propionate ratio. Treatments PO, LO and with WS decreased by around 50% the concentration of protozoa (p<0.001). Diets with some type of protection (PF and WS) decreased the effects of lipid on ruminal fermentation and presented similar outflow of benefit UFA as LO.

Lipid Sources with Different Fatty Acid Profile Alters the Fatty Acid Profile and Quality of Beef from Confined Nellore Steers.

The present study was conducted to determine the effects of lipid sources with different fatty acids profile on meat fatty acids profile and beef quality traits of Nellore. A total of 45 Nellore animals with an average initial body weight of 419±11 kg (at 15±2 mo) were distributed in a completely randomized design consisting of 5 treatments and 9 replicates. The roughage feed was maize silage (600 g/kg on a dry matter [DM] basis) plus concentrate (400 g/kg on a DM basis). The dietary treatments were as follows: without fat (WF), palm oil (PO), linseed oil (LO), protected fat (PF), and soybean grains (SG). No effects of lipid sources were observed (p>0.05) on beef color, pH, water-holding capacity, and sarcomere length. Beef from cattle fed PO had greater shear-force values (p<0.05) compared to beef from cattle fed WF. Deposition of main unsaturated fatty acids (oleic, linoleic, and linolenic) was greater in treatments WF, SG, and LO, respectively, while the values of conjugated linoleic acid (CLA) were greater when animals were fed LO. The inclusion of LO in the diet enhances the concentration of CLA in longissimus muscle and subcutaneous fat besides improving the atherogenicity index and elongase activity. As such, LO can be used with the aim to improve the quality of beef from confined Nellore cattle. Conversely, the use of PO is not recommended since it may increase the concentration of undesirable unsaturated fatty acids in muscle and subcutaneous fat, shear-force and the atherogenicity index.