Effect of supplementation frequency and supplemental urea level on dormant tallgrass-prairie hay intake and digestion by beef steers and prepartum performance of beef cows grazing dormant tallgrass-prairie

Nitrogen Utilization in Goats Consuming Buffelgrass Hay and Molasses-Based Blocks with Incremental Urea Levels

The use of goats for meat production faces challenges from environmental and nutritional factors. Urea is an affordable non-protein nitrogen source commonly utilized in ruminant nutrition. The objective of this study was to investigate nitrogen utilization in goats fed low-quality hay supplemented with molasses blocks containing urea. Twenty Anglo-Nubian doelings were individually housed in metabolic cages and provided with chopped Buffelgrass (Cenchrus ciliaris) hay ad libitum. Goats were randomly assigned to four urea levels (0, 2, 4, and 6%; n = 5 per treatment) in molasses blocks for a duration of 30 days. A negative nitrogen balance (-2.458 g/day) was observed in doelings consuming blocks without urea, compared with a positive balance (0.895 g/d) for those consuming the 6% urea blocks. Block nitrogen intake significantly increased with urea level, but urea supplementation did not affect dry matter (DM) or neutral detergent fiber (NDFom) intake or digestibility. A minimum crude protein (CP) requirement of 8% for maintenance in doelings consuming low-quality forage with a urea-based supplement was determined through regression analysis between CP intake (% of DM) and N balance (r2 = 0.479; p < 0.002). The value of 8% of CP obtained in this study is similar to several previous studies reported in the literature, but in this case, the increments in CP came exclusively from urea. In this study, increasing the urea content of molasses blocks up to 6% significantly increased nitrogen intake, retention, and balance in goats. These results contribute to a better understanding of nitrogen utilization in goats fed low-quality hay with urea supplementation.

Functional Changes of the Community of Microbes With Ni-Dependent Enzyme Genes Accompany Adaptation of the Ruminal Microbiome to Urea-Supplemented Diets

Urea is an inexpensive non-protein nitrogen source commonly supplemented to the diets of ruminants. It is cleaved to ammonia by bacterial ureases, which require Ni as a catalyst for ureolysis. The key event in the changes of the ruminal microbiome after urea supplementation remains unknown. We have therefore investigated changes in the ruminal microbiome and its community with Ni-dependent enzyme genes following urea supplementation and analyzed the associations of rumen environmental factors, including fermentation variables and Ni concentrations, with the compositional and functional changes of these communities. We found that urea supplementation increased urease activity and the concentrations of ammonia and Ni, and tended to increase concentrations of short chain fatty acids and acetate, whereas it decreased rumen pH and the L-/D-lactate ratio. With standards for genome completeness >60% and strain heterogeneity <10%, 20 bacterial species containing five Ni-dependent enzyme genes were detected in the metagenome sequences. For the five Ni-dependent enzyme genes, urea supplementation increased the relative abundances of genes of urease and acetyl-CoA synthase, whereas it decreased the relative abundances of genes of glyoxalase I, [NiFe]-hydrogenase, and lactate racemase. For the 20 microbes with Ni-dependent enzyme genes, urea supplementation increased the relative abundances of five bacteria exhibiting high capacities for the utilization of hemicellulose and pectin for butyrate and fatty acid biosynthesis. For the ruminal microbiome, urea supplementation increased the metagenomic capacities for hemicellulose and pectin degradation, butyrate generation, fatty acid biosynthesis, and carbon fixation, whereas it decreased the metagenomic capacities for starch degradation, propionate generation, and sulfur and nitrogen metabolism. Constrained correspondence analysis identified rumen ammonia and Ni concentrations as likely driving factors in the reshaping of the ruminal microbiome and, together with pH, of the community of microbes with Ni-dependent enzyme genes. Thus, the functional change of the latter community is probably an important event in the adaptation of the ruminal microbiome to urea-supplemented diets. This result provides a new perspective for the understanding of the effects of urea supplementation on rumen fermentation.

In vivo ruminal degradation characteristics and apparent digestibility of low-quality prairie hay for steers consuming monensin and Optimase

Seven ruminally cannulated crossbred steers (BW = 720 ± 62 kg) were used in a randomized crossover design (4 periods, each 18 d) to evaluate in vivo rumen characteristics and apparent digestibility of steers consuming low-quality prairie hay and 1 of 4 isonitrogenous protein supplements. Treatments included 1) 40% CP (DM basis) cottonseed meal and wheat middlings-based supplement (Control), 2) a cottonseed meal and wheat middlings-based supplement with slow-release urea and a fibrolytic feed enzyme (Optimase; Alltech, Inc., Nicholasville, KY) designed to replace 30% of plant-based CP provided in the Control (OPT), 3) the Control plus 0.40 mg∙kg BW∙d monensin (Rumensin 90; Elanco Animal Health, Greenfield, IN; MON), and 4) the OPT plus 0.40 mg∙kg BW∙d monensin (COMBO). Steers were allowed ad libitum access to prairie hay (5.0% CP and 76% NDF) and were provided each respective supplement at 0800 h daily at a rate of 1.0 g/kg of BW. Steers were adapted to diets for 10 d before sample collection. Beginning on d 11, DMI was measured and samples were collected to determine apparent digestibility. On d 15 of the 18-d period, rumen fluid was collected 10 times over a 24-h period. Forage DMI was greater ( ≤ 0.02) for steers consuming the OPT compared with steers consuming the MON or COMBO, although forage DMI was not different ( = 0.10) among steers consuming the Control compared with steers consuming the OPT, MON, or COMBO. Steers fed the MON and COMBO had lower ( ≤ 0.05) passage rate compared with steers fed the Control and the OPT. The MON-fed steers had lower ( = 0.01) ruminal pH and increased ( = 0.03) propionate as a percentage of total VFA production. A time × treatment ( = 0.01) interaction was observed for ruminal NH-N due to a rapid (0 to 1 h after feeding) increase followed by a quick (1 to 4 h after feeding) decline in NH-N by steers consuming the OPT and COMBO that was not observed for steers consuming all other treatments. Apparent digestibility of DM ( = 0.01) and NDF ( = 0.03) were improved for steers fed the COMBO supplement compared with steers consuming all other experimental supplements. This work suggests that the OPT may be an effective replacement for a portion of supplemental degradable intake protein in low-quality forage. Further research is necessary to determine if the combination of monensin and the Optimase consistently improves low-quality forage utilization.

Supplementation with Calliandra calothyrsus improves nitrogen retention in cattle fed low-protein diets

Ruminant productivity in the tropical Africa has remained low despite decades of research on animal nutrition and introduction of new breeds of animals mainly because of low-quality feeds available, especially during the dry season that is inefficiently utilised. This results in prolonged time for animals to mature and increased nutrient excretion to the environment. We conducted a study using yearling steers (n = 12, liveweight (LW) = 161.8 ± 10.89 kg) in a 3 × 3 Latin square to evaluate the effect of protein supplementation and supplementation frequency on intake, digestibility, nitrogen (N) retention and microbial N supply in cattle consuming low-protein diets. The steers were maintained on ad libitum wheat straw (DM = 877 ± 5 g/kg, crude protein (CP) = 20.0 ± 1.1 g/kg), with supplemental protein supplied as air-dried Calliandra calothyrsus leaves (DM = 897 ± 3 g/kg, CP = 257.5 ± 4.1 g/kg on a DM basis). Samples of basal diet, supplement, refusals, faecal matter and urine were collected and analysed per treatment. Supplementation increased intakes by the steers (P < 0.001), with no difference between the two supplementation frequencies (P > 0.404). Steers lost bodyweight (P < 0.05) on all treatments, but less so when supplemented. Nitrogen losses was reduced (P < 0.001) with supplementation (–33.3% vs 15.7%, s.e.m. 0.06). The increased N balance in animals receiving supplemented diets indicated that N retention actually improves with increased protein supplementation in animals fed low-protein diets, implying that improving protein supply to animals fed submaintenance diets will not only ameliorate production losses, but will actually decrease non-enteric greenhouse gas production and environmental N losses per animal product unit obtained.

Supplementation of monensin and Optimase to beef cows consuming low-quality forage during late gestation and early lactation

Two experiments were designed to investigate the effects of feeding monensin and/or slow release urea with a fibrolytic feed enzyme (Optimase; Alltech, Inc., Nicholasville, KY) on performance, milk production, calf growth performance, and blood metabolites in beef cows. Spring-calving cows and heifers were used in a completely randomized design in Exp. 1 (N = 84; 534 ± 68 kg initial BW) and Exp. 2 (N = 107; 508 ± 72 kg initial BW). Exp. 1 supplements were formulated to meet cow protein requirements and fed daily and included 1) cottonseed meal with no monensin (control); or 2) monensin added to control to supply 200 mg per head per d (MON). In Exp. 2, experimental supplements included 1) cottonseed meal/wheat middlings (CS) fed at a rate to provide adequate DIP and CP according to , 2) the CS plus soybean hulls and 61 g per cow per d Optimase (OPT), 3) the CS plus monensin to supply 200 mg per cow per d (MON2), and 4) OPT plus MON2 (Combo). Cows were fed in last trimester through early lactation in Exp. 1 and during 2nd trimester in Exp. 2. Data were analyzed using the Mixed procedure in SAS with animal as the experimental unit. In Exp. 1, treatment did not affect cow BW or BCS change (P > 0.19). Calf birth BW was not affected by dam treatment (P = 0.24); however, calves from dams consuming MON weighed more (P < 0.04) at d 45 and at trial end. Calves also had greater (P = 0.04) ADG from birth to trial end. Milk production did not significantly differ among treatments (P > 0.41). In Exp. 2, mean cow BW and BCS were similar (P > 0.35) among treatments on d 90. However, from d 0 to 54, cows assigned to the OPT supplement gained less BCS (P = 0.02) compared with cows assigned to the CS supplement. Cumulative BCS gain was greater (P < 0.01) for CS-fed cows than for cows fed the OPT and MON2 supplements, although it was not significantly different for cows fed the Combo supplement. These studies indicate that the influence of monensin on cow BW and BCS change is inconsistent. The potential for monensin supplementation to positively impact calf performance during early lactation seems to be clearer. Replacing a portion of oilseed N in the supplement with Optimase may marginally reduce cow performance. Further research is needed to determine both the effects of monensin and the implications of combining monensin with Optimase on forage intake and cow performance at various stages of production.

Beef Species Symposium: an assessment of the 1996 Beef NRC: metabolizable protein supply and demand and effectiveness of model performance prediction of beef females within extensive grazing systems

Interannual variation of forage quantity and quality driven by precipitation events influence beef livestock production systems within the Southern and Northern Plains and Pacific West, which combined represent 60% (approximately 17.5 million) of the total beef cows in the United States. The beef cattle requirements published by the NRC are an important tool and excellent resource for both professionals and producers to use when implementing feeding practices and nutritional programs within the various production systems. The objectives of this paper include evaluation of the 1996 Beef NRC model in terms of effectiveness in predicting extensive range beef cow performance within arid and semiarid environments using available data sets, identifying model inefficiencies that could be refined to improve the precision of predicting protein supply and demand for range beef cows, and last, providing recommendations for future areas of research. An important addition to the current Beef NRC model would be to allow users to provide region-specific forage characteristics and the ability to describe supplement composition, amount, and delivery frequency. Beef NRC models would then need to be modified to account for the N recycling that occurs throughout a supplementation interval and the impact that this would have on microbial efficiency and microbial protein supply. The Beef NRC should also consider the role of ruminal and postruminal supply and demand of specific limiting AA. Additional considerations should include the partitioning effects of nitrogenous compounds under different physiological production stages (e.g., lactation, pregnancy, and periods of BW loss). The intent of information provided is to aid revision of the Beef NRC by providing supporting material for changes and identifying gaps in existing scientific literature where future research is needed to enhance the predictive precision and application of the Beef NRC models.

Opportunities to enhance performance and efficiency through nutrient synchrony in forage-fed ruminants

Increasingly, the need for optimized nutrient utilization to address increasing production costs and environmental considerations will necessitate opportunities to improve nutrient synchrony. Historically, attempts at synchronizing nutrient supply in ruminants, particularly in cattle consuming high-forage diets, have met with variable results. The success of nutrient synchrony has been measured primarily in ruminants by increases in microbial yield, microbial efficiency, nutrient utilization, and to a lesser extent, animal performance. Successful synchrony of nutrient supply to cattle consuming forage-based diets faces several challenges. From a feed supply aspect, the challenges to nutrient synchrony include accurately measuring forage intake and consumed forage chemical composition. The issue of forage intake and chemical composition is perhaps the most daunting for producers grazing cattle. Indeed, for forage-fed cattle, the availability of forage protein and carbohydrate can be the most asynchronous aspect of the diet. In most grazed forages, digestion rates of the carbohydrate fractions are much slower than that of the corresponding protein fractions. Additionally, the forage-supplement interaction exerts a large impact on the synchrony of nutrients. The supplemental feedstuffs compose the component of the nutrient synchrony scenario that is most often manipulated to influence synchrony. The supplement type (e.g., starch vs. fiber, dry vs. liquid), nutrient profile, and degradation rates are often prime considerations associated with nutrient synchrony on high forage diets. Other considerations that warrant attention include temporal intake patterns of the forage and supplement, increased use and types of coproduct supplements, and an assessment of the success of nutrient synchrony. Synchronization of nutrient utilization by forage-fed ruminants has and will continue to encounter challenges for successful outcomes. Ultimately it is the improvement in animal performance and optimization of nutrient utilization efficiency that dictates whether nutrient synchrony is a successful strategy.