Impact of Supplementing a Backgrounding Diet with Nonprotein Nitrogen on In Vitro Methane Production, Nutrient Digestibility, and Steer Performance.

Two experiments were conducted to evaluate the effect of nonprotein nitrogen (NPN) supplementation on in vitro fermentation and animal performance using a backgrounding diet. In experiment 1, incubations were conducted on three separate days (replicates). Treatments were control (CTL, without NPN), urea (U), urea-biuret (UB), and urea-biuret-nitrate (UBN) mixtures. Except for control, treatments were isonitrogenous using 1% U inclusion as a reference. Ruminal fluid was collected from two Angus-crossbred steers fed a backgrounding diet plus 100 g of a UBN mixture for at least 35 d. The concentration of volatile fatty acids (VFA) and ammonia nitrogen (NH3-N), in vitro organic matter digestibility (IVOMD), and total gas and methane (CH4) production were determined at 24 h of incubation. In experiment 2, 72 Angus-crossbred yearling steers (303 ±â€…29 kg of body weight [BW]) were stratified by BW and randomly allocated in nine pens (eight animals/pen and three pens/treatment). Steers consumed a backgrounding diet formulated to match the diet used in the in vitro fermentation experiment. Treatments were U, UB, and UBN and were isonitrogenous using 1% U inclusion as a reference. Steers were adapted to the NPN supplementation for 17 d. Then, digestibility evaluation was performed after 13 d of full NPN supplementation for 4 d using 36 steers (12 steers/treatment). After that, steer performance was evaluated for 56 d (24 steers/treatment). In experiment 1, NPN supplementation increased the concentration of NH3-N and VFA (P < 0.01) without affecting the IVOMD (P = 0.48), total gas (P = 0.51), and CH4 production (P = 0.57). Additionally, in vitro fermentation parameters did not differ (P > 0.05) among NPN sources. In experiment 2, NPN supplementation did not change dry matter and nutrient intake (P > 0.05). However, UB and UBN showed lower (P < 0.05) nutrient digestibility than U, except for starch (P = 0.20). Dry matter intake (P = 0.28), average daily gain (P = 0.88), and gain:feed (P = 0.63) did not differ among steers receiving NPN mixtures. In conclusion, tested NPN mixtures have the potential to be included in the backgrounding diets without any apparent negative effects on animal performance and warrant further studies to evaluate other variables to fully assess the response of feeding these novel NPN mixtures.

Nonprotein nitrogen (NPN) supplements can be used as a nitrogen source for ruminants fed low-protein diets. The most common NPN source is urea, included typically at a range between 0.5% and 1% of the diet dry matter in growing beef cattle. Although other NPN sources and mixtures are available, there is scarce information regarding their use in ruminant production. Two experiments were conducted to evaluate the effect of NPN sources on in vitro fermentation and animal performance using a backgrounding diet. In experiment 1, three different incubations were performed for 24 h. Treatments were control (without NPN), urea (U), urea­biuret (UB), and urea­biuret­nitrate (UBN) mixtures. In experiment 2, 72 crossbred yearling steers were randomly assigned to one of the following treatments: U, UB, and UBN mixtures. Diets were formulated to contain the same nitrogen concentration in both experiments. In experiment 1, supplementation of NPN increased the in vitro fermentation, but there were no differences among NPN sources. In experiment 2, steers performed similarly among NPN sources. These findings suggest that NPN mixtures have the potential to be included in the backgrounding diets without detrimental effects. Further studies should evaluate other variables (e.g., fermentation dynamic and microbial protein supply) when using these novel mixtures.

Effects of Processing Methods and Inclusion Levels of Dried Garlic on In Vitro Fermentation and Methane Production in a Corn Silage-Based Substrate.

Garlic (Allium sativum) contains secondary compounds that are known to modify rumen fermentation parameters and decrease methane (CH4) emissions. The objective was to evaluate the effects of increasing the inclusion levels and processing methods of garlic on in vitro fermentation and CH4 production. Treatments were arranged in a randomized complete block design with a 2 × 3 × 2 + 1 factorial arrangement, where the main factors were the initial condition of garlic (intact or smashed), drying process (freeze-dried, oven-dried, or autoclaved), and garlic proportion in the diet (2.5 and 5%) and one control (without garlic supplementation). Incubations were conducted using corn silage and cotton-gin trash (80:20, respectively) as basal substrates on three different days. Final pH, the concentration of volatile fatty acids (VFA) and ammonia nitrogen (NH3-N), in vitro organic matter digestibility (IVOMD), total gas production, and CH4 concentration were determined after 24 h. Initial garlic condition or drying processing neither modify (p > 0.05) the in vitro fermentation nor the CH4 production. However, increasing garlic inclusion linearly increased (p < 0.05) IVOMD, the concentration of the total VFA, and the proportion of propionate. Also, the concentration of NH3-N and the proportion of acetate increased quadratically (p < 0.05) with greater garlic inclusions. Finally, garlic inclusion did not affect (p > 0.05) gas and CH4 production. In conclusion, increasing garlic levels, but not the processing methods, improved in vitro fermentation but did not modify CH4 emissions under in vitro conditions.