PSIV-9 Effective ruminal degradability of steam-flaked corn is influenced by flake density and starch retrogradation

The objective of this study was to evaluate in situ ruminal digestion characteristics of steam-flaked corn with large differences in starch availability (SA) using two different models: 1) increasing flake density and 2) exposure to 55°C temperatures to induce starch retrogradation. Five ruminally-cannulated steers (body weight = 390 ± 7.86 kg) were pen-fed a starter diet. In Exp. 1, sifted flakes with flake densities of 257, 296, 335, 373, and 412 g/L (SA: 87%, 76%, 66%, 43%, and 49%, respectively) were evaluated. In Exp. 2, three steam-flaked corn fractions were evaluated: flakes + fines (not sifted), sifted flakes (>4-mm), and sifted fines (< 4-mm). Feed fractions were stored for 3-d at either 23°C or 55°C (average SA across steam-flaked corn fractions: 53.3% and 25.5% respectively). Treatments of Exp. 2 were arranged with a 3 × 2 factorial. Both experiments were duplicated and analyzed as randomized complete block designs. In Exp. 1, the fractional rate of degradation linearly decreased (P < 0.001) and effective ruminal dry matter degradability (ERD) linearly decreased (P < 0.001) from 80.8% to 60.3% as flake density increased from 257 to 412 g/L. In Exp. 2, storage of steam-flaked corn samples at 55ºC for 3-d decreased (P < 0.001) the fractional rate of degradation and ERD by 38.6% and 21.7% across all feed fractions, respectively. Using data from Exp. 1 and 2, SA of sifted flakes was positively correlated (Pearson = 0.8435; R2 = 0.71; P < 0.001) to ERD. The results of the current study demonstrate that decreased SA resulting from starch retrogradation or increased flake density is associated with decreased ERD. Decreases in SA and ERD may indicate that increasing flake density or starch retrogradation could potentially alter the site of digestion in cattle, by increasing postruminal starch flows.

Mathematical modeling applied to ruminal digestion and gas production in vitro

The ruminal digestion performed by ruminants is one of the essential and most important processes for the use of dietary nutrients. However, the use of mathematical models applied to digestion kinetics has been widely applied to provide prediction of animal performance, maximize the use of nutrients and reduce nutritional losses due to excreta and a reduction in the cost of animal production. In this context, it aimed to conduct a literature review on the use of mathematical models and to analyze comparisons of different models to predict ruminal digestion. The in vitro gas production technique provides direct measurement of the ruminal digestion rate associated with gas production and the respective gravimetric measurement of the food or diet under test. Nonlinear models are chosen to evaluate ruminal digestion due to a better interpretation of biological parameters, they produce exponential and sigmoidal growth equations. However, the most suitable model for evaluation depends on the type of food or diet. The two-compartment logistical model presents a better adjustment of the gas production curve, mainly for foods with a high proportion of fiber. Among this, single-compartment models can be well applied to evaluate the degradation kinetics of foods with low fibrous carbohydrate content. Therefore, the choice of the most appropriate model is up to the researcher to assess which model best suits the chemical-chemical composition of the food or diet.

194 Effects of feeding increased roughage to feedlot steers the last 56 days of finishing

Finishing cattle are fed high concentrate diets to increase deposition of both muscle and adipose tissue and decrease cost of gain. The objective of this experiment was to evaluate the effects of increased roughage inclusion late in the finishing period on growth performance, carcass traits, and ruminal and fecal characteristics of feedlot steers. Treatments included a control (CON; 6% roughage DM), intermediate (INT; 12% roughage DM), and high (HGH; 18% roughage DM) roughage diets. Crossbred beef steers (n = 54; BW = 289 ± 35.6 kg) were assigned to treatments for the late finishing period in a randomized complete block design (4 pens of INT and HGH, 5 pens of CON; 4 steers per pen). Experimental diets contained prairie hay, Sweet Bran, rolled corn, dry supplement, urea, and a corn steep and molasses-based liquid supplement. The inclusion rate of roughage and rolled corn were adjusted for each treatment diet. Steers in HGH tended to have increased overall DMI (P = 0.07). No differences in final BW, overall ADG, or gain:feed were observed among treatments (P ≥ 0.72). Steers fed HGH had the greatest REA (P = 0.03) and a tendency for a lower yield grade (P = 0.08). Fat thickness, HCW, marbling, liver scores, and KPH did not differ (P ≥ 0.29) among treatments. Steers fed the HGH diet had a lower fecal pH at the end of finishing (P = 0.05) compared to CON and INT steers. Ruminal lactate was increased on d 14 for CON steers compared to other treatments (P < 0.001). No differences were observed for ruminal pH (P ≥ 0.11). Results of this experiment suggest that increasing roughage late in the finishing period does not negatively impact growth performance or carcass characteristics, but may alter ruminal fermentation and post ruminal digestion.

24 Condensed tannins: structure, activity and characterization

As a class of plant polyphenolic compounds contained in some forages [i.e., sainfoin (Onobrychis viciifolia Scop.), big trefoil (Lotus pedunculatus Cav.), birdsfoot trefoil (Lotus corniculatus L.)], condensed tannins (CTs) exhibit a variety of biological effects on ruminants. The potential positive impact of CTs on the agricultural industry stems from their ability to modulate proteolysis during forage conservation and ruminal digestion, to prevent bloat, to reduce intestinal parasite burdens, and to abate methane and ammonia emissions from ruminants. How CTs exert these effects on ruminants focuses on the interaction of CTs with proteins. The structure-activity relationship in CT–protein interaction is not well understood but is known to be dependent on the structure and properties of both the CT and the protein. The objectives of this presentation are fivefold. First, examples of the structural diversity of CTs will be provided to enable the audience members to appreciate that not all CTs are the same. Second, examples of how CTs structural diversity affects their interaction with the protein, which in turn, dictates the biological response from the animal will be discussed. Third, the presentation will outline hurdles in obtaining highly pure and well-characterized CTs from natural sources for use in CT structural analysis and in vitro experiments. This will be followed by brief descriptions of improved and emerging techniques for CT analysis and, finally, the presentation concludes with questions to address in future investigations and a list of recommendations for CT researchers to follow.

Microbial Patterns in Rumen Are Associated with Gain of Weight in Beef Cattle

Ruminal microorganisms play a pivotal role in cattle nutrition. The discovery of the main microbes responsible for enhancing the gain of weight in beef cattle might be used in therapeutic approaches to increase animal performance and cause less environmental damages. Here, we examined differences in bacterial and fungal composition of rumen samples of Braford heifers raised in a natural grassland from Pampa Biome in Brazil. We aimed to detect microbial patterns in the rumen that could be correlated with the gain of weight. 16S and ITS1 genes were amplified from ruminal samples and sequenced to identify the closest microbial relatives within the microbial communities. A predictive model based on microbes responsible for the gain of weight was build and further tested using the entire dataset. The model detected a set of microorganisms associated with animals in the high gain of weight group, including the bacterial taxa RFN20, Prevotella, Anaeroplasma and RF16 and the fungal taxa Aureobasidium, Cryptococcus, Sarocladium, Pleosporales and Tremellales. Most of these organisms have been correlated to the production of substances that improve the ruminal digestion process. These findings provide new insights about cattle nutrition and suggest the use of these microbes to improve beef cattle breeding.

Chemical composition and ruminal digestion of corn silage with Morus alba L. foliage

Chemical composition and ruminal digestion parameters were mea- sured in the silage of the whole corn plant (Zea mays L.) mixed with mulberry foliage (Morus alba L.) in ratio of 100:0, 80:20, 60:40, 40:60, 20:80 and 00:100% of fresh forage weight, respectively. The 40:60 ratio of corn: mulberry increased crude protein content (CP = 14.28%) and decreased hemicellulose (12.15%), neutral (NDF = 28.00%) and acidic (ADF = 15.85%) detergent fiber, compared to 100: 0% ratio, respectively, which led to a 21.3% increase in in vitro dry matter digestibility (IVDMD). Also ammoniacal nitrogen 7.40% (NH3-N/total N) was higher in the ratio 40:60%, with pH of 4.19 which is normal for silages, which translates the buffer activity correct of ammonia and its importance for silage fermentation stability. The correlation (r = 0.61, p < 0.001) indicated that at higher CP content, higher is IVDMD and hemicellulose (r = -0.99), ADF (r = -0.98) and NDF (r = -0.98) indicated that these fibrous compounds decreased IVDMD (p < 0.001). The regression showed that the increase in content CP (0.555%, p < 0.01) and IVDMD (0.3391%, p < 0.001) with the decrease of NDF (-0.3526%), ADF (-0.1623%) and hemicellulose (-0.1903%) (p < 0.001) in mixed mini silos, was attributed to mulberry foliage addition. It is concluded that the contribution of dry matter and nitrogen of mulberry, decreased the fiber content and increased digestibility parameters of silage when it is elaborated in ratio of 40:60 corn and mulberry, respectively.

PSXIV-41 Warm-season annual or perennial hay fed to growing beef steers with or without dried distillers grains supplementation: ruminal fermentation characteristics, digestion, and feeding behavior

The effects of hay type and protein supplementation on intake, feeding behavior, nutrient digestion, and ruminal digestion characteristics were evaluated. Ruminally cannulated Angus beef steers (n = 6; BW = 304 kg ± 11 kg) were randomly assigned within a sequence of treatments using a 4 × 6 unbalanced Latin square design (6 steers; and 4 diets; fed once-daily). A 2 x 2 factorial treatment arrangement was used as follows: 1) ‘WW-B. Dahl’ Old World bluestem [Bothriochloa bladhii (Retz) S.T. Blake; WWBD or Eragrostis tef (Zucc.) Trotter; TEFF); and 2) dried distillers grain (DDGS) at 0 or 0.5% BW. Each period consisted of a 14-d of adaptation and 7-d collection. Steers were observed (5-min intervals, 24 h) for behavioral assessment; while ruminal pH was continuously measured (wireless pH probe), and ruminal fluid collected at 0, 2, 4, 8, and 16 h after-feeding. Steers fed TEFF hay and those fed DDGS (both, P = 0.04) had greater DMI compared to WWBD and not supplemented. Chewing activity did not differ (P ≥ 0.54). Non-supplemented steers spent more time eating hay (P &lt; 0.01) than supplemented steers. Average ruminal pH of TEFF (6.32) was lower (P &gt; 0.01) than WWBD (6.56). Non-supplemented steers produced less in vitro total gas and methane (both, P = 0.02) per g rumen fluid DM. The VFA profile was not affected (P ≥ 0.45) by treatments. Apparent total-tract digestibility and ruminal degradation (P ≤ 0.01) were greater with TEFF fed steers than WWBD. Hemicellulose digestion was reduced by 6.95% (P = 0.03) with DDGS supplementation. An annual hay in place of a conventional perennial hay improved intake, ruminal digestion of nutrients, without affecting feeding behavior, while supplementation with DDGS reduced forage intake time and quantity, without negatively affecting ruminal fiber digestion.