Comparison of Ruminal Degradability, Indigestible Neutral Detergent Fiber, and Total-Tract Digestibility of Three Main Crop Straws with Alfalfa Hay and Corn Silage

Three main crop straws including corn straw (Zea mays, CS), rice straw (Oryza sativa, RS), and wheat straw (Triticum aestivum, WS), and two forages including alfalfa hay (Medicago sativa, AH) and corn silage (Zea mays, CSil) were analyzed in order to compare their ruminal degradability, indigestible neutral detergent fiber (iNDF), intestinal digestibility (ID), and their total-tract digestibility (TTD) of crude protein (CP), neutral detergent fiber (NDF), and acid detergent fiber (ADF) using both an in situ nylon bag technique and a mobile nylon bag technique. The forage samples were incubated in the rumen for 6, 12, 16, 24, 36, 48, 72, and 288 h, respectively, to determine their ruminal degradability. Prior to intestinal incubation, forage samples were incubated in the rumen for 12 h and 24 h to determine the ruminal degradable content of CP, NDF, and ADF, respectively, and for 288 h to determine their iNDF288 content. Residues from the ruminal undegradable fractions (12 h for CP, 24 h for NDF and ADF) were subsequently inserted into the duodenum through a cannula to determine their intestinal digestible content. Here, the TTD of CP, NDF, and ADF were determined as the ruminal degradable content + intestinal digestible content. The results showed that AH had the highest iNDF2.4 (calculated as acid detergent lignin content × 2.4) and iNDF288 values (379.42 and 473.40 g/kg of NDF), while CS and CSil had the lowest iNDF2.4 values (177.44 and 179.43 g/kg of NDF). The ruminal degradability of CP, NDF, and ADF for CS, RS, and WS were lower than those of AH and Csil during the first 48 h of incubation. The potential degradation fraction of CP, NDF, and ADF for CSil was the highest; CS, RS, and WS were intermediate; and AH was the lowest (p < 0.05). CS, RS, and WS had a lower intestinal digestibility with respect to their rumen undegradable content of NDF (p < 0.05), and lower TTD of CP, NDF, and ADF (p < 0.05) compared to AH and CSil. General regression equations with satisfactory accuracy (R2 ≥ 0.828) were derived to predict iNDF288 and TTD based on their chemical compositions and the ruminal degradation kinetics of different forages. Incorporating this information into rations could improve our ability to optimize main crop straws utilization and milk production.

Bromatological composition and ruminal degradability of Xaraés palisade grass under grazing in integrated systems

To evaluate the bromatological composition and ruminal degradability of dry matter (DM), crude protein (CP), neutral detergent fiber (NDF) and acid detergent fiber (ADF) of Xaraés palisade grass (Urochloa brizantha ‘Xaraes’ syn Brachiaria brizantha) under grazing in integrated crop, livestock (ICL), and forest (ICLF) systems, we conducted an in situ degradability trial in randomized blocks with three non-lactating 3/4 Gyr × 1/4 Holstein cows, provided with ruminal cannula. The management of Xaraés palisade grass was similar in both systems, differing only regarding shading in the ICLF system provided by eucalyptus trees (average 65% crown cover). Grass samples were incubated for 0, 3, 6, 9, 12, 24, 36, 48, 72, and 96 hours. Considering the passage rate 2% h-1, the Xaraés palisade grass of ICL system had greater NDF effective degradability in relation to ICLF (46.38% vs 44.98%). However, the palisade grass CP potential degradability was greater in the ICLF than in the ICL system (68.92% vs. 65.40%). The presence of trees in the pasture has effect on nutritional traits of the Xaraés palisade grass, increasing its protein content and degradability and reducing its fiber degradability.

PSIX-7 Differences in rumen degradability according to the degree of corn gelatinization

This study was conducted to evaluate the difference in ruminal degradability by the degree of gelatinization of corn grain. The treatments were Control (whole corn grain), T1 (70% gelatinized corn grain steam flake), and T2 (30% gelatinized corn grain steam flake). Corn grain steam flaked for T1 was produced by a pressurized steam chamber for a longer time than T2. For this reason, the thickness of T1 and T2 was 1.5 and 2.5mm on average, respectively. Two Holstein cows (BW.405±15.4kg, 26.5±12 months) fitted with ruminal cannula were fed 4 kg of tall fescue and 3 kg of a formulated concentrate mix. Immediately after morning feeding, the nylon bags containing the sample from all treatments were incubated in the ruminal ventral sac for 0, 2, 4, 8, 12, 18, 24, 36, and 48h. At 0h of incubation, the DM degradability of T1 (16.70%) was higher (P&lt; 0.05) than Control (9.74%) and T2 (12.00%). The degradability of both Control and T2 slightly increased from 4 (23.08 and 27.57%) to 18h (36.65 and 35.52%), exponentially increased from 18 to 48h. On the other hand, the degradability for T1 exponentially increased from 2 (28.74%) to 18h (77.31%), only slightly increased thereafter. The final degradability (48h) of Control, T1, and T2 were 78.07, 89.20, and 84.86%, respectively (P&lt; 0.05). The fraction a of DM degradability for T1 (24.29%) was higher than Control (2.26%) and T2 (6.26%) (P&lt; 0.05). The effective degradability (ED) of T1 (75.31%) was higher (P&lt; 0.05) than Control (57.42%) and T2 (60.86%). Therefore, this study demonstrated that 70% gelatinized corn grain steam flake showed a higher rate of ruminal degradability than other treatments. Thus, it is necessary to determine how these differences affect ruminant productivity through additional feeding experiments.

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 (&gt;4-mm), and sifted fines (&lt; 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 &lt; 0.001) and effective ruminal dry matter degradability (ERD) linearly decreased (P &lt; 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 &lt; 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 &lt; 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.

Fractionation of carbohydrates and proteins and in vitro rumen kinetics of corn silage under various storage durations

The experiment evaluated the effects on the chemical composition (fermentation, kinetic parameters, and protein and carbohydrate fractions) of corn silage after various storage durations (45, 90, 180, and 360 days). Experimental mini silos of the corn plants were made and opened after various storage periods. The experimental design was completely randomized with four treatments and four replications per treatment. Variables such as pH, lactic acid and acetic acid showed a quadratic effect, whereas effluent and gas losses increased linearly with prolonged storage. Proteolysis was observed with an increase in storage, resulting in a rise in ammonia-N, soluble N, and non-protein N concentration and reduction in true protein. The soluble carbohydrate fractions were reduced, and digestible and indigestible fibre were increased. For the kinetic degradation parameters of the silages obtained through in vitro gas methodology, the highest fermentation rate occurred in the first 12 hours of incubation, and the highest volume of gas produced within 96 hours was obtained for silages with shorter storage (45 days). The increase in storage resulted in greater losses and lower ruminal degradability in vitro, causing a decrease in protein quality and nutritional value.

In situ ruminal degradability and fermentation characteristics of novel mixtures of winter cereal and Italian ryegrass plus winter cereal silages

This study was conducted using three multiparous non-lactating rumen-cannulated Holstein-Friesian dairy cows, with the objective of evaluating the in situ ruminal degradability and fermentation characteristics of novel mixtures of winter cereal and Italian ryegrass (Lolium multiflorum Lam.) plus winter cereal silages (mixture A: triticale, oats, barley and wheat; mixture B: triticale, barley and wheat; mixture C: Italian ryegrass and oats; mixture D: Italian ryegrass, oats, triticale, barley and wheat). The rumen fermentation study was conducted replacing the ensiled mixtures (experimental diets) with vetch-triticale haylage in a total mixed ration (control diet). It was found that the effective protein degradability at 0.08 rumen outflow rates was 80.6% (mixture A), 66.2% (mixture B), 79.7% (mixture C) and 79.3% (mixture D). The effective neutral detergent fibre (NDF) and acid detergent fibre (ADF) effective degradability at 0.08 rumen outflow rates was 18.0% and 17.7% (mixture A), 19.7% and 20.5% (mixture B), 19.1% and 17.0% (mixture C), and 15.2% and 14.6% (mixture D), respectively. Different dietary treatments did not change (P &gt; 0.05) the rumen fermentation characteristics as there was no difference (P &gt; 0.05) between control and experimental diets, and the inclusion of 40–55% Italian ryegrass (mixture C and D) did not cause any difference. These results suggest that the mixture of winter cereals and Italian ryegrass plus winter cereal-based silages had good potentially degradable dry matter, effective dry matter and effective protein degradability at 0.01, 0.05 and 0.08 rumen outflow rates without affecting the rumen environment maintaining neutral pH. The ensiled mixtures had a moderate level of potentially degradable NDF and ADF fractions.

In situ ruminal degradation of sallow tree leaves using different mathematical models

Objective. The objective of this study was to determine the in situ digestion parameters of sallow leaves (Salix Alba) as an alternative food, not commonly used in animal diets using mathematical models. Materials and methods. Four mathematical models were used to describe the ruminal disappearance of dry matter (DM) and crude protein (CP) of sallow leaves: non lagged exponential (Model I); lagged exponential (Model II); Gompertz (Model III), and generalized Mitscherlich (Model IV). Results. Results of DM and CP degradability characteristics showed that all the models fitted well (r2>0.98) to the disappearance data. There were minor differences between the models in terms of statistical evaluations. However, the models differed in the estimated parameters depending on the model’s nature and structure and the parameters included. Conclusions. Given that some models estimated negative values for the studied parameters, they were not biologically acceptable. For this reason, the only model I can be used for estimating the degradability of DM and CP of sallow leaves. In terms of effective degradability (ED) of DM, model III was not used in the calculations because of calculating negative values for part A. Sallow leaves constitute the largest possible proportion of the ruminal degradability fractions, and effective degradability can be used as a forage source in ruminant feeds.