Effective Ruminal Degradability Research Articles

PSI-15 In-Situ Ruminal Dry Matter Degradability of Three Hydroponic Fodders and Corn Silage in Lactating Holstein Cows

Abstract Climate change may have an adverse effect on feed production. Hydroponic fodders produced in controlled environments are alternative feeds that may be used for dairy cattle. The objective of this study was to evaluate in-situ dry matter ruminal degradability of hydroponic fodders and corn silage. Two rumen-canulated lactating Holstein cows were used in a complete randomized block design with four treatments and 9 times (0, 2, 4, 8, 12, 24, 48, 72, and 240 h). Treatments were corn silage (CS), hydroponic sprouts of barley, wheat, and triticale. Quadruplicate samples were placed in Dacron bags (10 x 20 cm, 50 μm porosity) and incubated in the rumen. After incubation, samples were washed and dried in an air-forced oven set at 60°C for 48 h and DM recovery was weighted. Ingredients nutrient composition were CS (32.3% NDF, 8.4% CP, and 41.6% starch, 1.3% WSC; % of DM), barley (34.3% NDF, 17.1% CP, and 4.2% starch, 32.9% WSC; % of DM), wheat (23.7% NDF, 23.3% CP, and 8.5% starch, 32.7% WSC; % of DM), triticale (20.0% NDF, 16.2% CP, and 21.7% starch, 33.2% WSC; % of DM). Model included fixed effects of treatment and random effects of cow and replicate(cow). Data were analyzed using PROC MIXED of SAS. Degradation fractions were calculated based on DM disappearance. There were treatment effects (P < 0.01) on fraction A (degradable), fraction B (potentially degradable), fraction C (undegradable), effective ruminal degradability (ERD), and rate of degradation (kd: %/h). Fraction A was greater for triticale (74.1%) compared with wheat (70.2%), CS (63.1%), and barley (55.0%). Fraction B was greater for barley (28.5%) compared with CS (23.2%), wheat (19.1%), and triticale (13.9%). Fraction C was less for wheat (10.6%) than triticale (12.0%), CS (13.7%), and barley (16.4%). The ERD was greater for wheat (90.8%) compared with triticale (89.0%), CS (88.0%), and barley (85.6%). The kd for barley (2.4%) was less than triticale (4.9%). The kd for CS (1.8%) was less than triticale (4.9%). Overall, triticale had the greatest fraction A, barley had the greatest fraction B, and wheat had the least fraction C and the greatest ERD and kd.

Particle size and storage length affect fermentation and ruminal degradation of rehydrated corn grain silage

ABSTRACT Particle size and storage time are factors that can affect the fermentation quality and digestibility of rehydrated corn grain silage (RCS). The objective of this study was to evaluate the effect of particle size and storage time on chemical and microbiological characteristics, aerobic stability, and ruminal degradability of RCS. Corn grains were ground to pass through either a 3 mm (fine) or 9 mm (coarse) screen, rehydrated to 44.3% moisture and ensiled in 200 L polyethylene buckets. Samples were taken before and after ensiling at 10, 30, 90 and 200 days of storage to assess microbial counts, fermentation end products, and DM ruminal degradability. DM degradation was evaluated with incubation times of 0 (bag wash), 3, 6 and 48 h in 3 rumen-cannulated cows. The effective ruminal degradation (ERD) was calculated based on soluble fraction (A), degradable fraction (B) and passage rate (kp) defined as 7.0%/h: A + B [kd/(kd + kp)]. Aerobic stability was evaluated in silages after 200 days of storage, and pH and temperature were analysed up to 240 h of aerobic exposure. At 90 and 200 d of storage, fine RCS resulted in lower crude protein and greater NH3-N concentrations than coarse RCS. Coarsely ground RCS had a lower temperature at the beginning of storage than finely ground corn. Finely ground RCS had greater yeast counts and ethanol concentrations than coarsely ground RCS during storage time. Fine RCS was more susceptible to aerobic deterioration, reaching maximum temperature and pH values faster than coarse RCS. DM ruminal degradability increased over the storage time. The particle size of the rehydrated corn grain silage did not affect the kd values after 90 d of storage, while for the ERD, a long fermentation time was necessary (200 d). Considering the fermentation characteristics and the kinetics of ruminal DM degradation, fine grinding is recommended for short storage periods and coarse grinding may be a strategy to increase the rate of grinding when the storage period is greater than 200 d.

Effect of drought stress on neutral detergent fiber degradation kinetics of corn for silage

The objective of this study was to determine the effect of irrigation on in situ neutral detergent fiber (NDF) degradability of corn tissues from plants grown under controlled conditions in a greenhouse. Five commercial corn hybrids were planted in 6 pots that were placed in a greenhouse. Pots were randomly subjected to 2 irrigation regimens, which consisted of either abundant (A; 598 mm) or restricted (R; 273 mm) irrigation. At harvesting, leaf blades and stem internodes were collected from the upper and bottom portion of the plants. Tissue samples were incubated in the rumen of 3 rumen-cannulated cows for 0, 3, 6, 12, 24, 48, 96, and 240 h to determine in situ NDF degradation kinetics. Drought stress did not affect the concentration of undegraded NDF (uNDF) in upper or bottom internodes but slightly decreased it in upper leaf blades (17.5 and 15.7% for A and R, respectively). The concentration of uNDF differed substantially among corn hybrids in upper internodes (13.4 to 28.3% uNDF), bottom internodes (21.5 to 42.3% uNDF), and upper leaf blades (11.6 to 20.1% uNDF). No interactions existed between irrigation treatment and corn hybrid for uNDF concentration. Drought stress did not affect the fractional degradation rate (kd) of NDF in upper internodes, bottom internodes, or upper leaf blades. The kd of NDF differed among corn hybrids in upper (3.8 to 6.6%/h) and bottom internodes (4.2 to 6.7%/h) but did not vary in upper leaf blades (3.8%/h). No interactions existed between irrigation treatment and corn hybrids for the kd of NDF. Significant interactions existed between irrigation treatment and corn hybrids for the effective ruminal degradation (ERD) of NDF in upper and bottom internodes. This interaction did not exist for upper leaf blades. The ERD of NDF differed substantially among corn hybrids in upper leaf blades (32.5 to 39.1%). In conclusion, drought-stressed corn had a marginal increase of NDF degradability of leaf blades but not in stem internodes, and drought stress had no effects on ERD of NDF. The effect of drought stress on NDF degradability of corn for silage is still inconclusive and deserves further investigation.

Effect of various chemical processing on nutritional value of common bean (Phaseolus vulgaris) residues determined via in vitro, in situ, and X-ray powder diffraction techniques

Context Utilising crop residues is an effective strategy to compensate for the shortage of common feed resources. Different processing methods can improve the nutritional value of these by-products. Aims This study aimed to investigate the effect of sodium hydroxide (NaOH, 50 g/kg dry matter (DM)), calcium oxide (CaO, 160 g/kg DM), hydrobromic acid (HBr, 60 mL/kg DM), and hydrogen peroxide (H2O2, 57 mL/kg DM) processing on the nutritional value of common bean (Phaseolus vulgaris) residues (CBR). Methods The chemical composition of the samples was determined using standard methods. In addition, a degradability trial was conducted using the nylon-bag technique. Furthermore, in vitro digestibility of the samples was determined by the batch-culture method. Moreover, the X-ray powder diffraction technique was used to calculate the crystallinity degree of the samples. Key results Chemical processing was effective on the chemical composition of the residues (P < 0.05). Treatments of CaO, H2O2, and NaOH increased the ash content. Chemicals reduced the neutral detergent fibre and acid detergent fibre. Other treatments, excluding CaO, increased total digestible nutrients, net energy for lactation, and net energy for gain. NaOH, H2O2 and HBr treatments increased the effective ruminal degradability of DM at ruminal outflow rates of 0.02, 0.05, and 0.08/h (P < 0.0001). Chemical processing caused a decrease in gas production (GP) and estimated parameters of CBR (P < 0.0001). The decrease in GP, short-chain fatty acids, metabolisable energy, and organic-matter digestibility in the NaOH and CaO treatments was more than in HBr and H2O2 treatments. After 24 h of incubation, all treatments except CaO increased the partitioning factor and decreased the gas yield (P < 0.0001). Furthermore, processing with NaOH and H2O2 increased the microbial biomass (P = 0.0128) and its efficiency (P < 0.0001) at the end of a 24 h incubation period. Moreover, different treatments reduced the crystallinity degree of CBR compared with the control. Notably, the lowest crystallinity percentage was observed in HBr-treated samples. Conclusions This study shows that chemical treatments (except for CaO) improve CBR nutritional value under in vitro and in situ conditions. Implications In vivo tests are required to validate the results.

Effect of Molasses Addition at Ensiling on Ruminal <i>In Situ</i> Dry Matter and Nutrient Degradation of Whole-Plant Soybean Silage Harvested at Different Phenological Stages

Whole-plant soybean ensiling has limitations and challenges that affect silage fermentation patterns and reduce ruminal nutrient degradation. Perhaps either the addition of molasses at ensiling or harvesting at different phenological stages has the potential to enhance whole-plant soybean silage (WSS) ruminal degradation. This experiment was a completely randomized design with a 3 × 2 factorial arrangement of treatments evaluating the effects of molasses (0 and 40 g/kg fresh forage) and phenological stage (R5: beginning seed, R6: full seed, and R7: beginning maturity) on ruminal in situ degradation. Molasses increased effective ruminal degradability (ERD) of dry matter (DM) regardless of the phenological stage and increased ERD of crude protein at R5 and R6. The addition of molasses at later phenological stages increased ERD of neutral detergent fiber (NDF). There was a molasses × phenological stage interaction effect with greater fractions A and B of NDF at R7 and R5, respectively, but lower undegraded NDF at R5 and R6 with molasses addition. Although the benefits of adding molasses were more pronounced in R5 and R6, adding molasses to whole-plant soybean at ensiling is recommended regardless of phenological stage. Increasing the proportion of digestible nutrients at harvesting either by harvesting at later phenological stages or the addition of molasses is a powerful strategy to manage ruminal degradation of DM and nutrients in WSS.

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

Abstract 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.

Effect of feeding a diet comprised of various corn silages inclusion with peanut vine or wheat straw on performance, digestion, serum parameters and meat nutrients in finishing beef cattle.

ObjectiveThe objective of this study was to compare the feeding value, meat nutrients and associative effects of a diet comprised of various corn silages inclusion with peanut vine or wheat straw in finishing beef cattle.MethodsOne hundred and eighty Simmental crossbred beef steers were blocked and assigned to the follow treatments: i) whole plant corn silage-based diet (control, WPCS), ii) mixed forages-based diet (replacing a portion of corn silage with wheat straw, WPCSW), iii) corn stalklage-based diet (CS), and iv) sweet corn stalklage-based diet (SCS). Each group consisted of 5 repeated pens with 9 steers/pen. The diets were formulated to be isonitrogenous and isoenergetic with same forage to concentrate ratio. Experimental diets were fed for 90 d.ResultsThe effective ruminal degradability of dry matter and crude protein were highest for WPCS diet (p<0.05), for neutral detergent fiber was highest in SCS diet (p<0.05). The average daily gain was greater for cattle offered the WPCS diet, intermediate with WPCSW and SCS and lowest with CS (p<0.001). The concentration of non-esterified fatty acid in serum was higher for steers fed with CS and SCS diets than those offered WPCS and WPCSW steers (p<0.001). The treatments did not affect the general nutritional contents and amino acids composition of Longissimus dorsi of steers (p>0.05).ConclusionThe corn silage-based diet exhibited the highest feeding value. The sweet corn stalklage and wheat straw as an alternative to corn silage offered to beef cattle had limited influence on feeding value and meat nutrients. However, the value of a corn stalklage-based diet was relatively poor. To sum up, when the high quality forage resources, such as corn silage, are in short supply, or the growth rate of beef cattle decreases in the later finishing period, the sweet stalklage and wheat straw could be used as a cheaper alternative in feedlot cattle diet without sharp reducing economic benefits.

Effects of dietary rumen-protected Lys levels on rumen fermentation and bacterial community composition in Holstein heifers.

This study aimed to evaluate the effects of partial reducing rumen-protected Lys (RPLys) on rumen fermentation and microbial composition in heifers. Three ruminal fistulated Holstein Friesian bulls were used to determine the effective degradability of RPLys using an in situ method at incubation times of 0, 2, 6, 12, 16, 24, 36, and 48 h. Thereafter, 36 Holstein heifers at 90 days of age were assigned to one of two dietary treatments: a theoretically balanced amino acid diet (PC group; 1.21% Lys, 0.4% Met) or a 30% Lys-reduced diet (PCLys group, 0.85% Lys, 0.4% Met). Rumen fluid samples from five heifers in each group were extracted using esophageal tubing on day 90 to determine pH, microprotein, ammonia, volatile fatty acids, and microbial communities. Results showed that the effective ruminal degradability was 25.76%. Furthermore, differences in rumen fermentation parameters and alpha diversity of the microbiota between the two groups were not significant, but beta diversity was significant. Based upon relative abundance analysis, short-chain fatty acid-producing bacteria, including Sharpea, Syntrophococcus, [Ruminococcus]_gauvreauii_group, Acetitomaculum, and [Eubacterium]_nadotum_group belonging to Firmicutes, were significantly decreased in the PCLys group. Spearman's analysis revealed a positive correlation between the butyrate molar proportion and the relative abundance of butyrate-producing bacteria such as [Eubacterium]_nadotum_group, Coprococcus_1, Ruminococcaceae_UCG_013, Pseudoramibacter, and Lachnospiraceae_UCG_010. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States analysis further validated that RPLys deduction influenced energy metabolism. Together, our findings highlight the role of RPLys or Lys in butyrate-producing bacteria. However, the number of bacteria affected by Lys was very limited and insufficient to alter rumen fermentation. Key Points • Reducing 30% Lys via rumen-protected Lys did not affect rumen fermentation parameters and alpha diversity of microbiota of Holstein heifers. It meant that the ruminal fermentation pattern was not changed. • Reducing 30% Lys via rumen-protected lysine significantly decreased relative abundance of short-chain fatty acid-producing bacteria belonging to Firmicutes. • Functions of microorganisms were changed by reducing 30% Lys via rumen-protected Lys, especially amino acid metabolism. It may affect the amino acid composition of microprotein.

Ruminal degradation and estimated energy and protein values for ruminants of Durum wheat varieties grown in three locations.

Durum wheat is mainly used in pasta production, but may also be used as animal feed, for example as concentrate for dairy cows. Data on the ruminal degradation of Durum grains are scarce. Hence, the objective of the present study was to describe ruminal in situ crude protein (CP) and starch (ST) degradation, to investigate in vitro gas production kinetics, and to estimate utilisable CP at the duodenum (uCP) in vitro of five Durum varieties from three growing locations. Metabolisable energy (ME) and digestibility of organic matter (dOM) were also estimated using in vitro data. In situ incubations were conducted in three lactating jersey cows over defined timespans from 1 to 72hr. Ruminal degradation parameters were estimated using exponential regression, and effective ruminal degradation was predicted for a ruminal passage rate of 8%/hr (ED8 ). In situ CP (a=11%-19%; b=80%-88%; c=23%-33%/hr) and ST (a=22%-39%; b=60%-78%; c=61%-123%/hr) degradation kinetics varied among samples and were influenced by location. Some samples showed a remarkably high ST degradation rate of up to 123%/h, which can significantly influence rumen pH and health when high amounts are incorporated into dairy rations. However, the ED of CP (77%-82%) and ST (91%-95%), and the in vitro estimates of ME (13.6-14.1MJ/kg DM), dOM (92%-96%), and uCP (183-195k/g DM) varied within a relatively small range. Hence, it may be adequate to use the mean values of these Durum grain characteristics when rations for ruminants are calculated and a differentiation depending on variety and location may not be necessary.

Effect of ammonia fibre expansion (AFEX) treatment of rice straw on in situ digestibility, microbial colonization, acetamide levels and growth performance of lambs

The objective of this study was to evaluate the effect of AFEX treatment (ARS) of rice straw (RS) on the in situ degradability, microbial colonization, growth performance and acetamide levels in ewe lambs. Alfalfa, rice straw and AFEX-treated rice straw were incubated in nylon bags in the rumen for 0, 1, 3, 6, 12, 24, 36, 48, 72 and 120 h to determine DM and NDF disappearance kinetics. Sequencing of 16S rRNA was used to characterize colonizing bacterial and archaeal profiles. Lambs (N = 40; 37.1 ± 3.5 kg) were fed pelleted diets that contained: 1) ALF = 250 g/kg of alfalfa; 2) RS = 250 g/kg of rice straw; 3) ARS = 250 g/kg of AFEX rice straw; 4) ARSW = ARS withdrawn from the diet 7 d before slaughter. Blood samples were collected biweekly and after ARSW on d 1, 3, 5 and 7 and at slaughter, the diaphragm muscle was used for measurement of acetamide. Alfalfa had greater Kd and A fraction (P < 0.05), whereas ARS had higher (P < 0.05) B and A + B fractions. Alfalfa DM and NDF degradability was greater at 12 h, but lower than ARS thereafter. Effective ruminal degradability (Ed) at 0.02, 0.04 and 0.06/h was greater (P < 0.05) for ARS than other forages. Digestion of ALF and ARS plateaued after 48 h, while RS continued to be degraded. Compared to other forages, alpha and beta microbial diversity of ARS was reduced (P < 0.05). The phylogenetic profile of initial colonizers of ARS was more similar to ALF than RS and was dominated by Bacteroidetes. Lambs fed RS exhibited similar growth to those fed ALF, while the DMI of ARS lambs was similar, but ADG and feed efficiency were reduced (P < 0.05). ALF exhibited greater (P < 0.05) DM, OM, CP, NDF, ADF and starch digestibility than ARS. ARS exhibited lower CP, but higher NDF and ADF digestibility than RS. A strong correlation (R² = 0.81) was observed between blood and muscle acetamide levels in lambs fed ARS. Withdrawal of ARSW reduced (P < 0.05) blood acetamide levels after 3 d, but levels in the diaphragm remained similar to ARS lambs at slaughter. Although AFEX improved the NDF and DM digestibility of RS and altered the phylogenetic profile of primary colonizers, it did not improve the growth of ewe lambs, likely as a result of reduced intake.

Recombinant fibrolytic feed enzymes and ammonia fibre expansion (AFEX) pretreatment of crop residues to improve fibre degradability in cattle

Low digestibility of crop residues limits their use as animal feeds. The study examined the potential of Ammonia Fibre Expansion (AFEX) technology and dietary supplementation of a preselected recombinant xylanase to improve the in situ degradability of four crop residues for ruminants. AFEX pretreatment uses anhydrous ammonia, moisture, moderate temperature, and a short period of high pressure and results in partial lignin solubilization and hemicellulose hydrolysis, and increased surface area of substrate for microbial attachment. In situ neutral detergent fibre degradabilities of untreated (control) and AFEX pretreated crop residues (barley straw, corn stover, rice straw, and wheat straw) were determined in 8 heifers using a 2-period cross-over design with two dietary treatments (without and with XYL10C; 1,4-β-xylanase; recombinant enzyme from glycoside hydrolase family 10 produced by Aspergillus niger). The enzyme was diluted in water and applied to the barley straw (6.6 × 104 IU enzyme/kg straw dry matter) component of the basal diet (30 g/100 g diet dry matter) and to the control and AFEX crop residues incubated in situ. There were no interactions between enzyme and crop residues for A, B, or A + B fractions, indicating no enzyme × substrate specificity. Averaged across crop residues, enzyme slightly decreased the A fraction (P < 0.001) and slightly increased the B fraction (P = 0.02), such that there was no overall effect on A + B (P = 0.21). However, there were significant interactions between enzyme and AFEX for kd (P = 0.026); enzyme had no effect on control crop residues but it increased kd of AFEX residues by 12% (0.0323 vs. 0.0361 /h). As a result, xylanase supplementation increased the effective rumen degradability of crop residues by about 3%, but only when they were pretreated with AFEX (interaction, P ≤ 0.098). AFEX greatly increased effective ruminal degradability (+ 28 to + 126% depending upon the crop residue; P < 0.001), mainly by increasing the B fraction and decreasing the undigested fibre fraction, indicating increased accessibility of substrate to rumen microbial enzymes. The study demonstrates the tremendous potential of AFEX treatment to improve the feeding value of crop residues. Enzyme XYL10C was more effective for AFEX crop residues, possibly due to increased accessibility to substrate, suggesting that this enzyme may be more effective for less lignified and pretreated feeds.

Determination of in situ ruminal crude protein and starch degradation values of compound feeds from single feeds

ABSTRACTDairy cows are commonly fed compound feed concentrates, whose accurate formulation relies on the additivity of ruminal degradation characteristics of single feeds, and the absence of associative effects. The main aim of this study was to evaluate the additivity of single feeds in compound feeds made thereof. Twelve single feeds were used to produce eight compound feeds in mash and pelleted form. Samples of single and compound feeds were incubated in situ in three ruminally fistulated dairy cows, and effective ruminal degradation (ED) of CP and starch (ST) was computed. The ED values of examined compound feeds could be, in most cases, accurately calculated from ED values of single feeds. Observed EDCP values were significantly lower than that calculated, but differences were overall small and not exceeded 5% points. No significant differences were observed between calculated and observed EDST. The study also examined the effects of pelleting of compound feeds on in situ degradation. Pelleting significantly increased EDCP (up to 8% points), and EDST (up to 4% points) of most compound feeds. This could have been caused by the pelleting process increasing the proportion of fine feed particles with fast disappearance from the bags. It was concluded that small associative effects between the examined single feeds could be disregarded when formulating compound feeds for dairy cows, and that additivity of EDCP and EDST can be assumed in most cases.

Replacing alfalfa hay with triticale hay has minimal effects on lactation performance and nitrogen utilization of dairy cows in a semi-arid region of Mexico

In the semi-arid highlands of central Mexico, triticale (× Triticosecale L.) is emerging as an alternative, less water-demanding forage crop than alfalfa for dairy cattle. Studies reported here were aimed at evaluating triticale hay (TH) relative to alfalfa hay (AH) for lactating cow performance, apparent digestibility, N partition, and ruminal degradation kinetics of dry matter (DM), crude protein (CP), and neutral detergent fiber (NDF). Study 1 was conducted on a privately owned farm. Four barns were used to conduct 4 replicated 3 × 3 Latin squares (1 barn = 1 square), where each barn included 3 pens (experimental units) receiving 1 of 3 dietary treatments. Each pen had 62 Holstein dairy cows. All diets included a forage-to-concentrate ratio of 42:58 (DM basis), which is typical for intensive dairy farms of the region. Dietary treatments were formulated to replace AH with TH on a CP basis, and included (DM basis) 15.1% AH and 0% TH, 9.0% AH and 7.4% TH, and 0% AH and 16.4% TH. Diets were iso-energetic (1.64 Mcal of net energy for lactation/kg of DM) and iso-nitrogenous (17.9% CP). Pen-level DM intake and milk production were from all cows in the pen, but pen-level milk composition, apparent digestibility, and N partitioning were from 8 cows (observational units) randomly selected in each pen. Orthogonal contrasts were used to determine linear and quadratic effects of increasing TH from 0 to 7.4, and 16.4% of dietary DM. Although DM intake was not affected, there was a tendency for CP intake to decline linearly and for NDF intake to increased linearly as TH replaced AH in the diet. Milk production declined linearly by 0.077 kg/d for each additional percentage unit of TH in the diet, which amounted to a 3.5% decline when TH replaced AH entirely. However, no effect was observed on energy-corrected milk production because of a compensatory linear effect of increasing milk fat concentration with the incorporation of TH in the diet. Total-tract NDF digestibility tended to increase linearly by 18.5%, but no differences were detected for urinary urea-N excretion and for N utilization estimated as milk N/(fecal N + urinary N + milk N). Study 2 was an in situ trial conducted to determine the degradation kinetics of AH and TH used in study 1. In spite of differences in degradation kinetics parameters for DM, CP, and NDF, only NDF effective ruminal degradation tended to be greater for TH than AH. Replacing AH with TH at the level typically found in intensive dairy farms of the semi-arid regions of Mexico had minimal effects on milk production and N utilization.

Effect of different methods for conserving rice grain on insitu ruminal degradation and invivo nutrient digestion and rumen fermentation in steers.

We investigated the effects of different rice conservation techniques on insitu ruminal degradation and invivo nutrient digestibility and rumen fermentation in steers. Raw rice grain was dried before crushing (DRY), ensiled after crushing (ENS-A), or ensiled before crushing (ENS-B). Six ruminally cannulated steers were used in a replicated 3×3 Latin square design with three dietary treatments: diets containing DRY, ENS-A, or ENS-B at 36% of the dietary dry matter. The insitu rapidly degradable fraction and effective ruminal degradability were higher for ensiled rice than for DRY, and higher for ENS-A than for ENS-B. The ruminal pH was lower and the lactic acid and total volatile acid concentrations were higher for the steers fed ensiled rice than those fed the DRY diet, but a treatment effect was not observed in the comparison between ENS-A and ENS-B. The whole-tract digestibility of crude protein and ether extract was improved when the rice grain was ensiled, but there were no differences in nutrient digestibility between ensiling methods. These results show that ensiling treatment can be a strategy to improve the nutrient value of rice grain, but the ensiling method has little impact on invivo digestion.

Effects of heat processing methods on protein subfractions and protein degradation kinetics in dairy cattle in relation to protein molecular structure of barley grain using advanced molecular spectroscopy

The objectives of this study were: (1) to investigate the effect of three different heat processing methods on chemical profile, CNCPS protein subfraction, rumen degradation characteristics, and protein molecular structure of barley grain (CDC Meredith) using Fourier transform infrared attenuated total reflectance advanced molecular spectroscopy; (2) to detect association between protein degradation and availability and protein molecular structure profiles in dairy cows. The grains were kept as raw (control) or heated in an air-draft oven at 120 °C for 60min or in an autoclave at 120 °C for 60min or in a microwave at 900w for 5min. The results showed that autoclave heating decreased the ruminal effective degradability and increased the intestinal digestion of protein. The molecular spectroscopy was able to identify heating-induced changes in protein molecular structure, revealing that dry heating increased the amide I to II area ratio when compared with control. The α-helix to β-sheet ratio was greater in microwave heating than autoclave heating, suggesting protein damage in microwave-heated grains. The autoclave heating decreased the effective degradability of protein while increased the intestinal digestion of rumen undegradable protein. Protein subfractions, rumen degradable, undegradable and intestinal digestible protein fractions and degradation characteristics could be predicted by amide I area or α-helix.

Nutrient composition, ruminal degradability and whole tract digestibility of whole crop maize silage from nine current varieties

ABSTRACTSince maize silage is an important forage in cattle nutrition, it is important to know its nutritive value. Much effort is put into breeding maize, and several new varieties are introduced on the market every year. This requires periodical analyses of the nutritive value of current maize varieties for the formulation of cattle rations. The aim of this study was to examine the nutritive value of whole crop maize silage (WCMS) from nine maize varieties in 3 consecutive years. For the analysis of nutrient composition and ruminal degradability of organic matter (OM), crude protein (CP), neutral detergent fibre (aNDFom) and non-fibre carbohydrates (NFC), varieties were harvested at three harvest dates (50%, 55% and 60% dry matter content in ear). Due to capacity limitations, the digestibility of WCMS was tested only for the middle harvest date. The CP and acid detergent fibre (ADFom) content was affected (p < 0.05) while aNDFom and NFC content was not influenced by variety. With advancing maturity, CP, aNDFom and ADFom content declined while NFC content increased. Variety influenced effective ruminal degradability (ED) of nutrients, except for CP. The ED of all examined nutrients decreased as maturity advanced from first to third harvest date. Digestibility of OM, ADFom and NFC was significantly and digestibility of aNDFom was tendentially (p = 0.064) influenced by variety. Additionally, an effect of year and a harvest date × year interaction was found for almost all examined parameters. In conclusion, variety, harvest date and year influence the nutritive value of WCMS. A comparison with earlier studies shows that current varieties have a higher fibre digestibility and a slower-ripening stover compared to older varieties.

Prediction of CP and starch concentrations in ruminal in situ studies and ruminal degradation of cereal grains using NIRS

Ruminal in situ incubations are widely used to assess the nutritional value of feedstuffs for ruminants. In in situ methods, feed samples are ruminally incubated in indigestible bags over a predefined timespan and the disappearance of nutrients from the bags is recorded. To describe the degradation of specific nutrients, information on the concentration of feed samples and undegraded feed after in situ incubation (‘bag residues’) is needed. For cereal and pea grains, CP and starch (ST) analyses are of interest. The numerous analyses of residues following ruminal incubation contribute greatly to the substantial investments in labour and money, and faster methods would be beneficial. Therefore, calibrations were developed to estimate CP and ST concentrations in grains and bag residues following in situ incubations by using their near-infrared spectra recorded from 680 to 2500 nm. The samples comprised rye, triticale, barley, wheat, and maize grains (20 genotypes each), and 15 durum wheat and 13 pea grains. In addition, residues after ruminal incubation were included (at least from four samples per species for various incubation times). To establish CP and ST calibrations, 620 and 610 samples (grains and bag residues after incubation, respectively) were chemically analysed for their CP and ST concentration. Calibrations using wavelengths from 1250 to 2450 nm and the first derivative of the spectra produced the best results (R2Validation=0.99 for CP and ST; standard error of prediction=0.47 and 2.10% DM for CP and ST, respectively). Hence, CP and ST concentration in cereal grains and peas and their bag residues could be predicted with high precision by NIRS for use in in situ studies. No differences were found between the effective ruminal degradation calculated from NIRS estimations and those calculated from chemical analyses (P>0.70). Calibrations were also calculated to predict ruminal degradation kinetics of cereal grains from the spectra of ground grains. Estimation of the effective ruminal degradation of CP and ST from the near-infrared spectra of cereal grains showed promising results (R2>0.90), but the database needs to be extended to obtain more stable calibrations for routine use.

Dynamics of methanogenesis, ruminal fermentation, and alfalfa degradation during adaptation to monensin supplementation in goats

This study aimed to examine the temporal (hourly within a day and daily over the long term) effects of monensin on CH4 emissions, ruminal fermentation, and in situ alfalfa degradation in dairy goats during dietary monensin supplementation by controlling the confounding effects of feed intake and ambient temperature. Six ruminally cannulated dairy goats were used, and they were housed in environmental chambers and fed a restricted amount of ration throughout the experiment. The experiment included a baseline period of 20 d followed by a treatment period of 55 d with 32 mg of monensin/d. During the whole experiment, CH4 production was measured every 5 d, whereas fermentation characteristics and in situ alfalfa degradation were analyzed every 10 d. The CH4-depressing effect of monensin was time dependent on the duration of treatment, highly effective at d 5 but thereafter decreased gradually until d 55 even though CH4-suppressing effect still remained significant. The decreasing effects of monensin on ruminal acetate proportion and acetate to propionate ratio also faded over days of treatment, and the acetate proportion returned up to the pre-supplementation level on d 50. Monensin supplementation elevated ruminal propionate proportion and decreased the effective ruminal degradability of alfalfa NDF, but both measurements tended to recover over time. The postprandial increase rate of hourly CH4 emissions was reduced, whereas that of propionate proportion was enhanced by monensin supplementation. However, the postprandial responses to monensin in CH4 emission rates, ruminal VFA profiles, and in situ degradation kinetics declined with both hours after feeding and days of treatment. Our results suggest that the CH4-suppressing effect of monensin supplementation in goats was attributed to reductions in both ruminal feed degradation and acetate to propionate ratio, but those reductions faded with time, hours after feeding, and days of treatment.

Effect of variety and harvest date on nutritive value and ruminal degradability of ensiled maize ears

ABSTRACTThe nutritive value of whole crop forage maize is influenced by the proportion of ears and stover in the whole crop and by the nutrient composition and digestibility characteristics of the plant parts. An experiment investigating the impact of variety, harvest date and year on the nutritive value of ensiled maize ears was carried out in three consecutive years (2007, 2008 and 2010). Nine different maize varieties were harvested at three different maturity stages (50, 55 and 60% dry matter (DM) content in the ears). After harvest, ears and stover were ensiled separately and afterwards nutrient composition and ruminal nutrient degradability (organic matter (OM), crude protein (CP) and non-fibre carbohydrates (NFC)) were analysed. Variety had a significant influence on content of CP and effective ruminal degradability (ED) of OM at low passage rates, whereas ED of CP and NFC was not affected by variety. In contrast, harvest date and year significantly influenced nutrient composition and ruminal degradability of ensiled maize ears. The content of NFC increased and the content of fibre components as well as ED of OM, CP and NFC declined with processing maturity of the maize plants. At a passage rate of 5% h−1, ED of OM declined from 75.9% to 68.4%, ED of CP from 82.5% to 73.8% and ED of NFC from 88.0% to 82.3% between the early and late harvest date. The results of this study indicate that the nutrient composition and ruminal degradability of ensiled maize ears are affected mainly by maturity stage at harvest and by year, whereas variety has only little influence.

In situ and in vitro estimation of mineral release from common feedstuffs fed to cattle

SUMMARYThe objective of the current study was to quantify the dry matter (DM) digestibility, and total ash (TA) and mineral release from 12 concentrate and 12 forage feedstuffs commonly fed to cattle using in situ and in vitro methods. Concentrate and forage feedstuffs were incubated in the rumen of ruminally cannulated beef bulls at eight different time points. Two different trials were conducted for concentrates and forages, with maximum incubation time of 72 and 120 h, respectively. The residue from samples incubated for 24 h were treated with pepsin and hydrochloric acid to simulate abomasum digestion in vitro. The initial and residual samples after in situ and in vitro incubations were measured. An asymptotic model was adopted for estimating solubility of minerals, disappearance rate of DM, and TA. Correlations between feedstuff contents and mineral release were evaluated. Residual samples from rumen fermentation after 24 h were incubated in simulated abomasal conditions and mineral release was measured. Cluster analysis was performed to group feedstuffs in relation to TA release. Large variability was observed between concentrate and forage feedstuffs for all constituents analysed. Large variability was observed for the effective ruminal degradation of TA and individual mineral release. When feedstuffs were clustered according to the immediately soluble fraction (‘a’), the insoluble by potentially releasable fraction (‘b’) and the release rate of ‘b’ (‘kd’,/h) estimates of TA ruminal release, four groups were identified. From group ‘1’ to group ‘4’, an increase in the soluble fraction and a reduction in both moderate releasable fraction and release rate was observed. Neutral detergent fibre content had a negative correlation with mineral release in the rumen, while mineral content had a positive correlation. These results demonstrate that mineral solubilization in the digestive tract is not the limiting factor for mineral absorption from the feedstuffs tested.