Effect of dietary protein level on nitrogen metabolism in the growing bovine: II. Diffusion into and utilization of endogenous urea nitrogen in the rumen

Six Angus heifer calves (234 kg) were assigned to either a high (HP; 126.1 g N/d) or low (LP; 66.5 g N/d) protein intake to evaluate ruminal criteria associated with movement of blood urea-N (BUN)-derived NH3-N from the rumen wall into interior ruminal digesta. Calves received 4.8 kg DM/d of diets containing 30% cottonseed hulls and 70% cornsoybean meal in equal portions at 4-h intervals. Following single i.v. injections of 15N-urea, ruminal fluid was collected serially for 4 h postinjection from digesta located adjacent to the rumen wall (wall-proximate digesta; WPD) and from the center of the rumen digesta mass after manual agitation (center mixed digesta; CMD). Mean ruminal NH3-N (RAN) concentrations were higher (P less than .05) for HP than for LP, but were not affected (P greater than .05) by digesta sampling site. Ruminal urease activity was higher (P less than .05) for LP than for HP and tended (P = .14) to be higher for WPD than for CMD. Area under the 15N enrichment curve (AUC) ratios between sampling sites (WPD/CMD x 100) for RAN were greater (P less than .05) for LP than for HP. However, AUC ratios for bacterial N were not affected (P greater than .05) by protein level. Whereas BUN-derived 15NH3 appeared to thoroughly equilibrate with RAN in interior ruminal digesta with HP, there appeared to be a declining enrichment gradient for RAN from the rumen wall to the interior ruminal digesta with LP. Data are interpreted to suggest that bacteria at or near the rumen wall may preferentially utilize some BUN-derived NH3-N entering through the rumen wall in calves fed LP diets.     

Effect of dietary protein level on nitrogen metabolism in the growing bovine: I. Nitrogen recycling and intestinal protein supply in calves

Eight Angus heifer calves (234 kg) were assigned to either a high (HP; 126 g N/d) or low (LP; 66.5 g N/d) protein intake. Calves received 4.8 kg DM/d consisting of 30% cottonseed hulls and 70% corn-soybean meal in equal portions at 4-h intervals. Single doses of 14C- and 15N-urea and 15N-ammonium sulfate were injected into the blood urea-N (BUN) and ruminal NH3-N (RAN) pools, respectively, to measure rate of flux through, and transfer of N between, these and bacterial N. Nitrogen balance was greater (P less than .05) for HP than for LP (56.9 vs 25.1 g N/d), but abomasal N flow as a percentage of N intake was greater (P less than .05) for LP than for HP (124 vs 71.1%). Pool size and net synthesis rate for both RAN and BUN pools were greater (P less than .05) for HP than for LP. Calves fed HP degraded more (P less than .05) BUN in the gastrointestinal tract than calves fed LP (37.4 vs 14.0 g N/d). Quantities of RAN absorbed from the rumen also were greater (P less than .05) for HP than for LP (14.2 vs 2.8 g N/d). The proportion of total gastrointestinal BUN degradation occurring in the rumen averaged 53 and 26% for LP and HP. Data are interpreted to suggest that net incorporation of BUN into bacterial protein (urea recycling) is inversely related to level of protein intake.     

Effects of the feeding sequence of concentrate and forage and the feeding ratio of sake cake to grass hay on the characteristics and the entrapment effect of the ruminal mat in non‐lactating dairy cows

The effects of the feeding sequence of concentrate and forage, and of the feeding ratio of sake cake (SC) to grass hay (GH) on the ruminal mat characteristics and the entrapment effect for steamed flaked corn (SFC) by the mat were evaluated. Three non‐lactating, rumen‐cannulated Holstein cows were offered SC and GH using a ratio of 35:65 (SC35) or 65:35 (SC65). For SC35, SFC was fed at 1 h after or immediately before offering SC and GH, while for SC65, SFC was only fed at 1 h after. To estimate the degree of SFC entrapment in the ruminal mat, the location of SFC in the rumen and two types of mean retention time (MRT) were measured, that is, MRT for the SFC marker placed directly on the mat or taken orally. The ruminal mat was formed even when SC65 diet was consumed. The entrapment effect was not affected by the feeding sequence or the ratio. However, a more interesting finding is that the entrapment effect of the ruminal mat may not be as absolute as previously considered because of the large amount of SFC particles which precipitated at the bottom of the rumen 1 h after feeding.     

Influence of mass and volume of ruminal contents on voluntary intake and digesta passage of a forage diet in steers.

To assess the influence of volume and mass of ruminal contents on voluntary intake and related variables, five ruminally cannulated steers (550 kg) were fed a low-quality forage diet (43.1% ADF, 8.1% CP) in a 5 x 5 Latin square experiment. Mass and volume of ruminal contents were altered by adding varying numbers and weights of filled tennis balls (6.7-cm diameter) to the rumen immediately before the initiation of each experimental period. Treatments consisted of 0 balls (control), 50 balls with a 1.1 specific gravity (SG), 100 balls with a 1.1 SG, 50 balls with a 1.3 SG, and 100 balls with a SG of 1.3. The total volume of balls was 7.25 and 14.5 L for 50 and 100 balls, respectively. The total weight of balls was 8.5 and 17 kg for 50 and 100 balls with a 1.1 SG and 10.75 and 21.5 kg for 50 and 100 balls with a 1.3 SG, respectively. Daily DMI was 8.3, 7.3, 7.0, 6.5, and 6.0 kg for control; 50, 1.1 SG; 50, 1.3 SG; 100, 1.1 SG; and 100, 1.3 SG, respectively. Addition of balls to the rumen reduced (P < .01) DMI. Increasing the number (P < .01) and SG (P <. 01) of the balls decreased DMI further. However, digestibilities of DM, NDF, ADF, and CP were not influenced by treatment. Increasing the number of balls in the rumen increased (P < .05) rate of passage of digesta from the rumen, but increasing SG of the balls did not alter rate of passage. There was a treatment x hour interaction (P < .05) in the proportion of ruminal digesta with a functional specific gravity (FSG) less than 1.1, which decreased with time after feeding for the control but increased with time after feeding for other treatments. Ruminal passage rate of inert particles added in the rumen of different SG (1.1 and 1.3) and length (1 and 3 mm) decreased (P < .05) as SG of the balls increased. Mean fecal particle size was greater for those treatments with the heavier balls. Both the number and SG of balls (P < .10) influenced total VFA, and total concentrations were greater for the control and for the 1.1 SG than for the 1.3 SG treatments.     

Effect of dietary protein level on nitrogen metabolism in lambs: studies using 15N-nitrogen

Six wether lambs (31 kg) were randomly assigned to two treatments (three lambs/treatment): a high protein intake (HP; 21 g N/d) or a low protein intake (LP; 12 g N/d). Each lamb received 860 g/d dry matter (DM) of a pelleted diet (75% corn-soybean meal, 25% cottonseed hulls) offered hourly in 24 equal portions. Single injections of 15N-labelled compounds were made into the ruminal NH3-N and blood urea-N pools to measure the rate of flux through, and transfer of N between, these and the bacterial N pool. Total tract digestibilities of DM and N were lower (P less than .05) for the LP than the HP treatment. Abomasal flows of total, feed or bacterial N tended to be greater (P greater than .05) in lambs fed HP than LP. Lambs fed HP excreted more (P less than .01) urinary N, yet retained a greater (P less than .01) amount of N than lambs fed LP (6.2 vs 1.8 and 9.7 vs 4.1 g N/d, respectively). Pool size and production rate for both ruminal NH3-N and blood urea-N were greater (P less than .05) for the HP than LP treatment. Lambs consuming HP degraded more (P less than .05) blood urea-N in the gastro-intestinal tract (13.4 vs 6.9 g N/d); however, lambs fed LP degraded a greater (P less than .05) percentage of synthesized body urea-N (88.7 vs 71.8%). Ruminal NH3-N absorption was greater (P less than .01) for the HP than LP treatment (3.1 vs .5 g N/d). Although the percentage of bacterial N derived from ruminal NH3-N was similar (P greater than .05) between diets (51.1 vs 63.9), a greater (P less than .05) percentage of bacterial N was derived from blood urea-N in lambs fed LP than HP (77.1 vs 30.2%). Lambs fed LP incorporated a greater (P less than .10) amount of blood urea-N into bacterial N than lambs fed HP (5.5 vs 2.6 g N/d). These data are interpreted to suggest that blood urea-N may provide a substantial quantity of N for bacterial protein synthesis and, thus, may be an important source of protein in the deficient animal. In addition, urea recycling may play an important role in the recovery of ruminal NH3-N lost through absorption in animals fed a high level of protein.     

Supplementation of dormant tallgrass-prairie forage: I. Influence of varying supplemental protein and(or) energy levels on forage utilization characteristics of beef steers in confinement

Three experiments were conducted to evaluate effects of supplemental protein vs energy level on dormant forage intake and utilization. In Exp. 1, 16 ruminally cannulated steers were blocked by weight (avg wt = 242 kg) and assigned randomly to a negative control or to one of three isocaloric supplement treatments fed at .4% BW: 1) control, no supplement (NS); 2) 12% CP, low protein (LP); 3) 28% CP, moderate protein (MP); 4) 41% CP, high protein (HP). In Exp. 2 and 3, 16 ruminally cannulated steers were blocked by weight (avg wt = 332 kg, Exp. 2; 401 kg, Exp. 3) and assigned randomly to a 2 x 2 factorial arrangement of treatments. The treatments contrasted low (LP) and high (HP) levels of supplemental protein (.66 g CP/kg BW vs 1.32 g CP/kg BW) with low (LE) and high (HE) levels of supplemental ME (9.2 kcal/kg BW vs 18.4 kcal/kg BW). In Exp. 1, forage DMI as well as ruminal DM and indigestible ADF fill at 4 h postfeeding were greater (P less than .10) with the MP and HP steers than with control and LP steers. Total DM digestibility increased (P less than .10) for supplemented steers (35.5% for control vs 47.3 for supplemented steers); however, LP depressed (P less than .10) NDF digestibility. In Exp. 2, forage DMI, indigestible ADF flow and liquid flow were depressed (P less than .10) in LP-HE supplemented steers. In Exp. 3, HP steers had greater (P less than .10) forage DMI, indigestible ADF fill values (4 h postfeeding), liquid volume and tended (P = .11) to have greater ruminal DM fill (4 h postfeeding). In summary, increased levels of supplemental protein increased intake and utilization of dormant tallgrass-prairie forage (less than 3% CP). Increasing supplemental energy without adequate protein availability was associated with depressed intake and digestibility.     

The effect of physical form of orchardgrass hay on the passage of particulate matter through the rumen of sheep

Four Texel wethers (60 to 64 kg) fitted with ruminal and duodenal cannulas were used to study the kinetics of particulate matter in the rumen and the series of processes involved in their selection and passage. They were fed, in eight equal meals, 1,200 g of a mixture of a chopped orchardgrass hay and ground (8-mm screen) and pelleted orchardgrass hay in 90/10, 50/50, 30/70, or 10/90 ratios, according to a 4 x 4 Latin square design. The particle size distributions in feed, chewed feed, and ruminal, reticular, and duodenal digesta were determined by a wet-sieving procedure. Indigestible lignin was used as an internal marker to trace the passage of particles through the rumen. Digesta flow measurement was performed using the double-marker technique. We used a three-pool model, which partitions particles through the large, medium, and small particle pools, to determine the passage of lignin through those pools. Particle pool sizes and rumen and pool mean retention times (MRT) of lignin and of the rumen MRT of an ideal marker introduced separately in each pool were corrected for the "filter bed" effect. Grinding and pelleting of hay decreased the MRT of the indigestible lignin pool in the rumen. Particle MRT decreased and then reached a plateau with increased proportion of ground/pelleted hay in the diet. The diet with a ratio of 50/50 of chopped and ground/pelleted hay was the most favorable for the exit of particles from the rumen because of both a higher outflow rate from the rumen of particles eligible to exit and a sufficient comminution rate of larger particles to supply particles that were able to pass. For all diets, the large-particle comminution rate was always higher than the small-particle outflow rate, indicating that comminution was not the limiting step for passage. These results were the consequence of the curvilinear and opposite evolutions of both the particulate lignin pool in, and outflow from, the rumen. Those results contribute to an improved explanation of the mechanisms involved in the outflow of particles from the rumen.     

Effects of soybean meal supplementation on ruminal kinetics of feed particle size reduction and passage in dairy cows fed rice straw

Six ruminal-cannulated nonlactating Holstein Friesian cows (mean body weight:660 ± 42.9 kg) were used to investigate the effect of soybean meal (SBM) supplementation on voluntary rice straw (RS) intake, feed particle size reduction, and passage kinetics in the rumen. They were allocated to two dietary treatments: RS alone or RS supplemented with SBM. Voluntary dry matter intake of RS and total tract fiber digestibility was increased by SBM supplementation (p < 0.05). Supplementation with SBM decreased rumination time per dietary dry matter (DM) and neutral detergent fiber (NDFom) intake (p < 0.01). Particle size distribution in the rumen and total ruminal NDFom digesta weights were not affected by SBM supplementation. However, the disappearance rates of total digesta and large and small particles from the rumen were increased by SBM supplementation (p < 0.01). Moreover, SBM supplementation increased the rate of size reduction in ruminal particles (p < 0.05). In situ disappearance of DM and NDFom of RS in the rumen was greater in SBM-supplemented cows than in nonsupplemented cows (p < 0.05). This study clearly showed that increased ruminal RS particle size reduction, passage, and fermentation due to SBM supplementation accelerated the RS particle clearance from the rumen and resulted in increased voluntary RS intake of dairy cows.     

Digestive processes of dairy cows fed silages harvested at four stages of grass maturity

The objective of this experiment was to quantify ruminal digestive processes that could help to identify factors limiting DMI when silages differing in grass maturity were fed to dairy cows. Four silages were harvested at 1-wk intervals from a primary growth of a timothy-meadow fescue sward, resulting in feeds with digestible OM content in DM (D-value) of 739, 730, 707, and 639 g/kg in the order of succeeding harvest date. Four ruminally cannulated dairy cows were given ad libitum access to these silages supplemented with 7 kg concentrate per day in a 4 x 4 Latin square design. Rumen function was clearly affected by decreasing digestibility of silage fed. Passage rate of digestible NDF (DNDF) and indigestible NDF (INDF) increased, but it could not prevent the accumulation of DM, NDF, DNDF, and INDF into the rumen when silages of progressing grass maturity were fed. The greatest proportional increases in rumen pool were found in INDF and in medium particles (separated by wet sieving and measuring 315 to 2,500 microm). The passage of medium INDF particles decreased (P < 0.01) linearly (from 0.0365/h to 0.0281/h) with increasing maturity of grass ensiled, and it was slower than passage of small (80 to 315 microm) particles (on average 0.0524/h). Particle size reduction of large INDF particles to medium INDF particles was slower (P < 0.001) in the early cut silages (0.0216/h to 0.0484/h) but reduction of medium INDF particles to small INDF particles was faster (P < 0.001) in early cut silages (0.0436 to 0.0305). Passage of medium size particles and(or) rate of medium particle breakdown to small particles were potential intake-constraining properties of low digestibility forages, whereas large particle reduction to medium particles seemed not to be limiting. The increased feed intake of the early-cut silages was accompanied by decreased rumen fill, suggesting that rumen fill was not at least solely responsible for feed intake control.     

Relationship between pH and Temperature in the Ruminal Fluid of Cows, Based on a Radio-Transmission pH-Measurement System

To assess the relationship between pH and temperature in the ruminal bottom fluid, circadian changes were monitored using cows fed a control diet (C diet) or a rumen acidosis-inducing diet (RAI diet) by using a wireless radio-transmission pH- measurement system. These two parameters were measured simultaneously at 10-min intervals on day 14 after commencement of feeding. Compared to the mean ruminal pH for 60 min immediately after the morning feeding (0 hr), significantly lower pH was noted 3-13 hr later (P<0.05) and 4-19 hr later (P<0.01) in cows fed the C and RAI diets, respectively, although the reduction in the latter was much higher than that in the former. In contrast, significantly higher ruminal temperature was found at 8 and 12-14 hr later (P<0.05) and 6, 8, and 10-19 hr later (P<0.01) in cows fed the C and RAI diets, respectively. A significant negative correlation was observed between the lowest ruminal pH and its corresponding ruminal temperature in cows fed the C and RAI diets (r=-0.722 and -0.650, P<0.01, respectively), suggesting active fermentation and volatile fatty acid production in the rumen. However, ruminal pH profiles may not be predictable by measuring only ruminal temperature because decreases in ruminal pH were preceded by increases in ruminal temperature, and circadian changes in pH and temperature were associated with ruminal fermentation.     

Effects of substituting kraft pulp with corn silage on dry matter intake,ruminal mat formation,rumen fermentation,and rumination activity in non‐lactating cows

The present study examined the effects of substituting kraft pulp (KP) with corn silage (CS) on dry matter intake (DMI), ruminal mat and rumen fermentation characteristics, and rumination. Four non‐lactating, rumen‐cannulated Holstein cows were fed a CS diet comprising 36% grass silage (GS) and 64% CS or a KP diet comprising 36% GS, 57% KP, and 7% soybean meal. DMI was significantly lower in cows fed the KP diet than in those fed the CS diet (p < 0.05), whereas rumination time did not significantly differ between the treatments. Dry matter content in the rumen immediately before and 3 h after feeding was significantly higher in cows fed the KP diet than in those fed the CS diet (p < 0.05). The consistency and thickness of the ruminal mat did not significantly differ between the treatments. The ruminal mean retention time of feed particles tended to be longer in cows fed the KP diet than in those fed the CS diet (p < 0.10). The ruminal digestion rate of KP was comparable to that of GS and CS. Because ruminal mat was formed and rumination was stimulated, KP was considered to have the equivalent physical effectiveness as CS.     

Effects of Saccharomyces cerevisiae on ruminal pH and microbial fermentation in dairy cows: Yeast supplementation on rumen fermentation

An experiment was conducted with eight ruminally-cannulated cows using a crossover design with 2 periods to determine the effects of yeast supplementation on rumen fermentation. Holstein dairy cows in late lactation were either supplemented with 0.5 g/hd/d of Saccharomyces cerevisiae, an active dry yeast (CNCM-1077, Levucell SC20 (r) SC, Lallemand Animal Nutrition) or not supplemented (control). A basal diet consisting of 60% forage and 40% concentrate (DM basis) was fed once daily to both groups of cows throughout the entire experiment. Ruminal pH was measured continuously every 22 min using a pH probe that was placed in the ventral rumen sac for 6 consecutive days. Volatile fatty acid and ammonia N concentrations in the rumen were measured on days 5 or 6 of the 12-d period for each cow and DM intake was monitored throughout the experiment. Data were analyzed using a mixed-effects model with repeated measures. There were no differences in dry matter intake between treatments. Mean ruminal pH was greater (P < 0.05) when yeast was supplemented (6.53 ± 0.07) compared with the control (6.32 ± 0.07). Average maximum and minimum ruminal pH were also greater (P < 0.05) when yeast was supplemented (7.01 ± 0.09 and 5.97 ± 0.08, respectively) compared with the control (6.80 ± 0.09 and 5.69 ± 0.09, respectively). Time spent under the subacute acidosis threshold, pH less than 5.6, was lower (P < 0.05) with yeast supplementation compared with control cows. No difference was observed for ruminal ammonia N concentrations (mean = 14.0 ± 1.2 mg/dL) between treatments. Total VFA concentration (mM) in the rumen tended to be lower (P = 0.10) in the yeast-supplemented cows (107.3 ± 6.35) than in the control cows (122.4 ± 6.35), which could be related to the greater pH observed with yeast supplementation. Supplementing dairy cows with active dry yeast in the current experiment increased the mean, minimum and maximum ruminal pH; decreased time spent in subacute rumen acidosis, and tended to decrease total VFA concentration in the rumen compared with control cows.     

Effects of tallow supplementation and protein withdrawal on ruminal fermentation, microbial synthesis and site of digestion

The effects of tallow supplementation [0% (NT) vs 7.5% (T)] and crude protein level [8.5% (LP) vs 12.0% (HP)] on ruminal fermentation, microbial protein (MCP) synthesis, digesta passage and site of digestion were estimated using yearling Angus X Simmental steers (390 kg) fitted with ruminal and T-type duodenal cannulae. Chromium-EDTA and ytterbium (Yb) chloride were used as markers of the liquid and solid phases. Passage and site of digestion data were estimated from the concentrations of Yb in the duodenal digesta and feces. Dry matter (DM) intakes were 6.8, 6.5, 6.3 and 6.6 kg/d for the NT-LP, NT-HP and T-HP diets, respectively. Ruminal ammonia concentrations (mg/100 ml) for the NT-LP, NT-HP, T-LP and T-HP diets were 1.22, 4.75, 1.05 and 3.41, respectively. Tallow decreased (P less than .05) acetate (mol/100 mol), increased (P less than .01) propionate (mol/100 mol) and decreased the total volatile fatty acid concentration. Tallow depressed apparent ruminal DM and organic matter (OM) digestibilities only on the HP diet. High protein increased ruminal DM, OM and fiber digestibilities. Tallow and LP tended to shift the site of OM digestion to the lower tract. The liquid and solid dilution rates for the NT-LP, NT-HP, T-LP and T-HP diets were 9.53, 3.37; 5.63, 3.28; 6.66, 5.10 and 6.79, 5.34%/h, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Performance of lactating simmental cows fed two diets differing in the content of digestible intestinal protein (PDI)

In each of two trials, two diets differing in intestinal digestible protein (PDI) content (LP: low protein, 70 g kg⁻¹ dry matter; HP: high protein, 120 g kg⁻¹ dry matter) were given to multiparous Simmental cows in early lactation. Effective rumen degradabilities of nitrogen and non-protein dry matter of feed ingredients, estimated by the nylon-bag technique, were used to calculate PDI contents of diets. In trial 1, two groups of six cows were fed, in two successive periods of 7 weeks each, the diets LP and HP allocated according to energy requirements (LPR and HPR). In trial 2, the diets LP and HP were fed in two periods of 6 weeks each to 24 cows (six cows/group) according to energy requirements (LPR and HPR) or ad libitum (LPL and HPL).In trial 1, total and energy-corrected milk (ECM) yields were significantly higher (P < 0.01) for cows receiving diet HPR (20.7 and 19.2 vs. 18.9 and 17.4 kg day⁻¹), while milk fat and protein contents were similar. Live weight changes were different between groups (−126 and +39 g day⁻¹ respectively, for LPR and HPR diets) but this difference was not significant.In trial 2, cows fed HPL diets had significantly higher milk yields compared with the LPL and LPR diets (20.0 vs. 17.7 and 17.4 kg day⁻¹, respectively, P < 0.05), but not with the HPR diet (19.0 kg day⁻¹). ECM yield was higher (P < 0.05) for cows receiving more protein both between restricted groups (18.4 vs. 16.4 kg day⁻¹, respectively for HPR and LPR groups) and between ad-libitum groups (18.8 vs. 17.0 kg day⁻¹, respectively for HPL and LPL groups). Milk composition was not affected by dietary treatments. Diets fed according to requirements caused negative, but differing, live weight changes (−783 and −44 day⁻¹ respectively for LPR and HPR diets, P < 0.05). For ad-libitum treatments, LPL cows lost live weight while HPL cows gained live weight (−221 vs. 433 day⁻¹, respectively, P < 0.05). In the present experiments, increasing the supply of dietary PDI improved milk production even if the recycled nitrogen and live weight change could have contributed to protein requirements.     

Effects of grass hay proportion in a corn silage‐based diet on rumen digesta kinetics and digestibility in dairy cows

In this study, we aimed to evaluate the effects of six levels of orchardgrass hay (GH) proportion (0%, 10%, 20%, 30%, 40% or 50% of dry matter) in finely chopped corn silage (CS)‐based diets on digesta kinetics of CS and GH in the rumen. Six non‐lactating, rumen‐cannulated Holstein cows were used in a 6 × 6 Latin square design. Ruminal digesta kinetics was measured by ruminal dosing of feed particle markers (dysprosium for CS, erbium for GH) followed by fecal sampling. The increase of GH proportion had a quadratic effect (P < 0.01) on total tract digestibility of neutral detergent fiber (NDF) and acid detergent fiber. The proportion of GH did not affect the particle size distribution of rumen digesta, total weight of dry matter or NDF in the rumen. The rates of large particle size reduction in the rumen for CS tended to increase linearly with increasing GH proportion (P = 0.077). A quadratic effect (P < 0.05) was found with increasing the GH proportion for the ruminal passage rate of small GH particles, but not for CS particles. The results suggested that associative effects between CS and GH could be generated on rumen digesta kinetics when cows were fed a CS‐based diet with an increased proportion of GH.     

In vivo mechanical and in vitro electromagnetic side-effects of a ruminal transponder in cattle

This work was undertaken to assess the long-term impacts of a ruminal transponder, used for electronic identification, on ruminal motility and on health and performance of cattle, as well as to study the electromagnetic effects on ruminal bacteria in vitro. A passive transponder (51.4 g, 67 x 17 mm) was delivered into the forestomachs of 8 calves, 32 bulls, 10 heifers, and 40 dairy cows. Final readability was 87.5% in calves, 96.9% in bulls, 90% in heifers, and 100% in cows at 481, 360, 650, and 601 d, respectively, after transponder administration. The transponder did not affect production or reproduction of cows over a 2-yr period, or performance of bulls, or mortality compared with control animals. Chewing movements per bolus were lower (P <0.01) in treated animals than in controls (49.6 vs. 52.2, 51.2 vs. 63.6, and 57.0 vs. 59.7 for bulls, heifers, and cows, respectively). Regurgitation frequency (number of boluses/10 min) tended to be greater in treated cattle: 12.4 vs. 11.3 (P = 0.07), 11.3 vs. 10.6, and 11.3 vs. 10.7 (P = 0.08) for bulls, heifers, and cows, respectively. Rumination patterns of calves fitted with transponders within the first weeks of life were similar to controls. During the experiment, 43 treated animals (8 calves, 29 bulls, and 6 cows) were slaughtered. Thirty transponders were localized in the reticulum (3 calves, 24 bulls, and 3 cows), 11 in the rumen (4 calves, 4 bulls, and 3 cows), and 2 were not recovered (1 calf and 1 bull). Within the calves, 57% of the boluses were found in the rumen. In 8 reticula (2 calves and 6 bulls) and 1 rumen (1 cow), an impression left by physical contact of the transponder was observed, although histological examination did not reveal specific lesions in the mucosa of the dystrophic areas. In strained, whole ruminal contents incubated in vitro, pH values were lower after 24 and 48 h (P <0.001) of continuous exposure to an electromagnetic field induced by the transponder-reading system. After 48 h of incubation, total bacterial numbers and NH3-N concentration were greater (P <0.001) in exposed flasks than in controls. These data indicate that the transponder may alter, via mechanical action, the reticuloruminal mucosa and rumination patterns. Furthermore, the transponder may increase, via its electromagnetic action, the growth rate and metabolic activity of ruminal bacteria.     

Effect of cereal straw and alfalfa hay diet on amino acid profile of gastrointestinal digesta in lactating dairy cows

This study was conducted to evaluate the effects of replacing alfalfa hay with rice straw (RS) or corn stover (CS) on amino acid (AA) profiles of gastrointestinal digesta in lactating cows. Eighteen lactating dairy cows were randomly assigned to one of three groups (n = 6) and fed identical concentrate and corn silage with different forages on dry matter basis: (i) 23% alfalfa hay and 7% Chinese wild rye hay (AH); (ii) 30% CS; and (iii) 30% RS. After the 14‐week feeding, a total of 18 cows were slaughtered to collect digesta from four representative organs, including rumen, omasum, duodenum and jejunum. The AA profiles of ruminal microbial fraction were similar among the treatments, except for greater Arg in cows fed RS than in cows fed AH or CS. Most of the analysed AA changed under different diets. Significant differences were found among the microbial fraction, rumen fluid and rumen digesta, with greater essential AA in digesta than in microbial fraction or rumen fluid and greater essential AA in microbial fraction than rumen fluid. Significant differences in individual AA profiles of digesta and relevant fluid were found across the four representative digestive tract parts, including rumen, omasum, duodenum and jejunum, showing much lower Leu proportion in CS and RS than in AH in duodenal fluid. In summary, ruminal microbes may prefer using essential AA, rather than non‐essential AA. The AA profile of ruminal microbes was constant except for Arg. The AA composition of digesta across the four digestive tracts changed dramatically, which indicated differences in the ability and efficiency of AA absorption. The lower duodenum absorbable Leu proportion in cows fed CS or RS indicated the shortage of Leu in CS or RS diets, which might also restrict the balanced AA absorption.     

Effects of dietary forage proportion on digestive function in maintenance-fed beef cows. 3. Bermudagrass and clover hays

Five crossbred beef cows (Hereford X Angus, 438 kg), cannulated in the rumen and duodenum, were used in a Latin square experiment to determine the effects of dietary proportions of bermudagrass (B) and clover (C) hays (0: 1, .25: .75, .5: .5, .75: .25 and 1: 0) on digestive function. Feed intake was 85% of ad libitum intake of B alone (1.35% of body weight). Bermudagrass contained 1.88% nitrogen (N), 79.6% neutral detergent fibre (NDF) and 5.2% acid detergent lignin (ADL), and C contained 2.30% N, 55.3% NDF and 6.3% ADL. Molar proportion of acetic increased linearly while propionic acid moved in the opposite direction as B replaced C (P less than .05). Mean particle size of duodenal digesta increased linearly (P less than .05) as B increased, but specific gravity of particles was constant (P greater than .10). Fluid passage rate decreased while volume increased linearly with increasing B (P less than .05) so that ruminal fluid outflow rate increased quadratically (P less than .10). Particulate passage rate ranged from 3.0 to 3.4% h. Apparent ruminal organic matter (OM) digestion was 69.0, 54.0, 53.0, 49.1 and 49.7% for 0, 25, 50, 75 and 100% B, respectively, decreasing quadratically as B rose (P less than .05). Postruminal OM digestibilities as percentages of intake and available OM changed quadratically (P less than .05) as dietary B increased, causing total tract OM digestion to decrease linearly (P less than .05; 73.8, 66.4, 63.1, 60.3 and 58.2% for 0, 25, 50, 75 and 100% B diets, respectively). Duodenal microbial-N flow increased quadratically with increasing B (P less than .05), being 45, 108, 103, 105 and 101 g/d, and microbial growth efficiency increased quadratically as well (P less than .05). True ruminal N disappearance ranged from 69.0 to 79.4% and was not affected by diet (P greater than .10). Ruminal digestibilities of fibre fractions were similar to OM. Little digestive function benefit was achieved by mixing warm season grass and legume hays in diets of maintenance-fed beef cows.     

Effects of extrusion of flaxseed on ruminal and postruminal nutrient digestibilities.

A study was conducted to determine the effects of extrusion on ruminal, post-ruminal and whole tract digestibility of flaxseed. Extrusion was performed at 155 degrees C with a residence time of 43 s. Two non-lactating Holstein cows fitted with ruminal and duodenal cannulas were used in a randomized complete block design. Results showed that extruded flaxseed had higher (P < 0.05) in situ soluble and lower (P < 0.05) slowly degradable DM and CP fractions than unheated flaxseed. Extrusion increased (P < 0.05) ruminal DM and CP degradability of flaxseed by 7 and 13%, respectively. Ruminal undegraded DM, CP and NDF were all lower (P < 0.05) for extruded flaxseed than for unheated flaxseed. Extrusion increased (P < 0.05) ruminal degradability and reduced (P < 0.05) post-ruminal availability of most amino acids of flaxseed. Whole tract digestibility of DM, CP, NDF and amino acids were higher (P < 0.05) for extruded than for unheated flaxseed. It was concluded that extrusion under the conditions used in the present experiment increases ruminal and whole tract nutrient degradabilities of flaxseed and therefore was ineffective in increasing the post-ruminal supply of amino acids from flaxseed.     

Ruminal phytate degradation of maize grain and rapeseed meal in vitro and as affected by phytate content in donor animal diets and inorganic phosphorus in the buffer

The ruminal disappearance of phytate phosphorus (InsP₆‐P) from maize grain and rapeseed meal (RSM) was determined in two in vitro studies. In experiment 1, two diets differing in phosphorus (P) and InsP₆‐P concentration were fed to the donor animals of rumen fluid (diet HP: 0.49% P in dry matter, diet LP: 0.29% P). Maize grain and RSM were incubated in a rumen fluid/saliva mixture for 3, 6, 12 and 24 h. In experiment 2, a diet similar to diet HP was fed, and the rumen fluid was mixed with artificial saliva containing 120 mg inorganic P/l (Pi) or no inorganic P (P0). Maize grain and RSM were incubated with either buffer for 3, 6, 12 and 24 h. Total P (tP) and InsP₆ concentration were analysed in the fermenter fluids and feed residues. The disappearance of InsP₆‐P from maize was completed after 12 h of incubation in both experiments. From RSM, 93% (diet LP) and 99% (diet HP) of the InsP₆‐P in experiment 1 and 80% (Pi) and 89% (P0) in experiment 2 had disappeared after 24 h of incubation. InsP₆‐P disappearance was higher when diet HP was fed (maize: 3 and 6 h; RSM: 6 and 24 h of incubation) and when rumen fluid was mixed with buffer P0 (maize: 6 h; RSM: 12 and 24 h of incubation). InsP₆‐P concentration in the fermenter fluids was higher for maize, but no accumulation of InsP₆‐P occurred, indicating a prompt degradation of soluble InsP₆. These results confirmed the capability of rumen micro‐organisms to efficiently degrade InsP₆. However, differences between the feedstuffs and diet composition as well as the presence of inorganic P in the in vitro system influenced the degradation process. Further studies are required to understand how these factors affect InsP₆ degradation and their respective relevance in vivo.