Comparison of methods, markers, sampling sites and models for estimating digesta passage kinetics in cattle fed at two levels of intake

Individual differences in digesta retention and their relation to chewing in cattle-A pilot investigation

While information on individual differences in digesta mean retention time (MRT) might be interesting when selecting phenotypes for digestive efficiency, MRT measurements are prohibitively labour-intensive for large-scale application. Therefore, more easily measured proxies of MRT might be helpful. We used the opportunity of an experiment applying saliva stimulant in cattle to investigate the effect of different individual chewing behaviour on fluid and particle MRT with a consistent diet. Four non-lactating cattle (670-850 kg body mass [BM]) were used in a 4 × 4 Latin square design, treated with the saliva stimulant pilocarpine in dosages of 0, 1, 2.5 and 5 mg/kg BM per day. The cattle were fed hay with dry matter intake (DMI) assigned according to their metabolic body weight. MRT in the whole gastrointestinal tract (GIT), the reticulorumen (RR) and the distal tract were measured using Co-EDTA, Cr-mordanted fibre and La-mordanted fibre as markers representing fluid, small particles (2 mm) and large particles (1 cm), respectively. The chewing behaviour was measured via noseband pressure sensor and expressed as chewing frequency (chews per time) and chewing intensity (chews per DMI), both for total chewing (ingestion plus rumination) and rumination chewing alone. The animals differed considerably in chewing behaviour and MRT measures. BM did not show a significant effect on chewing behaviour and MRT measures, though it tended to negatively correlated to total chewing intensity. Chewing intensity exerted a significant negative influence on MRT of fluid and particles in the RR, which was not the case for chewing frequency. Chewing frequency showed a significant relationship with MRT of large particles in the GIT. We suggest that chewing behaviour could influence MRT in two ways: (i) by affecting saliva production via the masticatory-salivary reflex and subsequently, the fluid inflow to the RR; (ii) by contributing to particle size reduction. Should the link between chewing behaviour and MRT be corroborated in larger studies, chewing measures, with their large interindividual variation, could emerge as an easy-to-measure proxy for MRT characteristics.

Effect of induced saliva flow on fluid retention time, ruminal microbial yield and methane emission in cattle

Both in vitro and animal studies indicated that a higher dilution rate is related to a more efficient microbial synthesis and a lower methane (CH₄ ) yield. The latter could be a consequence of the former, as an increase in microbial cell synthesis offers an alternative hydrogen sink competing with methanogenesis. To test this assumption in live animals, we applied a saliva stimulant, pilocarpine, to modify liquid flow rate in cattle. Four non-lactating cows (750 ± 71 kg) were fed forage only (restricted to constant intake) in a 4 × 4 Latin square design with oral doses of 0, 1, 2.5 and 5mg pilocarpine/kg body weight and day. We quantified feed and water intake, ruminal and total tract mean retention time (MRT) of solute and particle markers, ruminal microbial yield (via urinary purine bases or metabolic faecal nitrogen), CH₄ emission, digestibility, chewing behaviour, reticular motility and rumen fluid parameters. The effect of induced saliva flow was evident by visibly increased salivation and water intake. Increasing the pilocarpine dosages resulted in a linearly decreased MRT of fluid and small particles (p < 0.001 and p< 0.05, respectively) and methane yield as related to digested DM (p < 0.05), the latter at a magnitude of 5%. No effect of treatment was found on ruminal microbial yield estimated via purine derivates. Metabolic faecal N as an indicator of microbial growth linearly correlated with pilocarpine dosages (p < 0.05). No significant relationship was found between pilocarpine dosages and large particle MRT, nutrient digestibility, ruminal pH and short-chain fatty acids. In conclusion, different from some in vitro studies, there was little indication of a reciprocal effect of CH₄ and microbial biomass production in cows fed a forage-only diet.

Accuracy of methane emissions predicted from milk mid-infrared spectra and measured by laser methane detectors in Brown Swiss dairy cows

Since heritability of CH₄ emissions in ruminants was demonstrated, various attempts to generate large individual animal CH₄ data sets have been initiated. Predicting individual CH₄ emissions based on equations using milk mid-infrared (MIR) spectra is currently considered promising as a low-cost proxy. However, the CH₄ emission predicted by MIR in individuals still has to be confirmed by measurements. In addition, it remains unclear how low CH₄ emitting cows differ in intake, digestion, and efficiency from high CH₄ emitters. In the current study, putatively low and putatively high CH₄ emitting Brown Swiss cows were selected from the entire Swiss herdbook population (176,611 cows), using an MIR-based prediction equation. Eventually, 15 low and 15 high CH₄ emitters from 29 different farms were chosen for a respiration chamber (RC) experiment in which all cows were fed the same forage-based diet. Several traits related to intake, digestion, and efficiency were quantified over 8 d, and CH₄ emission was measured in 4 open circuit RC. Daily CH₄ emissions were also estimated using data from 2 laser CH₄ detectors (LMD). The MIR-predicted CH₄ production (g/d) was quite constant in low and high emission categories, in individuals across sites (home farm, experimental station), and within equations (first available and refined versions). The variation of the MIR-predicted values was substantially lower using the refined equation. However, the predicted low and high emitting cows (n = 28) did not differ on average in daily CH₄ emissions measured either with RC or estimated using LMD, and no correlation was found between CH₄ predictions (MIR) and CH₄ emissions measured in RC. When individuals were recategorized based on CH₄ yield measured in RC, differences between categories of 10 low and 10 high CH₄ emitters were about 20%. Low CH₄ emitting cows had a higher feed intake, milk yield, and residual feed intake, but they differed only weakly in eating pattern and digesta mean retention times. Low CH₄ emitters were characterized by lower acetate and higher propionate proportions of total ruminal volatile fatty acids. We concluded that the current MIR-based CH₄ predictions are not accurate enough to be implemented in breeding programs for cows fed forage-based diets. In addition, low CH₄ emitting cows have to be characterized in more detail using mechanistic studies to clarify in more detail the properties that explain the functional differences found in comparison with other cows.

Effects of Dietary Stevioside Supplementation on Feed Intake, Digestion, Ruminal Fermentation, and Blood Metabolites of Goats

Simple Summary

This study evaluated the effects of stevioside, a natural sweetener that is an extract of Stevia, on feed intake and feeding behavior of goats. The results demonstrated that the consumption of forage was improved after supplementation with stevioside. Supplementation of stevioside resulted in improved total diet consumption of goats. These results are useful for ruminant producers to use natural sweeteners to regulate the intakes of animals.

Abstract

The objective of this study was to evaluate the effects of dietary inclusion of stevioside on feed intake, feeding behavior, nutrient digestion, rumen fermentation, and serum biochemical parameters in goats. Nine male Xiangdong black goats (21.8 ± 1.5 kg of body weight) were used in a replicated 3 × 3 Latin square. All goats were fed a basal diet including concentrate and forage (chopped rice straw). The three treatments were 0, 400, or 800 mg stevioside per kg chopped rice straw on a dry matter (DM) basis. Dry matter intake of forage and total diet linearly increased (p = 0.03 and p = 0.04) with increasing stevioside in the diet. There was no effect (p > 0.05) of stevioside inclusion in the diets on eating time, rumination time, or total mastication time for the goats. Total volatile fatty acid (VFA) concentration in the rumen responded quadratically (p < 0.01), decreasing from 0 to 400 mg/kg stevioside inclusion and increasing thereafter. The inclusion of steviosid in the diets promoted a quadratic increase in the apparent total tract digestibilities of neutral detergent fiber (NDF) (p = 0.02) and acid detergent fiber (ADF) (p = 0.01). Based on the results of this experiment, it could be concluded that supplementing goat diets with stevioside at 400 mg/kg to 800 mg/kg forage (about 270 to 541 mg/kg diet) resulted in increased dry intake of forage and total diet, suggesting that stevioside has positive potential as a feed additive to improve feed intake.

Performance, carcass and meat quality traits of grazing cattle with different exit velocity

To evaluate the effect of grazing cattle temperament on performance, as well as carcass and meat quality traits, exit velocity (EV) was assessed throughout two production cycles (PC1, n = 38 and PC2, n = 52). Individual EV determinations were assessed throughout each PC and then 100-days period averages were calculated for each animal. Animals were ranked based on their EV (EV-RANK) in the first 100-days period as SLOW, FAST and MEDIUM. The EV decreased from weaning to slaughter in FAST and MEDIUM (P &lt; 0.05); but did not change in SLOW (P &gt; 0.10). Initial liveweight was lowest in FAST and highest in MEDIUM (P = 0.03). DM intake (P = 0.08) and average daily gain (P = 0.94) were not affected by EV-RANK, but carcass subcutaneous fat thickness was lowest in FAST and highest in MEDIUM (P = 0.02). Longissimus muscle colour and shear-force were not affected by EV-RANK (P &gt; 0.05), but muscle glycogen content at slaughter was higher in MEDIUM than in SLOW or FAST (P = 0.047). No EV-RANK effects were observed in the present study on meat colour and shear-force. However, its effects on subcutaneous fat thickness and muscle glycogen could result in low meat quality of temperamental cattle under more stressful handling situations.

Changes in ruminal and reticular pH and bacterial communities in Holstein cattle fed a high-grain diet

BACKGROUND

Subacute ruminal acidosis (SARA) is characterized by a ruminal pH depression, and microbiota can also be affected by a higher acidity and/or dietary changes. Previous studies have revealed similar patterns in pH reduction in the rumen and reticulum, whereas changes in reticular pH and bacterial community following a high-grain diet are not fully understood. The aim of this study was to investigate the changes in reticular pH and bacterial community structure following a high-grain diet simultaneously with those in the rumen.

RESULTS

SARA was diagnosed when ruminal and reticular pH remained under 5.6 for 350 ± 14 and 312 ± 24 min/d, respectively, on the last day of the CON period. During the CON period, lower proportion of acetic acid and higher proportion of butyric acid were observed compared with the HAY period. The proportions of acetic acid and propionic acid were lower and higher, respectively, in the rumen compared with the reticulum. From 454 pyrosequencing analysis, the relative abundance of several genera differed significantly between the two periods and the two locations. During the HAY period, higher relative abundances of Prevotella, Eubacterium, Oscillibacter, and Succiniclasticum and lower relative abundances of Ruminococcus, Clostridium, and Olsenella were identified compared with the CON period. Furthermore, the relative abundance of Eubacterium was lower in the rumen compared with the reticulum. Bacterial diversity indices were significantly different between the HAY and CON periods, being higher in the HAY period. The quantitative real-time PCR showed that the copy numbers of several cellulolytic bacteria (Fibrobacter succinogenes and Ruminococcus albus) were higher during the HAY period.

CONCLUSION

A high-grain diet showed similar impacts on the pH, fermentation, and bacterial community structure in the rumen and reticulum. During the CON period, ruminal and reticular pH decreased following the high-grain challenge, and lower bacterial diversity and changes in the bacterial composition, similarity, and bacterial copy numbers were observed due to a higher acidity and dietary changes compared with the HAY period. These changes may influence the fermentative ability of the rumen and reticulum.

Effects of supplementation of Brachiaria brizantha cv. Piatá and Napier grass with Desmodium distortum on feed intake, digesta kinetics and milk production in crossbred dairy cows

This study was planned to analyse the basis that make Brachiaria species with greater feeding value than Napier grass (Pennisetum purpureum) for lactating dairy cows. Forty lactating crossbred cows were stall-fed on Brachiariabrizantha cv. Piatá or Napier grass cv. French Cameroon supplemented (mixed on fresh matter basis) or unsupplemented with Desmodium distortum, a forage legume. All cows were fed on fresh matter basis under small-holder farming conditions. Results showed that B. brizantha cv. Piatá had higher contents of dry matter (DM), crude protein (CP) and organic matter (OM), but lower contents of neutral detergent fibre (NDF) and acid detergent fibre (ADF) than Napier grass (P < 0.001). The legume supplementation increased intakes of CP and metabolizable energy (ME; P < 0.001), with higher effect on cows fed B. brizantha cv. Piatá than on cows fed Napier grass. Average daily milk yield was lower on diets based on Napier grass than those based on B. brizantha cv. Piatá (P < 0.001). The retention time of the particle phase of digesta in the digestive tract was longer on Napier grass (83.1 h) than on B. brizantha cv. Piatá (62.8 h) (P < 0.05). It was concluded that in dairy cows, legume supplementation of B. brizantha cv. Piatá increases nutrient intake, hence resulting in higher milk yields than supplementation of Napier grass.

Dietary forage to concentrate ratio and sunflower oil supplement alter rumen fermentation, ruminal methane emissions, and nutrient utilization in lactating cows

The effects of supplementing high- or low-concentrate diets with sunflower oil (SO) on rumen fermentation, nutrient utilization, and ruminal methane (CH₄) emissions in lactating cows were examined. Four multiparous Nordic Red dairy cows fitted with rumen cannulae were used in a 4 × 4 Latin square with a 2 × 2 factorial arrangement of treatments and 35-d periods. Experimental treatments comprised iso-nitrogenous total mixed rations based on grass silage with forage to concentrate ratio of 65:35 or 35:65 supplemented with 0 or 50 g/kg diet DM of SO. Apparent ruminal OM and starch digestibility was greater (P < 0.05) with high- than low-concentrate diets but was unaffected by SO. Inclusion of SO in high-concentrate diet decreased (P ≤ 0.05) apparent total tract OM, fiber, and GE, and apparent ruminal fiber digestibility. High-concentrate diets and SO shifted (P < 0.05) fiber digestion from rumen to the hindgut. High-concentrate diet resulted in a lower rumen pH and elevated total rumen VFA concentration compared with low-concentrate diet, whereas SO increased rumen pH and decreased rumen VFA concentration when included in high-, but not low-concentrate diet (P < 0.05 for interaction). High-concentrate diet reduced rumen ammonia-N (P < 0.01) and molar proportion of acetate to propionate (P < 0.01), and decreased (P < 0.05) ruminal CH₄ emissions when expressed as g/d or g/kg OM digested in the rumen. With both low- and high-concentrate diets, SO reduced (P < 0.05) daily emissions of CH₄ as g/d or g/kg OM digested in the rumen, but SO reduced CH₄ emissions expressed as g/kg OM intake, OM digested in total digestive tract, energy-corrected milk or % of GE intake only with low-concentrate diet (P ≤ 0.05 for interaction). In conclusion, replacing grass silage with concentrates led to a reduction in daily ruminal CH₄ emissions that were accompanied by a shift in rumen fermentation toward the synthesis of propionate, and decreases in rumen pH and fiber digestion. Sunflower oil was effective in reducing daily CH₄ emissions in lactating cows which was accompanied by a noticeable lower feed intake with high- but not low-concentrate diet. Overall the effects of SO and greater proportion of concentrates in the diet on daily CH₄ emissions were additive but the additivity declined or vanished when different indices of CH₄ emission intensity were considered. Consequently, SO was more effective in reducing CH₄ emissions when low-concentrate diet was fed.

Effects of Dietary Forage and Calf Starter Diet on Ruminal pH and Bacteria in Holstein Calves during Weaning Transition

We investigated the relationship between ruminal pH and bacteria in calves fed calf starter with and without forage during weaning transition. First, 16 Holstein bull calves were obtained from dairy farms and equipped with rumen cannulas by cannulation surgery. Then, calves (73.5 ± 4.2 kg; mean ± SE) were assigned to groups fed calf starter either with forage (HAY, n = 8) or without forage (CON, n = 8), and all calves were weaned at 8 weeks of age. Ruminal pH was measured continuously, and rumen fluid samples were collected at 7, 8, 9, and 11 weeks of age, namely −1, 0, 1, and 3 weeks after weaning, respectively, to assess volatile fatty acid concentrations and bacterial DNA. The 24-h mean ruminal pH was significantly (P < 0.05) different between the two groups. Diurnal changes in the 1-h mean ruminal pH were observed throughout the study in the HAY group; however, they were not observed at 0 and 1 weeks after weaning in the CON group. Moreover, the HAY group had significantly (P < 0.05) higher proportions of acetate and butyrate and lower proportion of propionate, and significantly (P < 0.05) lower ruminal acetate-to-propionate ratios were observed in the CON group. The ruminal bacterial diversity indices decreased after −1 week in both groups and increased at 0 and 1 weeks after weaning in the HAY and CON groups, respectively. From the 454 pyrosequencing analysis, significant differences (P < 0.05) were observed in the relative abundance of several phyla (Bacteroidetes, Actinobacteria, and Tenericutes) and one genus (Prevotella) between the two groups. From quantitative real-time PCR analysis, the HAY group had the higher copy numbers of cellulolytic bacteria (Ruminococcus flavefaciens and Ruminococcus albus) compared with the CON group. This study demonstrated that feeding of dietary forage alleviates subacute ruminal acidosis due to diurnal changes in ruminal pH. Furthermore, changes in ruminal pH affect the ruminal bacterial diversity and relative abundance, and these changes might have influenced the establishment of fermentative ruminal functions during weaning transition.

Effect of dietary fish oil on biohydrogenation of fatty acids and milk fatty acid content in cows

Mechanisms underlying milk fat conjugated linoleic acid (CLA) responses to supplements of fish oil were investigated using five lactating cows each fitted with a rumen cannula in a simple experiment consisting of two consecutive 14-day experimental periods. During the first period cows were offered 18 kg dry matter (DM) per day of a basal (B) diet formulated from grass silage and a cereal based-concentrate (0·6 : 0·4; forage : concentrate ratio, on a DM basis) followed by the same diet supplemented with 250 g fish oil per day (FO) in the second period. The flow of non-esterified fatty acids leaving the rumen was measured using the omasal sampling technique in combination with a triple indigestible marker method based on Li-Co-EDTA, Yb-acetate and Cr-mordanted straw. Fish oil decreased DM intake and milk yield, but had no effect on milk constituent content. Milk fat trans-11 C18:1, total trans-C18 : 1, cis-9 trans-11 CLA, total CLA, C18 : 2(n-6) and total C18 : 2content were increased in response to fish oil from 1·80, 4·51, 0·39, 0·56, 0·90 and 1·41 to 9·39, 14·39, 1·66, 1·85, 1·25 and 4·00 g/100 g total fatty acids, respectively. Increases in the cis-9, trans-11 isomer accounted for proportionately 0·89 of the CLA response to fish oil. Furthermore, fish oil decreased the flow of C18 : 0(283 and 47 g/day for B and FO, respectively) and increased that of trans-C18 : 1fatty acids entering the omasal canal (38 and 182 g/day). Omasal flows of trans-C18 : 1acids with double bonds in positions from delta-4 to -15 inclusive were enhanced, but the effects were isomer dependent and primarily associated with an increase in trans-11 C18 : 1 leaving the rumen (17·1 and 121·1 g/day for B and FO, respectively). Fish oil had no effect on total (4·36 and 3·50 g/day) or cis-9, trans-11 CLA (2·86 and 2·08 g/day) entering the omasal canal. Flows of cis-9, trans-11 CLA were lower than the secretion of this isomer in milk. Comparison with the transfer of the trans-9, trans-11 isomer synthesized in the rumen suggested that proportionately 0·66 and 0·97 of cis-9, trans-11 CLA was derived from endogenous conversion of trans-11 C18 : 1in the mammary gland for B and FO, respectively. It is concluded that fish oil enhances milk fat cis-9, trans-11 CLA content in response to increased supply of trans-11 C18:1that arises from an inhibition of trans-C18 : 1reduction in the rumen.

Dose and time response of ruminally infused algae on rumen fermentation characteristics, biohydrogenation and Butyrivibrio group bacteria in goats

BACKGROUND

Micro-algae could inhibit the complete rumen BH of dietary 18-carbon unsaturated fatty acid (UFAs). This study aimed to examine dose and time responses of algae supplementation on rumen fermentation, biohydrogenation and Butyrivibrio group bacteria in goats.

METHODS

Six goats were used in a repeated 3 × 3 Latin square design, and offered a fixed diet. Algae were infused through rumen cannule with 0 (Control), 6.1 (L-Alg), or 18.3 g (H-Alg) per day. Rumen contents were sampled on d 0, 3, 7, 14 and 20.

RESULTS

H-Alg reduced total volatile fatty acid concentration and acetate molar proportion (P < 0.05), and increased propionate molar proportion (P < 0.05), whereas L-Alg had no effect on rumen fermentation. Changes in proportions of acetate and propionate in H-Alg were obvious from d 7 onwards and reached the largest differences with the control on d 14. Algae induced a dose-dependent decrease in 18:0 and increased trans-18:1 in the ruminal content (P < 0.05). H-Alg increased the concentrations of t9, t11-18:2 and t11, c15-18:2 (P < 0.05). L-Alg only seemed to induce a transient change in 18-carbon isomers, while H-Alg induced a rapid elevation, already obvious on d 3, concentrations of these fatty acid rose in some cases again on d 20. Algae had no effect on the abundances of Butyrivibrio spp. and Butyrivibrio proteoclasticus (P > 0.10), while H-Alg reduced the total bacteria abundance (P < 0.05). However, this was induced by a significant difference between control and H-Alg on d 14 (-4.43 %). Afterwards, both treatments did not differ as increased variation in the H-Alg repetitions, with in some cases a return of the bacterial abundance to the basal level (d 0).

CONCLUSIONS

Changes in rumen fermentation and 18-carbon UFAs metabolism in response to algae were related to the supplementation level, but there was no evidence of shift in ruminal biohydrogenation pathways towards t10-18:1. L-Alg mainly induced a transient effect on rumen biohydrogenation of 18-carbon UFAs, while H-Alg showed an acute inhibition and these effects were not associated with the known hydrogenating bacteria.

Effects of grain source, grain processing, and protein degradability on rumen kinetics and microbial protein synthesis in Boer kids

Microbial protein synthesis in the rumen would be optimized when dietary carbohydrates and proteins have synchronized rates and extent of degradation. The aim of this study was to evaluate the effect of varying ruminal degradation rate of energy and nitrogen sources on intake, nitrogen balance, microbial protein yield, and kinetics of nutrients in the rumen of growing kids. Eight Boer goats (38.2 ± 3.0 kg) were used. The treatments were arranged in a split-plot Latin square design with grain sources (barley or corn) forming the main plots (squares). Grain processing methods and levels of protein degradability formed the subplots in a 2 × 2 factorial arrangement for a total of 8 dietary treatments. The grain processing method was rolling for barley and cracking for corn. Levels of protein degradability were obtained by feeding untreated soybean meal (SBM) or heat-treated soybean meal (HSBM). Each experimental period lasted 21 d, consisting of a 10-d adaptation period, a 7-d digestibility determination period, and a 4-d rumen evacuation and sampling period. Kids fed with corn had higher purine derivatives (PD) excretion when coupled with SBM compared with HSBM and the opposite occurred with barley-fed kids ( ≤ 0.01). Unprocessed grain offered with SBM led to higher PD excretion than with HSBM whereas protein degradability had no effect when processed grain was fed ( ≤ 0.03). Results of the current experiment with high-concentrate diets showed that microbial N synthesis could be maximized in goat kids by combining slowly fermented grains (corn or unprocessed grains) with a highly degradable protein supplement (SBM). With barley, a more rapidly fermented grain, a greater microbial N synthesis was observed when supplementing a low-degradable protein (HSBM).

Kinetics of ruminal passage rate of particles of signal grass silage, maize and intercropped

<p>The purpose of this study was to evaluate the kinetics of ruminal passage rate of particles from the subsequent associations: corn and signal grass; corn, signal grass and Calopogônio; corn, signal grass and Macrotiloma; and corn, signal grass and Estilosantes. It was used four crossbred holstein-zebu cattle with the rumen tubed in order to determine the the kinetics of ruminal passage rate of particles. The feces were collected at the times zero (immediately after addition of fibers complexed with chromium), 1, 2, 4, 6, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, 56 , 64, 72, 80, 88, 96, 120, 132, 144 and 192 hours. The profile parameters of passage rate estimative were adjusted according to robust regression procedures. The average time of particles retention in the raft (ATPR1); the average time in the rumen liquid phase (ATRLP2) and the average time of total ruminal retention (ATTRR) were adjusted for the passage kinetics and estimated with the NLIN procedure of SAS. From the observed results, may be suggested that the transference rate <italic>λ</italic> has an inverse behavior to the escape rate <italic>κ</italic>, the <italic>τ</italic> average values, the average retention time and average particles retention time in the rumen liquid phase (ATRLP2) were not statistically different. The feed characteristics after the raft escape and reach to ATRLP2, were very similar; (ATTRR), related to treatments, were not statistically different (P<0,05). There were observed small TMRR numerical differences in different foods. The corn and signal grass; corn, signal grass and calopogônio; corn, signal grass and macrotiloma, corn, signal grass and estilosantes silage fibers had similar rates of<italic>λ</italic>, k, ATPR1, ATRLP2 and ATTRR. Therefore, the the kinetics of ruminal passage rate of particles is similar. Thus, the choice of the system should be based on other factors, such as viability of the management ease and silage cost.</p>

Quantifying body water kinetics and fecal and urinary water output from lactating Holstein dairy cows

Reliable estimates of fresh manure water output from dairy cows help to improve storage design, enhance efficiency of land application, quantify the water footprint, and predict nutrient transformations during manure storage. The objective of the study was to construct a mechanistic, dynamic, and deterministic mathematical model to quantify urinary and fecal water outputs (kg/d) from individual lactating dairy cows. The model contained 4 body water pools: reticulorumen (QRR), post-reticulorumen (QPR), extracellular (QEC), and intracellular (QIC). Dry matter (DM) intake, dietary forage, DM, crude protein, acid detergent fiber and ash contents, milk yield, and milk fat and protein contents, days in milk, and body weight were input variables to the model. A set of linear equations was constructed to determine drinking, feed, and saliva water inputs to QRR and fractional water passage from QRR to QPR. Water transfer via the rumen wall was subjected to changes in QEC and total water input to QRR. Post-reticulorumen water passage was adjusted for DM intake. Metabolic water production and respiratory cutaneous water losses were estimated with functions of heat production in the model. Water loss in urine was driven by absorbed N left after being removed via milk. Model parameters were estimated simultaneously using observed fecal and urinary water output data from lactating Holstein cows (n=670). The model was evaluated with data that were not used for model development and optimization (n=377). The observations in both data sets were related to thermoneutral conditions. The model predicted drinking water intake, fecal, urinary, and total fresh manure water output with root mean square prediction errors as a percentage of average values of 18.1, 15.6, 30.6, and 14.6%, respectively. In all cases, >97% of the prediction error was due to random variability of data. The model can also be used to determine saliva production, heat and metabolic water production, respiratory cutaneous water losses, and size of major body water pools in lactating Holstein cows under thermoneutral conditions.

Effects of forage provision to young calves on rumen fermentation and development of the gastrointestinal tract

Fifteen Holstein male calves were randomly assigned to 1 of 3 dietary treatments according to age and body weight (BW) to determine the effects of feeding different forages sources on rumen fermentation and gastrointestinal tract (GIT) development. Treatments consisted of a starter (20% crude protein, 21% neutral detergent fiber) fed alone (CON) or supplemented with alfalfa (AH) or with oat hay (OH). All calves received 2L of milk replacer (MR) at 12.5% dry matter twice daily until 49 d of age. Calves received 2L of the same MR from 50 to 56 d of age and were weaned at 57 d of age. Individual starter, forage, and MR intakes were recorded daily and BW was recorded weekly. A rumen sample was taken weekly to determine rumen pH and volatile fatty acid concentrations. Three weeks after weaning, animals were harvested and each anatomical part of the GIT was separated and weighed with and without contents. Rumen pH was lower in CON than in OH and AH calves. Furthermore, acetate proportion in the rumen liquid tended to be greater in AH than in CON and OH treatments. Total GIT weight, expressed as a percentage of BW, tended to be greater in AH compared with the other 2 treatments. Rumen tissue tended to weigh more in CON than in OH animals. Animals with access to forage tended to have a greater expression of monocarboxylate transporter 1 than CON calves. In conclusion, calves supplemented with oat hay have a better rumen environment than calves offered no forage and do not have an increased gut fill.

Effect of incremental amounts of fish oil in the diet on ruminal lipid metabolism in growing steers

Based on the potential benefits to human health, there is interest in developing sustainable nutritional strategies to enhance the concentration of long-chainn-3 fatty acids in ruminant-derived foods. Four Aberdeen Angus steers fitted with rumen and duodenal cannulae were used in a 4 × 4 Latin square experiment with 21 d experimental periods to examine the potential of fish oil (FO) in the diet to enhance the supply of 20 : 5n-3 and 22 : 6n-3 available for absorption in growing cattle. Treatments consisted of total mixed rations based on maize silage fed at a rate of 85 g DM/kg live weight0·75/d containing 0, 8, 16 and 24 g FO/kg diet DM. Supplements of FO reduced linearly (P < 0·01) DM intake and shifted (P < 0·01) rumen fermentation towards propionate at the expense of acetate and butyrate. FO in the diet enhanced linearly (P < 0·05) the flow oftrans-16 : 1,trans-18 : 1,trans-18 : 2, 20 : 5n-3 and 22 : 6n-3, and decreased linearly (P < 0·05) 18 : 0 and 18 : 3n-3 at the duodenum. Increases in the flow oftrans-18 : 1 were isomer dependent and were determined primarily by higher amounts oftrans-11 reaching the duodenum. In conclusion, FO alters ruminal lipid metabolism of growing cattle in a dose-dependent manner consistent with an inhibition of ruminal biohydrogenation, and enhances the amount of long-chainn-3 fatty acids at the duodenum, but the increases are marginal due to extensive biohydrogenation in the rumen.

A generalized compartmental model to estimate the fibre mass in the ruminoreticulum: 2. Integrating digestion and passage

Models used to predict digestibility and fill of the dietary insoluble fibre (NDF) treat the ruminoreticular particulate mass as a single pool. The underlying assumption is that escape of particles follows first-order kinetics. In this paper, we proposed and evaluated a model of two ruminoreticular sequential NDF pools. The first pool is formed by buoyant particles (raft pool) and the second one by fluid dispersed particles (escapable pool) ventrally to the raft. The transference of particles between these two pools results from several processes that reduce particles buoyancy, assuming the gamma distribution. The exit of escapable pool particles from the ruminoreticulum is exponentially distributed. These concepts were evaluated by comparing ruminoreticular NDF masses as 43 and 27 means from cattle and sheep, respectively, to the same predicted variable using single- and two-pools models. Predictions of the single-pool model were based on lignin turnover and the turnover associated to the descending phase of the elimination of Yb-labelled forage particles in the faeces of sheep. Predictions of the two-pool model were obtained by estimating fractional passage rates associated to the ascending and descending phases of the same Yb excretion profiles in sheep faeces. All turnovers were scaled to the power 0.25 of body mass for interspecies comparisons. Predictions based on lignin turnover (single pool) and the two-pool model presented similar trends, accuracies and precisions. The single-pool approach based solely on the descending phase of the marker yielded biased estimates of the ruminoreticular NDF mass.

Marker concentration patterns of labelled leaf and stem particles in the rumen of cattle grazing bermuda grass (Cynodon dactylon) analysed by reference to a raft model

Large (>1600 μm), ingestively masticated particles of bermuda grass (Cynodon dactylon L. Pers.) leaf and stem labelled with 169Yb and 144Ce respectively were inserted into the rumen digesta raft of heifers grazing bermuda grass. The concentration of markers in digesta sampled from the raft and ventral rumen were monitored at regular intervals over approximately 144 h. The data from the two sampling sites were simultaneously fitted to two pool (raft and ventral rumen–reticulum) models with either reversible or sequential flow between the two pools. The sequential flow model fitted the data equally as well as the reversible flow model but the reversible flow model was used because of its greater application. The reversible flow model, hereafter called the raft model, had the following features: a relatively slow age-dependent transfer rate from the raft (means for a gamma 2 distributed rate parameter for leaf 0.0740 v. stem 0.0478 h-1), a very slow first order reversible flow from the ventral rumen to the raft (mean for leaf and stem 0.010 h-1) and a very rapid first order exit from the ventral rumen (mean of leaf and stem 0.44 h-1). The raft was calculated to occupy approximately 0.82 total rumen DM of the raft and ventral rumen pools. Fitting a sequential two pool model or a single exponential model individually to values from each of the two sampling sites yielded similar parameter values for both sites and faster rate parameters for leaf as compared with stem, in agreement with the raft model. These results were interpreted as indicating that the raft forms a large relatively inert pool within the rumen. Particles generated within the raft have difficulty escaping but once into the ventral rumen pool they escape quickly with a low probability of return to the raft. It was concluded that the raft model gave a good interpretation of the data and emphasized escape from and movement within the raft as important components of the residence time of leaf and stem particles within the rumen digesta of cattle.

Determination of reticulo-rumen and whole-stomach digestion in lactating cows by omasal canal or duodenal sampling

Four ruminally and duodenally cannulated multiparous Finnish Ayrshire cows were fed on diets consisting of grass silage (0·6 kg/kg DM) and one of four concentrates: barley, barley + urea, barley + rapeseed meal and barley + rapeseed cake. The objective of the present study was to compare omasal canal and duodenal digesta flows. Values for digesta flow into the omasal canal and duodenum were determined using a triple-marker method based on Co-EDTA, Yb-acetate and indigestible neutral-detergent fibre (NDF) markers. Microbial non-NH3 N (NAN) flow was assessed by purine flow. Microbial samples to determine the bacterial purine: N ratio were harvested from the rumen, omasum and duodenum. Organic matter flow was significantly lower into the omasum than the duodenum, indicating an endogenous organic matter secretion into the abomasum. In contrast, NDF and acid-detergent fibre flows were significantly higher into the omasum indicating digestion of fibre in the omasum. Microbial NAN flows were significantly different (P < 0·001) when estimates were based on bacterial samples harvested from different sites. Differences in total NAN, microbial NAN and dietary NAN flows entering the omasal canal and duodenum were non-significant. The results indicated that the omasal sampling technique provides a promising alternative to the duodenal sampling technique to investigate forestomach digestion in dairy cows and offers an alternative means to study rumen N metabolism.

Models for estimating digesta passage kinetics in the gastrointestinal tract of the horse

Fecal samples were collected to evaluate mathematical models to describe the kinetics of digesta passage in the segments of the equine gastrointestinal tract and to compare the passage kinetics of hay and oats. Four Norwegian Cold-blooded trotters (cecally cannulated, approximately 500 kg of BW) were fed Cr-mordanted hay and Yb-marked oats with their morning meal. The meal consisted of 2 kg of hay and 1 kg of oats processed as ground, pelleted, extruded, or micronized. Each horse was fed each type of oats on different days of collection, after a 5-d adaptation period, in a 4 x 4 Latin square design. Fecal samples were collected 5, 6, 7, 8, 9, 10, 11, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 48, and 52 h after administration of the marker dose. The samples were analyzed for Cr and Yb, and values were plotted using 1- and 2-compartment nonlinear passage models and an algebraic model. The 1-compartment G4 model and the 2-compartment G4G1 model showed an equally good fit to the observed excretion curves, based on low mean square error and SE. The excretion curves for hay (Cr) and oats (Yb) showed a striking similarity, and there seemed to be no difference in retention time between hay and oats in the horse. The mixing compartments in the horse are believed to be the cecum or both the cecum and the right ventral and dorsal segments of the colon, but further research in this area is needed to make a final conclusion.

Effects of size of ingestively masticated fragments of plant tissues on kinetics of digestion of NDF

Ingestively masticated fragments were collected and sized via sieving. Different sizes of esophageal masticate and ruminal digesta fragments, and ground fragments of larger masticated pieces were incubated in vitro, and undigested NDF remaining at intervals of up to 168 h of incubation was determined. The ruminal age-dependent time delay (tau) for onset of digestion of NDF was positively correlated (P < 0.004) with the mean sieve aperture estimated to retain 50% of the fragments between successive sieve apertures (MRA). Degradation rate of potentially degradable NDF (PDF) and level of indigestible NDF were not related (P > 0.10) to MRA of masticated and ground fragments. Estimates of tau were positively related to MRA, with slopes of bermudagrass < corn silage < ruminal fragments of corn silage. It was concluded that fragment size-, and consequently, ruminal age-dependent onset of PDF degradation of a mixture of different fragment sizes results in an age-dependent rate of degradation of the more rapidly degrading of two subentities of PDF. Models are proposed that assume a tau before onset of simultaneous degradation of PDF from two pools characterized as having gamma-modeled age-dependency and age-constant rates. The ruminal age-dependent pool seems to be associated with the faster-degrading pool, and its rate parameter increases with range in MRA in the population of fragments. Conceptually, the ruminal age-dependent rate parameter for PDF degradation seems to represent a composite of several effects: 1) effects of the size-dependent tau; 2) range in MRA of the population of ingestively masticated fragments; and 3) subentities of PDF that degrade via more rapid age-dependent rates compared with subentities of PDF that degrade via age-constant rates. The estimated fractional rates of ruminative comminution of ingestively masticated fragments (0.060 to 0.075/h) were of a magnitude similar to the mean fractional rates of PDF digestion (0.030 to 0.085/h), which implies that ruminative comminution may be first-limiting to fractional rate of PDF digestion. The in vivo roles of ingestive and ruminative mastication of fragments on PDF degradation must be considered in any kinetic system for estimating PDF digestion in the rumen. These results and others in the literature suggest that the rate of surface area exposure rather than intrinsic chemical attributes of PDF may be first-limiting to degradation rate of PDF in vivo.

Flow paths of plant tissue residues and digesta through gastrointestinal segments in Spanish goats and methodological considerations1

A sequence of eight twice-daily meals, each marked with different rare earth elements, was fed to 24 Spanish goats (BW = 20.6 +/- 1.94 kg) to produce meal-based profiles of rare earth markers within segments of the gastrointestinal digesta on subsequent slaughter. Accumulative mean residence time and time delay of rare earths and segmental and accumulative mean residence times of indigestible NDF (IDF) were estimated for each sampled segment. Diets consisted of ad libitum access to bermudagrass hay with a limit feeding of one of four supplements: 1) minerals (basal, B); 2) B + energy (E); 3) B + CP (CP); or 4) B + E + CP for 84 d. Mean daily intake (g/kg of BW) during the 5 d before slaughter differed (P < 0.05) via diet for DM but not for IDF (8.0 +/- 0.35 g/kg of BW). Larger estimates of cumulative mean residence time for IDF vs. rare earths were suggested to be the consequence of a meal-induced bias in the single measurement of IDF pool size by anatomical site. The rare earth compartment method was considered more reliable than the IDF pool dilution method because it yielded flow estimates based on the flux of eight meal-dosed rare earth markers over 4 d and was independent of anatomical definitions of pool size. Statistically indistinguishable estimates for gastrointestinal mean residence times for IDF and rare earths conform to assumed indelibility for the specifically applied rare earths and indigestibility of IDF. The potentially digestible NDF (PDF):IDF ratio of dietary fragments (0.8) progressively decreased in the following order: caudodorsal reticulorumen (0.390) > crainodorsal reticulorumen (0.357) approximately reticulum (0.354) > mid-dorsal reticulorumen (0.291) approximately ventral reticulorumen (0.286), to that within the omasal folds and in the abomasum (0.259). Such a gradient of progressively aging mixture of plant tissue fragments is consistent with age-dependent flow paths established in the reticulorumen and flowing to the omasum and abomasum. Such heterogeneity of fragment ages within the reticulorumen is also indicated by the superior fit of marker dose site double dagger marker sampling site model assumptions. Additionally, cyclic meal- and rumination-induced variations in escape rate occur. Estimates of mean escape rates over days, needed for the practice of ruminant nutrition, must consider the complex interactions among plant tissues and the dynamics of their ruminal digestion of PDF.