Rumen Variables Research Articles

Performance, digestibility and meat quality from lambs fed diets with plantago lanceolata, Italian ryegrass or sainfoin herbages.

Plantago species, which is known to adapt to different climatic conditions, drought, temperature and different soil types. The aim of this study was to compare the effects of P. lanceolata herbage on fattening performance, rumen variables, digestibility, meat quality, meat nutrients and meat textural variables in lambs with the values of Italian ryegrass and sainfoin herbages. The lambs were fed total mix ration (TMR) with concentrated feed (about 30%) plus forage (about 70%) (P. lanceolata, PLA, Italian ryegrass (Lolium multiflorum); IRY or sainfoin (Onobrychis viciifolia) herbages, SAI). Twenty-four male lambs (Akkaraman breed) were assigned to three treatments with 8 lambs in each group. Fattening performance parameters, digestibility and carcass variables were determined. Meat quality and shelf life variables (oxidation, fatty acid profile and textural variables) was detected in the loin (Musculus longissimus), shoulder (M. deltoideus) and leg (M. semitendinosus) muscle samples, which were rested for 24 h +4°C and stored at -20°C for one week, one month, three months and six months. The dry matter (DM) intake, body weight gain, feed efficiency and carcass yield values of lambs, the DM and organic matter (OM) digestions (DMD and OMD) of TMRs, and the pH value, ammonia-nitrogen and short chain fatty acid (SCFA) concentrations of rumen fluid in lambs consuming PLA were similar to those of IRY and SAI (p > 0.05). PLA increased water holding capacity (WHC) and decreased cooking loss of meat compared to feeding with those of IRY and SAI (p < 0.05). The peroxide value (PV) and malondialdehyde (MDA) concentration increased with the stocking time in the meats (p < 0.05). Therefore, PV and MDA concentrations of shoulder, leg and loin meats up to 6th months for PLA were lower than those of IRY and SAI (p < 0.05). The linoleic acid concentration of loin and shoulder meats in PLA were higher than those of IRY and SAI (p < 0.05). The average oleic acid and ∑ω6 fatty acids concentration of meat in PLA was lower than those in IRY and SAI (p < 0.05). Atherogenic index and thrombogenic index values and palmitic acid levels of meat in PLA were similar to those in IRY, but lower than those in SAI (p < 0.05). Springiness, cohesiveness, resilience, hardness and chewiness values of the textural analysis parameters in meat of PLA were lower than those of IRY and SAI. As a result, effect of P. lanceolata on the fattening performance and rumen fermentation of lambs were similar with those of Italian ryegrass (Gramineae family) and sainfoin (Leguminosae family) forages and, it had a positive effect on meat quality (water holding capacity, cooking loss) and meat shelf life criteria (MDA, PV, fatty acid profile and textural variables). For functional lamb meat production, P. lanceolata can be included in the diet of lamb fattening.

Growth Performance, Rumen Fermentation, In Vivo Digestibility, and Meat Quality of Pelibuey Lambs Fed a Diet with Ensiled Coffee Pulp.

Coffee pulp has been included in ruminant diets; but until now, little has been known about how the addition of ensiled coffee pulp (ECP) affects the growth performance of lambs. This study explores the diet's antioxidant capacity, tannins, and caffeine concentration and its effect on water intake, growth performance, rumen variables, in vivo digestibility, nitrogen balance, and carcass and meat characteristics of lambs fed ECP. Thirty-six male Pelibuey lambs were distributed randomly to one of three treatments (n = 12): without ECP0; diet with 10% ECP10, and diet with 20% ECP20. The diets' antioxidant capacity, tannins, and caffeine concentration were similar (p > 0.05) for all treatments. The diets' antioxidant compounds and the blood serum's antioxidant capacity were affected (p < 0.05). Dry matter and water intake, body-weight gain, and feed conversion were not significant (p > 0.05). No differences (p > 0.05) were found in the rumen variables or the nitrogen balance. However, the in vivo digestibility of crude protein was affected (p < 0.05). Carcass and meat quality were not affected (p > 0.05) by the inclusion of ECP, except temperature and redness (a*) at seven days of storage, respectively. Including up to 20% of ECP in the diet of lambs did not affect the growth performance, rumen variables, or nitrogen balance; however, the antioxidant compounds of the diets, the antioxidant capacity in blood serum, and the in vivo digestibility of crude protein were different. There was an increase in the redness (a*) and lower temperature in the Longissimus dorsi muscle, keeping lightness (L*), yellowness (b*), water-holding capacity, and texture at seven storage days.

DIGESTIBILITY, RUMEN FERMENTATION, RUMEN MICROBIOTA, AND LIPID PEROXIDATION IN SHEEP SUPPLEMENTED WITH LIPOIC ACID

Lipoic acid (LA) reduces oxidative stress and stimulates the immune system. However, data on its use in ruminants is limited. The objective of this study was to determine the effects of LA supplementation on free radical production, rumen variables, and feed digestibility in sheep fed high-grain diets. Nine rumen-cannulated Suffolk sheep were randomly assigned to three treatments: control (LA0 ), no LA inclusion; supplementation of 10 (LA10) mg LA kg-1 body weight (BW); and supplementation of 20 (LA20) mg LA kg-1 BW. In situ (ISDMD) and in vitro (IVDMD) degradation of dry matter and ruminal variables were evaluated. Total bacteria (TB), cellulolytic bacteria (CB), and protozoa (P) were also determined. Thiobarbituric acid reactive substances (TBARS) were evaluated in blood samples at the beginning and end of each experimental period. The ruminal variables and IVADDM were analyzed using a PROC GLM model with a repeated 3 × 3 latin square design, while means were compared using pairwise Tukey tests. LA supplementation did not affect (p 0.05) the ruminal variables under study. LA modified (p 0.05) ISDMD at 4 h in LA10, while no differences were found in terms of IVDMD among the treatments. The LA dose of 10 mg kg-1 BW increased CB (p 0.05) and decreased TB (p 0.05). TBARS differed (p 0.01) among the treatments and evaluation periods and were higher (p 0.05) 15 d after administration. In conclusion, LA supplementation in sheep had an antioxidant effect, reducing oxidative stress 15 d after administration, with slight differences in the ruminal variables evaluated.

Differential effects of rapeseed, sunflower and linseed oils on rumen microbial functions in dual effluent fermenters on maize silage-based diet

Quantitative information on the concurrent changes in major rumen microbial functions induced by dietary lipids in relation with the degree of unsaturation of fatty acids is scarce. During a three-period essay (9 days per period), rapeseed (Brassica napus L., RO), sunflower (Helianthus annuus L., SO) and linseed (Linum usitatissimum L., LO) oils at the high level of 80 g/kg dry matter input (DMI) and a control without oil were compared in four 1-L dual outflow fermenters inoculated with bovine rumen microbiota and maintained on a maize silage-based diet. Neither the fermentation medium pH and redox potential nor starch and protein degradabilities were significantly altered. Oil supply significantly decreased butyrate and methane specific productions of to the benefit of propionate and hydrogen specific productions and decreased the microbial protein outflow and synthesis efficiency while increasing the outflows of ammonia and isovalerate, these effects being amplified by the fatty acids’ unsaturation degree. Besides, with no impact of the degree of unsaturation, oil supply increased the amount of fermented hexose, the productions of all SCFAs except butyrate and the specific production of acetate. The rumen variables apparently sensitive to oil unsaturation degree were thus related either to metabolic hydrogen removal pathways or to protein metabolism.

Influence of partial replacement of alfalfa with two Salicornia forages on digestion, rumen variables, blood biochemistry metabolites and antioxidant capacity in sheep

In a completely randomized design, 24 Shall rams (average initial body weight [BW]: 43 ± 1.4 kg, aged 1.5 years) were used to evaluate the effects of partial replacement of alfalfa (Medicago sativa) hay with 2 species of Salicornia forage (i.e. bigelovii and persica) on in vivo total tract apparent digestibility, estimated microbial N synthesis (EMNS), rumen fluid parameters, blood metabolites, total antioxidant capacity (TAC) and production of methane in vitro. The three diets offered to sheep (8 per diet) prepared on a dry matter basis were 1- alfalfa hay (990 g/kg DM) + 10 g/kg DM vitamin-mineral supplement (control; AD), 2- alfalfa hay + Salicornia bigelovii (SBF) + vitamin-mineral supplement at a ratio of 690:300:10 (SBD), and 3- alfalfa hay + Salicornia persica (SPF) + vitamin-mineral supplement at a ratio of 690:300:10 (SPD). Salicornia diets did not affect DM, organic matter, crude protein or neutral detergent fiber digestibility. There was no dietary effect on in vivo ruminal pH, volatile fatty acids, or in vitro methane production. Salicornia diets increased rumen concentration of ammonia-N, total numbers of protozoa, and the population of Entodiniinae, whereas the cellulolytic bacteria population and EMNS decreased. Feeding SBD and SPD had no effect on the concentration of plasma albumin, cholesterol, glucose, total protein, triglyceride, and the albumin-globulin ratio but urea-N and TAC increased. Overall, replacing part of the alfalfa hay ration with SBF or SPF improved TAC in sheep with no negative effects on nutrient digestibility or in vitro methane production. This trial showed that Salicornia could be used as a partial substitute for conventional forage in the diet of sheep.

Rumen protozoal dynamics during the transition from milk/grass to high-concentrate based diet in beef calves as affected by the addition of tannins or medium-chain fatty acids

Changes in rumen protozoal community during adaptation of 7-month-old beef calves from a milk/grass diet to a high-energy diet consisting of cereal-based concentrate plus wheat straw, both given ad libitum (diet C), were studied. Eighteen rumen-cannulated Limousine crossbred male calves were randomly assigned to three diets (C; C plus 20 g/kg of a 65:35 chestnut and quebracho tannin extract, T; and C plus 6 g/kg medium-chain fatty acid (MCFA) mixture, M). Fermentation variables were studied, and rumen ciliates were quantified and classified from rumen fluid sampled just before the morning feeding on days 0, 7, 14, 21 and 28 of the experiment. Protozoal population changed over time, but all calves harbored a stable population at the end of the experiment. Diversity decreased on time, and Entodinium and Isotricha species were the most abundant at the end of the trial. When occurred, defaunation was transient as protozoa were absent from M calves in three occasions on days 7 and 14 but were refaunated thereafter reaching a consistent population. Regardless the diet, proportions of Isotricha spp. and Dasytricha ruminantium, Epidinium spp. and Subfamily Diplodiniinae, decreased throughout the experiment, whereas Entodinium spp. increased reaching 0.93 of total protozoa. Dasytricha and protozoa from Subfamily Diplodiniinae disappeared from the rumen of all calves at the end of the study, except for Polyplastron multivesiculatum. Rumen variables were not affected by the addition of additives (P > 0.05). Rumen pH decreased across the study (P < 0.001) but did not reach acidotic values despite the high fermentability of the diet. Higher levels of lactate were observed on C calves at d14, but not in other dates (diet by day interaction, P = 0.03). Addition of tannin extract did not affect protozoal concentration and diversity, but MCFA might even lead to a transient defaunation. Transition to a high-concentrate diet does not necessarily reduce initial protozoal concentration, but diversity is affected towards a major proportion of Entodinium and, to a lesser extent, Isotricha. Dietary shift from weaning to a high-concentrate ration promotes a less diverse rumen protozoal population, but a high concentration is still maintained thereafter.

Reducción de metano in vitro con el glucósido cianogénico Linamarina

Objetivo. Evaluar el efecto de dosis crecientes del glucósido cianogénico Linamarina, en la reducción de metano ruminal in vitro. Materiales y Métodos. Se empleó líquido ruminal de dos ovejas fistuladas de la raza Merino Precoz, con el que se inoculó un sustrato fermentativo constituido por heno de alfalfa (Medicago sativa) y grano de avena molido (Avena sativa L.), se adicionó solución buffer y Linamarina (pureza de ≥98%) en dosis crecientes, lo que se llevó a incubación por ocho horas in vitro. El metano se midió cada hora, con un monitor de gases infrarrojo. Resultados. De acuerdo con el incremento de las dosis de Linamarina (0, 6, 13, 20 y 26 mg/L), la concentración de metano disminuyó de forma lineal (p≤0.05) en (9.7, 9.2, 18.1 y 29.4%) respectivamente. Se observó una reducción significativa de metano con la dosis más alta de Linamarina. Conclusión. La Linamarina, en su estado puro, fue eficaz en la reducción de metano durante la fermentación ruminal in vitro. Por lo tanto, este estudio constituye una base para futuros experimentos que incluyan fuentes vegetales de Linamarina y otras variables ruminales, lo que puede conducir a encontrar estrategias para reducir los gases de efecto invernadero.

Modulation of ruminal fermentation profile and microbial abundance in cows fed diets treated with lactic acid, without or with inorganic phosphorus supplementation

This study evaluated the effects of lactic acid (LA) treatment of concentrates without or with inorganic P supplementation on ruminal fermentation profile and microbial abundances in non-lactating cows. Six rumen-fistulated Holstein cows were assigned to a double 3×3 Latin square design with 3 experimental periods. Each period lasted 14 d, whereby the measurements were performed during the last 2days. Cows were fed 3 diets containing untreated control concentrate supplemented with inorganic P, and two LA-treated concentrates, either without (LA−P) or with (LA+P) the inorganic P supplementation. The concentrate mixtures of the LA diets were soaked in 5% LA for 24h before feeding, whereas the concentrate of control diet was not. All diets were offered as a total mixed ration (forage to concentrate ratio of 53:47). Ruminal pH, ammonia and short-chain fatty acid (SCFA) concentrations were determined in free ruminal liquid (FRL) and particle associated ruminal liquid (PARL) that was collected at 0, 2, 4, 8, and 12h post-morning feeding. Target ruminal microbes in FRL and rumen solid digesta collected at 2h post-feeding were analyzed using quantitative PCR. Cows consumed on average 17±1.0kg DM/d (mean±SEM), irrespective of the treatment. The concentration of total SCFA in FRL was increased by LA treatment (P<0.001) without affecting the pH. Irrespective of P supplementation, feeding of LA-treated diets shifted SCFA profile towards more propionate in the FRL and PARL. The LA−P diet lowered ammonia concentration compared to the other diets (P<0.05). The LA−P diet also reduced the fungal gene copies in solid digesta by 7.6% compared to the LA+P diet (P<0.05). The total bacterial abundance in both ruminal fractions was not affected by diet; however, compared to the control, LA treatment enhanced (P<0.05) the relative abundance of genus Prevotella in FRL (18%) and in solid digesta (27%). In contrast, the same treatment decreased the abundances of Clostridium cluster IV (23%) in FRL and Selenomonas ruminantium group (30%) in solid digesta (P<0.05). Abundances of fibrolytic microbes correlated with acetate and butyrate only in the rumen solid digesta. In conclusion, the LA treatment of concentrates caused major bacterial shifts, an increase of ruminal fermentation output, and enhancement of propionate fermentation without affecting ruminal pH. The lack of inorganic P supplementation did not impair rumen variables measured, but additional P supply and LA treatment of concentrates beneficially affected ruminal fungi. Lowered ruminal ammonia and branched-chain SCFA concentrations by the LA−P diet suggest lowered protein breakdown in the rumen by this treatment.

Enteric methane production, rumen volatile fatty acid concentrations, and milk fatty acid composition in lactating Holstein-Friesian cows fed grass silage- or corn silage-based diets

The objective of this study was to determine the effects of replacing grass silage (GS) with corn silage (CS) in dairy cow diets on enteric methane (CH4) production, rumen volatile fatty acid concentrations, and milk fatty acid (FA) composition. A completely randomized block design experiment was conducted with 32 multiparous lactating Holstein-Friesian cows. Four dietary treatments were used, all having a roughage-to-concentrate ratio of 80:20 based on dry matter (DM). The roughage consisted of either 100% GS, 67% GS and 33% CS, 33% GS and 67% CS, or 100% CS (all DM basis). Feed intake was restricted (95% of ad libitum DM intake) to avoid confounding effects of DM intake on CH4 production. Nutrient intake, apparent digestibility, milk production and composition, nitrogen (N) and energy balance, and CH4 production were measured during a 5-d period in climate respiration chambers after adaptation to the diet for 12 d. Increasing CS proportion linearly decreased neutral detergent fiber and crude protein intake and linearly increased starch intake. Milk production and milk fat content (on average 23.4kg/d and 4.68%, respectively) were not affected by increasing CS inclusion, whereas milk protein content increased quadratically. Rumen variables were unaffected by increasing CS inclusion, except the molar proportion of butyrate, which increased linearly. Methane production (expressed as grams per day, grams per kilogram of fat- and protein-corrected milk, and as a percent of gross energy intake) decreased quadratically with increasing CS inclusion, and decreased linearly when expressed as grams of CH4 per kilogram of DM intake. In comparison with 100% GS, CH4 production was 11 and 8% reduced for the 100% CS diet when expressed per unit of DM intake and per unit fat- and protein-corrected milk, respectively. Nitrogen efficiency increased linearly with increased inclusion of CS. The concentration of trans C18:1 FA, C18:1 cis-12, and total CLA increased quadratically, and iso C16:0, C18:1 cis-13, and C18:2n-6 increased linearly, whereas the concentration of C15:0, iso C15:0, C17:0, and C18:3n-3 decreased linearly with increasing inclusion of CS. No differences were found in short- and medium-straight, even-chain FA concentrations, with the exception of C4:0 which increased linearly with increased inclusion of CS. Replacing GS with CS in a common forage-based diet for dairy cattle offers an effective strategy to decrease enteric CH4 production without negatively affecting dairy cow performance, although a critical level of starch in the diet seems to be needed.

Influence of different sources of zinc and protein supplementation on digestion and rumen fermentation parameters in sheep consuming low-quality hay

This experiment studied the effect of ZnCl2 or ZnSO4 included into a protein supplement on dry matter intake (DMI), DM digestibility (DMD) and rumen fermentation parameters in sheep consuming low-quality native pasture hay (NPH) as a basal diet. Four ruminally fistulated Corriedale weathers (31±4kg BW) were randomly assigned to a 4×4 latin square design, and received NPH ad libitum in the following treatments: (1) Control (CON) mineral mix only, (2) protein supplement (PROT), (3) PROT+ZnCl2 (CZProt) and (4) PROT+ZnSO4 (SZProt). All supplements were fed at the rate of 150ganimald−1. The Zn concentration in CZProt and SZProt was 460ppm for a total intake of 100ppm daily as a proportion of total diet. The NPH contained 5.3 and 77.4 of CP and NDF as % of DM respectively. Protein supplements were isonitrogenous (30% CP) with barley grain, wheat middlings and sunflower meal as main components. Mean NPH intake and total DMI were not affected by protein supplementation or Zn addition to the diet. DM digestibility as well as DDMI (digestible DMI) increased 31 and 37% respectively for SZProt compared to CON (P<0.05). Sampling hour affected most rumen variables with the exception of butyric and total volatile fatty acids (VFA; P<0.05). A treatment by sampling hour interaction (P<0.05) was only found for ruminal ammonia-N (NH3-N) concentration. At time intervals of 2, 4, 8 and 12h, [NH3-N] was much lower in CON than in protein supplemental treatments (P<0.05). A trend was observed for increased NH3-N concentration in SZProt (39.76mgdL−1) vs. CZProt (29.25mgdL−1) at 4h (P=0.0897). The rumen pH was not affected by treatments; the lowest values found 12h after feeding were 6.2. Zinc, particularly from SZProt, seems to modulate [NH3-N] by sustaining higher concentrations during the 24h period. A clear effect on major VFA was not observed. The inclusion of 100ppm of Zn, and source could differentially affect animal response to protein supplementation and utilization of low quality roughages by affecting some rumen fermentation patterns.

Rumen development and blood metabolites of Criollo kids under two different rearing systems

This study compared rumen development and blood metabolite concentrations of Criollo kids under two different rearing systems. Forty goat kids were reared by their dams, suckling goat milk from birth until weaning at 45 (TR, traditional rearing system, n=20) or 30 days of age (AR, alternative rearing system, n=20). Goat kids in the AR group were offered a solid starter diet ad libitum from birth until 45 days of age and a growing diet (80% alfalfa hay and 20% ground corn) from 30 to 90 days of age. The TR group was fed a growing diet (without starter diet) between 30 and 90 days of age. Blood samples were analyzed for serum concentration of glucose, total protein, blood urea nitrogen (BUN), <beta>-hydroxybutyrate (<beta>HB), and non-esterified fatty acids (NEFA). Five kids from each group were slaughtered at 21, 45, 70 and 90 days of age to determine rumen variables. AR kids consumed 32.7 % less goat milk than TR kids throughout the trial. Body weight of AR kids at 45–60 days of age was lower than the traditional market weight. Rumen weight (as % of body weight) was higher (P<0.01) in AR kids than in TR kids at 21 and 45 days of age. Furthermore, rumen weight (as % of weight of all compartments) was higher in AR kids compared to TR kids at 21, 45 and 70 days of age. Rumen papillae of AR kids tended (P<0.10) to be longer than those of TR kids at 21 and 45 days of age. Blood glucose concentration decreased with increasing age of kids, indicating a shift from glucose to short-chain fatty acids as primary energy source. Serum <beta>HB and BUN concentrations at 30 and 45 days of age were higher (P<0.05) in AR kids than in TR kids. The higher serum concentrations of BUN and <beta>HB were attributed to early development of rumen microbial fermentation activity and to greater metabolic development of the rumen epithelium of AR kids compared to TR kids. In conclusion, the alternative rearing system improves the physical and metabolic development of the rumen and promotes the transition of kids from pre-ruminant to ruminant. In dry periods with shortage of forage, the alternative rearing system could be used, but these goat kids should be reared above the traditional age to enable them to achieve an appropriate weight for marketing.

Effect of exogenous phytase on degradation of inositol phosphate in dairy cows

The effect of exogenous phytase on inositol phosphate degradation in the rumen of dairy cows was investigated in a 4×4 Latin square design. Four lactating Danish Holstein cows fitted with ruminal, duodenal, and ileal cannulas were offered a total mixed ration (TMR) with a high content of inositol phosphate and supplemented with 1 of 4 concentrations of phytase [none, low, medium, or high, corresponding to 23, 2,023, 3,982, and 6,015 phytase units/kg of dry matter (DM)]. Exogenous phytase lead to a higher rumen pool of phytase. Inositol phosphate content in digesta samples from rumen, duodenum, ileum, and feces was almost entirely composed of myo-inositol hexakisphosphate (InsP6), indicating that degradation of this compound is the rate-limiting step in inositol phosphate degradation in the digestive tract. Ruminal and total-tract degradations of InsP6 were higher when exogenous phytase was added to the TMR. Degradation of InsP6 occurred mainly before the duodenum. The ruminal degradability of InsP6 was increased with increasing dietary concentrations of phytase: 86.4, 93.7, 94.5, and 96.3% for none, low, medium, or high, respectively. A comparison of the InsP6 content in individual feedstuffs and in samples of the TMR revealed that the exogenous phytase started degrading the inositol phosphate when feeds and phytase were mixed, and thus the InsP6 phosphorus (InsP6-P) content in the TMR was found to decrease with higher doses of phytase (1.69, 1.51, 1.39, and 1.25g/kg of DM for the none, low, medium, and high phytase doses, respectively). It was not possible to distinguish between the degradation of inositol phosphate occurring in the TMR and in the rumen. Exogenous phytase had no effect on total P intake or flow of total P to the duodenum and ileum, whereas exogenous phytase increased flow of microbial P to the duodenum and total fecal P excretion. None of the investigated rumen variables (pH, degradability of neutral detergent fiber, and rumen kinetics for neutral detergent fiber) were affected by treatment. Rumen and total-tract degradations of inositol phosphate were increased when exogenous phytase was added to the TMR, which offers the potential for reducing P excretion through reduced dietary P.

Feeding rolled barley grain steeped in lactic acid modulated energy status and innate immunity in dairy cows

Feeding dairy cows large proportions of cereal grain is commonly associated with rumen acidosis, activation of innate immunity, and perturbation of intermediary metabolism. We previously showed that steeping barley grain in 0.5% lactic acid (LA) decreased the rate of starch degradation, lowered the risk of subacute rumen acidosis, modulated rumen fermentation profile, and increased milk fat content in dairy cows. This study sought to investigate whether feeding of LA-treated barley grain would affect carbohydrate and lipid metabolism as well as innate immunity. Eight rumen-fistulated late-lactation (approximately 217 d in milk, DIM) Holstein cows were randomly assigned, in a 2 × 2 crossover design, to 1 of the 2 dietary treatments consisting of 27% (dry matter basis) rolled barley grain steeped for 48h in an equal volume (wt/vol) of tap water (CTR) or 0.5% LA (TRT). Each experimental period lasted 21 d, with the first 11 d for diet adaptation. Blood and rumen samples were collected on d 12, 15, 17, and 21 of the experimental period before the morning feeding to evaluate the effects of dietary treatment on preprandial day-to-day variation of plasma and rumen variables. To establish the effect of treatment on diurnal variation of plasma variables, blood samples were collected on the last day of each period at 0, 2, 4, 6, 8, 10, and 12h after the morning feeding (i.e., 0800h). Results of the day-to-day study showed that cows fed the TRT diet had greater overall preprandial concentrations of glucose, cholesterol, and insulin, and a lower concentration of haptoglobin in plasma. Diurnal data indicated lower concentrations of haptoglobin and serum amyloid A and a tendency for greater plasma lactate in cows fed the TRT diet. A treatment by time interaction was observed for glucose, lactate, insulin, haptoglobin, and lipopolysaccharide-binding protein, suggesting a role for both the processing of grain and the time of sampling on those variables. No effect of diet on plasma concentrations of cortisol, β-hydroxybutyrate, and nonesterified fatty acids or rumen endotoxin was evidenced. Taken together, our results demonstrated that feeding barley grain steeped in 0.5% LA modulated both energy status and innate immunity of dairy cows fed relatively high levels (45% of dry matter) of dietary concentrate.

Increasing amounts of crushed wheat fed with pasture hay reduced dietary fiber digestibility in lactating dairy cows

Sixteen cows in mid-lactation (milk yield of 23.8±2.3 kg/d) were individually fed diets consisting of chopped perennial ryegrass hay, offered at 3kg of dry matter (DM)/100kg of body weight (BW), fed either alone or supplemented with amounts of crushed wheat ranging from 0.4 to 1.6kg of DM/100kg of BW (increasing at nominal intervals of 0.4kg of DM/100kg of BW; 5 nominal treatments in total). Three cows were allocated to each treatment except the mid-range wheat treatment, which had 4 cows. Results were analyzed by regression because the intake of the wheat by cows within treatments varied. The hay was used to reflect the characteristics of summer pastures in southeastern Australia. Feed intake and fecal output were measured to determine digestion coefficients, feeds were incubated in nylon bags in the rumen, and rumen variables were monitored. Estimates of metabolizable energy (ME) of the hay from in vivo or in vitro digestibility were also compared. The digestibility of neutral detergent fiber (NDF) was depressed linearly as the amount of crushed wheat consumed increased to 36% of DM intake. The extent to which negative associative effects on NDF digestion were associated with the hay could not be determined, as it was not possible to distinguish between the NDF from hay and that from wheat. However, acid detergent fiber (ADF) digestion also declined, suggesting that most of the response lay with the hay because ADF was negligible in the wheat. Most data indicated that effects of proportion of wheat in the diet on the utilization of consumed nutrients were small. Despite substitution of wheat for hay reducing the forage intake of cows, there was a positive linear effect on marginal milk responses (1.3kg of energy-corrected milk/kg of DM wheat). Mean rumen fluid pH declined as the proportion of wheat in the diet increased. The lowest pH for any individual cow during a 24-h period was 5.4, and the amount of time that rumen fluid pH was <6.0 ranged from 0 to 14h depending on the amount of wheat consumed. It was concluded that these perturbations of the rumen environment were probably sufficient to result in negative associative effects. In addition, estimates of the ME content of the hay were higher when calculated from in vitro compared with in vivo digestibility, which has implications when estimating the amount of feed required for production.

Effects of an exogenous fibrolytic enzyme preparation on in vitro ruminal fermentation of three forages and their isolated cell walls

This study was completed to investigate whether a fibrolytic enzyme preparation with xylanase and cellulase activities (Fibrozyme™, Alltech Inc., Nicholasville, KY, USA), could stimulate in vitro rumen fermentation of alfalfa hay, grass hay and barley straw, and their isolated cell walls as neutral detergent fibre (NDF). Samples (500 mg) of each substrate were incubated in 120 ml bottles with 50 ml of buffered rumen fluid from sheep at 39 °C. The enzyme preparation was added directly to the bottles at the beginning of the incubation at levels of: 0 (control; CON), 50 mg/g substrate DM (LOWFIB) and 100 mg/g substrate DM (HIGHFIB). Effects on volatile fatty acid (VFA) production depended on substrate and incubation time. After incubation for 5 h, enzyme addition increased (P<0.05) production of VFA and acetate compared to CON for both alfalfa hay and its isolated cell wall, and increased (P<0.05) propionate and butyrate production in isolated cell wall, but reduced (P<0.05) them in alfalfa hay. After incubation for 10 h, addition of both doses of enzyme preparation increased (P<0.05) VFA and propionate production versus CON for both alfalfa hay and its isolated cell wall, and decreased (P<0.05) acetate to propionate ratios with both substrates, with intermediate values for LOWFIB and highest for HIGHFIB. After 24 h of incubation, there were no effects due to enzyme treatment or enzyme dose on rumen variables. Addition of both doses of supplemental enzyme increased (P<0.05) VFA, acetate and propionate production after 5 and 10 h incubation in both grass hay and its isolated cell wall, with increases being greater (P<0.05) for HIGHFIB versus LOWFIB in all variables. Both doses of enzyme addition reduced (P<0.05) the acetate to propionate ratio at 5 and 10 h of incubation. After 24 h of incubation, enzyme addition increased (P<0.05) VFA, acetate and butyrate production in both grass hay and its isolated cell wall versus CON, with some dose effects on both substrates. Enzyme supplementation also increased (P<0.05) VFA, acetate and propionate production versus CON in barley straw and its isolated cell wall at 5 and 10 h of incubation, with dose dependent effects after incubation for 5 h with higher (P<0.05) increases for HIGHFIB versus LOWFIB in both substrates. Both enzyme doses also reduced (P<0.05) the acetate to propionate ratio in both barley straw and its cell wall after incubation for 5 h. Production of total VFA and butyrate increased (P<0.05) with both doses of enzyme after incubation for 24 h. Final pH, ammonia-N and disappearance of aNDF and ADF did not differ among enzyme treatments after incubation of grass hay and barley straw or their isolated cell wall for 24 h. Results indicate that this fibrolytic enzyme preparation stimulated in vitro fermentation of substrates at short (5 and 10 h), but not at long (24 h) incubation times, and that effects depended on both the dose used and the presence of neutral detergent soluble components in the substrate.

Feeding an energy supplement with white clover silage improves rumen fermentation, metabolisable protein utilisation, and milk production in dairy cows

Six rumen-fistulated Holstein-Friesian cows were used in a Latin square design to test the hypothesis that more frequent feeding of a high energy supplement to cows consuming high-protein white clover silage would improve microbial protein production, resulting in greater N retention and higher milk yields. The white clover silage (10.7 MJ metabolisable energy (ME)/kg DM) was fed to cows either alone (WCS) or with 4.5 kg DM of rolled barley grain (12.1 MJ ME/kg DM). The grain was offered either 24 times (WCS/24B) or twice daily (WCS/2B, at 0800 and 1700 hours). Cows offered the supplements, regardless of feeding frequency, had higher (P &lt; 0.05) organic matter (17.3 v. 16.0 kg/day) and estimated ME (208 v. 189 MJ/day) intakes than cows offered white clover silage alone. Mean daily ruminal fluid pH (P &lt; 0.05) and ammonia-N concentrations (P &lt; 0.05) were lower in the supplemented treatments, with total VFA concentrations being highest (P &lt; 0.05) in the WCS/2B treatment. Nitrogen intake and output in the faeces were similar for all 3 treatments. However, nitrogen excretion was lower (P &lt; 0.05) in urine (174 v. 218 g/day) and higher (P &lt; 0.05) in milk (115 v. 93 g/day) of cows offered the supplements. The crude protein consumed by cows on all 3 diets was estimated to be well in excess of cow requirements. The supplements reduced the calculated net losses of ammonia-N from the rumen from 25% of total crude protein intake for WCS to 14% in the 2 supplement treatments, and increased the metabolisable protein supply available for milk production. Increases in metabolisable protein were estimated to be due to a higher microbial crude protein contribution in the supplemented treatments compared with the WCS treatment. Grain supplements increased (P &lt; 0.05) milk yield (22.4 v.19.6 kg/day) and although there were no significant differences in milk fat and protein concentrations between treatments, the latter tended to increase with grain supplementation. Milk yield was higher in the WCS/24B treatment than in the WCS/2B treatment, but neither the calculated nor the measured rumen variables were sufficiently different to explain this effect of frequency of feeding the grain. One possible explanation for the difference was the marked fluctuations in key rumen variables throughout the day in the WCS/2B compared with the WCS/24B treatment. Such fluctuations in the rumen environment are not accounted for in theoretical calculations since associative effects are not considered. The benefits of a higher milk production as a result of more frequent feeding of the supplement to cows should be considered in context of the additional effort or costs associated with more frequent feeding.

The development of the Dorper, its nutrition and a perspective of the grazing ruminant on veld

The development of the non-woolled Dorper sheep breed is briefly reviewed. Despite the large number of Dorpers in South Africa, precious little research results have been published on its nutrition under harsh, arid grazing conditions, especially since this has been an objective for creating and developing the breed. Results from the limited number of trials with free ranging Dorpers on natural pasture (veld) regarding diet selection, voluntary feed intake and rumen variables are used in conjunction with production data to create a nutritional perspective of the free ranging ruminant.

Mode of action of yeast culture (YEA-SACC 1026) for stimulation of rumen fermentation in buffalo calves

The effect of daily supplementation of 5 g Saccharomyces cerevisiae yeast culture (YC, YEA-SACC 1026), 30 g NaHCO3, supernatant from 5 g YC (YCS), 5 g autoclaved YC (YCH) or 5 g γ-irradiated YC (YCR) to the diet of buffalo calves on rumen microbial populations and fermentation pattern was examined. Addition of 30 g NaHCO3 increased the rumen pH to the level observed with YC group. The pH and the concentrations of total, total viable and cellulolytic bacteria and total volatile fatty acids (VFA) were significantly higher while that of lactic acid, hexose-unit oligosaccharides and NH3-N were significantly lower in the rumen fluid of YC compared with the control group. The effect of NaHCO3 was 39·5 and 59·5% in decreasing the concentrations of lactic acid and hexose-unit oligosaccharides, 48·1, 47·2 and 45·5% in increasing the numbers of total, total viable and cellulolytic bacteria, 50·0 and 58·1% in increasing the concentrations of total VFA and protein and 51·3% in decreasing the concentration of NH3-N of YC. The corresponding values for YCR addition in the diet were 38·6, 45·7, 48·5, 44·4, 51·5, 39·1, 48·1 and 46·5%. The effect of YCS and YCH was only marginal, but conspicuous up to 2 h after feeding, in changing the above rumen variables when compared with the YC group. The results indicated that contribution of increase in pH in changing the rumen variables was approximately 50% of YC and almost all the stimulatory activity was associated with live yeast cells. Autoclaving of YC destroyed almost all and γ-irradiation of YC retained about 50% of stimulatory activity of YC. The effect of YC on rumen fermentation, which was maximum up to 2 to 4 h after feeding, decreased with time. © 1998 SCI.

Food intake and diet selection in sheep: the effect of manipulating the rates of digestion of carbohydrates and protein of the foods offered as a choice.

An experiment was designed to investigate whether the degree of synchrony between the rates of digestion of carbohydrates and N of foods offered as a choice would have an effect, through their consequences, on the short- and long-term diet selection of sheep. Four foods (RL, RH, SL and SH) with the same high metabolizable energy, and similar high metabolizable protein contents were made into pellets. Foods RL and RH were based on a rapidly fermentable carbohydrate source and foods SL and SH on a slowly fermentable carbohydrate source; within each source one food (RL or SL) had a low, and the other (RH or SH) a high, rumen-degradable protein (RDP) content. The foods within a carbohydrate source were offered either singly or as a choice (RL/RH or SL/SH) to eleven rumen-fistulated mature sheep. The design was two 3 x 3 Latin squares (replicated once) with 5-week periods; squares consisted of two single foods and their respective choice. Weeks 1, 3 and 5 were considered to be controls, and weeks 2 and 4 used for rumen infusions of either urea or fructose infused over 4 h (10.00-14.00 hours). Food intake (FI) and diet selections (DS) were recorded daily and every 2 h (08.00-16.00 hours) on days 2-5 of each week; rumen pH and NH3 concentrations were also measured during these time intervals of day 5. As expected, feeding treatment affected significantly the rumen measurements: rumen NH3 concentrations were higher on foods RH and SH, and rumen pH lowest on RL. Daily FI was lowest on treatments SL, and choice SL/SH. The mean daily proportion of the low-RDP food in the selected diet was lower when the carbohydrate source was rapidly (choice RL/RH) rather than slowly fermentable (choice SL/SH); this was consistent with the experimental hypothesis. Short-term infusions affected further rumen variables (in the expected directions), irrespective of feeding treatment. However, DS over the 4h infusion period were unaffected; these short-term DS were consistent with the ones selected over the longer term (daily). The results suggest that the long-term (daily) diet selection of sheep may be affected by the degree of synchrony of energy and protein to the rumen. The fact that diet selections were not altered further by short-term manipulations of these supplies might reflect inadequacies of the methodology (infusions) adopted here.

Effect of Yeast Culture Supplement on Ruminal Microbial Populations and Metabolism in Buffalo Calves Fed a High Roughage Diet

The effect of Saccharomyces cerevisiae yeast culture (YC, Yea-Sacc 1026) as a supplement to the high-roughage diet of buffalo calves on the rumen microbial populations, fermentation pattern and in sacco dry matter disappearance of dietary constituents was examined. A control group was fed a diet consisting of, on a dry matter basis, 2·12 kg bajra (Pennisetum typhoides) hay and 0·45 kg groundnut cake per day per calf, while the treatment group had the same diet plus 5 g YC. After feeding for 6 weeks, inclusion of YC was stopped and both groups were given the control diet for 2 weeks. At week 4 the pH in the rumen fluid (RF) was significantly higher (P<0·05) up to 6 h post-feeding in the treatment group compared with the control group. The concentrations of total, total viable and cellulolytic bacteria were increased by 41·0 (P<0·05), 33·5 and 57·4% (P<0·01), respectively, with YC supplement. The concentration of total volatile fatty acids (P<0·05), particularly at 4 h post-feeding (P<0·01) and acetate (P<0·01) and acetate to propionate ratio (P<0·05) were higher in the treatment compared with the control group. On YC supplementation, the concentration of NH3-N was decreased (P<0·05) while that of TCA-precipitable protein in RF was marginally but non-significantly increased. Withdrawal of YC from the diet reversed these effects and the rumen variables returned to values close to control levels after 2 weeks. The in sacco dry matter disappearance of dietary components was higher in the treatment compared with the control group, particularly during the first 24 h of incubation. © 1997 SCI.