Effects of prenatal dietary rumen-protected choline supplementation during late gestation on calf growth,metabolism, and vaccine response

The objective of this study was to examine the effects of prenatal supplementation and dose of rumen-protected choline (RPC) on neonatal calf growth, metabolism, and vaccine response. Parous Holstein cows were blocked by calving month and randomly assigned within block to receive 45 g/d of RPC [20.4 g/d of choline ions (CHOL45), n = 19], 30 g/d of RPC [13.6 g/d of choline ions (CHOL30), n = 22], or no RPC (CON, n = 19) as a top-dress, starting 24 d before expected calving. Calf body weights were recorded for the first 3 wk of life. All calves were fed colostrum replacer (300 g of IgG) at birth, and apparent efficiency of IgG absorption was calculated. On d 1, 7, 14, and 21, blood samples were taken to quantify plasma reactive oxygen and nitrogen species, antioxidant potential, haptoglobin, nonesterified fatty acids (NEFA), β-hydroxybutyrate, and glucose. Calves received an intranasal vaccine at birth, and nasal secretions were collected on d 0, 7, 10, 14, and 21 to quantify bovine respiratory syncytial virus-specific IgA. Data were analyzed using linear mixed models including the fixed effects of treatment, time (when applicable), calf sex, and prepartum dam data (?24 d) along with interactions. Treatment did not affect calf body weight, β-hydroxybutyrate, or glucose concentrations. For apparent efficiency of IgG absorption, treatment interacted with the dam's prepartum body condition score. Where the dam's body condition score was ≤3.25, IgG absorption was reduced in calves born from CHOL45 dams as compared with calves from either CHOL30 or CON dams. Calves from CHOL30 dams had a lesser oxidative stress index (OSi; reactive oxygen and nitrogen species/antioxidant potential) than calves from CON dams. Haptoglobin concentrations were less in heifer calves from CHOL45 dams as compared with heifers from CON dams. The dam's prepartum NEFA concentration interacted with treatment. When dam NEFA was minimal, calves from CHOL45 and CHOL30 dams had greater or tended to have greater NEFA, respectively. Conversely, when dam NEFA was greater, calves from CHOL30 and CHOL45 dams had lesser or tended to have lesser NEFA than calves from CON dams, respectively. For vaccine response, treatment interacted with the dam's prepartum OSi. Among calves born from dams with a greater OSi, calves from CHOL45 and CHOL30 dams had lesser bovine respiratory syncytial virus-specific IgA concentrations in nasal secretions as compared with CON. Prenatal RPC supplementation during late gestation affected IgG absorption, neonatal calf metabolism, and vaccine response with some effects dependent on the dam's prepartum parameters.     

Rumen microbiota and its relation to fermentation in lactose-fed calves

In our previous studies, we revealed the effect of lactose inclusion in calf starters on the growth performance and gut development of calves. We conducted the present study as a follow-up study to identify the shift in rumen microbiota and its relation to rumen fermentation when calves are fed a lactose-containing starter. Thirty Holstein bull calves were divided into 2 calf starter treatment groups: texturized calf starter (i.e., control; n = 15) or calf starter in which starch was replaced with lactose at 10% (i.e., LAC10; n = 15) on a dry matter basis. All calves were fed their respective treatment calf starter ad libitum from d 7, and kleingrass hay from d 35. Rumen digesta were collected on d 80 (i.e., 3 wk after weaning) and used to analyze rumen microbiota and fermentation products. There was no apparent effect of lactose feeding on the α-diversity and overall composition of rumen microbiota. Amplicon sequencing and real-time PCR quantification of the 16S rRNA gene confirmed that the abundance of butyrate-producing bacteria (i.e., Butyrivibrio group and Megasphaera elsdenii) did not differ between the control and LAC10 groups. Conversely, the relative abundance of Mitsuokella spp., which produce lactate, succinate, and acetate, was significantly higher in the rumen of calves that were fed lactose, whereas the lactate concentration did not differ between the control and LAC10 groups. These findings suggest that the lactate production can be elevated by an increase of Mitsuokella spp. and then converted into butyrate, not propionate, since the proportion of propionate was lower in lactose-fed calves. In addition, we observed a higher abundance of Coriobacteriaceae and Pseudoramibacter-Eubacterium in the LAC10 group. Both these bacterial taxa include acetate-producing bacteria, and a positive correlation between the acetate-to-propionate ratio and the abundance of Pseudoramibacter-Eubacterium was observed. Therefore, the higher abundance of Coriobacteriaceae, Mitsuokella spp., and Pseudoramibacter-Eubacterium in the rumen of lactose-fed calves partially explains the increase in the proportion of rumen acetate that was observed in our previous study.     

Technical note: A simple rumen collection device for calves: An adaptation of a manual rumen drenching system

A limited amount of research is available related to the rumen microbiota of calves, yet there has been a recent spike of interest in determining the diversity and development of calf rumen microbial populations. To study the microbial populations of a calf's rumen, a sample of the rumen fluid is needed. One way to take a rumen fluid sample from a calf is by fistulating the animal. This method requires surgery and can be very stressful on a young animal that is trying to adapt to a new environment and has a depressed immune system. Another method that can be used instead of fistulation surgery is a rumen pump. This method requires a tube to be inserted into the rumen through the calf's esophagus. Once inside the rumen, fluid can be pumped out and collected in a few minutes. This method is quick, inexpensive, and does not cause significant stress on the animal. This technical note presents the materials and methodology used to convert a drenching system into a rumen pump and its respective utilization in 2 experiments using dairy bull calves.     

Changes in the rumen and colon microbiota and effects of live yeast dietary supplementation during the transition from the dry period to lactation of dairy cows

The first objective of this study was to evaluate the dynamics and their potential association with animal performance of the microbiota in both the rumen and colon of dairy cows as they move from a nonlactation to a lactation ration. The second objective was to assess the potential effects on the microbiota of live yeast supplementation. Twenty-one Holstein cows were split in 2 treatments consisting of 1 × 10¹⁰ cfu/d of live yeast (LY; n = 10) or no supplementation (control; n = 11) starting 21 d before until 21 d after calving. At 14 d before and 7 and 21 d after calving, samples of rumen and colon digesta were obtained from each cow using an endoscope. Total DNA was extracted and submitted to high-throughput sequencing. Shannon diversity index, in both the rumen and colon, was unaffected by LY; however, in the rumen it was lowest 7 d after calving and returned to precalving values at 21 d in milk, whereas in the colon it was greatest 14 d before calving but decreased after calving. In the rumen, LY supplementation increased the relative abundance (RA) of Bacteroidales (group UCG-001), Lachnospiracea (groups UCG-002 and UCG-006), and Flexilinea 14 d before calving, and increased RA of Streptococcus 21 d after calving compared with control cows. However, changes in the ruminal microbiota were more drastic across days relative to calving than as influenced by the dietary treatment, and the effect of LY in the colon was milder than in the rumen. The ruminal RA of several genera was associated with postcalving DMI, and that of Gastranaerophilales was the only order positively associated with milk yield. Several genera were positively correlated with feed efficiency, with Clostridiales (unclassified) being the only genus negatively associated with feed efficiency. In the colon, Prevotellaceae (group Ga6A1) was the only genus positively associated with feed efficiency. The ruminal RA of Prevotella 7 and Ruminobacter 14 d precalving was negatively correlated with dry matter intake and milk yield postcalving. The RA of Parabacteroides in the colon 14 d before calving was negatively correlated with milk yield, whereas the RA of Eggerthellaceae (unclassified) and Erysipelotrichaceae (groups c and unclassified) were positively correlated with feed efficiency. Interestingly, LY supplementation doubled the RA of Eggerthellaceae (unclassified) in the colon. It is concluded that microbial diversity in the rumen experiences a transient reduction after calving, whereas in the colon, the reduction is maintained at least until 21 d in milk. Most of the effects of LY on rumen microbiota were observed before calving, whereas in the colon, LY effects were more moderate but consistent and independent of the stage of production. The microbial community of the rumen after calving is more associated with feed intake, milk yield, and feed efficiency than that of the colon. However, the colon microbiota before calving is more associated with feed efficiency after calving than that of the rumen.     

Longitudinal assessment revealed the shifts in rumen and colon mucosal-attached microbiota of dairy calves during weaning transition

The objectives of this study were to investigate the shifts in rumen and colon mucosa-associated microbiota in dairy calves fed a high milk replacer feeding rate before and after weaning and to determine whether such shifts are associated with tissue physiological measures. Longitudinal biopsy was performed to collect rumen and colon mucosal tissues of 4 ruminally cannulated Holstein dairy bull calves (weaned at 6 wk of age) at the end of wk 5 (before weaning), 7 (weaning adaptation) and 12 (after weaning), and were used to assess mucosa-associated microbiota and their changes using amplicon sequencing. Both rumen and colon mucosa-associated bacterial communities shifted during the weaning process, as evidenced by their clear separation among 3 different weaning periods and increased α diversity (Shannon and Chao1 indices) during weaning transition. Among the 3 dominant bacterial phyla identified (relative abundance >1.0%), the relative abundance of Proteobacteria and Bacteroidetes decreased in the rumen mucosa, whereas the relative abundance of Firmicutes increased in both rumen and colon mucosa during weaning transition. In the rumen mucosa, Campylobacter (0.6–22.1%) gradually became prevalent during weaning transition, whereas Succinivibrio (6.2–10.3%) and Prevotella 1 (4.7–10.5%) were dominant regardless of weaning transition. In the colon mucosa, Bacteroides (12.8–25.4%) was dominant during weaning transition, although its relative abundance decreased after weaning. In the meantime, relative abundance of uncultured Lachnospiraceae increased from 2.2% to 25.7% during this period. In addition, genera Pyramidobacter (in the rumen mucosa) and Lachnoclostridium (in the colon mucosa) were positively correlated with rumen papilla surface area and colon mucosal thickness, respectively. Moreover, genera Ruminococcaceae UCG-005 and Sharpea in the rumen mucosa were positively correlated with the molar proportion of propionate and butyrate, respectively. Overall, our findings revealed that rumen and colon mucosa-associated bacterial communities altered in response to the weaning transition, and some bacterial taxa in these communities may have positive effects on rumen and colon mucosa development during this period.     

Subacute ruminal acidosis phenotypes in periparturient dairy cows differ in ruminal and salivary bacteria and in the in vitro fermentative activity of their ruminal microbiota

Both ruminal microbial structure and functionality might play a role in inter-individual variation in susceptibility for subacute rumen acidosis (SARA) observed in dairy cows. The aims of this study were to determine whether differences between cows with distinct SARA susceptibility were reflected in distinct (1) ruminal microbial communities, (2) salivary bacterial communities, and (3) fermentative capacity of ruminal microbiota assessed in vitro. To test this hypothesis, rumen samples were collected via an esophageal tube on 21 d postpartum from 38 multiparous Holstein cows, which were classified into 4 groups differing in median and mean time of reticular pH below 6 as well as area under the curve of pH below 6.0. During the 21 d postpartum, all cows within a group fulfilled following criteria: susceptible (S, n = 10; mean or median ≥180 min/d), moderately susceptible (MS, n = 7; 60 min/d < mean time of pH below 6 < 180 min/d, and median time of pH below 6 <180 min/d), moderately unsusceptible (MU, n = 11; 10 min/d < mean < 60 min/d, and median time of pH below 6 ≤30 min/d), or unsusceptible (U, n = 10; median = 0 min/d, and mean <10 min/d). Groups did not differ in total daily dry matter intake nor in total, roughage, or concentrate intake during daily 6-h time intervals. Rumen bacterial α-diversity did not differ among groups, but β-diversity varied and bacterial 16S rRNA gene copy numbers were lower in S compared with U cows. The relative abundance of genera Streptococcus, Sharpea, Prevotellaceae_YAB2003, Succinivibrionaceae_UCG-001, Ruminococcus, and Ruminococcaceae_UCG-001 were higher in S compared with U cows. In contrast, Lachnospiraceae_ND3007 and Oscillospiraceae_V9D2013 were more abundant in U cows. Although pH-associated, inter-animal differences were also observed in the salivary bacteria, common differences in ruminal and salivary bacterial genera were limited. The functionality of the rumen microbiota was evaluated in vitro through exposure of the microbial inoculum of S and U cows to an anaerobic buffer at pH 5.8 and 6.8, in the presence of sterile supernatant of their own and of dry cows' rumen fluid (2 × 2 design). Generally, the S inoculum produced more volatile fatty acids, except at low pH with dry cows' supernatant, where volatile fatty acid production was completely impaired and lactate accumulation was highest. Compared with the microbes of U cows, microbes of S cows showed less fermentative activity in situations with 2 stress factors (low pH and an unfamiliar environment, i.e., rumen fluid supernatant of dry cows).     

Effects of corn processing on growth characteristics, rumen development, and rumen parameters in neonatal dairy calves

Neonatal Holstein calves were fed texturized calf starters containing 33% whole (WC), dry-rolled (DRC), roasted-rolled (RC), or steam-flaked (SFC) corn to investigate how corn processing method affects intake, growth, rumen and blood metabolites, and rumen development. In the first experiment, 92 Holstein calves (52 male and 40 female) were started at 2 +/- 1 d of age and studied for 42 d. Starter dry matter (DM) intake was measured and fecal scoring conducted daily. Growth and blood parameter measurements were conducted weekly. A subset of 12 male calves (3/treatment) was euthanized at 4 wk of age and rumen tissue sampled for rumen epithelial development measurements. Experiment 2 consisted of 12 male Holstein calves ruminally cannulated at 7 +/- 1 d of age. Rumen fluid and blood samples were collected during wk 2 to 6. In the first experiment, postweaning and overall starter and total DM intake were significantly higher in calves fed starter with DRC than RC or SFC. Postweaning and overall starter and total DM intake were significantly higher in calves fed starter with WC than SFC. Postweaning average daily gain was significantly greater in calves fed starter with DRC than SFC. Blood volatile fatty acid concentrations were significantly higher in calves fed starter with SFC than in calves fed all other treatments. Papillae length and rumen wall thickness at 4 wk were significantly greater in calves fed starter with SFC than DRC and WC, respectively. In experiment 2, calves fed starter with WC had higher rumen pH and lower rumen volatile fatty acid concentrations than calves fed all other starters. Rumen propionate production was increased in calves receiving starter with SFC; however, rumen butyrate production was higher in calves fed starter with RC. Results indicate that the type of processed corn incorporated into calf starter can influence intake, growth, and rumen parameters in neonatal calves. Calves consuming starter containing RC had similar body weight, feed efficiency, and rumen development but increased structural growth and ruminal butyrate production when compared with the other corn processing treatments.     

Differential effects of monensin and a blend of essential oils on rumen microbiota composition of transition dairy cows

In response to oral application, monensin alters the rumen microbiota, increasing ruminal propionate production and energy availability in the animal. Data from different studies indicate that the susceptibility of rumen bacteria to monensin is mainly cell-wall dependent but tracing its activity to specific microbial groups has been challenging. Several studies have shown a similar effect for essential oils but results are inconsistent. To investigate the influence of monensin and a blend of essential oils (BEO, containing thymol, guaiacol, eugenol, vanillin, salicylaldehyde, and limonene) on the rumen microbiome, rumen liquid samples were collected orally on d 56 postpartum from cows that had either received a monensin controlled-release capsule 3 wk antepartum, a diet containing a BEO from 3 wk antepartum onward, or a control diet (n = 12). The samples were analyzed for pH, volatile fatty acid, ammonia, and lipopolysaccharide concentrations and protozoal counts. A 16S rRNA gene fingerprinting analysis (PCR–single-strand conformation polymorphism) and sequencing revealed that the BEO treatment had no effect on the rumen microbiota, whereas monensin decreased bacterial diversity. Twenty-three bacterial species-level operational taxonomic units were identified for which monensin caused a significant decrease in their relative abundance, all belonging to the phyla Bacteroidetes (uncultured BS11 gut group and BS9 gut group) and Firmicutes (Lachnospiraceae, Ruminococcaceae, and Erysipelotrichaceae). Ten bacterial operational taxonomic units belonging to the phyla Actinobacteria (Coriobacteriaceae), Bacteroidetes (Prevotella), Cyanobacteria (SHA-109), and Firmicutes (Lachnospiraceae and Ruminococcaceae) increased in relative abundance due to the monensin treatment. These results confirm the hypothesis that varying effects depending on cell-wall constitution and thickness might apply for monensin sensitivity rather than a clear-cut difference between gram-negative and gram-positive bacteria. No effect of monensin on the archaea population was observed, confirming the assumption that reported inhibition of methanogenesis is most likely caused through a decrease in substrate availability, rather than by a direct effect on the methanogens. The data support the hypothesis that the observed increase in ruminal molar propionate proportions due to monensin may be caused by a decrease in abundance of non-producers and moderate producers of propionate and an increase in abundance of succinate and propionate producers.     

Effects of supplemental butyrate and weaning on rumen fermentation in Holstein calves

The objectives of this study were to determine the effects of the weaning transition and supplemental rumen-protected butyrate on subacute ruminal acidosis, feed intake, and growth parameters. Holstein bull calves (n = 36; age = 10.7 ± 4.1 d; ± standard deviation) were assigned to 1 of 4 treatment groups: 2 preweaning groups, animals fed milk replacer only (PRE-M) and those fed milk replacer, calf starter, and hay (PRE-S); and 2 postweaning groups, animals fed milk replacer, calf starter, and hay without supplemental rumen-protected butyrate (POST-S) or with supplemental rumen-protected butyrate at a rate of 1% wt/wt during the 2-wk weaning transition (POST-B). Milk replacer was provided at 1,200 g/d; starter, water, and hay were provided ad libitum. Weaning took place over 14 d by reducing milk replacer provision to 900 g/d in wk 7, 600 g/d in wk 8, and 0 g/d in wk 9. Rumen pH was measured continuously for 7 d during wk 6 for PRE-S and PRE-M and during wk 9 for POST-S and POST-B. After rumen pH was measured for 7 d, calves were euthanized, and rumen fluid was sampled and analyzed for volatile fatty acid (VFA) profile. Individual feed intake was recorded daily, whereas, weekly, body weights were recorded, and blood samples were collected. Compared with PRE-M, PRE-S calves tended to have a greater total VFA concentration (35.60 ± 11.4 vs. 11.90 ± 11.8 mM) but mean rumen pH was unaffected (6.25 ± 0.22 vs. 6.17 ± 0.21, respectively). Between PRE-S (wk 6) and POST-S (wk 9), calf starter intake increased (250 ± 219 vs. 2,239 ± 219 g/d), total VFA concentrations increased (35.6 ± 11.4 vs. 154.4 ± 11.8 mM), but mean rumen pH was unaffected (6.25 ± 0.22 vs. 6.40 ± 0.22, respectively). Compared with POST-S, POST-B calves had greater starter intake in wk 7, 8, and 9, but POST-B tended to have lower total VFA concentration (131.0 ± 11.8 vs. 154.4 ± 11.8 mM) and lower mean ruminal pH (5.83 ± 0.21 vs. 6.40 ± 0.22). In conclusion, the weaning transition does not appear to affect rumen pH and VFA profile, but supplementing rumen-protected butyrate during the weaning transition increased starter intake and average daily gain. Further, these data suggest that the ability of the rumen to manage rumen pH changes fundamentally postweaning. Why weaned calves with lower rumen pH can achieve higher calf starter intakes is unclear; these data suggest the effect of rumen pH on feed intake differs between calves and cows.     

Structural growth, rumen development, and metabolic and immune responses of Holstein male calves fed milk through step-down and conventional methods

Structural growth, feed consumption, rumen development, metabolic response, and immune response were studied in Holstein calves fed milk through either a conventional method or a step-down (STEP) method. In the conventional method, calves (n = 20) were fed colostrum and then milk at a rate of 10% of their BW for the entire period of 44 d. In the STEP method, calves (n = 20) were given colostrum and then milk at a rate of 20% of their BW for 23 d, which was reduced (between d 24 to 28) to 10% of their BW for the remaining 16 d. The calves on both methods were weaned gradually by diluting milk with water between d 45 and 49. After weaning, feed consumption, structural growth, and body weight gain were monitored until calves were 63 d of age. At d 63, twelve calves (6/treatment) were euthanized and rumen papillae length, papillae width, rumen wall thickness, and emptied forestomach weight were recorded. At wk 4, 7, and 9, ruminal contents were collected to enumerate rumen metabolites. The STEP-fed calves consumed a greater amount of milk than conventionally fed calves during the pre-STEP (d 1 to 28), post-STEP (d 29 to 49), and preweaning (d 1 to 49) periods. Consumption of starter and hay was greater during the pre-STEP period and lesser during the post-STEP and postweaning (d 50 to 63) periods in calves on the conventional method than on the STEP method. Body weight gain and structural growth measurements of calves were greater on the STEP method than on the conventional method. A hypophagic condition caused by greater milk consumption depressed solid feed intake of STEP-fed calves during the pre-STEP period, and a hyperphagic response caused by a reduced nutrient supply from milk triggered their consumption of solid feed during the post-STEP and postweaning periods. Ruminal pH and concentrations of ammonia, total volatile fatty acids, acetate, propionate, butyrate, and plasma β-hydroxybutyrate were higher in calves on the STEP method and at weaning and postweaning (d 63) were lower in calves on the conventional method. Emptied weight of the forestomach, rumen wall thickness, papillae length, papillae width, and papillae concentration were higher in calves on the STEP method than in those on the conventional method. Blood glucose was lower, and blood urea nitrogen and β-hydroxybutyrate at weaning and postweaning were higher in STEP-fed calves. Serum IgG, IgA, and triglycerides for 1, 2, and 3 wk of age were higher in calves on the STEP method than in those on the conventional method. In conclusion, greater feed consumption, BW gain, and structural growth, and a more metabolically and physically developed rumen were observed in calves on the STEP method than in those on the conventional method.     

Fecal shedding and rumen growth of Escherichia coli O157:H7 in fasted calves.

Nine weaned calves aged from 8 to 12 weeks were fitted with rumen cannulas and were inoculated by cannula with 10(10) CFU of a five-strain mixture of nalidixic acid-resistant Escherichia coli O157:H7. Six calves were fasted for 48 h on days 15 and 16 and days 22 and 23 after inoculation. Samples of rumen contents and feces were obtained daily to enumerate E. coli O157:H7 populations and to determine rumen volatile fatty acid (VFA) concentrations and rumen pH. Fasting resulted in a marked decrease in rumen VFA concentrations from a mean of 135 mmol/liter before the fast to a mean of 35 mmol/liter during the second day of the fast. However, there was no correlation between daily VFA concentration and daily rumen or fecal numbers of E. coli O157:H7 in any of the calves. Fasting generally had no significant effect on the rumen or fecal numbers of E. coli O157:H7. The exception was a single fasted calf that experienced a 3-log(10) CFU/g increase in fecal shedding during and after the first fast. Despite the consistent changes in VFA concentrations in fasted calves, the fluctuations in rumen numbers of E. coli O157:H7 in the rumen of fasted calves were minimal. At the end of the experiment, E. coli O157:H7 was detected in either the rumen or omasum in two of three control calves at necropsy and in either the rumen or reticulum in five of six fasted calves. E. coli O157:H7 was detected in the colon in two of three control calves and in six of six fasted calves at necropsy. These results suggest that in cattle already shedding E. coli O157:H7, feed withdrawal and the associated changes in rumen pH and VFA concentrations have little effect on fecal shedding and rumen proliferation of E. coli O157:H7.     

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 2 L of milk replacer (MR) at 12.5% dry matter twice daily until 49 d of age. Calves received 2 L 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.     

Hay intake improves performance and rumen development of calves fed higher quantities of milk

Research to date has suggested that access to forage before weaning can limit rumen development in calves, but no research has yet addressed the role of forage for calves fed higher quantities of milk. This study compared performance and rumen development of calves provided high volumes (equivalent to approximately 20% of calf birth weight) of milk with and without access to hay. At d 3 of age, individually housed calves were randomly assigned to treatment (either ad libitum access to chopped grass hay or no forage; n = 15 calves per treatment, 10 heifers, and 5 bulls). All calves were provided ad libitum access to water and starter throughout the study. All calves were offered 8 L of milk/d from a nipple bottle from d 3 to 35, 4 L/d from d 36 to 53, and 2 L/d until weaning at d 56. Solid feed intake and growth parameters were monitored from d 3 to 70. At d 70, males from both treatments were slaughtered to measure rumen development parameters. Overall dry matter (DM) intake from solid feed did not differ between treatments before wk 5. However, during wk 6 to 10, calves fed forage consumed more total DM (starter plus hay) than did calves fed no forage. Hip and wither height, heart girth, and body barrel at d 3, 56, and 70 did not differ between treatments. Reticulorumen weight was heavier in calves fed hay versus those fed only starter (12.77 ± 1.29 vs. 7.99 ± 0.69 kg with digesta; 1.89 ± 0.05 vs.1.60 ± 0.09 kg without digesta). Body weight without digesta was similar in calves fed forage or no forage. Mean rumen pH was higher in calves fed hay compared with those fed no forage (5.49 ± 0.08 vs. 5.06 ± 0.04). In conclusion, provision of chopped hay to calves fed high volumes of milk can promote solid feed DM intake and rumen development without affecting BW gain.     

Effects of starch content of calf starter on growth and rumen pH in Holstein calves during the weaning transition

The objective of this study was to evaluate the effects of substituting high fiber byproducts for dry ground corn in calf starter on growth and rumen pH during the weaning transition. Holstein bull calves were raised on an intensified nursing program using milk replacer containing 26% CP and 18% fat. Calves were fed a texturized calf starter containing either dry ground corn at 18.8% of dry matter (DM; CRN), beet pulp replacing dry ground corn at 10.2% dietary DM (BP), or triticale dried distillers grains with solubles replacing dry ground corn and high-protein feedstuffs at 18.6% of dietary DM (DDGS) in the pellet; treatment calf starters differed only in the pellet portion. Starch concentrations of CRN, BP, and DDGS were 35.3, 33.4, and 31.4%, respectively. After a calf consumed 2.50 kg of starter for 3 consecutive days, a small ruminant rumen pH data logger was inserted orally and rumen pH was measured continuously for 4d. Calves were then killed and rumen fluid was sampled to determine volatile fatty acid profile. No difference was found in overall average daily gain or growth rates of hip height, withers height, and heart girth. During the weaning transition, rate of increase in calf starter intake was greater for calves fed DDGS compared with those fed CRN (87.7 vs. 77.5 g/d), but lower for calves fed BP compared with CRN (68.1 vs. 77.5 g/d). The area under pH 5.8 (470 vs. 295 min × pH/d) or pH 5.2 (72.7 vs. 16.4 min × pH/d) was greater for calves fed DDGS than those fed CRN. Rumen pH profile was not affected by BP treatment compared with CRN, but calves fed BP tended to have greater water intake than those fed CRN (6.6 vs. 5.8 L/d). Volatile fatty acid profile was not affected by treatment with the exception of molar proportion of butyrate, which tended to be lower for calves fed BP compared with those fed CRN (15.0 vs. 16.6%). Hay intake was positively correlated to mean rumen pH for calves used in this study (r=0.48). Decreasing dietary starch concentration did not mitigate rumen acidosis in calves during weaning transition, and low rumen pH did not adversely affect growth during the weaning transition.     

Different feed presentations affect subsequent feed sorting and rumen pH for a short period in weaned calves

The objective of this study was to investigate the short- and long-term effects of different feed presentations on feed sorting and rumen pH in weaned calves. Thirty-six weaned female calves at the age of 12 wk (78 d) were raised in pairs (18 pens; n = 6/treatment) and randomly exposed to 1 of 3 feed presentation treatments: (1) concentrate ration (CON, only exposed to concentrate); (2) separate ration (CH, exposed to concentrate and hay as separate components); and (3) mixed ration (Mix, exposed to a mixed diet containing 75% concentrate and 25% hay). After 4 wk (from d 78 to 105) on different feed presentations, all weaned calves were introduced to a novel total mixed ration (TMR) for another 12 wk (from d 106 to 189). Fresh feed and orts were sampled daily before (wk 12 to 15) and after (wk 16, 17, and 28) transitioning to a TMR diet for analysis of feed sorting. Rumen fluid was sampled in wk 12, 13, 15, 16, 17, and 28 to determine rumen pH. The performance of weaned calves was affected by the different feed presentations during the pre-changing period, such that calves fed CON had a lower dry matter intake (DMI) and average daily gain than calves fed CH and Mix diets. When calves were introduced to the Mix diet, they immediately developed a higher degree of sorting behavior against the long particle fractions. Upon transition to TMR, we did not observe any differences in the performance of calves. However, the sorting behavior established in Mix calves persisted and was similar to calves previously fed the CON diet, whereas the extent of feed sorting in calves initially fed CH was less compared with that in the other 2 treatments in wk 16 and 17. Before changing the diet was transitioned to a TMR, calves fed CON had a lower rumen pH than calves fed CH and Mix. Although rumen pH in all treatments increased to the same level after the diet changed, we observed a tendency toward lower rumen pH in calves fed Mix compared with calves fed CH at wk 17, which might have resulted from the higher degree of feed sorting in these calves. However, by the end of the experiment (wk 28), feed sorting and rumen pH were similar across all treatments. These results indicated a short-term effect of previous feed presentations on subsequent feed sorting and rumen pH, but in the long term disappeared.     

Effects of supplemental yeast (Saccharomyces cerevisiae) culture on rumen development, growth characteristics, and blood parameters in neonatal dairy calves

Yeast (Saccharomyces cerevisiae) culture was added to a texturized calf starter at 0 (control), 1, or 2% of dry matter to determine effects on intake, growth, blood parameters, and rumen development. Seventy-five Holstein calves (38 male; 37 female) were started on the experiment at 2 +/- 1 d of age and were studied for 42 d. Starter intake was measured, and fecal scoring was conducted daily. Growth and blood parameter measurements were recorded at weekly intervals. A subset of 6 male calves (2 per treatment) was euthanized at 5 wk of age, and rumen tissue was sampled for rumen epithelial growth measurements. An additional 6 male calves were euthanized at 6 wk of age for rumen epithelial growth measurements. Inclusion of yeast culture at 2% of the starter ration significantly increased starter and total dry matter intake, average daily gain, and daily hip width change when compared with the control treatment. Average daily gain was improved by 15.6% for the 2% yeast treatment. Daily change in hip height was also significantly greater for calves receiving 2% supplemental yeast culture than for calves receiving 1%. No significant treatment differences were observed for any other variables. These data suggest that the addition of yeast culture in a dairy calf starter at 2% enhances dry matter intake and growth and slightly improves rumen development in dairy calves.     

Nitrogen metabolism in the rumen

Nitrogen metabolism is reviewed with emphasis on methods for quantitating various nitrogen-transactions in the rumen of animals on a variety of diets. Ammonia kinetics, microbial cell synthesis, the inputs of endogenous nitrogen, degradation of dietary protein, and availability to the animal of dietary bypass protein are discussed. The efficiency of microbial protein from the rumen is discussed in relation to the ratio of protein to energy in the nutrients available to meet the requirements of the animal. The ratio is determined largely by the maintenance requirements of microbes and the breakdown of microbial materials, which result in the recycling of microbial nitrogen in the rumen. Emphasis is placed on the role of rumen protozoa in decreasing the ratio of protein to energy in absorbed nutrients in ruminants on diets that are marginally deficient in protein. Recent studies of the dynamics of protozoa in the rumen and their contribution to microbial protein outflow are summarized.     

Effect of a garlic and citrus extract supplement on performance,rumen fermentation,methane production,and rumen microbiome of dairy cows

The aim of this trial was to determine the effect of a garlic and citrus extract supplement (GCE) on the performance, rumen fermentation, methane emissions, and rumen microbiome of dairy cows. Fourteen multiparous Nordic Red cows in mid-lactation from the research herd of Luke (Jokioinen, Finland) were allocated to 7 blocks in a complete randomized block design based on body weight, days in milk, dry matter intake (DMI), and milk yield. Animals within each block were randomly allocated to a diet with or without GCE. The experimental period for each block of cows (one for each of the control and GCE groups) consisted of 14 d of adaptation followed by 4 d of methane measurements inside the open circuit respiration chambers, with the first day being considered as acclimatization. Data were analyzed using the GLM procedure of SAS (SAS Institute Inc.). Methane production (g/d) and methane intensity (g/kg of energy-corrected milk) were lower by 10.3 and 11.7%, respectively, and methane yield (g/kg of DMI) tended to be lower by 9.7% in cows fed GCE compared with the control. Dry matter intake, milk production, and milk composition were similar between treatments. Rumen pH and total volatile fatty acid concentrations in rumen fluid were similar, whereas GCE tended to increase molar propionate concentration and decrease the molar ratio of acetate to propionate. Supplementation with GCE resulted in greater abundance of Succinivibrionaceae, which was associated with reduced methane. The relative abundance of the strict anaerobic Methanobrevibacter genus was reduced by GCE. The change in microbial community and rumen propionate proportion may explain the decrease in enteric methane emissions. In conclusion, feeding GCE to dairy cows for 18 d modified rumen fermentation and microbiota, leading to reduced methane production and intensity without compromising DMI or milk production in dairy cows. This could be an effective strategy for enteric methane mitigation of dairy cows.     

Short communication: Effect of calf starter on rumen pH of Holstein dairy calves at weaning

The objective of this study was to evaluate the effect of feeding calf starter on rumen pH of dairy calves during weaning transition. Twenty Holstein bull calves were paired into 10 blocks by starting date of the study and body weight, and fed either milk replacer and hay (MR) or MR, hay, and a commercial texturized calf starter (MR+S) in a randomized complete block design. All calves were fed 750 g/d of milk replacer as the basal diet. Calves on MR+S treatment were also fed a calf starter ad libitum to maintain similar energy intake between calves within blocks, and MR calves were fed additional milk replacer that was equivalent to energy from calf starter intake. When MR+S calves consumed a calf starter at 680 g/d for 3 consecutive d, rumen pH of a MR+S calf and his MR counterpart was measured continuously for 3 d using a small ruminant rumen pH measurement system. Treatment did not affect minimum pH, mean pH, maximum pH, standard deviation of mean pH, and duration or area under pH 5.8, indicating that calf starter consumption did not appear to affect rumen pH. However, hay intake was negatively correlated to area under pH 5.8, with a breakpoint at 0.080 kg/d intake, suggesting hay intake might play an important role in mitigating ruminal acidosis in dairy calves during weaning transition.