The evolution of ruminants was largely influenced by the symbiotic relationship between ruminal microbiota and the host. Within the rumen, these microorganisms degrade feedstuffs to produce organic ...acids and synthesize microbial protein, as energy and protein source for ruminants, respectively. This process is accelerated when these animals are transferred to feedlot diets. This review brings the most current studies that reported the most used nutritional managements in this transition process, in order to avoid metabolic disturbances, in which rumen development is a fundamental point. Also, this review brings the main biomolecules used as feed additive, which can in the help control of fermentation processes in order to minimize energetically inefficient processes within the rumen, as well as losses by excretion to the environment, which are widely questioned by be environmental pollutants. Furthermore, the main results of research on animal performance in response to these additives are reported, supplemented alone or associated with different feed additives when used on diets with high grain contents, as well as evaluating the potential of additives as antibiotics alternatives, a fact that has been discussed and is worrying since the use of ionophores or non-ionophores antibiotics represent practically the totality of feedlot diets.
Abstract
The objectives of this study were to compare ruminal total tract digestibility, bacterial communities, and eating and rumination activity between Holstein and Angus steers fed grain- or ...forage-based diets. Six Holstein steers (average body weight BW = 483 ± 23 kg) and six Angus steers (average BW = 507 ± 29 kg), previously fitted with rumen cannulae, were fed in a crossover design with a 2 × 2 factorial arrangement of four treatments: 1) Holsteins fed a grain-based diet, 2) Holsteins fed a forage-based diet, 3) Angus fed a grain-based diet, and 4) Angus fed a forage-based diet. Each period was 35 d with 26 d of diet adaptation and 9 d of sample collection. On days 1 and 2 of collection, feeding activity was recorded for 48 h. On day 3, rumen contents were sampled to measure ruminal pH at 0, 3, 6, 12, and 18 h after feeding. A portion of the strained ruminal fluid was subsampled at 0, 3, and 6 h for volatile fatty acids (VFA) analysis. Rumen contents were subsampled at 3 h for analysis of bacterial communities. From day 4 to 8, total fecal excretion, feed, and refusals samples were collected and analyzed for dry matter (DM), neutral detergent fiber (NDF), and starch. On days 8 and 9 (0 and 3 h post-feeding, respectively), total reticulorumen evacuation was conducted and contents were weighed. Data were analyzed using the MIXED procedures in SAS (v9.4 SAS Inst. Inc., Cary, NC). Repeated measures were used to analyze changes in ruminal pH and VFA over time. There were no interactions of diet × breed (P ≥ 0.07). While the main effects of diet were expected, unique to these data is the fact that bacterial diversity and richness were reduced (P < 0.01) in cattle fed grain-based diets. There was no main effect (P > 0.34) of breed on total tract DM, organic matter, and starch digestibility, but Angus cattle had greater (P = 0.01) NDF digestibility than Holsteins. The increased NDF digestibility may be associated with a numerical (P = 0.08) increased numbers of bacterial species in Angus steers compared with Holstein steers. Holstein steers also spent more time (P ≤ 0.05) ruminating than Angus steers. There was no effect (P > 0.80) of breed on reticulorumen content at feeding time; however, Holstein steers had greater (P = 0.04) reticulorumen content on a wet basis 3 h post-feeding. Although Holstein steers spent more time ruminating, Angus steers were better able to digest NDF when compared with Holsteins, regardless of basal diet, and this improvement may be related to changes in bacterial communities in the rumen or to rumination activity.
Beef cattle are key contributors to meat production and represent critical drivers of the global agricultural economy. In Brazil, beef cattle are reared in tropical pastures and finished in feedlot ...systems. The introduction of cattle into a feedlot includes a period where they adapt to high-concentrate diets. This adaptation period is critical to the success of incoming cattle, as they must adjust to both a new diet and environment. Incoming animals are typically reared on a variety of diets, ranging from poor quality grasses to grazing systems supplemented with concentrate feedstuffs. These disparate pre-adaptation diets present a challenge, and here, we sought to understand this process by evaluating the adaptation of Nellore calves raised on either grazing on poor quality grasses (restriction diet) or grazing systems supplemented with concentrate (concentrate diet). Given that nutrient provisioning from the diet is the sole responsibility of the ruminal microbial community, we measured the impact of this dietary shift on feeding behavior, ruminal fermentation pattern, ruminal bacterial community composition (BCC), and total tract digestibility. Six cannulated Nellore bulls were randomly assigned to two 3 × 3 Latin squares, and received a control, restriction, or concentrate diet. All cohorts were then fed the same adaptation diet to mimic a standard feedlot. Ruminal BCC was determined using Illumina-based 16S rRNA amplicon community sequencing. We found that concentrate-fed cattle had greater dry matter intake (
P
< 0.01) than restricted animals. Likewise, cattle fed concentrate had greater (
P
= 0.02) propionate concentration during the adaptation phase than control animals and a lower Shannon’s diversity (
P
= 0.02), relative to the restricted animals. We also found that these animals had lower (
P
= 0.04) relative abundances of
Fibrobacter succinogenes
when compared to control animals during the pre-adaptation phase and lower abundances of bacteria within the
Succinivibrio
during the finishing phase, when compared to the control animals (
P
= 0.05). Finally, we found that animals previously exposed to concentrate were able to better adapt to high-concentrate diets when compared to restricted animals. Our study presents the first investigation of the impact of pre-adaptation diet on ruminal BCC and metabolism of bulls during the adaptation period. We suggest that these results may be useful for planning adaptation protocols of bulls entering the feedlot system and thereby improve animal production.
There may be an increased risk of metabolic disorders, such as rumen acidosis, in cattle fed high‐concentrate diets, particularly those from Bos taurus indicus genotypes, which have shown to be more ...sensitive to ruminal acidification. Therefore, this study aimed to estimate (co)variance components and identify genomic regions and pathways associated with ruminal acidosis in feedlot Nellore cattle fed high‐concentrate diets. It was utilized a dataset containing a total of 642 Nellore bulls that were genotyped from seven feedlot nutrition studies. The GGP Indicus 35k panel was used with the single step genome‐wide association study methodology in which the effects of the markers were obtained from the genomic values estimated by the GBLUP model. A bivariate model to estimate genetic correlations between the economically important traits and indicator traits for acidosis was used. The traits evaluated in this study that were nutritionally related to rumen acidosis included average daily gain (ADG), final body weight, time spent eating (TSE), time spent ruminating, rumenitis score (RUM), rumen absorptive surface area (ASA), rumen keratinized layer thickness (KER) and hot carcass weight (HCW). The identified candidate genes were mainly involved in the negative or non‐regulation of the apoptotic process, salivary secretion, and transmembrane transport. The genetic correlation between HCW and ASA was low positive (0.27 ± 0.23), and between ADG and ASA was high moderate (0.58 ± 0.59). A positive genetic correlation between RUM and all performance traits was observed, and TSE correlated negatively with HCW (−0.33 ± 0.21), ASA (−0.75 ± 0.48), and KER (−0.40 ± 0.27). The genetic association between economically important traits and indicator traits for acidosis suggested that Nellore cattle may be more sensitive to acidosis in feedlot systems.
The objective of this study was to examine the relationships among ruminal microbial community, rumen morphometrics, feeding behavior, feedlot performance, and carcass characteristics of Nellore ...cattle, classified by residual feed intake (RFI). Twenty-seven Nellore yearling bulls with an initial body weight (BW) of 423.84 ± 21.81 kg were fed in feedlot for 107 d in individual pens to determine the RFI phenotype. Bulls were categorized as high RFI (>0.5 SD above the mean, n = 8), medium RFI (±0.5 SD from the mean, n = 9), and low RFI (<0.5 SD below the mean, n = 10). At harvest, whole rumen content samples were collected from each bull to evaluate ruminal microbial community, including bacteria and protozoa. The carcass characteristics were determined by ultrasonography at the beginning and at the end of the experimental period, and behavior data were collected on d 88. As a result of ranking Nellore bulls by RFI, cattle from low-RFI group presented lesser daily dry matter intake (DMI), either in kilograms (p < 0.01) or as percentage of BW (p < 0.01) than high-RFI yearling bulls, resulting in improved gain:feed (G:F). However, variables, such as average daily gain (ADG), final BW, hot carcass weight (HCW) and other carcass characteristics did not differ (p > 0.05) across RFI groups. The eating rate of either dry matter (DM )(p = 0.04) or neutral detergent fiber (NDF) (p < 0.01) was slower in medium-RFI yearling bulls. For ruminal morphometrics an RFI effect was observed only on keratinized layer thickness, in which a thinner layer (p = 0.04) was observed in low-RFI Nellore yearling bulls. Likewise, Nellore yearling bulls classified by the RFI did not differ in terms of Shannon’s diversity (p = 0.57) and Chao richness (p = 0.98). Our results suggest that the differences in feed efficiency of Nellore bulls differing in phenotypic RFI should be attributed to metabolic variables other than ruminal microorganisms and epithelium, and deserves further investigation.
Flint corn processing method coarse ground corn (CGC; 3.2 mm average particle size) or steam-flaked corn (SFC; 0.360 kg/L flake density) was evaluated in conjunction with 4 levels of neutral ...detergent fiber (NDF) from sugarcane bagasse (SCB) as roughage source (RNDF; 4, 7, 10, and 13%; dry matter basis) to determine impact on growth performance, carcass characteristics, starch utilization, feeding behavior, and rumen morphometrics of Bos indicus beef cattle. Two hundred and forty Nellore bulls were blocked by initial body weight (BW = 350 ± 37 kg), assigned to 32 feedlot pens and pens within weight block were randomly assigend, in a 2 × 4 factorial arrangement (2 corn processing and 4 levels of RNDF) to treatments. Effects of corn grain processing × RNDF level were not detected (P ≥ 0.14) for growth performance, dietary net energy concentration, carcass traits, rumen morphometrics, and feeding behavior, except for time spent ruminating and time spent resting (P ≤ 0.04), and a tendency for papillae width (P ≤ 0.09). Bulls fed SFC-based diets consumed 7% less (P = 0.001), had 10.6% greater carcass-adjusted average daily gain (P < 0.001) and 19% greater carcass-adjusted feed efficiency (P < 0.001) compared to bulls fed CGC-based diets. Observed net energy for maintenance and gain values were 14.9 and 19.4% greater (P < 0.001), respectively, for SFC than for CGC-based diets. Fecal starch concentration was less (P < 0.001) for bulls fed SFC compared to those fed CGC. No grain processing effects were detected (P = 0.51) for rumenitis score; however, cattle fed SFC presented smaller ruminal absorptive surface area (P = 0.03). Dry matter intake increased linearly (P = 0.02) and carcass-adjusted feed efficiency tended (P = 0.06) to decrease linearly as RNDF increased. Dietary RNDF concentration did not affect carcass characteristics (P ≥ 0.19), except for dressing percentage, which tended to decrease linearly (P = 0.06) as RNDF in finishing diets increased. Increasing RNDF in finishing diets had no effect (P = 0.26) on time spent eating, but time spent ruminating and resting increased linearly (min/d; P < 0.001) with increased dietary RNDF. Steam flaking markedly increased flint corn energy value, net energy of diets, and animal growth performance, and led to improvements on feed efficiency when compared with grinding, regardless of RNDF content of diets. Increasing dietary RNDF compromised feedlot cattle feed efficiency and carcass dressing.
The objective of this study was to evaluate the addition of cane molasses during a 60 day dry period on performance and metabolism of Holstein cows during prepartum and postpartum periods. For ...experiment 1, 26 primiparous and 28 multiparous cows were used. Upon freshening, all cows were offered a common lactation diet. For experiment 2, six multiparous cows fitted with rumen cannulas were used to measure performance and metabolism, following the same protocol as experiment 1. Ruminal propionate increased by 10% during both prepartum and postpartum periods; however, papillae area was greater for cows not fed molasses, and volatile fatty acids (VFA) absorption from the rumen was not increased, resulting in similar glucagon-like-peptide-2 receptor (GLP-2R) density. The improved dry matter intake, when molasses was added into prepartum diets, translated into increased milk yield and energy-corrected milk (ECM) in Experiment 1 only for multiparous cows. For experiment 2, the improvement on milk performance was also observed, where cows fed molasses had 18.5% greater ECM production. Feeding molasses during a 60 day dry period positively influenced transition cow performance, and it was not accompanied by changes in rumen morphometrics; however, this indicates enhanced adaptation by the rumen epithelium based on similar capabilities for VFA absorption.
This study was designed to evaluate a spray-dried multivalent polyclonal antibody preparation (PAP) against lactate-producing bacteria as an alternative to monensin (MON) to control ruminal ...acidification. Holstein cows (677 ± 98 kg) fitted with ruminal cannulas were allocated in an incomplete Latin square design with two 20 days period. Cows were randomly assigned to control (CTL), PAP, or MON treatments. For each period, cows were fed a forage diet in the first 5 days (d-5 to d-1), composed of sugarcane, urea and a mineral supplement, followed by a 74% concentrate diet for 15 days (d 0 to d 14). There were no treatment main effects (
> 0.05) on dry matter intake (DMI) and microbial protein synthesis. However, there was a large peak (
< 0.01) of intake on d 0 (18.29 kg), followed by a large decline on d 1 (3.67 kg). From d2, DMI showed an increasing pattern (8.34 kg) and stabilized around d 8 (12.96 kg). Higher mean pH was measured (
< 0.01) in cattle-fed MON (6.06 vs. PA
= 5.89 and CTL = 5.91). The ruminal NH
-N concentration of CTL-fed cows was lower (
< 0.01) compared to those fed MON or PAP. The molar concentration of acetate and lactate was not affected (
> 0.23) by treatments, but feeding MON increased (
= 0.01) propionate during the first 4 days after the challenge. Feeding MON and PAP reduced (
= 0.01) the molar proportion of butyrate. MON was effective in controlling pH and improved ruminal fermentation of acidosis-induced cows. However, PAP was not effective in controlling acidosis. The acidosis induced by the challenge was caused by the accumulation of SCFAs. Therefore, the real conditions for evaluation of this feed additive were not reached in this experiment, since this PAP was proposed to work against lactate-producing bacteria.
Feed additives such as monensin (MON) and virginiamycin (VM) are commonly utilized in feedlot diets to enhance rumen fermentation. Nevertheless, the precise effects of combining MON and VM during ...specific feedlot periods and the advantages of this combination remain unclear. This study was designed to investigate the effects of withdrawal of MON when associated with VM during the adaptation and finishing periods on ruminal metabolism, feeding behavior, and nutrient digestibility in Nellore cattle. The experimental design was a 5 × 5 Latin square, where each period lasted 28 days. Five rumen-cannulated Nellore yearling bulls were used (414,86 ± 21,71 kg of body weight), which were assigned to five treatments: (1) MON during the entire feeding period; (2) VM during the entire feeding period; (3) MON + VM during the adaptation period and only VM during the finishing period 1 and 2; (4) MON + VM during the entire feeding period; (5) MON + VM during the adaptation and finishing period 1 and only VM during the finishing period 2. For the finishing period 1, animals fed T3 had improved potential degradability of dry matter (
= 0.02). Cattle fed T3 and T5 had the highest crude protein degradability when compared to animals receiving T2 (
= 0.01). Animals fed T2 and T3 had reduced the time (
< 0.01) and area under pH 6.2 (
= 0.02). Moreover, animals fed T4 had greater population of protozoa from the genus
(
= 0.04) when compared to those from animals fed T2, T3 and T5. For the finishing period 2, animals fed T3 had greater starch degradability when compared to animals receiving T4 and T5 (
= 0.04). Animals fed T3, T4 and T5 had increased the duration of time in which pH was below 5.6 (
= 0.03). The area under the curve for ruminal pH 5.2 and pH 5.6 was higher for the animals fed T3 (
= 0.01), and the area under pH 6.2 was higher for the animals fed T3 and T5 (
< 0.01) when compared to animals receiving T2. There is no substantial improvement on the rumen fermentation parameters by the concurrent utilization of MON and VM molecules, where the higher starch and protein degradability did not improve the rumen fermentation.
Feed additives used in finishing diets improve energy efficiency in ruminal fermentation, resulting in increased animal performance. However, there is no report evaluating the effect of BEO ...associated with exogenous α-amylase in response to increased starch content in feedlot diets. Our objective was to evaluate increasing levels of starch in the diet associated with a blend of essential oils plus amylase or sodium Monensin on performance, carcass characteristics, and ruminal and cecal morphometry of feedlot cattle. 210 Nellore bulls were used (initial body weight of 375 ± 13.25), where they were blocked and randomly allocated in 30 pens. The experiment was designed in completely randomized blocks in a 3 × 2 factorial arrangement: three starch levels (25, 35, and 45%), and two additives: a blend of essential oils plus α-amylase (BEO, 90 and 560 mg/kg of DM, respectively) or sodium Monensin (MON, 26 mg/kg DM). The animals were fed once a day at 08:00
and underwent an adaptation period of 14 days. The diets consisted of sugarcane bagasse, ground corn, soybean hulls, cottonseed, soybean meal, mineral-vitamin core, and additives. The animals fed BEO35 had higher dry matter intake (
= 0.02) and daily weight gain (
= 0.02). The MON treatment improved feed efficiency (
= 0.02). The treatments BEO35 and BEO45 increased hot carcass weight (
< 0.01). Animals fed BEO presented greater carcass yield (
= 0.01), carcass gain (
< 0.01), rib eye area gain (
= 0.01), and final rib eye area (
= 0.02) when compared to MON. The MON25 treatment improved carcass gain efficiency (
= 0.01), final marbling (
= 0.04), and final subcutaneous fat thickness (
< 0.01). The use of MON reduced the fecal starch% (
< 0.01). Cattle-fed BEO increased rumen absorptive surface area (
= 0.05) and % ASA papilla area (
< 0.01). The MON treatment reduced the cecum lesions score (
= 0.02). Therefore, the use of BEO with 35 and 45% starch increases carcass production with similar biological efficiency as MON; and animals consuming MON25 improve feed efficiency and reduce lesions in the rumen and cecum.
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