Digestion and metabolism of low and high residual feed intake Nellore bulls

Abstract

Understanding the reasons why animals of similar performances have different feed requirements is important to increase profits for cattle producers and to decrease the environmental footprint of beef cattle production. This study was carried out aiming to identify the associations between residual feed intake (RFI) and animal performance, nutrient digestibility, and blood metabolites related to energy balance of young Nellore bulls during the finishing period. Animals previously classified as low (n = 13) and high RFI (n = 12), with average initial body weight of 398 kg and age of 503 days were used. Cattle were fed a high energy diet and were slaughtered when rib fat thickness measured by ultrasound between the 12th and 13th ribs reached the minimum of 4 mm. A completely randomized design was adopted, being data analyzed with a mixed model that included the random effect of slaughter group, the fixed effect of RFI class, and linear effect of the covariate feedlot time. No differences were found (p > 0.10) between RFI classes for performance, dry matter, and nutrients intake. However, dry (p = 0.0911) and organic matter (p = 0.0876) digestibility tended to be lower, and digestibility of neutral detergent fiber corrected for ash and protein (p = 0.0017), and total digestible nutrients (p = 0.0657) were lower for high RFI animals, indicating lesser capacity of food utilization. Difference between low and high RFI animals was also found for blood cortisol at the end of the trial (p = 0.0044), having low RFI animals lower cortisol concentrations. Differences in the ability to digest food can affect the efficiency of transforming feed into meat by Nellore cattle.

Residual feed intake in beef cattle and its association with carcass traits, ruminal solid-fraction bacteria, and epithelium gene expression

“…E. ruminantium , a Gram-positive bacteria, also plays a cellulolytic role in the rumen [ 41 ]. A better ability to ferment fiber through greater abundance F. succinogenes and E. ruminantium is supported by previous reports showing that the most-efficient beef bulls and heifers had greater rates of DM, OM, NDF, protein, and TDN digestibility [ 4 , 5 ]. M. elsdenii , a Gram negative bacterium, utilizes lactate to produce butyrate and propionate by reverse β-oxidation [ 15 ].…”

“…A previous study indicated that ~ 20% of RFI variation in beef cattle could be explained by differences in rumen-related functions such as microbial digestion and epithelial metabolism [ 3 ]. Evidence indicates that efficient beef bulls and heifers have greater digestibility for dry matter (DM), organic matter (OM), neutral detergent fiber (NDF), protein, and total digestible nutrients (TDN) [ 4 , 5 ], underscoring the vital role of ruminal microbes and epithelial tissue as key drivers of divergence in RFI. Thus, additional work to evaluate ruminal microbes and epithelium tissue between divergent RFI classes should help in identifying potential physiological mechanisms to enhance nutrient uptake and production efficiency in the most-efficient cattle.…”

Residual feed intake divergence during the preweaning period is associated with unique hindgut microbiome and metabolome profiles in neonatal Holstein heifer calves

“…For instance, M-eff cows had greater total bacterial density including fibrolytics (Fibrobacter succinogenes) around parturition [7], and abundance of bacterial genera Anaerovibrio and Butyrivibrio also was greater in established lactation [8]. Those data suggested that, compared with L-eff cattle, changes in ruminal bacteria in M-eff cattle might contribute, at least in part, to better rates of digestibility of dry matter, organic matter, and neutral detergent fiber [9]. Other studies detected greater concentrations of energy-related metabolites in the rumen of M-eff lambs and dairy cows including butyrate and propionate [10,11], suggesting a contribution of these microbial-derived compounds to energy metabolism and milk production [12].…”

Review: Biological determinants of between-animal variation in feed efficiency of growing beef cattle

“…Since methane production (g CH 4 /day) is linearly related to DM intake, selection of cattle for low-RFI may substantially reduce methane production without reducing the growth of the animal (Basarab et al, 2013). Lower methane production is not always seen in animals of lower RFI, however, because (1) divergent RFI cattle do not always exhibit differences in DM intake when digestibility is measured outside the RFI test period (Jones et al, 2011) and (2) low RFI cattle often exhibit up to a 4% points increase in whole tract DM digestibility, increasing the quantity of substrate available for fermentation and methanogenesis per unit feed (Bonilha et al, 2017). concluded that the processes of digestion were responsible for at least 10% of variance in RFI.…”