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.
Feedlot cattle are usually adapted to high-concentrate diets containing sodium monensin (MON) in more than 14 days. However, considering that the dry matter intake DMI is usually lower during ...adaptation when compared to the finishing period, the use of MON during adaptation may decrease even further the DMI, and virginiamycin (VM) may be an alternative. This study was designed to investigate the effects of shortening the adaptation length from 14 to 9 or 6 days on ruminal metabolism, feeding behavior, and nutrient digestibility of Nellore cattle fed high-concentrate diets containing only VM as the sole feed additive. The experimental design was a 5 × 5 Latin square, where each period lasted 21 days. Five 17 mo-old Nellore yearling bulls were used (415 ± 22 kg of body weight), which were assigned to five treatments: (1) MON (30 mg/kg) and adaptation for 14 days; (2) MON (30 mg/kg) + VM (25 mg/kg) and adaptation for 14 days; (3) VM (25 mg/kg) and adaptation for 14 days; (4) VM (25 mg/kg) and adaptation for 9 days, and (5) VM (25 mg/kg) and adaptation for 6 days. A quadratic effect for adaptation length when only VM was fed was observed for mean pH (
= 0.03), duration of pH below 5.2 (
= 0.01) and 6.2 (
= 0.01), where cattle consuming VM adapted for 9 days had higher mean pH and shorter period of pH below 5.2 and 6.2. Cattle that consumed only MON had a lower concentration of butyrate (
= 0.02) and a higher concentration of propionate (
= 0.04) when compared to those consuming VM and adapted for 14 days. As the adaptation length decreased for animals consuming only VM, the rumen degradability of dry matter (
< 0.01), neutral detergent fiber (
< 0.01), and starch (
< 0.01) decreased; however, protozoa numbers of
and total protozoa increased. It is not recommended to shorten the adaptation length of these animals to either 6 or 9 days without negatively impacting nutrient disappearance and ruminal fermentation patterns.
Feedlot cattle are usually adapted to high-concentrate diets containing sodium monensin (MON) in more than 14 days. However, for finishing diets with lower energy content, the use of MON during ...adaptation may hold dry matter intake (DMI), and virginiamycin (VM) may be an alternative. This study was designed to determine the potential of shortening the adaptation of Nellore cattle to high-concentrate diets using only VM as a sole feed additive relative to feedlot performance, feeding behavior, and ruminal and cecum morphometrics. The experiment was designed as a completely randomized block replicated six times (four animals/pen) in which 120 Nellore bulls (390.4 ± 19.0 kg) were fed in 30 pens for 111 days according to the following treatments: (1) MON and adaptation for 14 days (MON14), (2) MON + VM and adaptation for 14 days (MONVM14), (3) VM and adaptation for 14 days (VM14), (4) VM and adaptation for 9 days (VM9), and (5) VM and adaptation for 6 days (VM6). At the end of the adaptation, 30 animals (
n
= 1 per pen) were randomly slaughtered for rumen and cecum evaluations. The remaining 90 bulls were harvested at the end of the study. No effects of treatments were observed (
P
< 0.10) for final body weight, average daily gain (ADG), and hot carcass weight (HCW). Cattle fed VM14 presented a greater (
P
≤ 0.03) DMI, expressed as percent of body weight (BW), than animals fed either MON14 or MONVM14; however, cattle fed either MON14 or MONVM14 improved (
P
≤ 0.02) the gain-to-feed ratio (G/F) by 10.4 or 8.1%, respectively, when compared to bulls fed VM14. Bulls fed VM14 had smaller (
P
< 0.05) papillae area (0.34 vs. 0.42 cm
2
) and rumen absorptive surface area (28.9 vs. 33.8 cm
2
) than those fed MON14. The shortening of the adaptation period linearly decreased the 12th rib fat (
P
= 0.02) and biceps femoris fat daily gain (
P
= 0.02) of Nellore bulls fed only VM, which linearly decreased the final biceps femoris fat thickness (
P
< 0.01). Feedlot cattle fed VM as a sole feed additive should not be adapted to high-concentrate diets in less than 14 days. Regardless of either adaptation length or feed additive, feedlot cattle need at least 14 days to adapt to finishing diets.
Abstract
This study, conducted at São Paulo University feedlot, Dracena, Brazil, was designed to evaluate the effect of adding either high-moisture corn, calcium salts of fatty acids (CSFA), or ...organic Zn+Cr on feedlot performance and carcass traits of Nellore cattle fed for 112 days. One-hundred fifty 18-mo-old Nellore bulls (404±24kg) were used and initially ranked, according to sires’ information, into groups of high and low EPD. Secondly, cattle were blocked by weight and randomly allocated to 30 pens (n = 5/pen), which were randomly assigned to the following 2x2 + 1 arrangement of treatments: Finely-ground corn, High-moisture corn, Finely-ground + CSFA, High-moisture corn + CSFA, and High-moisture corn + CSFA + Zn (90 ppm) and Cr (0.45 ppm). All diets contained 25 ppm of monensin. On day 0, one animal per pen was randomly selected to be slaughtered for baseline purposes. The replacement of finely-ground by high-moisture corn increased (P < 0.05) final BW (585 vs. 573 kg), ADG, HCW (321 kg vs. 315 kg) and decreased (P < 0.01) DMI (9.7 vs. 10.1 kg). Likewise, the addition of CSFA increased final BW, ADG (1.62 vs. 1.50 kg), and HCW (321 vs. 314 kg). The addition of Cr+Zn led to increased (P = 0.02) dressing percentage. No treatment effect was observed on final marbling (P > 0.55). It was observed interactions between treatments and EPD for G:F (P = 0.02) and final 12thrib-fat thickness (P = 0.03), where cattle from low-EPD groups needed high-moisture corn, CSFA and organic Zn+Cr to improve G:F and increase fat deposition; however, animals from high-EPD groups required only high-moisture corn. The adding of either high-moisture corn, CSFA, or organic Zn+Cr improved feedlot performance of Nellore cattle, and its effects seemed to be more effective in animals from low-EPD groups.
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