The aim of this trial was to test the effects of the use of eubiotics (pro- and prebiotics) alone or in combination in the diet of lambs finished under subtropical climate conditions. For this purpose, 40 Pelibuey × Katahdin lambs (29.5 ± 4.8 kg initial live weight) were used in a 93 day growth-performance experiment. Dietary treatments consisted of a cracked corn-based finishing diet supplemented with (1) no eubiotics (control), (2) 3 g of probiotics (live Saccharomyces cerevisiae, SC), (3) 3 g of prebiotics (mannan oligosaccharide plus b-glucans, MOS), and (4) a combination of 1.5 g of SC and 1.5 g of MOS (SC+MOS). Throughout the study, the average temperature humidity index (THI) was 78.60. Compared to controls, supplementation with SC or MOS, alone did not affect average daily gain (ADG), but enhanced feed efficiency by 5.6% and 6.9% (gain-to-feed ratio, G:F) and dietary net energy by 4.6% and 5.9%, respectively. Compared to controls, SC+MOS enhanced ADG (10%), G:F (9.5%), and dietary net energy (7.2%). Lambs fed SC+MOS had also greater ADG, G:F, and dietary net energy compared to lambs fed SC alone. When compared to MOS, the combination enhanced ADG (10.4%, p = 0.04). This effect could be attributed to the increased dry matter intake (7.6%, p = 0.06), as neither G:F nor dietary energy was significantly affected. Compared with controls and SC, supplementation with MOS alone and SC+MOS increased kidney–pelvic–heart fat, while SC supplementation tended (p = 0.08) to reduce 4.1% the relative intestinal mass (as a proportion of empty body weight) when compared to controls. Treatment effects on the other carcass measures were not significant. In the present study, supplemental probiotics and/or prebiotics improved dietary energetic efficiency in lambs finished under subtropical climatic conditions. The combination of probiotics with prebiotics reinforced this positive effect.

This study utilized fifty bull calves of the Continental × British crossbreed, with an average body weight of 147.0 ± 1.67 kg (BW), in a completely randomized design. The objective was to examine the impact of varying levels and duration of calcium propionate (CaPr) supplementation on the growth performance, body fat reserves, serum metabolites, and hemogram of high-risk newly received stocker calves. These calves were individually housed and fed a received diet for 56 d. The calves received the following treatments: (1) no CaPr (CTL), (2) 20 g CaPr/calf/d, (3) 40 g CaPr/calf/d, (4) 60 g CaPr/calf/d, and (5) 80 g CaPr/calf/d at 14, 28, 42, and 56 d after their arrival. Supplementing with 20 g CaPr from 28 to 56 d after arrival increased average daily gain (ADG) and BW (p < 0.05), and DMI was not affected (p > 0.05). This was reflected at 28 d with increases (p < 0.05) in the ADG/DMI ratio and longissimus muscle area (LMA), and at 56 d in back fat thickness (BFT) and fat thickness at the rump (FTR). Also, with 20 g, blood urea nitrogen decreased (p < 0.05), and increases were observed in the activity of gamma glutamyltransferase, monocytes (quadratic trend, p < 0.07), and granulocytes % (quadratic effect, p < 0.03). However, as the level of CaPr increased during the first 14 d after arrival, daily water intake, creatinine, total cholesterol, mean corpuscular hemoglobin concentration (linear effect, p < 0.05), globulin, calcium, and mean corpuscular volume (linear trend, p = 0.08) increased, while alkaline phosphatase (linear trend, p = 0.07) and lymphocytes (linear effect, p = 0.05) decreased. Finally, the different levels of CaPr supplementation did not produce any significant effects or differences (p > 0.05) in the remaining serum metabolites and hemogram (p > 0.05). Ultimately, the inclusion of 20 g CaPr/calf/d in the diet for 28 d in newly received stocker calves increased ADG, ADG/DMI ratio, and LMA. If extended to 42 or 56 d, the increases in ADG persisted, but there was also a rise in body fat reserves (BFT and FTR) at the expense of a reduction in the ADG/DMI ratio. Furthermore, the different supplementation levels did not impact the reference range for most serum metabolites or the health of stocker calves.

Fifty bull calves of the Continental × British crossbred (147.0 ± 1.67 kg body weight, BW) were used in a completely randomized design to investigate the effect varying levels and duration of calcium propionate (CaPr) supplementation on the growth performance, body fat reserves, serum metabolites, and hemogram of high-risk newly received stocker calves. These calves were individually housed and fed a received-diet for 56 d. The calves received the following treatments: 1) No CaPr (CTL), 2) 20 g CaPr/calf/d, 3) 40 g CaPr/calf/d, 4) 60 g CaPr/calf/d, and 5) 80 g CaPr/calf/d, during 14, 28, 42 and 56 d the after arrival. The supplementation with 20 g CaPr from 28 to 56 d after arrival increases average daily gain (ADG) and BW (p < 0.05), and DMI is not affected (p > 0.05). This is reflected at 28 d with increases (p < 0.05) in ADG:DMI ratio and longissimus muscle area (LMA), and at 56 d in back fat thickness (BFT) y fat thickness at the rump (FTR). Also, with 20 g, blood urea nitrogen decreased (p < 0.05); and increases were observed in the activity of gamma glutamyltransferase, monocytes (quadratic trend, p < 0.07) and granulocytes% (quadratic effect, p < 0.03). However, as the level of CaPr increased during the first 14 d after arrival, daily water intake, creatinine, total cholesterol, mean corpuscular hemoglobin concentration (linear effect, p < 0.05), globulin, calcium and mean corpuscular volume (linear trend, p = 0.08) increased, while alkaline phosphatase (linear trend, p = 0.07) and lymphocytes (linear effect, p = 0.05) decreased. Finally, the different levels of CaPr supplementation did not produce any significant effects or differences (p > 0.05), in the remaining serum metabolites and hemogram (p > 0.05). Ultimately, the inclusion of 20 g CaPr/calf/d in the diet for 28 d in newly received stocker calves increases ADG, ADG:DMI ratio and LMA. If extended to 42 or 56 d, the increases in ADG persist, but there is also a rise in body fat reserves (BFT and FTR) at the expense of a reduction in ADG:DMI ratio. Furthermore, the different supplementation levels did not impact the reference range for most serum metabolites or the health of stocker calves.

Energy availability is a critical point in newly received calves. This study was conducted to examine the effect of daily calcium propionate (CaPr), chromium-methionine (Cr-Met), or CaPr plus Cr-Met (CaPr + Cr-Met) supplementation on growth performance, dietary energetics, body fat reserves, serum metabolites, and hematological responses in high-risk beef calves. Forty-eight crossbred bull calves (148.7 ± 2.05 kg body weight) were involved in a fully randomized experimental design. Calves which were individually pen allocated (12 repetitions/treatment) were subjected to one of the following treatments daily over 56 d: (1) Control, no additives; (2) CaPr, 19 g CaPr; (3) Cr-Met, 4 g Cr-Met; and (4) CaPr + Cr-Met, 19 g CaPr plus 4 g Cr-Met. Compared to controls, feed additive supplementation alone or in combination did not modify dry matter intake (DMI), but increased average daily gain (ADG), improving the ADG/DMI ratio. However, no synergistic effect on dietary energy utilization efficiency was observed with the combination of CaPr and Cr-Met; individual supplementation proved more effective. Because of the magnitude of the effects of Cr-Met on the efficiency of dietary energy utilization, this resulted in an increase (p < 0.05) in rump fat thickness (RFT). The supplementation of CaPr + Cr-Met decreased ALB/GLO ratio, MPV, and RBC, but increased TCHO, GLU, and MCH (p > 0.05). It is concluded that supplementation with CaPr or Cr-Met independently is an effective strategy to improve growth performance, energy utilization and retention, and body fat reserves, without adverse effects on health among high-risk beef calves.

Due to their specific properties, the autolyzed yeast Saccharomyces cerevisiae (SC) and bacterial Bacillus subtilis (BS) theoretically can have a synergistic effect when combined and offered in ruminant diets. Thus, the aim of this experiment was to evaluate the effect of their combination as feed additives on growth performance, dietary energy, carcass traits, and visceral organ mass in finishing lambs. For this reason, 48 Pelibuey × Katahdin lambs (98 ± 17 d age; initial weight = 20.25 ± 3.37 kg) were used in a feeding trial lasting 83 d. Lambs were blocked by weight and assigned to 24 pens. Treatment consisted in supplementing a high-energy diet with probiotic and/or prebiotic as follows: (1) finishing diet without probiotic or prebiotic supplementation (Control), (2) finishing diet supplemented with 1.5 g SC/kg diet, (3) finishing diet supplemented with 1.5 g BS/kg diet, and (4) finishing diet supplemented with 1.5 g SC plus 1.5 g BS/kg diet. There were no synergistic (interaction) effects by combining SC + BS in any of the variables evaluated. Lambs that were supplemented with BS showed a very similar response on dry matter intake (DMI, p = 0.41), average daily gain (ADG, p = 0.64), carcass traits (p ≥ 0.08), tissue composition (p ≥ 0.32), and relative visceral organ mass (g/kg EBW, p ≥ 0.15) than non-supplemented lambs. Compared to the control group, lambs that received SC alone or in combination with BS showed greater average daily gain (12.0%, p = 0.03), gain efficiency (6.1%, p = 0.04) and observed-to expected dietary energy efficiency (5.5%, p = 0.04). Supplemental SC and SC + BS increased hot carcass weight (p = 0.04) without effects on the rest of the variables evaluated including the shoulder tissue composition whole cuts, and visceral organ mass. It was concluded that SC improves growth performance and dietary energy in finishing lambs without changes in carcass traits or carcass composition. Combining SC with BS did not improve the magnitude of the response of SC supplemented alone. In this study, the inclusion of a 1.5 g/kg diet of BS during a long-term period (83 d) did not show benefits to finishing lambs.

Leonardite (LEO), a microbial derived product rich in humic and fulvic acids, has been tested, due to its beneficial properties for health and well-being, as a feed additive, mainly in non-ruminant species. Although there are some reports of LEO supplementation in ruminants fed with high-to medium-forage based diets, there is no information available of the potential effects of LEO in ruminants fed, under sub-tropical climate conditions, with high-energy diets during long-term fattening. For this reason, the objective of the present experiment was to evaluate the effects of LEO levels inclusion in diets for feedlot lambs finished over a long-term period. For this reason, 48 Pelibuey × Katahdin lambs (initial weight = 20.09 ± 3.55 kg) were fed with a high-energy diet (88:12 concentrate to forage ratio) supplemented with LEO (with a minimum of 75% total humic acids) for 130 days as follows: (1) diet without LEO, (2) diet supplemented with 0.20% LEO, (3) diet supplemented with 0.40% LEO, and (4) diet supplemented with 0.60% LEO. For each treatment, Leonardite was incorporated with the mineral premix. Lambs were blocked by weight and housed in 24 pens (2 lambs/pen). Treatment effects were contrasted by orthogonal polynomials. The average climatic conditions that occurred during the experimental period were 31.6 ± 2.4 °C ambient temperature and 42.2 ± 8.1% relative humidity (RH). Those values of ambient temperature and RH represent a temperature humidity index (THI) of 79.07; thus, lambs were finished under high heat load conditions. The inclusion of LEO in diet did not affect dry matter intake (p ≥ 0.25) and average daily gain (p ≥ 0.21); therefore, feed to gain ratio was not affected (p ≥ 0.18). The observed to expected dietary net energy averaged 0.96 and was not affected by LEO inclusion (p ≥ 0.26). The lower efficiency (−4%) of dietary energy utilization is an expected response given the climatic conditions of high ambient heat load presented during fattening. Lambs that were slaughtered at an average weight of 49.15 ± 6.00 kg did not show differences on the variables measured for carcass traits (p ≥ 0.16), shoulder tissue composition (p ≥ 0.59), nor in visceral mass (p ≥ 0.46) by inclusion of LEO. Under the climatic conditions in which this experiment was carried out, LEO supplementation up to 0.60% in diet (equivalent to 0.45% of humic substances) did not did not help to alleviate the extra-energy expenditure used to dissipate the excessive heat and did not change the gained tissue composition of the lambs that were fed with high-energy diets during long-term period under sub-tropical climate conditions.