Performance, eating behavior and carcass characteristics of feedlot lambs fed diets without forage containing sodium bicarbonate


 The study was carried out to evaluate the effect of inclusion of sodium bicarbonate (SB) in diets based on ground corn without forage for feedlot lambs. Twenty-eight ram lambs (Dorper x Santa Inês), with initial body weight of 30.2 ± 4.5 kg and 94 ± 8.4 days old were used. They were assigned to a randomized complete block design. Experimental diets were positive control, diet without forage containing soybeans hulls replacing ground flint corn in 400g/kg of dry matter (DM) (CONT); and three diets without forage based on ground flint corn containing 10 (10SB), 20 (20SB) or 30 (30SB) g/kg DM of SB. The inclusion of SB quadratically increased final body weight (P = 0.02), dry matter intake (DMI; P < 0.01), average daily gain (P < 0.01), feed eficiency (P < 0.01), slaughter body weight (P = 0.02), hot and cold carcass weight (P = 0.02), loin muscle area (P = 0.05), leg compacity index (P = 0.05) and the weights of: neck (P = 0.01), shoulder (P = 0.02), rib (P = 0.03) and leg (P = 0.01), with higher values for the 20SB. Feeding SB linearly decreased the area (P < 0.01) and height (P = 0.01) of the papillae. The use of SB improved the performance and increased hot and cold carcass weights, with better results observed in the 20 g/kg level (20SB), showing to be efficient in diets without forage for feedlot lambs.


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Samples of diets and ingredients were frozen at -20 ºC for later analysis.

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Animals of all treatments started the experiment receiving their respective diets, however, they were 84 subjected to an adaptation by restriction, with a progressive increase in the amount offered over the period 85 until reaching ad libitum consumption, as follows: 1 st d: offer of total feed equivalent to 2.0% of the animal's 86 BW; 2 nd d: offer of total feed equivalent to 2.4% of the animal's BW; 3 rd d: offer of total feed equivalent to 87 2.8% of the animal's BW; 4 th d: offer of total feed equivalent to 3.2% of the animal's BW; 5 th d: offer of total 88 feed equivalent to 3.6% of the animal's BW; from the 6 th d: offer of total ration to ensure ad libitum 89 consumption.

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The BW was recorded after a 16-h fast on d 0, 28, 56 and 84 of the experimental period to determine 91 the ADG and feed efficiency (FE). At the end of each period, orts were recorded and composited by 92 treatment, then a sample were frozen at -20 ºC for later analysis.  At the end of each period, the fecal score of each animal was evaluated for three consecutive days 102 according to the methodology described by Dickson and Jolly (2011). Grades from 1 to 5 were assigned: 1 -103 uniformly shaped and rigid feces; 2 -slightly uneven and friable feces; 3 -uneven feces, forms a soft pile; 4 -104 pasty feces forms a loose pile; 5 -liquid feces, including diarrhea. 105 2.5 Gastrointestinal tract evaluation 106 After slaughter, animals were eviscerated and rumen compartment was isolated and a fragment of 1 107 cm² was collected from the ventral region of cranial sac of rumen. The evaluated macroscopic morphological 108 variables were number of papillae/cm² of wall (NP), height, width and mean area of the papillae (MAP), 109 absorptive surface area/cm² of wall (ASA) and percentage of papillae per absorptive surface area (% 110 papillae/ASA). The absorptive surface area as well as the area and height of the papillae were measured using 111 the ImageJ (image analysis software). The ASA in cm² was calculated as: where 1 represents 1 cm² of collected fragment and 0.002 is the estimated basal area of the papillae in cm².

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The area of the papillae, expressed as a percentage of ASA, was calculated as:

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The averages were obtained using the comand LSMEANS. The effects of sodium bicarbonate levels 170 on diets were evaluated using linear and quadratic orthogonal polynomials. One contrast was performed:

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The final body weight (FBW) had a quadratic response (P = 0.02) among SB levels, with highest 180 value observed in the 20SB. Regarding the contrasts, there was no difference between the animals that 181 received CONT or sodium bicarbonate. The DMI showed a quadratic response in kg/d (P < 0.01), % of BW 182 (P = 0.01) and in g/kg of BW 0.75 (P = 0.02) according to SB levels, with highest value for 20SB. A higher 183 DMI in kg/d, % BW and g/kg of BW 0.75 (P = 0.0001, P < 0.0001 and P < 0.0001, respectively) was observed 184 for animals fed CONT when compared to those fed sodium bicarbonate (Table 2).

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There was a quadratic effect (P < 0.01) on the ADG in response to SB levels, with highest value 186 observed for 20SB. However, there was no difference between SB vs. CONT groups ( Table 1). The FE also 187 presented a quadratic response (P < 0.01) among SB levels, with higher value for animals that received 188 20SB.

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There was a quadratic effect (P < 0.01) of SB levels on DMI, with highest values for the animals 191 that received 20SB. Furthermore, the DMI was higher for CONT compared to the SB groups (P < 0.0001; 192 Table 3).

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Animals fed CONT showed higher neutral detergent fiber consumption (NDFC) values compared to 194 the SB groups (P < 0.001; Table 3). Among SB levels, there was no difference in NDFC.

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The ingestion time in min/g of DM showed a quadratic response (P < 0.01) among SB levels, with 196 lowest value for the animals that received 20SB. However, when CONT was compared to SB groups, there 197 was no difference. The ingestion time in min/g of NDF did not differ between the levels of sodium 198 bicarbonate, but it was lower for CONT compared to SB (P < 0.001), while ingestion in min/d did not differ 199 (Table 3).

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There was a negative linear association between SB levels and rumination time in min/d (P = 0.04) 201 and in min/g of NDF (P = 0.03), with lower values for 30SB. Rumination time in min/g DM showed a 202 quadratic response (P < 0.01), with lower values for animals that received 20SB. The rumination time in 8 min/d was higher for the CONT compared to SB groups (P < 0.001), but when expressed in min/g of NDF it 204 was smaller (P < 0.001) for CONT, with no difference in min/g of DM (Table 3).

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There was a quadratic effect between SB levels in chewing time in min/d (P = 0.04), min/g DM (P < 206 0.001) and min/g NDF (P = 0.04), with lower values for animals that received 20SB. Chewing time in min/d 207 was higher for CONT (P < 0.01) and in min/g of NDF was lower for CONT (P < 0.001) compared to SB 208 groups. There was no effect for chewing time in min/g DM (Table 3)   The SB level was quadratically associated with BW, HCW, CCW, LMA and CCI (P < 0.05) with 218 higher values observed for 20SB (Table 5). The other carcass characteristics were not affected by the 219 treatments. There was a difference between the FBW and slaughter body weight (SBW) of the animals due to 220 a difference of four days between the end of the experimental period and the day of slaughter.

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For the carcass cuts, there was a quadratic association between SB level and the neck (P = 0.01), 222 shoulder (P = 0.02), rib (P = 0.03) and leg weight (P = 0.01), with higher values observed for animals that 223 received 20SB (Table 6). The other carcass cuts were not affected by treatments.

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When CONT was compared with SB groups, there was no difference in any of the analyzed variables.

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Between SB levels, the ADG was higher for the 20SB, which can be justified by the higher DMI.