Substituição do milho por casca de soja em dietas de alta proporção de concentrado para novilhas nelore abatidas com diferentes pesos
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2013-12-16
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Universidade Federal de Goiás
Resumo
We studied the effect of substitution of 0, 33, 66 and 100% of ground corn (GC) by soybean
hulls (SH) in diet’s concentrate portion of 144 Nellore heifers of 24 to 30 months of age and
263.40 + 13.90 kg of body weight in beginning of feedlot and slaughtered at different weights
(<340, 340-370, 370-400 and >400 kg). There was no significant interaction between levels of
substitution of GC by SH and slaughter weight classes being these effects studied separately.
Diets were composed of 90 % concentrate and 10 % corn silage. The experimental period was
112 days, including the period of adaptation. The dry matter intake was not altered by
substitution of GC by SH with mean values of 2.51 % of body weight. The substitution level
of GC by SH resulted in a linear increase in NDF intake (1.08, 2.03, 2.92 and 3.78 kg/day)
and reduced consumption of NDT (5.78, 5 16, 5.03 and 5.12 kg/day) with the addition of 0,
33, 66 and 100 % of GC by SH substitution, respectively. The average daily weight gain
decreased linearly (1.24, 1.11, 1.02 and 0.89 kg / day), while feed conversion increased (6.20,
7.08, 7.77 and 8.67 kg DM intake/kg ADG) for the levels of 0, 33, 66 and 100% SH in the
diet, respectively. The body condition score was not influenced by levels of substitution of
GC by SH presenting mean values of 3.51 points. The body measurements were not affected
by treatments, both on the back as the withers, with mean values of 138.5 and 133.25 cm,
respectively. Measures of thorax perimeter and body length decreased linearly with the
inclusion of SH levels. The slaughter weight decreased linearly with values of 383.52, 374.71,
363.25 and 366.27 kg for levels of 0, 33, 66 and 100 % replacement of GC for SH,
respectively, however the hot carcass weight or cold were not affected by the replacement of
GC by SH and showed average values of 203.52 and 199.25 kg, respectively. There was no
effect of dietary treatment on hot carcass yield showing mean values of 54.92 %. The
conformation of the carcasses was not affected by the replacement of GC by SH, with average
values of 9.16 points. The subcutaneous fat thickness and loin eye area were not affected by
dietary treatments and showed mean values of 5.3 mm and 53.08 cm2, respectively. The
yields of primary carcass cut (front, special needle and side cut) were not affected by SH
inclusion levels and showed average values of 36.52, 51.72 and 11.55%, respectively. The
objective measurements of carcass were not affected by replacement levels of GC by SH. It
was found linear effect of treatments on the compactness of carcasses showing average values
of 1.56, 1.57, 1.51 and 1.45 cm/kg of cold carcass, to replacing levels of 0, 33, 66 and 100%
of SH, respectively. The color and texture of meat were not influenced by dietary treatments
and showed average values of 3.30 and 3.19 points, respectively. The marbling of the meat
was not influenced by the substitution of GC by SH presenting mean values 8.56 points, with
amplitude values between 2 and 17 points. The elevation of slaughter weight resulted in
increased weights of hot and cold carcass. Animals slaughtered with weight >400kg had hot
carcass yield of 52.76 %, lower than the group of 370-400 kg (56.55 %). The subcutaneous fat
thickness was not affected by slaughter weight in any of the expression forms of this variable,
with mean values of 5.26 mm and 2.67% of the cold carcass weight. The loin eye area
increased with the increase of slaughter weight, and the correlation between these variables
was 0.62 (P=0.001), however, when this variable was expressed to 100 kg cold carcass this
difference disappeared, with average scores of 26,72 cm2 for each 100 kg of cold carcass.
The animals slaughtered with weight >400kg showed better conformation (9.79 points)
compared to the other weight classes did not differ among themselves. There was a significant
effect of slaughter weight on the carcasses length, arm perimeter and cushion thickness which
increased 5.9, 2.3 and 3.12 cm, respectively, amounted to slaughter weight of <340 to >400
kg. Animals slaughtered with weight >400kg had higher carcass compactness compared to the
other treatments (1.65 cm long/ kg of cold carcass weight). The absolute weights of primary
cuts of the carcass increased with the slaughter weight, however to adjust the weights of the front and rear to 100 kg of cold carcass, this difference disappeared, with values of 36.59 and
51.99%, respectively. The color and texture of the meat were not influenced by slaughter
weights showing average values of 3.28 and 3.19 points, respectively. The marbling of the
meat was lower in the group of animals slaughtered weighing less than 340 kg compared to
the other weight classes did not differ among themselves. It was concluded which although
not influence the main carcass characteristics, the replace of ground corn by soybean hulls in
high concentrate diets is not efficient because has depressing effect on the productive
performance, notably weight gain and feed conversion. Feedlot Nellore heifers must not be
slaughtered weighing less than 340 kg because they have lower carcass weight and less
marbling of the meat.
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REZENDE, Pedro Leonardo de Paula. Substituição do milho por casca de soja em dietas de alta proporção de concentrado para novilhas nelore abatidas com diferentes pesos. 2013. 105 f. Tese (Doutorado em Ciência Animal), Universidade Federal de Goiás, Goiânia, 2013.