| The effects of castration on physiological mechanism of growth performance,endocrine metabolism and fat deposition were investigated in 17 to 21 months of Simmental bulls and steers. 50 healthy simmental cattle(16 month), after anthelmintic drugs, were used in a paired design of single factor by body weight. Experimental cattle were divided into castrated group and uncastrated group, each group of 25 cattle, the experimental cattle were fed the same diet in the same stage to fatten 150 d. Body weight, body size, serum hormones and serum biochemical indexes of experimental beef were measured in 17, 18, 19, 20 and 21 months of age. Five beef which each group were chosen, whose body weight close to the average weight of experimental cattle at the end of the experiment, To analysis the meat production performance, meat eating quality, nutrients, fatty acid and cholesterol content.The results followed: 1. The effects of castration on Body weight and body size. The daily gain and body weight of 17 to 21 months of age on the castrated group were higher than uncastrated group, but the difference was not significantly. The daily gain growth curve of uncastrated group Simmental cattle showed "s", and the daily gain growth curve of castrated group Simmental cattle was exponential curve. The body size increased pre month average of body height、body length、chest circumference、hip width、thurl width and Ischial-end width in the castrated group were lower than those of uncastrated group, the difference was not significant(P>0.05). The abdominal perimeter increased pre month average of castrated group were increaser than uncastrated group, the difference was extremely significant(P<0.01). 2. The effects of castration on serum hormone secretion. The content of serum testosterone in castrated group were significantly lower than that in the uncastrated group(P<0.05). The estradiol content in castrated group have a increaser trend than uncastrated group(0.05<P≤0.10). The content of growth hormone content in castrated group were extremely significant lower than that in uncastrated group(P<0.01). The somatostatin content of castrated group were significantly higher than uncastrated group(P<0.05). The content of cortisol in castrated group have a lower trend than in the uncastrated group(0.05<P≤0.10). The concentrations of adrerrmrticotropic hormone, glucagon, insulin, prostaglandin, Thyroxine and Triiodothyronine in the blood were not significantly different between castrated group and uncastrated group. 3. The effects of castration on enzymes and regulatory factors for serum lipid metabolism. The serum CHO, T3, HDL, LDL and FFA of castrated group were higher than uncastrated group 0.13%, 4.17%, 3.16%, 0.66% and 2.44%, respectively, the difference was not significant(P>0.05). The content of HSL in castrated group were lower than uncastrated group 4.01%, the difference was not significant(P>0.05); the content of lipoprotein lipase and alkaline phosphatase in the castrated group were higher than uncastrated group 1.40% and 5.15%, respectively, the difference were not significant(P>0.05). The content of creatine kinase in the castrated group were significant lower than uncastrated group(P<0.05). the content of BUN and ALB in castrated group were extremely significant higher than uncastrated group(P<0.01); the ratio of albumin and globulin in the castrated group were significantly higher than uncastrated group(P<0.05). The content of superoxide dismutase in the castrated group were higher than uncastrated group 0.01%; and the content of glutathione peroxidase and Malondialdehyde in the castrated group were lower than uncastrated group 0.85% and 1.32%(P>0.05), respectively. 4. The effects of castration on meat quality. The results showed that the myoglobin in Longissimus muscle of castrated group were very significantly higher than uncastrated group 58.45%(P<0.01). The marble patterns, fat, dry matter, oleic acid and single unsaturated fatty acids content in Longissimus muscle of castrated group were significantly higher than uncastrated group 66.67%, 207.11%, 9.81%, 24.86% and 24.01%(P<0.05). The ratio of MUFA/SFA and MUFA/PUFA in Longissimus muscle of castrated group were significantly higher than uncastrated group(P<0.05). The p H value in Longissimus muscle of castrated group were very significantly lower than uncastrated group(P<0.01). The stearic acid content in Longissimus muscle of uncastrated group were significantly higher than castrated group(0.05<P≤0.10). 5. The effects of castration on beef quality at different parts of the carcass. The p H values of uncastrated group in different parts showed chuck tender>thin flank>rump>striploin>topside,The p H values of Chuck tender were higher than striploin, topside and rump 3.88%(P<0.01), 5.35%(P<0.01) and 2.29%(P<0.05), respectively;The p H values of thin flank and Rump were higher than topside 3.30% and 2.99%,respectively, the difference were extremely significant(P< 0.01). The p H values of castrated group in different parts showed thin flank>chuck tender>striploin>rump>topside. The p H values of thin flank were higher than topside and rump 4.33%(P<0.01) and 2.36%(P<0.05), The p H values of chuck tender were higher than topside 3.37%, the difference was significantly(P < 0.05). The fat content of uncastrated group in different parts showed thin flank>striploin>rump>chuck tender>topside, there were no significantly difference(P>0.05). The fat content of castrated group in different parts showed thin flank>rump>striploin>chuck tender>topside, The fat content of thin flank were higher than striploin, chuck tender and topside 82.81%, 90.63% and 196.02%,respectively, the difference were significantly(P<0.05). The ash content of uncastrated group in different parts showed topside>striploin>rump>thin flank>chuck tender. The ash content of topside were higher than chuck tender 22.63%, the difference were significantly(P<0.05). The ash content of castrated group in different parts showed chuck tender=striploin>topside>rump>Thin flank. The ash content of chuck tender and striploin were higher than thin flank 30.60% and 30.60%, respectively, the difference were extremely significant(P<0.01). The shear stress, cooking loss, protein content, water loss rate, myoglobin and dry matter content in different parts of castrated group and uncastrated group have an similar statistics difference.The results showed: The effects of castration on physiological mechanism of fat deposition in Simmental cattle include two aspects, on the one hand, after castration, the testicular lost function to produce testosterone, resulting in testosterone concentration decreased and estradiol concentrations have am increased trend. The change of sex hormone concentration negative feedback regulated hypothalamus and pituitary gland, resulting in the concentration of castration cattle growth hormone decreased and somatostatin concentration increased. Growth hormone has a direct effect on fat target cells, increased the activity of lipoprotein lipase and alkaline phosphatase, decreased activity hormone sensitive lipase, and then make the serum cholesterol, triglyceride, high density lipoprotein, low density lipoprotein and free fatty acid content showed castrated cattle were higher than uncastrated cattle, increase in albumin were used for the transport of fatty acids and other nutrients, make the fat metabolism in serum in overall performance for fat synthesis and metabolism of slightly larger than catabolism; promotes the increase of fat content within the muscle. Increased fat deposition resulting in steers the backfat thickness greater than bulls, the tenderness and juicy of steers were better than the bull, increase dry matter content and marbling of beef in steer, improve the quality of beef. The other hand, after castration, the testicular lost function to produce testosterone, resulting in reducing the concentrations of testosterone and metabolic oxidation process slows down, and steers become gentle and the relative reduction in the amount of activity, resulting in the body’s demand for ATP decreased, the activity of serum creatine kinase and lactate dehydrogenase decreased, the blood sugar consumption reduce, serum glucose levels relatively elevated; the protein assimilation weakened, and blood oxidative stress becomes low. Resulting in growth performance on the growth curve of the bull is a "s" shape, and steers’ growth curve is an exponential. The better the quality of beef because of the beef in steers have more content of oleic acid and unsaturated fatty acids,improve the color and delay the shelf life of products of steer beef. |
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