| Evaluating the effect of using a gonadotropin-releasing factor (GnRF) vaccine (Improvac(?), Pfizer Animal Health) against boar taint on the slaughter preformance and meat quality of pigs, vaccinated pigs were compared with physically castrated. And it was investigated for meat nutritional characteristics of testis of vaccinated pigs. It was conducted to explore application value of GnRF vaccine and to provide some referenced information in pigs production industry. The study includes three parts and the results are presented as follows:The first part:An experiment was designed to study the effect of a GnRF vaccine on carcass composition and meat quality in pigs. A total of400healthy male pigs were randomly assigned to treatment groups:surgically castrated males and vaccinated males. Castrated males were physically castrated within3days of age. Vaccinated males received the GnRF vaccine twice, getting2ml/vaccination injected subcutaneously just behind and below the base of the ear. The first injection was given at the age of14weeks, and the second dose at the age of21weeks. At the end of the study,20pigs of each treatment were weighed individually and slaughtered at25weeks of age at random. The longissimus muscles were collected to evaluate the meat quality. The back fat samples were sampled to evaluate the fat quality. The vaccinated pigs had less dressing percentage and lower the back fat depth (P<0.01); however lean meat yield and eye muscle area were not significantly different between surgically castrated pigs and vaccinated pigs. Compared to the physical castrates, the vaccinated pigs had significantly increased elbow yield (P<0.01). There were no significant differences on shoulder, loin, belly and ham yield between the two treatment groups (P>0.05). Vaccination had no significant effect on the meat quality parameters of pH45, pH24, L*value, a*value, drip loss, shear force, cooking loss, intramuscular fat content (P>0.05); however the b*value was significantly lower in the vaccinated group (P<0.01). Compared to castration, a*value and b*value of fat were significantly higher (P<0.01), however there were no significant difference about L*value of fat, iodine value, hardness of fat and melting point (P>0.05). The results indicated that there were no significant differences texture profile analysis of muscle protein gel between the two treatment groups (P>0.05). But it had the tendency to improve storage modulus (G’) of salt-soluble meat proteins gel.The second part:The experiment was designed to study the effects of a GnRF vaccine on the contents of amino acid, IMP (inosine monophosphate) and fatty acids of vaccinated pork. The results indicated that there were no significant effects of the GnRF vaccine on ratio of essential amino acid:total amino acid (38.89%,38.95%) and flavor amino acid: total amino acid (41.06%,41.02%) of the pork between vaccinated pigs and physically castrated pigs (P>0.05). The IMP content in vaccinates was significantly higher than in physically castrated ones (P<0.05). On intramuscular fatty acids content, there was no significant difference about both the content of total saturated fatty acid and total monounsaturated fatty acid in two treatment groups (P>0.05). However total polyunsaturated fatty acid in vaccinates was significantly higher than in physically castrated ones (P<0.01). The arachidic acid (C20:0) concentrations in vaccinates was significantly lower than in physically castrated ones (P<0.01). The linoleic acid (C18:2) concentrations in vaccinates, were significantly higher than in physically castrated ones (P<0.01); The linolenic acid (C18:3) concentrations in vaccinates, were higher than in physically castrated ones (P<0.05). Identically, on fatty acids content of carcass fat, total SFA and total MUFA concentrations in vaccinates had no difference (P>0.05), however total PUFA concentrations in vaccinates was significantly higher than in physically castrated ones (P<0.01).The third part:The experiment was designed to study the effects of a GnRF vaccine on nutritional characteristics of the testis in the testis of vaccinated pigs, the contents of moisture, crude protein, ether extract, ash and nitrogen free extract were82.84%,12.98%,3.24%,0.97%and0.03%respectively. Generally speaking, the contents of each kind of nutrient component were balanced. The content of PUFA was28.38%. The content of Leu amino acid was0.81g/100g, and was more than other essential amino acids content.According to the above results, vaccinated pigs had less carcass yield and reduced the back fat depth. Vaccination could ameliorate the color of meat, improve the meat quality in a certain extent; the GnRF vaccine could increase the content of IMP in longissimus muscles, and increase the content of PUFA in longissimus muscles and back fat, consequently get higher nutritional pork. In the testis, the contents of each kind of nutrient component were balanced, and testis had essential amino acids for human, and the contents of PUFA were high. So the testis had edible value. |
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