Endocrine, growth, and carcass characteristics of bulls immunized against luteinizing hormone-releasing hormone fusion proteins

Abstract

This study evaluated the effectiveness of a LHRH fusion protein vaccine on endocrine changes, feedlot performance, and carcass quality of bulls compared with steers and hormone-implanted steers. Crossbred bulls (n = 30; mean weight, 179 +/- 4 kg; mean age, 130 +/- 2 d) were randomly assigned to three treatment groups: 1) castrated (castrated; n = 10); 2) castrated-implanted with trenbolone acetate (implanted; n = 10); and 3) immunized against a cocktail of recombinant fusion proteins, ovalbumin-LHRH-7 and thioredoxin-LHRH-7 (immunized bulls; n = 10). Blood was collected every 2 wk to evaluate antibody and hormone concentrations. Serum LHRH antibodies (P < 0.001) were detected in animals of the immunized group, which had reduced serum LH concentrations (P < 0.001) compared with the castrated groups and serum FSH concentrations, which did not decrease but were significantly different when compared with castrated and implanted animals. Serum testosterone concentrations in the immunized bulls were not different from the two castrated groups (P > 0.05) by d 60 after primary immunization. Initial mean scrotal circumference of the immunized bulls was 18.0 +/- 0.6 cm on d 0 and increased to 22.6 +/- 1.3 cm by d 310. No differences (P > 0.05) in ADG were observed among treatment groups. Immunized animals had an intermediate BW gain (P > 0.05) when compared with the castrates, whereas the castrated groups differed (P < 0.05) from each other. Carcass characteristics were similar (P < 0.05) among the three groups. Vaccinating bulls against a LHRH fusion protein cocktail suppressed LH and testosterone, which led to reduced testicular development and no bullock carcasses. Growth and carcass characteristics of the immunized animals were similar to the steers.

Vaccination against gonadotropin-releasing factor (GnRF) with Bopriva significantly decreases testicular development, serum testosterone levels and physical activity in pubertal bulls

“…Although it is known that testosterone has an anabolic effect, weight gain of vaccinated bulls which had low testosterone levels did not differ from control animals what is consistent with findings of previous studies [3][4][5][6]11,20]. This may be explained by the reduced physical activity in vaccinated animals improving their body condition.…”

“…As it has been shown in many investigations published during the last years [3][4][5][6][7][8][9][10]17,20,[29][30][31][32][33][34] vaccination against GnRF was able to induce an increase in anti-GnRF antibody titer.…”

“…The suppression of reproductive function using an anti-GnRF vaccine has been demonstrated in numerous studies in cattle [3][4][5][6][7][8][9][10][11][12][13], sheep [10,[14][15][16][17][18][19][20][21], pig [22][23][24][25][26][27][28], horse [29][30][31][32][33][34] and in wild animals [35][36][37][38][39].…”

Componentes Não Carcaça De Novilhos De Corte Submetidos À Castração Cirúrgica Ou Imunológica

“…A similaridade para esta característica deve-se à idade dos animais em que as castrações foram realizadas, todas em fase pré-púbere. Estudos avaliando o desenvolvimento corporal de bovinos machos castrados cirurgicamente ou imunologicamente em idade pré-púbere verificaram que os animais de ambos os grupos apresentaram desenvolvimento similar (10,11) ; dessa forma, a mesma intensidade de crescimento induz a semelhanças nos componentes periféricos. A castração em idade pré-púbere, sem que haja aproveitamento marcante da testosterona como hormônio natural de crescimento, é prática comumente realizada, na região Sul do Brasil.…”

“…No presente estudo, embora todos os animais tenham sido castrados, se considerarmos o intervalo entre castrações já descrito anteriormente, os resultados seguem uma lógica em comum com o trabalho mencionado acima. Por outro lado, ao comparar a castração imunológica à cirúrgica outras pesquisas obtiveram percentagem estimada de gordura cardíaca, pélvica e renal semelhante, porém para novilhos terminados em confinamento (10,21) . O conjunto destas gorduras representa o KPH, utilizado nos Estados Unidos pelo sistema USDA para determinação do Yeld Grade (grau de rendimento) de carcaças bovinas.…”