Testes function and feedlot performance of bulls actively immunized against gonadotropin-releasing hormone: effect of age at immunization.

Abstract

Testes function, feedlot performance, and carcass traits were evaluated in bulls actively immunized against gonadotropin-releasing hormone (GnRH) at different ages. Bull calves were randomly assigned to one of seven treatment groups (n = 15 calves/group). Calves were unimmunized (Group 1), immunized at 1.5, 4, 7, or 12 mo of age with a GnRH-keyhole limpet hemocyanin (KLH) conjugate (Groups 2 to 5, respectively), or castrated at 4 mo of age (Groups 6 and 7). Immunized bulls did not receive a secondary, or booster, immunization. Calves in group 6 received Synovex-C at castration and Synovex-S at weaning and feedlot entry. Anti-GnRH titer was evident at slaughter in all immunized bulls. However, the final immune response of bulls immunized at 1.5 mo was significantly lower than the response of bulls immunized at later stages of development. Final scrotal circumference and testis weight in bulls immunized at 4, 7, or 12 mo of age were significantly reduced relative to unimmunized bulls. The final live weight, feedlot gain, and carcass weight of immunized and unimmunized bulls did not differ (P > .05) from the same parameters in steers implanted with Synovex. Longissimus muscle area, marbling score, and backfat thickness did not differ between immunized and unimmunized bulls. The sex class score of the carcasses of immunized bulls did not differ from the score of steer carcasses. In contrast, a significantly higher proportion of carcasses from unimmunized bulls graded as bullock carcasses. Taken together, these data indicate that a single immunization against GnRH at 4 to 12 mo of age results in significant attenuation of testicular growth in bulls. These data also demonstrate that immunization against GnRH reduces the masculinity of carcasses from bulls, but does not affect feedlot performance, longissimus muscle area, marbling score, or backfat thickness. These results suggest that single immunization with the GnRH-KLH conjugate may have practical utility as a noninvasive alternative to surgical castration in management of beef cattle.

GnRH immunocontraception of male cats

“…In most reports, a series of prime-boost treatments was given and the follow-up period was short. GnRH immunization resulted in decreased testosterone, LH, and progesterone concentrations, testes size, estrus cycling, libido, aggression, and androgen-related taint in calves [18][19][20][21][22], piglets [23][24][25][26][27], and lambs [28][29][30]. Similar responses were observed in adult stallions [31] and cows [32].…”

Effects of castration age, dietary protein level and lysine/methionine ratio on animal performance, carcass and meat quality of Friesian steers intensively reared

“…The difference between the two groups of castrated animals in the current study is small. This may be explained by differences in performance between bulls and steers that are mainly manifested after puberty as a consequence of a greater production of anabolic hormones by the testes (Adams et al, 1996) which occurs at 9 months in Holstein bulls (Lunstra et al, 1978). Therefore, Knight et al (1999) have proposed post-pubertal castration of bulls at 13 months of age as a way to maintain the performance advantages and the benefits of castration on meat quality characteristics afterwards.…”

“…On the other hand, castration reduces average daily gain and feed efficiency (Rotta et al, 2009) as well as the incidence of a high ultimate pH, changing its chemical composition and fatty acid profile (Aricetti et al, 2008). The differences in performance between bulls and steers are mainly expressed after puberty as a consequence of a greater production of anabolic hormones by the testes (Adams et al, 1996) which happens at an age of 6-9 months in Friesian bulls (Lunstra et al, 1978). Knight et al (1999) have proposed post-pubertal castration of bulls at 13 months of age as a way to maintain the performance advantage and benefits of castration on meat quality.…”

Effects of castration age, protein level and lysine/methionine ratio in the diet on colour, lipid oxidation and meat acceptability of intensively reared Friesian steers

“…All L*, a* and b* were typical of the meat from beef reared intensively, characterised by a lower physical activity and fed a diet that is low in roughage and high in concentrate (Guerrero et al, 2013). The increased production of anabolic hormones by the testes (Adams et al, 1996) after the onset of puberty, which occurs at 9 months of age in Holstein bulls (Lunstra et al, 1978), is the main factor that creates differences in the characteristics of the meat from bulls and steers (Seideman et al, 1982). In our study, the animals were castrated at either 15 days of age or at 5 months of age, and slaughtered at about 12 months of age.…”