Effects of immunocastration performed at two live weights on the growth physiology, temperament and testicular development of feral beef bulls

Abstract

The aim of this study was to examine the effect of administering an anti-gonadotropin-releasing hormone vaccine (Improvac ® , developed for pigs) on the performance, temperament, testicular development, and hormone and metabolite profiles of feral bulls (Bos taurus) vaccinated at two different live weights (LW). In all, 16 Serrana de Teruel animals were involved in this 2 x 2 factorial design using the factors LW (LIGHT vs. HEAVY) and vaccine treatment (control, C vs. vaccinated, VA). All animals received the same diet (ad libitum concentrate plus straw) over a 164-day fattening period. Temperament was assessed using chute and flight speed tests. Testicular diameter and subcutaneous fat thickness were recorded. Testosterone, IGF-1, urea, NEFA, and creatinine profiles were analyzed. Bull weight gain was reduced in VA compared to C animals, regardless of the initial LW. The vaccine did not affect the temperament tests, subcutaneous fat thickness or NEFA and creatinine concentrations and had minor effects on linear body measures. The vaccine inhibited testicular growth, reduced plasma testosterone to residual levels, and increased urea concentrations. LIGHT-C animals exhibited increased mean plasma IGF-1 concentrations compared to LIGHT-VA animals. In conclusion, vaccination reduced bull growth and sexual development irrespective of LW at immunization.

Habituation of common eland (Taurotragus oryx) to intensive routine handling, and the effect of immunocastration thereon

“…Additionally, the fAM concentrations were unable to explain the differences in temperament scores in the male common eland in the present study, suggesting that genetic and environmental factors have a larger influence on their response to handling than their androgen levels. Noya et al (2019) studied the influence of immunocastration on the temperament of feral bulls with different live weights, but immunocastration had no influence, which is in line with the outcome of the present study. Androgens positively influence muscle fibre hypertrophy, and thus the growth and development of animals, which makes male animals more muscular, but also potentially more aggressive (Price et al, 2003).…”

“…Such attributes give male animals the opportunity to defend themselves, and to strive to surpass conspecifics in a social group by increasing their social rank (Pelletier and Festa-Bianchet, 2006), but this also makes them easily reactive to novel objects, due to their tendency for excitable temperaments. Noya et al (2019) also suggested that the inability of immunocastration to influence temperament might be related to other factors other than decreased androgen production, such as genetics and environment. Like other social animals, common eland are sensitive to their environment, and learn to improve their chance of survival by adjusting their behaviour through postural lateralization and ritualization (Kiley-Worthington, 1978;Wirtu et al, 2005;Bordes et al, 2018).…”

“…The combination of behavioural training together with handling in a hydraulic chute system after a mild sedative was successfully used by Wirtu et al (2005) to handle female eland for transvaginal ultrasound-guided oocyte retrieval, but the animals showed increased glucose levels which indicates that significant stress was still experienced (Phillips et al, 1998) While various methods of castration have been documented to reduce aggressive behaviour, immunocastration is mentioned as more welfare-friendly overall (Price et al, 2003;Moreira et al, 2016). Principally, immunocastration reduces aggressive behaviour by blocking the production of testosterone by the testes (Noya et al, 2019). Decreasing the incidences of aggressive behaviour in captive male eland is beneficial for the welfare of the herd and handlers, particularly due to their large body size and horns.…”

Effectiveness of a New Recombinant antiGnRH Vaccine for Immunocastration in Bulls

“…Differences between studies could be influenced by the age at which animals are castrated. Older animals are more susceptible to significant weight loss and stress, as suggested by Noya, Ripoll, Casasús, and Sanz [ 41 ]. In agreement with Amatayakul-Chantler et al [ 5 ], the greater final LW of immunocastrated bulls in this study seems to corroborate the advantages of immunocastration over surgery.…”

Multiple-Pathway Synergy Alters Steroidogenesis and Spermatogenesis in Response to an Immunocastration Vaccine in Goat

“…A series of complex biological processes occurred after immunocastration in animals, including retardation of testicular development, hormonal secretion, and spermatogenesis [ 18 ]. So far, previous studies have primarily focused on investigating changes in genes and pathways in the testes after testosterone deficiency in rodents [ 19 , 20 ].…”