Relationship between production characteristics and breeding potential of 25-month old extensively managed Bonsmara bulls

Abstract

________________________________________________________________________________ AbstractThe aim of the study was to determine if the breeding potential of 25-month old Bonsmara beef bulls could be predicted from production characteristics. Forty-one Bonsmara bulls were included in an on-farm performance test (also known as the Phase D growth test) for a period of 180 days. At an average age of 24.7 months the bulls were subjected to a libido test and overall breeding soundness evaluation (OBE). The bulls were categorised into independent breeding potential categories according to the scores they obtained for the measured reproductive traits. The categories included sperm morphology and motility. One-way ANOVA revealed that none of the production traits measured had a significant effect on the different breeding potential categories. A positive correlation (r = 0.33) was recorded between pre-weaning growth rate and percentage morphologically normal sperm, while a negative correlation (r = -0.36) was recorded between total acrosomal-and flagellar sperm defects and pre-weaning growth. A positive correlation was demonstrated between sperm motility and pre-weaning growth (r = 0.36), and a consequent negative correlation (r = -0.38) between the percentage aberrant sperm movement and pre-weaning growth. The correlation between the percentage morphologically normal sperm and percentage progressively moving sperm was r = 0.50, while the correlation between percentage morphologically normal sperm and aberrant and immotile sperm was r = 0.48 for both variables. The number of total defects correlated highly significantly with flagellar and acrosomal defects (r = 0.72 and r = 0.93, respectively) and correlated poorly with the total number of nuclear defects (r = 0.32). These results suggest that total sperm defects were mainly due to acrosomal and flagellar defects, rather than nuclear defects and as the percentage morphologically normal sperm decreased, the motility also decreased. High growth rates before weaning may have a positive effect, while high growth rates after weaning may have a negative effect on the breeding potential of a bull. None of the measured reproductive and production traits had a significant effect on libido score and thus, cannot be used to predict the libido of young extensively maintained bulls. ________________________________________________________________________________

Testicular development Sindi bulls

“…Em trabalhos com touros taurinos da raça Bonsmara aos 25 meses apresentou circunferência escrotal de 37 cm (Scheepers et al, 2010), touros da raça Devon, Red Angus e Polled Hereford, todos com idade média de 36 meses, obtiveram circunferência escrotal de 38,06cm, 37,88cm e 37,86cm, respectivamente (Menegassi et al, 2011), touros da raça Aberdeen Angus aos 48 meses revelaram circunferência escrotal média de 37,2 cm (Gottschall & Mattos, 1997).…”

A Perspective on the Impact of Reproductive Technologies on Food Production in Africa

“…Dietary manipulation of reproduction has been investigated in small stock by focussing on the effects of high protein intake. The effects of different protein sources on ovulation rates were also studied in sheep (Webb et al 2010) based on the concept of a lower level of protein degradation in the rumen and subsequent availability of protein in the lower digestive system. The results indicate that dietary protein supplementation in ewes has a positive effect on follicle development, but only a marginal effect on the number of lambs born per ewe mated (Webb et al 2010).…”

“…The latter as well as fertility tests before the onset of the breeding season contribute significantly towards better conception rates in beef herds. However, reproductive (semen quality) and growth data does not appear to be reliable predictors of libido in extensively managed bulls (Scheepers et al 2010). Scrotal circumference is used more effectively to select beef bulls for fertility and semen production potential.…”

Evaluation of some reproductive indices of the White Fulani indigenous bulls in Kwara State, Nigeria

“…Reproductive capacity in bull is influenced by semen quality and quantity, male dominance effect during breeding, libido and mating ability (Scheepers et al, 2010). However, reports on some of the reproductive indices of WF bulls are not adequate in Kwara state.…”