Correlations among South African indigenous ram-lambs’ physiological age and various mating behaviours at puberty

Abstract

<title>Abstract</title> Livestock must maintain traits that are beneficial to their survival and propagation, so that those genotypes that express the optimal phenotype most reliably, will be selectively favoured. One of these traits is the animal’s physiological age, which is correlated with, but not causal to its chronological age, and affects the animal’s age at attainment of puberty - an important management parameter and indicator of environmental adaptation. This study aimed to characterise the mating behaviours of pubertal ram-lambs of three of South Africa’s oldest indigenous sheep breeds, Bapedi (BP), Namaqua-Afrikaner (NM) and Zulu (ZL), which are landraces to areas of South Africa with different microclimates. Sampling included visual assessment of various mating behaviours (e.g., nosing, mounting) and measurement of bodyweight, scrotal circumference, and blood serum testosterone concentrations. The study found that NM ram-lambs were physiologically younger than BP and ZL ram-lambs at a similar chronological age, as bodyweights and blood serum testosterone concentrations between-breeds were similar (P &gt; 0.05) but significant between-breed differences of scrotal circumferences were found (P &lt; 0.05) at most ages, wherein NM ram-lambs had lower mean scrotal circumferences, had the lowest cumulative observations of all appraised mating behaviours; and began displaying their first mating behaviour (nosing) one month later than BP and ZL ram-lambs did. Thus, NM ram-lambs displayed younger physiological age, likely as an adaptation to the hotter and drier microenvironment to which they are indigenous. It is recommended that such breeds be profiled and used in mixed-breeding programs, as their adaptation to harsher environments will be invaluable as climate change’s impacts become more apparent in sub-Saharan Africa.