Abstract

Historically in New Zealand male lambs were castrated at the time of docking, however, there has been a move to instead create short-scrotum males, in which the testes are pushed within the body cavity and the scrotum removed (Johnson et al. 2007). This results in short- scrotum males, having similar physiological characteristics to entire ram lambs, except that they are almost always infertile and, therefore, do not present a management risk if they are accidently mixed with ewes or ewe lambs during the mating season. The normal ultimate pH of lamb meat is considered to be 5.50 to 5.80, with values above 5.8 and in particular above 6.0 considered high, and resulting in negative meat quality outcomes. There have been a number of studies that have investigated whether or not sex differences in the ultimate pH of lamb exist. The results are not always consistent with some studies reporting elevated ultimate pH in non-castrated male lambs (Johnson et al. 2005; Bain et al. 2009), whilst others have shown no differences (Kerslake et al. 2012; Schreurs 2013). In commercial farming operations there is a mix as to how farmers manage their lambs of different sexes during the finishing period prior to slaughter, and in many farming operations this period coincides with the on-set of the breeding season.

Given the most recent papers in this area have concluded that there is no sex-effect on ultimate pH, the purpose of this paper is to report on data collected from a trial that set out to invoke high ultimate pH (to investigate potential live-animal predictors of high ultimate pH) in short-scrotum male lambs during the breeding season.

Johnson, PL, AD Stuart, and A Mackie

Proceedings of the New Zealand Society of Animal Production, Volume 77, Rotorua, 194-196, 2017