Observation on the effect of levels of salt and stocking periods on putrefaction in preserving sheep skin at three altitudes in Ethiopia

Abstract

A field experiment was conducted to determine the effect of different levels (20, 30, 40, 50 and 60%) and durations (30, 45 and 60 days) of salt preservation for controlling putrefaction on sheepskin at low (Metehara), mid (Debre Zeit) and high (Debre Birhan) altitudes of Ethiopia to determine technically acceptable levels of salting and stocking periods. A randomized complete block design was applied, in which site (altitude) and stocking (preservation) period in shed were taken as blocks over the five treatments. Each treatment group had ten replications across sites and treatments, to test the null hypothesis that there is no difference in putrefaction due to different levels of salt, stocking periods and altitude. Therefore, a total of 3x3x5x10, or 450 individual skins were used in the trial. The experimental skins were collected from the major central market in Addis Ababa, and were randomly allocated to the three sites. The proportion of skin area putrefied (%) was used as the response variable. The results of the aggregate analysis for the three sites showed that the proportion of skin area putrefied differed highly significantly (P<0.0001) between sites, salt levels and stocking periods. The largest overall least squares mean putrefaction proportion of 17.15% was observed in Metehara, followed by 5.05% for Debre Zeit and 0.39% for Debre Birhan. The interaction of site with salt levels was found to be very highly significant, which led to separate analysis of the data by site. The results showed that in Metehara up to 40% salt level is required to meaningfully arrest putrefaction in preserved sheepskin for stocking periods of up to 60 days. For Debre Zeit and similar agro-ecological areas, a salt level of 30% suffices to provide similar protection. For areas like Debre Birhan, and possibly those at higher altitudes, salt levels between 20 and 30% provide adequate preservative for up to 60 days.