Open access publications in the SLU publication database

Abstract

This thesis characterizes reproductive traits of Ethiopian male goats raised under extensive husbandry and subjected to differential nutritional management. A total of 177 extensively-managed indigenous bucks of 5 breeds (i.e., Arsi–Bale [AB], Central Highlands [CH], Afar, Boran and Woito-Guji [WG]) were selected following stratified random sampling.The bucks were compared according to three age classes (<14 mo [young], 14–19.5 mo [intermediate] and 19.6–24 mo [old]) to determine whether breed and age influenced body size, testicular traits and epididymal sperm morphology. Bucks of a single goat breed (Ogaden; n= 35), selected by simple random sampling, were used to determine responses to differential nutritional treatments. Dietary treatments consisted of native hay fed ad libitum (control, C), native hay supplemented with 1% of body weight (BW) of agro–industrial by-products (Treatment 1, T1), native hay supplemented with 1% of BW of khat (Catha edulis) leftovers (Treatment 2, T2) and khat leftovers fed ad libitum (Treatment 3, T3). Breed, age and their interaction affected (P<0.05 to P<0.001) BW, body condition score (BCS), scrotal circumference (SC) and testicular weight (TW). Comparing all age classes, Boran displayed the highest (P<0.05) BW, greatest SC and heaviest TW, while Afar displayed the lowest values for these characteristics. Expressed as percentage of BW, Afar bucks had the highest TW. Regarding epididymal sperm morphology, most acrosome defects were displayed by CH (P<0.05) while AB mainly showed loose sperm heads (P<0.05). Bucks from a lowland agroclimate (i.e., Afar, Boran and WG) displayed more total sperm-head abnormalities (P<0.05) than did bucks of highland breeds (i.e., AB and CH). Younger bucks showed more (P<0.05) loose sperm heads, while older bucks had more (P<0.05) acrosome defects. Bucks fed according to the T1–T3 treatments improved (P<0.05) their BW, BCS, testicular size and testicular weight compared to controls. Goats in treatment groups T1–T3 showed higher (P<0.05) sperm motility, sperm concentration per mL and total number of spermatozoa per ejaculate compared to controls. Of groups T1–T3, bucks in T3 had the highest BW and testicular size. Feeding goats according to the T1–T3 regimes improved (P<0.001) feed dry matter (DM) and nutrient intake, and the occurrence of morphologically normal spermatozoa, compared to controls. Of the T1–T3 treatments, feeding according to T3 and T2 resulted in higher (P<0.05) DM, organic matter and gross energy intakes, while T1 followed by T3 resulted in the highest (P<0.05) crude protein intake, and T3 the highest occurrence of morphologically normal spermatozoa. In conclusion, body size, testicular traits and sperm morphology of Ethiopian bucks raised under extensive management were influenced by breed and age. Nutritional supplementation with khat leftovers and an agro–industrial by-product mix improved feed intake, growth and semen characteristics; these feedstuffs could be considered alternative feed resources to enhance goat production under smallholder farming systems in Ethiopia.