Effects of different feeding regimes on growth performance, intake, digestibility, and ruminal metabolic and morphological characteristics in Awassi lambs

Abstract

The aim of this research was to investigate the effects of different feeding regimes on the growth performance, nutrient intake, apparent digestibility, and ruminal metabolic and morphological characteristics of Awassi lambs. A total of 96 lambs (initial age: 10 ± 1 weeks; mean body weight: 23.62 ± 0.01 kg) were divided into four dietary groups in a completely randomised design (eight replicates/diet, three lambs/replicate). The four diets were as follows: control (CON: 50% barley grain, 50% long lucerne/alfalfa hay), diet 1 (D1: 100% complete pelleted feed), diet 2 (D2: 40% concentrate pellets, 60% long lucerne hay), and diet 3 (D3: 60% concentrate pellets, 40% roughage pellets). The lambs were fed the four diets for 84 days, and growth performance indicators were assessed twice (every 42 days) during this period. After 84 days, all target parameters, including morphometry, fermentation indicators, and bacterial activity in the lambs' rumens, were assessed. The primary findings indicated that treatments D2 and D3 led to increased body weights, weight gains, and feed intakes. Lambs fed D2 had a higher dry matter intake and nutrient digestibility, along with increased papilla height, density, and total surface area. Specific fibre-degrading bacteria were more prevalent in D1, D2, and D3 than in the CON lambs. The higher total volatile fatty acid concentrations measured in the rumens of the D1, D2, and D3 lambs signified an improved fermentation profile. In conclusion, these results highlight the potential of complete diets and concentrate pellets with roughage sources to optimise performance, rumen health, and nutrient utilisation in lambs. (Submitted 31 August 2025; Accepted 21 November 2025; Published 03 December 2025)