Effects of direct-fed lactic acid bacteria on weight gain and ruminal pH of two south African sheep breeds

Abstract

A ruminant’s digestion depends on microbial degradation of feed rather than endogenous enzyme degradation as in most monogastric animals. The study was conducted to assess the effects of Lactic Acid Bacteria (LAB) strains administered as direct-fed microbials on weight gain and ruminal pH of Damara and Meatmaster sheep breeds. Sixty-four Damara and Meatmaster sheep breeds [Damara males (36.6 } 8.3 kg); Damara females (28.9 } 6.9 kg); Meatmaster males (24.6 } 3.4 kg); Meat master females (21.5 } 3.1 kg)] were subjected to a 30-day trial and divided into five treatment groups as follows: pellets with no antibiotic and no probiotics administered (T1); pellets with no antibiotics, only Lactobacillus rhamnosus SCH administered (T2); pellets with no antibiotics, only Lactobacillus rhamnosus AF3G administered (T3); pellets with no antibiotics, with the combination of Lactobacillus rhamnosus SCH and Lactobacillus rhamnosus AF3G, administered (T4); pellets fortified with antibiotic and no probiotic administered (T5). The animals were fed on commercial pellets fortified with or without antibiotics. Animals were each weighed, and rumen fluids were collected using a stomach tube, and pH was read immediately, before and at the end of the trials. Data obtained were subjected to analysis of variance using SPSS version 4.0. The results showed that the effect of treatment, sex and some of their interactive effects were significant (p <0.001) on the body weight of sheep irrespective of breed. The effect of treatments revealed that the animals in the combination of probiotics gained more weight than those in other groups. Damara breed had a heavier body weight than Meatmaster while males were 6 kg heavier relative to females (p <0.001). Only breed was significant (p <0.05) on weight gained. Treatment (p <0.05), breed (p <0.001) and their interactive effect (p <0.05) were significant on ruminal pH. The highest pH value was 7.27 for the T5 group and 7.37 for the Damara breed. Results suggest that LAB may have beneficial effects on the growth performances of sheep and therefore may be suitable as future growth promoters in sheep production, as they don't have any harmful residues compared to antibiotics.