‏ Effect of feeding different levels of cotton by-product on performance, degradability, rumen fermentation parameters, microbial protein, and microbial population in fattening lambs

Introduction: Today, the increase in the world's population, especially in third world countries, has caused an increase in the demand for livestock products, which will subsequently require more livestock products and more food resources to meet these needs. The use of waste from factories of agricultural transformation industries in feeding livestock helps to make the cost of breeding more economical. Since cotton by-product is considered as a product of cotton ginning factories, it can be said that due to its nutritional value, its use in animal diets is to avoid wasting this huge source of feed. Cotton by-product contains 86.9% dry matter, 12.3% crude protein, 57.7% NDF, 12.2% ash, 1.7% calcium, 0.31% phosphorus and 1.06% Net energy. The results of the studies showed that cotton waste has the ability to be used as a source of protein in the diet of fattening animals. The expected hypothesis of the study was the significant effect of feeding different levels of cotton by-product on performance, degradability, rumen fermentation parameters, microbial protein, and microbial population in fattening lambs.
Materials and methods: In this study, 24 male Afshari lambs with a mean weight of 30±0.7 kg and a mean age of 4 months were used in a completely randomized design with 4 treatments and 6 replications for 90 days. The experimental treatments included: 1) diet without cotton by-product (control), 2) diet containing 33.33% cotton by-product instead of alfalfa, 3) diet containing 66.66% cotton by-product instead of alfalfa and 4) diet containing 100% cotton by-product instead. Hay was based on dry matter. The cotton by-product used in this study was obtained from Mahosh cotton ginning factory located in Razavi Khorasan province, Neyshabur city. After entering the test site, it was crushed by a chopper machine and then mixed with alfalfa with specified percentages; it was consumed by experimental lambs. Growth performance traits including daily feed intake, daily weight gain and feed conversion ratio were measured during the experiment period. To measure ruminal fermentation parameters and bacteria and protozoa populations, the rumen fluid of the experimental lambs was taken from the rumen on the 90th day of the experiment, three hours after morning feeding using an esophageal tube. In order to determine urine purine derivatives, the total 24-hour urine production of each animal was collected in a special container under the metabolic cage on five sampling days. The number of three fistulaized Afshari sheep with a mean weight of about 50±2 kg and a mean age of approximately 11 months was used to estimate the parameters of degradability of dry matter, crude protein and NDF.
Results and discussion: The growth performance results showed that replacing 100% of cotton by-product instead of dry alfalfa increased feed intake, increased daily weight and decreased feed conversion ratio (P<0.05). The results of ruminal parameters showed that the treatment containing 66.66 and 100% replacement of cotton by-product instead of dry alfalfa had the highest total concentration of volatile fatty acids, acetic acid and the ratio of acetate to propionate (P<0.05). There was no significant difference between the experimental treatments in the amounts of purine excretion derivatives and microbial protein production. The use of 66.66% of replacing cotton by-product instead of dry alfalfa in the diet increased the total rumen fluid bacteria population (P<0.05), but did not have a significant effect on the protozoa population. The results of meta-measures of dry matter degradability, crude protein and NDF showed that there was no significant difference between experimental treatments.
Conclusions: The general results of the study showed that replacing cotton by-product by 66.66 or 100% instead of dry alfalfa in the diet improved the performance, increased the bacterial population and the total concentration of volatile fatty acids in the rumen fluid of fattening lambs. The use of cotton by-product can be a suitable substitute for alfalfa in the diet of fattening lambs without negative effects on growth performance and rumen fermentation indices.
Keywords: Afshari lamb, Degradability, Microbial protein, Cotton by-product, Rumen microbial population.
Conflicts of interest: The authors declare no conflicts of interest.
Funding: The authors received no specific funding for this work.
Acknowledgments: The authors would like to acknowledge the Faculty of Animal Science of the Sari University of Agricultural Science and Natural Resources for their help in conducting this study.