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

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 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 can be used as a source of protein in the diet of fattening animals. This study aimed to assess the effect of feeding different levels of cotton by-products on performance, degradability, rumen fermentation parameters, microbial protein, and microbial population in fattening lambs.
In this study, 24 male Afshari lambs with a mean weight of 30±0.7 kg and a mean age of four months were used in a completely randomized design with four treatments and six replications for 90 days. The experimental treatments included: 1) a diet without cotton by-product (control), 2) a diet containing 33.33% cotton by-product instead of alfalfa, 3) a diet containing 66.66% cotton by-product instead of alfalfa, and 4) a 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, Iran. After entering the test site, it was chopped and then mixed with alfalfa in certain 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. 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.
The growth performance results showed that replacing 100% cotton by-products 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-products instead of dry alfalfa had the highest concentration of total volatile fatty acids, acetic acid, and acetate to propionate ratio (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 the substitute cotton by-product instead of dry alfalfa in the diet increased the total population of rumen fluid bacteria (P<0.05) but had no significant effect on the protozoan population. The results of meta-measures of dry matter degradability, crude protein, and NDF showed that there was no significant difference between experimental treatments.
The general results of the study showed that replacing cotton by-products by 66.66 or 100% instead of dry alfalfa in the diet improved the performance, increased the bacterial population, and concentration of total volatile fatty acids in the rumen fluid of fattening lambs. The use of cotton by-products can be a suitable substitute for alfalfa in the diet of fattening lambs without negative effects on growth performance and rumen fermentation indices.