The Effect of Different Levels of Whey Powder on Growth Performance, Fermentation Parameters, Ruminal Morphology, Degradability and Microbial Protein Biosynthesis in Fattening Lambs

Introduction : 

One of the valuable unconventional foods is whey powder, which is a by-product of cheese production. Whey powder is used as an important source of energy and protein in animal nutrition. By reviewing the composition of whey powder based on dry matter and comparing it with the needs of livestock, its nutritional value can be understood. Whey powder as a feedstuff also has properties of a prebiotic; it contains a significant amount of lactose that is not absorbed to a large extent, but is fermented and converted to lactic acid and volatile fatty acids, which may stimulate the establishment of lactobacilli in the small intestine. Whey powder in animal feed, in addition to preventing environmental problems, reduces feed costs and improves yield. Adding whey powder to this juice probably improves and increases the weight of animals fed with whey powder by stimulating the microorganisms of the digestive system and as a result, by better synthesizing the required nutrients and improving the absorption of nutrients from the digestive system. This study was conducted to determine the effect of different levels of whey powder on growth performance, fermentation parameters, ruminal morphology, degradability and microbial protein biosynthesis in fattening Zell lambs.

In the first experiment, ruminal degradability of dry matter and crude protein were measured with nylon bag technique using three fistulated Zell sheep with mean weight of about 40 kg and mean age of about 10 months. In this experiment, nylon bags made of polyester (Dacron) with a pore diameter of 45 ± 5 micrometers and dimensions of 9 ×7 cm were used. Incubation time in rumen consisted of 0, 4, 8, 16, 24, 36, 48, 72 and 96. In the second experiment, the effect of different levels of whey powder on fermentation parameters, ruminal morphology and microbial protein biosynthesis, an experiment in completely randomized design (CRD) with four diets containing zero, 1.5, 3 and 4.5 % whey powder on 24 male lambs with initial mean weight of 24± 2 kg and mean age of 4.5±0.52 months for 90 days was performed. Every day, a certain amount of feed in the form of TMR was weighed for each experimental treatment and was provided to the experimental lambs at 8 am and 5 pm. To determine the daily weight gain of the experimental lambs, weighing was done with a digital metal scale every 14 days until the end of the 90th day of the experiment. Data obtained were analyzed by statistical software SAS (version 1.9). Comparison of experimental treatment means was done using Duncan's multi-range test at a significance level of 0.05.

A significant difference was observed for final weight, dry matter consumption and daily weight gain among the experimental treatments, and the highest values ​​were found in the 4.5% whey powder treatment. Significant differences were observed in pH, ammonia nitrogen, total volatile fatty acids, and acetic acid among the experimental treatments. Specifically, the treatment with 4.5% whey powder exhibited the highest levels of fermentation parameters. Additionally, the 4.5% whey powder treatment showed the highest population of total bacteria at 2 and 4 hours after feeding, as well as the highest protozoa population at 4 hours after feeding. Moreover, the 4.5% whey powder treatment demonstrated the highest thickness, height, and density of villi compared to the other experimental treatments. Furthermore, significant differences were found in the degradability parameters of dry matter and crude protein among the experimental treatments. In particular, the soluble, degradable, and effective rumen degradability in passage rate constant parts exhibited significant differences. The amount of gas produced from the fermentable part also showed a significant difference between the experimental treatments. The control treatment showed the lowest amount of gas produced from the fermentable part, which was significantly lower than the other treatments. However, no significant difference was observed between the experimental treatments in other parameters of gas production.
The highest amount of microbial protein production was observed in the treatment of 3% whey powder.

The consumption of higher levels of whey powder at a maximum of 4.5% in the diet of fattening lambs improved the growth performance and some ruminal indices and decomposability of dry matter and crude protein.