The effect of different levels of whey powder on growth performances traits, apparent digestibility of nutrients, carcass quality and serum parameters in fattening male crossed Zell lambs

The use of dairy by-products as a new feed source in order to reduce the costs of raising livestock is very important. Whey powder is a residual cheese or casein, which is one of the animal proteins used in the human food chain. It is also a feed source of protein and contains some useful minerals. Whey can be used in the diet of livestock due to its proper nutrient balance. Also, the fact that whey can reduce the consumption of concentrate without any negative effect on daily weight gain and feed conversion ratio, so the purpose of this study was performed to investigate the effect of using different levels of whey powder in diet on growth performances traits, apparent digestibility of nutrients and some blood parameters in fattening male crossed Zell lambs.

To perform this study, 24 mixed fattening Zell lambs were examined with a means age of 4.5±0.52 months and a means initial weight of 24±2 kg in a completely randomized design for 90 days. Experimental treatments included control treatment (without adding whey powder in the diet) and treatments containing 1.5, 3 and 4.5% whey powder in the diet. Chemical analysis of whey powder used included pH, 6.8 to 5.8, protein 12.5%, lactose 64%, fat 1.5%, moisture 4.5%. Whey powder used in the study was given to the experimental animals at different levels after mixing with the diet. The daily diet was given as a TMR to the animal twice and the amount consumed was recorded. Live weight measurement was performed every 14 days with 12 hours of feed and water deprivation. Measurement of the apparent digestibility of nutrients in the last days of the experiment as well as the study of carcass traits and blood parameters were performed on day 90 of the experiment.

The growth performance results of experimental lambs showed that there was a significant difference in end weight, DMI and daily weight gain between experimental treatments (P <0.05); So that the highest final weight and daily weight gain was observed in the treatment containing 4.5% whey and the highest dry matter intake was observed in the treatment containing 3% whey. The results of apparent digestibility of nutrients showed that there was a significant difference in apparent digestibility of dry matter, crude protein and NDF between experimental treatments (P<0.05). The highest apparent digestibility of dry matter and crude protein was observed in the treatment containing 4.5% whey and the highest apparent digestibility of NDF was observed in the treatment containing 3% whey. The results of some blood parameters showed that there was a significant difference in the concentration of glucose, triglyceride, HDL and BUN between experimental treatments (P<0.05). The results of quantitative traits of carcasses of fattening lambs showed that there was a significant difference in hot carcass weight, hot carcass percentage, cold carcass weight, cold carcass percentage, thigh percentage and shoulder percentage between experimental treatments (P<0.05). The results of qualitative traits of carcasses of fattening lambs showed that there was a significant difference in the rate of TBARS of the straight muscle 48 hours after slaughter between experimental treatments (P <0.05).

The overall result of the present study showed that the weight at the end of the fattening period, dry matter intake and also the apparent digestibility of nutrients were significantly improved by consuming 3 and 4.5% levels of whey powder. There was a higher carcass percentage and improvement in valuable carcass parts in the treatment containing 3% whey powder.