Effects of whey powder on fermentation quality, nutritive value, and digestibility of alfalfa silage

Alfalfa (Medicago sativa L.) is a perennial legume with a high yield which is also rich in vitamins and minerals. It can be used as animal feed in the form of green herbage, hay, or silage. Because grazing on fresh alfalfa can cause tympani, it is very limited (Jonker and Yu, 2016). Although the dried form is generally preferred as animal feed, the leaves are easily broken and lost during this process when drying to the appropriate storage moisture of 12%, also the botanical fraction balance (leaf:stem ratio) shifts toward the cellulosic structure. This decreases protein content, digestibility, and quality of the forage, reduces the alfalfa nutritional value, and increases the cost of feed. On the other hand, it could be possible to obtain successful silage by using additives that stimulate fermentation, such as water-soluble carbohydrates (Keener, 2019). Whey is a byproduct resulting from the processes of converting milk into cheese. It has high water content (>90%) and its major constituent is lactose (77% of the total solids). Whey powder (WP) is the dried form of it. It contains high content of lactose (69–76%), low content of water (<7%) and is rich in protein (β-lactoglobulin and α-lactalbumin), vitamins (B2, B5 and C) and minerals (EWPA, 2016). Each year, more than 200 mln t of whey is generated globally, and this value is increasing by ~2% each year (Mariotti et al., 2020). ABSTRACT. The aim of the study was to investigate the effects of whey powder (WP) on the fermentation quality, nutritive value, and digestibility of ensiled alfalfa (Medicago sativa L.). Alfalfa treated with different doses of WP (0, 2, and 4% fresh matter silage) was ensiled in plastic drums for 60 days. The results of the study revealed that the physicochemical composition and fermentation quality of the alfalfa silage improved and that mold growth was inhibited in the groups treated with 2 and 4% WP in comparison to that in the control. Production of CO2 (day 7) was much lower in silages treated with 2 and 4% WP (3.77 and 1.85 g/kg dry matter (DM), respectively) than in the control group (21.36 g/kg DM). In addition, in vivo dry matter digestibility (DMD) was much higher in the group treated with 4% WP (76.45%) than in the control one (55.82%). In this treatment group, all apparent digestibility of coefficients in vivo from crude nutrient contents and cell wall fractions significantly increased and hence raised the net lactation energy value from 1.18 to 1.31 Mcal/kg DM. However, although the in vitro DMD was higher in the silages treated with WP than in the control one and the dose was significant, there was no strong correlation between in vivo and in vitro values. According to our results, WP could provide an advantage for the conservation of alfalfa silage. In addition, WP could be evaluated as a sustainable silage additive. Received: 21 September 2021 Revised: 15 December 2021 Accepted: 1 February 2022