Dried whey is often used as a source of lactose in diets for weanling pigs. Whey is a co-product from dairy processing plants that is generated after fat and protein in milk has been used to produce cheese. Whey powder is therefore, low in protein because the majority of the milk protein ends up in the cheese during processing. However, some of the cheese that is produced may not be suitable for human consumption, but can instead be used as a feed ingredient for pigs after being blended with other ingredients to improve flowability and handling.  One of the cheese co-products that is currently being marketed contains 40 to 50% crude protein and has a high digestibility of amino acids. There is, however, limited information about the energy value of cheese co-products fed to pigs although it is expected that because of the high concentration of fat in cheese, the energy value will also be high. Therefore, it was the objective of this experiment to test the hypothesis that digestibility of energy and concentrations of digestible energy (DE) and metabolizable energy (ME) in a cheese co-product is greater than that in fish meal and enzyme treated soybean meal when fed to weanling pigs.

Animals, Housing, Experimental design, and diets

A corn based basal diet and 3 diets containing a mixture of corn and cheese co-product (Pro88; Keys Manufacturing Inc., Paris Illinois), corn and fish meal (Select Menhaden; Omega Protein, Reedville, VA), or corn and enzyme treated soybean meal (HP 300; Hamlet protein, Findley, OH) were formulated. Thus, a total of 4 diets were used. Thirty-two weanling pigs with an average initial BW of 14.0 ± 1.1 kg were allotted to a randomized complete block design with 4 diets and 8 replicate pigs per diet. Feed was supplied in meal form and pigs were limit fed daily at 3.2 times the maintenance energy requirement (i.e., 197 kcal of ME/kg of BW^0.60; NRC, 2012) of the smallest pig in each replicate. Pigs were fed experimental diets for 12 days. The initial 5 d were considered an adaptation period to the diet. Fecal markers were fed on d 6 and d 11. At the conclusion of the experiment, fecal and urine samples were analyzed and concentrations of DE and ME in each diet and in each ingredient were calculated.  

Results

The daily DM and GE intake were greater (P < 0.01) for pigs fed diets containing the cheese co-product, fish meal, or enzyme treated soybean meal compared with pigs fed the corn diet (Table 1). However, GE excretion in feces and urine was also greater (P < 0.01) from pigs fed diets containing cheese co-product, fish meal, or enzyme treated soybean meal compared with pigs fed the corn diet. Digestible energy and ME were greater (P < 0.01) in the cheese co-product diet than in the other diets, and DE in diets containing fish meal or enzyme treated soybean meal was greater (P < 0.05) than in the corn diet. The ME in the fish meal diet was also greater (P < 0.05) than ME in the corn diet.

The ATTD of DM was greater (P < 0.05) in cheese co-product and corn compared with fish meal, and DE and ME were greater (P < 0.05) in the cheese co-product than in the other ingredients. On an as-fed basis, DE and ME in fish meal and enzyme treated soybean meal were greater (P < 0.05) than in corn, and on a DM-basis DE and ME in enzyme treated soybean meal were greater (P < 0.05) than in corn.

Key points

• The cheese co-product used in this experiment had greater digestibility of DM than fish meal and enzyme treated soybean meal.
• The cheese co-product used in this experiment had greater DE and ME than fish meal and enzyme treated soybean meal.
• The cheese co-product used has a high digestibility of energy.

Table 1. Apparent total tract digestibility (ATTD) of gross energy (GE) and dry matter (DM) and DE and ME in corn, cheese co-product, fish meal and HP 300^1,2

            ^a-cLeast squares withi a row lacking a common superscript letter are different (P < 0.05).

         ¹Data are means of 8 observations per treatment.

         ²Cheese co-product = Pro88; Keys Manufacturing Inc., Paris Illinois; fish meal = Select Menhaden; Omega Protein, Reedville, VA; and enzyme treated soybean meal = HP 300; Hamlet protein, Findley, OH.