Enhancing lactation performance and energy utilisation efficiency through dietary inclusion of apple pomace silage...

Apple pomace (AP) and hempseed cake (HC) are used for replacing conventional feed ingredients in dairy farming, but their effects on energy partitioning remains insufficiently explored. This study investigated the effects of dietary inclusion of AP silage and HC to mid-lactation dairy cows on lactation performance and energy utilisation efficiency. Fifteen dairy cows (133 ± 2.6 d in milk, 637 ± 13.1 body weight, 2.4 ± 0.28 parities) were used in a 3 (treatments) × 3 (periods) Latin square design study with three treatments and three periods (24 d/period). Treatment diets included (dry matter [DM] basis) control (CON, basal diet containing 50.0% concentrates, 45.7% grass silage and 4.3% barley straw), AP (10% of AP replaced grass silage in the CON diet), and HC diets (10% of HC replaced concentrates in the CON diet). Dietary inclusion of AP or HC significantly increased DM intake (DMI) by 6.7% and 3.4% (P = 0.001), milk yield by 8.8% and 11.3% (P < 0.001), respectively, compared with the CON. Milk yield/DMI was the highest in the HC group, followed by the AP and CON groups (P = 0.022). Crude protein digestibility was higher in the AP group than in the CON group (P = 0.038). When compared with the CON, both AP and HC tended to increase rumen propionate production (P = 0.082) and significantly decreased rumen acetate-to-propionate ratio (P = 0.040). Urinary and methane energy outputs and heat production as a proportion of gross energy (GE) intake significantly decreased when diets were supplemented with AP and HC (P < 0.05), and the inclusion of AP also increased retained energy as a proportion of GE intake. Feeding AP and HC significantly decreased heat production/metabolisable energy (ME) intake by 10.7% and 7.6%, respectively (P < 0.001). Higher efficiency of ME used for lactation was observed in the AP and HC groups, increasing by 4.3% and 7.7% (P = 0.017), respectively, compared to the CON. Overall, AP silage and HC are promising alternatives to high-quality grass silage and conventional protein feeds in dairy cow diets. These by-products can enhance the lactation performance and improve cow's energy utilisation efficiency.