Former food and cocoa bean shells in early-lactating cows on a herbage-based diet: effects on ruminal fermentation and blood metabolites

Rising food security concerns are driving the livestock sector to explore alternatives to cereal grains, like by-products from the food industry, but their effect on animals needs to be studied. The study assessed the impact of replacing 55% cereal grains with former food products (FFP) on ruminal fermentation, ruminal methane production, and blood metabolites, with or without cocoa bean shell (CBS) supplementation. We conducted a first (spring, E1) and a second (fall, E2) experiment, each with 17 early-lactating Holstein and Red Holstein cows. Each experiment lasted 6 weeks, including a 3-week adaptation and a 3-week experimental period. In each experiment, the animals were fed freshly cut grass as a basal diet and were balanced for milk yield, parity, and days in milk and assigned to three concentrate types (CCT): (i) a control concentrate (CON), (ii) a concentrate consisting of 55% FFP (FFP-), and (iii) an FFP concentrate that included an additional 5% CBS (FFP+ ). Feed intake and milk production were recorded daily during the 3-week sampling period; blood serum and ruminal fluid samples were collected twice, at the end of the adaptation and experimental periods. Statistical analyses were conducted on data from both experiments. DM, herbage, and most nutrient intakes were greater in E2 than in E1, probably because of seasonal changes in herbage quality. In E1, CON cows had lower DM intake (DMI) than FFP- cows, whereas in E2, CON cows had greater DMI than FFP+ cows. Across experiments, FFP- and FFP+ cows had greater water-soluble carbohydrates and fat and lower starch intakes than CON cows. The energy-corrected milk yield was greater in E1 than in E2 and unaffected by CCT. Irrespective of the experiment, the CON cows had the greatest, FFP- intermediate and FFP+ lowest milk lactose percentages and FFP+ cows had greater milk fat percentages than CON cows. The mean and maximum reticular pH were lower for CON than for FFP- cows in E1 and were unaffected by CCT in E2. Irrespective of the experiment, acetate proportions in ruminal fluid of CON cows were lower than those of FFP- and FFP+ cows. Methane yield was greater in E2 than in E1 and unaffected by CCT. Serum albumin, non-esterified fatty acids and glucose levels varied by CCT in E2, but not in E1. Combining FFP and CBS with herbage could help increase the sustainability of early-lactating dairy cow nutrition without compromising health, but results need future corroboration.