Influence of supplementing bakery by-products and cocoa bean shells to a grass-based diet on feed intake, milk production and ruminal fermentation of early-lactating dairy cows

Food leftovers from bakery industries (BBP) and cocoa bean shells (CBS) represent losses of food that are normally wasted despite their high energy and polyphenol content. Their use in ruminant nutrition could enhance the re-use of organic losses and convert them into valuable feed ingredients. This study aimed at evaluating if BBP and BBP containing CBS can replace most of a cereal-based concentrate in a herbage-based diet fed to dairy cows in early lactation without negative consequences on the cows’ ruminal fermentation and production. We used 17 early lactating Holstein and Red Holstein cows for 6 weeks, including a baseline measurement (day before start), a 2-wk adaptation (P1) and a 4-wk sampling period (P2). The cows were fed ad libitum freshly harvested herbage and were assigned to one of three concentrate types: (i) a control concentrate (CON), (ii) a concentrate including 55% BBP (BP-) and (iii) a concentrate including 55% BBP and 1% CBS (BP+). The concentrates were similar in protein and net energy contents and were offered according to a fixed allocation scheme from 5 kg in P1 to 6 kg in P2. Feed intake and milk yield were recorded daily, and milk composition twice weekly. Reticular pH was measured continuously (SmaXtec, Graz, Austria). Linear mixed models included the random effect cow and the fixed effects period, concentrate type, their interaction and – for feed intake – baseline herbage intake (R, package lme4). In P2, CON and BP- cows ingested more concentrate than BP + cows (p < 0.05). Across periods, CON cows ingested less water-soluble carbohydrates and more starch (p < 0.05) than BP- and BP + cows, which was more pronounced in P2 than P1 (p < 0.05). Milk yield decreased from P1 to P2, which was less pronounced feeding CON and BP- than BP+ (p < 0.05). In P2, milk lactose percentages were greater in CON than in BP- and BP + cows. Across all periods, the range of the reticular pH of CON cows was smaller compared to BP- and BP + cows (p < 0.05). The mean, min and max pH increased from P1 to P2, which was less pronounced feeding CON and BP + than BP- (p < 0.05). Feeding BBP increased water-soluble carbohydrate and decreased starch intake. The relationship between the BBP-related increases of reticular pH and pH range and rumen health needs to be further investigated. The lower concentrate intake and milk yield of cows receiving CBS need further investigation regarding possible anti-nutritional effects of CBS-derived tannins.