This experiment was conducted to determine the effects of pineapple stem by-product silage as a feed source in total replacement of Napier or corn silages on growth performance, feed intake and feed efficiency, ruminal fermentation, carcass characteristics and meat quality of Holstein crossbred steers. Forty-eight steers with an average age of 18 months (448.6 ± 51.5 kg) were randomly allocated to three groups (one diet per group) in a completely randomized design. Steers were fed total mixed ration (TMR) containing a roughage-to-concentrate ratio of 20 : 80. The TMR diets contained Napier grass silage (nTMR), whole corn silage (cTMR) or pineapple stem silage (pTMR) and were offered ad libitum for six months. The results revealed that pTMR and cTMR diets resulted in a significantly higher weight gain than nTMR. These results were observed because pTMR and cTMR diets provided more N-free extract (NFE) total digestible nutrients (TDN) than nTMR diet, and the feed conversion efficiencies for pTMR and cTMR diets were higher than those of nTMR. Ruminal pH, ammonia-nitrogen and volatile fatty acid concentrations were not significantly different among dietary treatments. The carcass characteristics of steers fed cTMR and pTMR diets included significantly larger rib eye areas than steers fed nTMR, whereas meat quality was not affected by treatment. Additionally, the current research showed that pTMR diet provided the lowest feed cost per gain. The results suggest that pineapple stem by-product could be regarded as a potential feed source for reducing costs in cattle feedlots.

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BACKGROUND Cardio‐renal syndrome (CRS) is an integrative problem related to chronic malnutrition, obesity, etc. Amino acids and peptides are regarded as protective and essential for tissues. Pepsin‐digested chicken liver hydrolysates (CLHs), which are made from the byproducts of the poultry industry, are amino‐acid based and of animal origin, and may be protective against the myocardial and renal damage induced by a high‐fat diet (HFD). RESULTS Our results showed that CLHs contain large quantities of anserine, taurine, and branched‐chain amino acids (BCAAs), and supplementing the diet with CLHs reduced (P < 0.05) weight gain, liver weight, peri‐renal fat mass / adipocyte‐area sizes, serum total cholesterol (TC), aspartate aminotransferase (AST), and low‐density lipoprotein cholesterol (LDLC) levels in HFD‐fed mice but increased (P < 0.05) serum high‐density lipoprotein cholesterol (HDLC) levels. By histological analyses, CLHs alleviated (P < 0.05) renal lipid deposition and fibrosis, as well as cardiac fibrosis and inflammation of HFD‐fed mice. Meanwhile, increased (P < 0.05) inflammatory and fibrotic cytokines levels in the myocardia of the HFD‐fed mice were downregulated (P < 0.05) by CLH supplementation. Regarding autophagy‐related protein levels, protective effects of CLHs on the myocardia against HFD feeding may result from the early blockade of the autophagy pathway to prevent autophagosome accumulation. CONCLUSION Functional CLHs could be a novel food ingredient as a cardio‐renal protective agent against a high‐fat dietary habit in a niche market. © 2020 Society of Chemical Industry

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