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The aim of this study was to explore the protective effects of squalene supplementation on growth performance, oxidative status, and liver function of diquat-challenged broilers. One hundred forty-four 1-day-old male Ross 308 broiler chicks were allocated to 3 groups, and each group consisted of 6 replicates of 8 birds each. The three groups were as follows: 1) nonchallenged broilers fed with a basal diet (control group), 2) diquat-challenged broilers fed a basal diet, and 3) diquat-challenged broilers fed with a basal diet supplemented with 1.0 g/kg of squalene. Broilers were intraperitoneally injected with 20 mg/mL of diquat solution at a dosage of 1 mL/kg of BW or an equivalent amount of saline at 20 d. Compared with the control group, weight gain and BW change rate during 24 h after injection were decreased by diquat challenge ( P < 0.05), and the diquat-induced compromised growth performance was improved by squalene supplementation ( P < 0.05). Diquat administration reduced plasma superoxide dismutase activity and increased malondialdehyde accumulation and glutathione peroxidase activity in both plasma and the liver ( P < 0.05). In contrast, plasma glutathione peroxidase activity in diquat-challenged broilers was reduced by squalene supplementation ( P < 0.05). The hepatic glutathione level was reduced by diquat administration ( P < 0.05), whereas its level in plasma and the liver of diquat-challenged broilers was increased by squalene supplementation ( P < 0.05). The relative liver weight of broilers was increased by diquat challenge ( P < 0.05), with its value being intermediate in the squalene-supplemented group ( P > 0.05). The plasma aminotransferase activities and total bilirubin concentration were increased by diquat challenge ( P < 0.05), which were reduced by squalene supplementation ( P < 0.05). The mRNA abundance of hepatic nuclear factor erythroid 2–related factor 2 ( P < 0.05) was upregulated by diquat treatment, regardless of squalene supplementation. The mRNA abundance of hepatic glutathione peroxidase 1 and B-cell lymphoma/leukemia 2–associated X protein was upregulated by diquat challenge ( P < 0.05), which was reversed by squalene administration ( P < 0.05). Squalene increased NAD(P)H quinone dehydrogenase 1 mRNA abundance and decreased caspase 3 mRNA abundance in the liver of diquat-challenged broilers ( P < 0.05). The results suggested that squalene can increase weight gain, improve oxidative status, and alleviate liver injury in diquat-challenged broilers.

Intestinal integrity, digestive enzyme activity, nutrient utilization, and egg quality of laying hens at different ages were evaluated and compared in this study. A total of 192 Hy-line Brown laying hens at 195-d-old (D195 group), 340-d-old (D340 group), and 525-d-old (D525 group) were allocated into one of 3 groups in accordance with their ages. Each group had 8 replicates of 8 birds each, and all birds were fed a maize-soybean meal basal diet for a 2-wk experiment. Compared with the D195 group, intestinal villus height and ratio of villus height to crypt depth, as well as serum D-lactate content increased in the D525 group ( P < 0.05). The sucrase and maltase activities in the jejunal mucosa, amylase activity in the pancreas, and trypsin activity in the jejunal chyme of 525-d-old hens were lower than their 195-d-old counterparts ( P < 0.05). In addition, there was a decline of trypsin and lipase activities in the ileal chyme of hens from D525 group in comparison with D195 or D340 group ( P < 0.05). Apparent retention of dry matter and crude protein of birds in D340 and D525 group decreased when compared with the D195 group ( P < 0.05). Moreover, birds in the D525 group exhibited a lower level of ether extract retention, and higher contents of several excreted amino acids than those in the D195 group ( P < 0.05). Compared with the D195 group, eggs harvested from D525 group exhibited lower albumen height, eggshell strength and thickness, and a higher egg weight ( P < 0.05). In conclusion, increased intestinal permeability (higher serum D-lactate content), compromised digestive function (lower digestive enzyme activities and apparent nutrient retention, and higher concentrations of excreted amino acids), and poor egg quality (lower albumen height, eggshell strength, and thickness) were observed with increasing age in the laying hens.

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