Feed utilization, blood metabolites and ingestive behavior in Sahiwal calves divergently selected for low and high residual feed intake. Vet. arhiv 89, 481-503, 2019. ABSTRACT This study aimed to evaluate differences in feed utilization between low and high residual feed intake (RFI) in Sahiwal calves by comparing performance, ingestive behavior and blood metabolites. Eighteen, growing, female Sahiwal calves (aged 10-14 months; body weight (BW) 100-125 kg) were fed ad libitum on a total mixed ration for 90 d. RFI varied from-0.53 to 0.40 kg dry matter (DM)/d with a mean RFI of-0.27 to 0.17 kg DM/d in low and high RFI Sahiwal calves, respectively. Calves with low RFI consumed 26% less DM and required 35% less metabolizable energy for body maintenance (MEm) compared to high RFI, yet gained at a similar rate. Low RFI calves digest feed more efficiently than less efficient calves. Conventional efficiency measures also showed better efficiency in low RFI than high RFI calves. Low RFI calves spent less time in feeding, rumination, and chewing. Higher plasma concentrations of insulin-like growth factor-1 (IGF-1), growth hormone (GH), and creatinine, and lower concentrations of albumin, plasma urea nitrogen (PUN), and triglycerides were observed in the low RFI group than the high RFI group. However, plasma total protein, glucose, cholesterol, non esterified fatty acid (NEFA), beta-hydroxy butyric acid (BHBA), calcium (Ca), and phosphorus (P) concentrations were similar in both groups. In summary, low RFI calves utilized feed more efficiently by spending less time and energy in feeding, and the variability in blood metabolites might be due to differences in body metabolism.
The effect of heat treatment (125°C for 3 m), formaldehyde treatment (3.4g /100 g CP) or extrusion cooking on the protein disappearance and the effective protein degradability (EPD) of protein sources such as babul seed meal, coconut cake, dried poultry waste, guar meal, mustard cake, rape seed meal and tobacco seed cake in the rumen was studied by nylon bag technique using 4 fistulated steers fed at maintenance ration. Formaldehyde treatment was highly effective in reducing the EPD of babul seed meal, mustard cake, rape seed meal and tobacco seed cake. Heat treatment was effective in protecting the protein of rape seed meal, mustard cake and coconut cake. The effect of extrusion cooking in reducing EPD was low (5.96%) as compared to 31.8% in heat treatment and 39.2% in formaldehyde treatment. The dried poultry waste and guar meal were found to be resistant to different processing methods employed. Method of processing did not influence the nitrogen content of protein sources as there was no loss or gain in nitrogen content due to processing.
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