Glycerol or glycerin is generally recognized as a safe compound to be used in animal feed, especially for ruminants. A number of in vitro studies related to glycerol supplementation in ruminant ration have been published but to date the results have not been summarized. The objective of this study was, therefore, to evaluate in vitro digestibility, ruminal fermentation characteristics, total gas and methane production through the meta-analysis approach. Meta-analysis was applied to 13 experiments and 42 treatments dealing with glycerol supplementation in ruminants. Data were analyzed by general linear model procedure in which the glycerol levels and the different studies were treated as fixed effects. Results revealed that glycerol supplementation did not affect the in vitro digestibility and total VFA production, but significantly decreased molar proportion of acetate and iso-valerate (P<0.05). In contrast, molar proportion of propionate, butyrate, and valerate significantly increased, and thus the ratio of acetate to propionate declined linearly (P<0.05). Methane production decreased linearly and accompanied with an increase of total gas production with increasing levels of glycerol supplementation (P<0.05). It is concluded that the use of glycerol as an energy substitution in animal feed has no detrimental effects in the rumen and environmentally friendly.

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We evaluated the precision and accuracy of equations from the Australian Ruminant Feeding Standards (ARFS) and the Large Ruminant Nutrition System (LRNS) in predicting the performance of Ongole (Bos indicus) cattle under Indonesian conditions. A database was constructed using information from 121 cattle in five different pen-feeding experiments. Cattle included mature cows and growing bulls, and they were fed a range of diets commonly used by Indonesian farmers. We compared observed and predicted dry matter intake and daily liveweight gain. Model predictions were evaluated for precision and accuracy using mean bias, mean square prediction error and regression of observed against predicted values. Across all experiments, the LRNS provided the better estimates of intake and growth. While both models included animal age, sex, weight and body condition score, the LRNS provided better estimates of metabolisable energy requirements for maintenance of liveweight, feed quality and efficiency of energy utilisation. The LRNS model also better accounted for environmental conditions by including correction factors for minimum night temperature and relative humidity, in addition to average daily temperatures. Based on our results, the LRNS model appears suitable for use in Indonesian beef-production systems.

Improving the productivity and profitability of smallholder cattle enterprises in Indonesia requires greater and more efficient utilisation of underutilised feed resources such as rice straw. The experiment tested the hypothesis that an Ongole cow with low energy requirements can maintain weight (W) on a rice straw-based diet with the addition of a small amount of tree legumes. Thirty-two Ongole cross (Bos indicus) cows were allocated to one of four treatments in a randomised block design with eight cows per treatment. Cows were offered untreated rice straw ad libitum with four levels of tree legumes (0, 11, 21, and 42 g DM/kg W0.75.day) for 20 weeks. Feed intake was determined daily and liveweight was measured every second week. There was no difference in total feed intake between the treatment groups (P > 0.05). Intake of tree legumes was higher when more was offered (P < 0.05), but cows did not consume all of the legumes offered to them. The inclusion of tree legumes in the diet had no effect on organic matter digestibility, ME content of the diet, liveweight gain or estimated energy balance of the cows (P > 0.05). Rice straw alone contained insufficient ME and rumen-degradable N to meet the maintenance requirements of the cows. From the regression relating liveweight change and ME intake for all cows across all diets, the inclusion of tree legumes in the diet at ~12 g DM/kg W0.75.day or 2.8 g DM/kg W.day was enough to meet the energy requirements for maintenance of Ongole cows fed rice straw ad libitum.

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