ASAS CENTENNIAL PAPER: Net energy systems for beef cattle--Concepts, application, and future models

The accuracy of predicted CowBytes® versus actual dry matter intake (DMI) and average daily gain (ADG) of 407 Hereford × Angus and Charolais × Maine Anjou (445.6 ± 36 kg) feeder cattle using digestable enery acid detergent fiber (DE) estimated from the (ADF) content [Laboratory analysis method (LAB)] and from values determined in vivo (INVIVO method) was examined. The diet consisted of a 73.3% concentrate diet, 22.0% barley silage, 1.6% molasses, and 3.1% feedlot supplement fed ad libitum (as-fed basis). The calculated DE values of the feed were used to predict the metabolizable energy (ME), net energy of maintenance (NEm), and net energy of gain (NEg) of the diet. These energy values were then used in CowBytes® to predict dry matter intake (DMI), ADG, and days on feed (DOF) necessary to meet targeted quality grade of AA and weights of 522 and 568 kg for the heifers and steers, respectively. There was no effect of gender and prediction method interaction (P > 0.10) on any of the variables measured. There were no (P > 0.05) differences in predicted DMI by either the INVIVO or LAB method but both methods underestimated DMI actually consumed by the cattle by 6.8 and 4.9% (P = 0.007), respectively. Indeed, regression values from these predictive methods and actual DMI were (P < 0.05) different from the one-to-one relationship expected by definition. In spite of the higher actual DMI, the actual ADG of the cattle was 14 and 11% (P = 0.0004) lower than was predicted by either the INVIVO or LAB methods. A possible reason for the lower ADG could be an overestimation of DE of the diet. Thus, if available, users of CowBytes® should use actual DMI from their experience in ration formulation. In addition, the effects of environmental temperature on digestibility of diets should be taken into consideration when using the DE of the diet as determined from in vivo digestibility trials or calculated from chemical analyses in determining the DMI of feedlot cattle. Key words: Beef cattle, performance, CowBytes®, National Research Council

Download Full-text

Net energy value of timothy and bromegrass silages for beef cattle

Canadian Journal of Animal Science ◽

10.4141/a97-023 ◽

1998 ◽

Vol 78 (1) ◽

pp. 107-114 ◽

Cited By ~ 2

Author(s):

D. R. Ouellet ◽

J. R. Seoane ◽

H. Lapierre ◽

P. Flipot ◽

J. F. Bernier

Keyword(s):

Beef Cattle ◽

Heat Production ◽

Stem Elongation ◽

Prediction Equation ◽

Metabolizable Energy ◽

Net Energy ◽

Beef Steers ◽

Boot Stage ◽

Ad Libitum ◽

Net Energy Value

Metabolizable energy (ME), net energy for maintenance and net energy for growth of grass silages were evaluated by the comparative slaughter technique using a 2 × 2 × 3 factorial design. Sixty medium frame beef steers (259 ± 29 kg BW) were divided in groups of five and fed during 3 months either Timothy (T) or Bromegrass (B) harvested at stem elongation (S) of the first cut or at boot stage of the aftermath (A). Forages were fed at one of three levels of intake: ad libitum (FF), 80% of FF, or 65% of FF. Silages averaged 26.9% DM, 16.0% CP and 37.7% ADF. Regression of logarithm of heat production (HE) against ME intake were similar for all silages (log HE = 0.00046*ME + 2.4923; r2 = 0.89). From this equation, fasting HE of 311 kJ kg−0.75 d−1, ME for maintenance of 559 kJ kg−0.75 d−1 and efficiency of utilization of energy for maintenance of 56% were determined. Regression of ME intake against retained energy (RE) were similar for all silages. Efficiency of ME utilization for growth was 33% using the regression of ME over RE with a ME requirement for maintenance fixed at 559 kJ kg−0.75 d−1. Net energy for maintenance and growth were similar for all silages, averaging 6.17 and 3.70 MJ kg−1, respectively. The use of a prediction equation based on ADF of forages underestimated ME values of silages by approximately 25%. Moreover, NRC (1984) equations that estimate NE from experimentally estimated ME values tended to overestimate the net energy of our grass silages. Key words: Net energy, grass silages, timothy, bromegrass, beef cattle

Download Full-text

Applicability assessment of central and solar hot water systems integration in Serbia

Thermal Science ◽

10.2298/tsci120130070k ◽

2012 ◽

Vol 16 (suppl. 1) ◽

pp. 173-188 ◽

Cited By ~ 1

Author(s):

Miroslav Kljajic ◽

Jovan Petrovic

Keyword(s):

Urban Communities ◽

Water System ◽

Energy Systems ◽

Efficient Solutions ◽

Hot Water ◽

Net Energy ◽

Total System ◽

Hot Water Supply System ◽

Novi Sad ◽

The City

Energy systems for consumers? supply with sanitary hot water (SHW) can be considered as a separate category of the system with many similar functions, performances and integral elements. This similarity of energy systems for SHW supply and the way in which they are used enable systemic planning, proposing and undertaking measures for improvements and advancements. This is possible not only by the reconstruction and modernization of existing technological solutions but also by their replacement with new, modern and more efficient solutions. The basic idea and the aim of this paper is the development of a concept for integrated and upgraded system of SHW supply for different types of buildings from residential to more complex buildings intended for different purposes. The analysis is based on the application of a systemic approach adapted to the conditions in urban communities and includes only modern but commercial technologies. This paper presents the results of a net energy analysis of integrated central and solar hot water supply system and compares it with the conventional sanitary hot water system in the City of Novi Sad, Serbia. The proposed methodology is demonstrated through a simulation example. It is shown that 23% reduction in the total system?s costs can be achieved as compared to the existing solution. Also, the methodology is applied to a residential block as a unit and obtained results indicate that investments in the development and construction of integrated systems are justified.

Download Full-text