The utilization of calcium soaps from animal fat by laying hens

Ground wheat was employed as a carrier to evaluate the utilization by laying hens of animal fat, calcium soaps of fatty acids from animal fat (CS), and animal fat in the presence of 3.8% added calcium. Birds trained to consume their daily feed in two 1-h periods were fed ground wheat with 0, 3, 6, and 9% animal fat, CS, or 10% ground limestone and animal fat to provide 11 experimental diets. Animal fat and preformed CS were highly available to laying hens with total fatty acid availabilities of 100.2 +/- 1.2 (SE) and 99.2 +/- 3.6%, respectively, estimated by the regression of added fat on determined fat retentions. However, 3.8% calcium reduced animal-fat fatty acid availability to 86.3 +/- .7%. The true metabolizable energy of animal fat, as determined by regression from bomb-calorimetry data, was 9.63 +/- .58 kcal per g; a value of 9.36 kcal per g was obtained from fat-retention data [100.2% of the gross energy (GE) of 9.34 +/- .78 kcal per g]. With added limestone, the respective TME values were 9.36 +/- 1.30 kcal per g (regression) and 8.06 kcal per g (retention). The TME of the CS fatty acids was 7.20 +/- 1.05 kcal per g, estimated by regression; and the value calculated from CS fat retentions was 8.14 kcal per g, representing 99.2% of the GE (8.20 +/- .58 kcal per g). Discrepancies between calorimetric and fat-retention TME estimates represented animal-fat effects on wheat starch, fat, and amino-acid retentions.

Indirect calorimetry evaluation of dietary protein and animal fat effects on energy utilization of laying hens

A multichamber indirect calorimeter was constructed and used to measure energy utilization of laying hens. Four basic diets were formulated by a least cost linear program for use in this study. The first diet was formulated to meet the 1984 National Research Council (NRC) recommendations and contained by analysis 14.5% protein, .58% TSAA, and .68% lysine (designated NRC). The second diet (NRCAA) was formulated to the same amino acid specifications without a protein restriction and contained 12.9% protein, .57% TSAA, and .69% lysine. Another pair of diets was formulated with higher protein (HP) and amino acid restrictions. The HP diet contained 16% protein, .67% TSAA, and .85% lysine; whereas the HPAA diet had 14% protein, .68% TSAA, and .86% lysine. Four additional diets were formulated with the inclusion of 3% animal fat, using the same protein and amino acid restrictions as were used to formulate the first four diets. Animal fat supplementation significantly (P less than .05) improved energy balance (retention) of birds fed all formulations compared with the diets without added fat. Formulation of a diet based on amino acid restrictions significantly increased net energetic efficiency of birds fed amino acid levels higher than those recommended by the NRC (79.2 for HPAA vs. 62.1% for HP), but did not significantly affect net efficiency of birds fed the lower amino acid levels (NRC and NRCAA).

Animal fat effects on nutrient utilization

Laying hens were employed to study the effects of carrier on the true metabolizable energy (TME) of tallow using corn, milo, soybean meal, wheat bran, and dehydrated alfalfa meal with tallow at 0, 2, 4, or 6%. In addition to bomb calorimetry measurements on feed and excreta samples, tallow TME values were calculated from absorbability data. Estimates of TME for tallow varied with carrier feedstuff from 7.19 kcal/g in soybean meal to 13.62 kcal/g when wheat bran was fed. For the corn, milo, and soybean meal series only fat retentions were significantly affected by tallow supplementation. Calculated tallow absorbabilities were 101.8% with corn, 95.8% with milo, and 107.3% with soybean meal. Highest tallow TME values were obtained with wheat bran and dehydrated alfalfa meal, apparently due to increase protein retention from wheat bran and to both improved protein retention and starch absorption with dehydrated alfalfa meal.

Dietary sulfur amino acid level and energy utilization in laying hens

Effects of marginal total sulfur amino acid (TSAA) deficiency and methionine toxicity on energy utilization of laying hens were studied with 7-month-old Single Comb White Leghorn pullets housed in individual cages at constant temperatures of 15.6 and 32.2 C. Diets containing .47, .49, .51, and 3.47% TSAA were fed throughout the 4-week study. Following a 2-week acclimation period, each diet was fed at three levels of intake for 2 weeks. Voluntary feed and metabolizable energy (ME) consumption of nontoxic TSAA diets was significantly reduced at the higher housing temperature, and a further significant reduction was observed with the toxic diet at both temperatures. Energy balance increased from 79.7 to 98.7 kcal/bird per day at 32.2 C and from 117.3 to 142.0 kcal at 15.6 C as dietary TSAA increased from .47 to .51%; energy balance of hens fed 3.47% TSAA was very low at both temperatures. Maintenance ME requirements were unaffected by dietary TSAA up to .51%, ranging from 123.3 to 131.1 and 155.5 to 163.5 kcal/hen per day at 32.2 C and 15.6 C, respectively; the requirement increased about 20 kcal/day at each temperature when the toxic TSAA diet was fed. As the amino acid balance of the diet was improved with methionine supplementation up to .51%, heat increment plus activity decreased from 70.2 to 37.0 kcal/bird per day for hens housed at 32.2 C. Consequently, efficiency of conversion of dietary ME to net energy improved from 52.1% with .47% TSAA to 63.8% with .51% TSAA. Housing temperature did not influence energetic efficiency.(ABSTRACT TRUNCATED AT 250 WORDS)

Energy utilization in laying hens. III. Effect of dietary protein level at 21 and 32 C

White Leghorn pullets housed at either 21 or 32 C were used to investigate the effects of dietary protein level on energy utilization. Protein levels of 12, 14, 16, 18, and 20% were employed in this study with three feeding levels of each (two restricted levels and ad lib.). All diets were isocaloric, and the duration of the study was 21 days. Maintenance metabolizable energy (ME) was estimated as 134 and 121 kcal/kg physiological body weight (BW.75) at 21 and 32 C, respectively. Fasting heat production/BW.75 was 21% higher at the lower temperature (89 vs. 70 kcal). Estimates of energetic efficiencies at 21 C varied from 60.9% for the 12% protein diet to 72.4% for the 18% protein diets. At 32 C, similar diets showed lower energetic efficiencies for ME conversion to net energy (50.6% for the 12% protein diet and 70.6% at 20% protein) due to lower feed intakes. Egg weights were significantly higher at the lower environmental temperature, and at each temperature they were increased with the feeding of the higher protein diets. The average feed efficiency (g egg/g feed) was significantly better at the higher environmental temperature (.46 vs. .53). Calculations of heat increment (HI) plus activity from a parabolic regression developed in relation to protein intakes showed higher (HI plus activity) values with either low or high protein intakes. Thus, the feeding of dietary protein levels which result in intakes commensurate with needs should result in maximum energetic efficiencies and dietary net energy.

Energy utilization by laying hens. I. Energetic efficiencies of maintenance and production

The energetic efficiency of metabolizable energy conversion to net energy for maintenance and/or production was determined in laying hens. The techniques employed indicated that maintenance and production had essentially the same efficiencies (.619 and .628, respectively). Fasting heat production was 69.28 kcal/Wkg75 (physiological body weight) and the maintenance requirement was 111.1 kcal/Wkg75. Limiting metabolizable energy intake in laying hens reduced both egg weight and hen-day production. Regression equations predicted a reduction of 1.53 g in egg weight and a reduction of 2.5% in egg production for each 10 kcal metabolizable energy reduction in intake. This paper reports techniques which may be employed for energetic efficiency evaluations of feedstuffs, mixed diets, and energy utilization by laying hens in short term studies.