The use of urea dilution for estimation of carcass composition of Holstein steers at 3, 6, 9, and 12 months of age.

Abstract

Every 3 mo for a 2-yr period, two weaned Holstein steer calves (94.5 kg) were randomly assigned to each of four slaughter age groups (3, 6, 9, and 12 mo). Urea dilution was performed before slaughter, and urea space (US) was calculated as total volume and as a percentage of body weight (BW) and empty body weight (EBW). The relationships between US (kg, % EBW and % BW), BW, and EBW and carcass soft tissue composition (protein, fat, moisture, and ash) were studied. One- and two-pool models were fitted using the urea dilution data and the coefficients of those equations (zero time, A + B), and the intercepts of compartments A and B were used to estimate body volume. Body weight and EBW effectively predicted the amount of water, fat, and protein in the carcass soft tissue. Equations expressed in kilograms were more accurate than those expressed as percentages. Urea space overestimated body water, probably because of the fast rate of urea disappearance in plasma. Correlation coefficients between US and carcass soft tissue water (kg) based on the pooled data ranged from .74 at 6 min to .48 at 42 min after infusion. The biexponential models coefficients explained more of the variation of carcass soft tissue composition than US; correlation coefficients using volume B and the soft tissue composition (in kg) with pooled data were .78 (water), .68 (fat), .69 (ash), and .76 (protein). The relationships between A and soft tissue composition were weaker (water .59, fat .51, ash .58 and protein .59). The highest correlation coefficients were obtained when A + B was used for water, fat, ash, and protein (.83, .70, .74 and .81, respectively). Equations combining BW, EBW, and two-model coefficients (A, B, A + B) explained much of the variation of soft tissue composition. No significant benefit was found in using the urea space at various times after infusion over BW or EBW alone to estimate carcass soft tissue composition in Holstein steers.

Utilization of bioelectrical impedance to predict carcass composition of Holstein steers at 3, 6, 9, and 12 months of age.

“…This experiment was conducted at the Kansas State University Beef Research Unit from February 1989 to August 1991. Animals used for our study were those used in a urea dilution and growth trial reported earlier (Velazco et al, 1997). Growth data and prediction of STC were determined for four groups of 16 Holsteins steers 3, 6, 9, or 12 mo of age; however, only 53 animals were included in this experiment (10 of 3 mo, 12 of 6 mo, 15 of 9 mo, and 16 of 12 mo).…”

“…Feed and water were withheld for 20 h before the BIA was applied. Body measurements and weight were obtained while steers were restrained; a detailed description of those procedures was published elsewhere (Velazco et al, 1997). Immediately thereafter, steers were sedated using Rompun ® (Mobay Corporation, Animal Health Division, Shawnee, KS) with a dose of 160 mg/100 kg BW.…”

“…Procedures to determine carcass composition were described in a previous article (Velazco et al, 1997). The right side of each carcass was separated physically into fat, lean, and bone.…”

“…As described by Swantek et al (1992), two predictors were calculated: Vol 1 = L 2 /R s and Vol 2 = Table 1. Least squares means and standard deviations for some physical characteristics and carcass soft tissue composition of Holstein steers at 3, 6, 9 and 12 mo of age, and the pooled data a L = distance traveled by electricity ( 2 × animal height + body length); L 2 = L × L; R s = resistance; X c = reactance; Z = impedance ( ( R s 2 + X c 2 ) .5 ) ; Vol 1 = L 2 /R s ; Vol 2 = L 2 /(R s 2 + X c 2 ) .5 ; Vol 3 = geometric volume, as described by Velazco et al (1997); BMI = BW 2/L 2 ; CFFM = carcass fat free mass; KgH 2 O = kg of carcass soft tissue water; KgFAT = kg of carcass soft tissue fat; KgPROT = kg of carcass soft tissue protein; KgASH = kg of carcass soft tissue ash; V = ohms. L 2 /(R s 2 +X c 2 ) .5 .…”

“…A third volume estimation (Vol 3 ) calculated from urea dilution measurements also was included in the model calculations. Details of volume calculation were described by Velazco et al (1997). Khaled et al (1988) suggested that body mass index ( BMI) , applied regularly in humans, could be used as a predictor of FFM.…”