Validation of real-time ultrasound technology for predicting fat thicknesses, longissimus muscle areas, and composition of Brangus bulls from 4 months to 2 years of age.

Sixty Brangus bulls were evaluated live using two real-time ultrasound instruments and four technicians to estimate longissimus muscle area (LMA) and 12th rib fat thickness (FT) every 4 mo beginning at 4 and 12 mo of age, respectively, and continuing until 24 mo of age. Ten bulls were slaughtered every 4 mo to determine actual LMA and FT, 9-10-11th rib chemical composition, yield grade (YG) factors, and empty body weight (EBW). Live animal traits were used to predict 9-10-11th rib composition, YG, and EBW. Scanned mean FT was accurate (P less than .05) at 16 mo and was not different (P = .09) from the actual mean FT (95% of the time the error in estimation was less than or equal to .33 cm). Scanned mean LMA was accurate (P less than .05) at 12 mo (95% of the time the error in estimation was less than or equal to 20.0 cm2). Absolute differences between scanned and actual mean FT and LMA were different (P less than .05) from zero for the main effects of month, operator and(or) interpreter, and instrument. Increased level of operator skill did not improve the accuracy of FT or LMA measurements, whereas increased level of skill of the interpreter of scans did improve the accuracy of LMA estimations. There was no difference (P greater than .05) between ultrasound instruments in accuracy of estimating FT or LMA. The most accurate prediction of YG occurred at 12 mo and incorporated LW, hip height (HH), and ultrasound LMA (R2 = .95, SD = .14). The most accurate prediction of EBW occurred at 16 mo and incorporated LW, HH, and ultrasound FT (R2 = .99, SD = 6.65 kg), whereas the most accurate equation for combined slaughter periods incorporated LW, HH, and ultrasound LMA (R2 = .99, SD = 20.71 kg). We conclude that scanning of LMA at 12 mo and of FT at 12 or 16 mo were sufficiently accurate to characterize groups of bulls; however, some individual measurements were quite inaccurate. Measurements at other months should not be considered accurate for either individuals or groups of bulls. Yield grade and EBW can be accurately estimated from live animal and ultrasound measurements, which may be useful in identifying Brangus cattle with superior cutability and may eliminate the need for serial slaughter in research projects.

Application of ultrasound for feeding and finishing animals: a review.

The ability to evaluate carcass traits in live animals is of value to research, educational, and industry personnel. Ultrasonic technology has been tested since the early 1950s and continues to be under investigation as a means of accomplishing this task. The accuracy of ultrasound in predicting carcass traits is variable and is dependent on species, ultrasonic instrumentation, and(or) the skill of the technician. Based on this review, the ranges of correlation coefficients (r) for carcass traits as predicted by ultrasound to the respective carcass measurement are as follows: swine (fat .20 to .94; longissimus muscle .27 to .93), sheep (fat .42 to .95; longissimus muscle .36 to .79) and beef (fat .45 to .96; longissimus muscle .20 to .94; marbling .20 to .91). Although these correlation coefficients give an indication of the accuracy of ultrasound, it should be noted that these statistics do not reflect population variation or bias. Applications of ultrasound in swine finishing programs include the successful prediction of market weight carcass characteristics and the prediction of percentage of lean cuts before slaughter. In contrast, the application of ultrasound in lamb finishing programs has met with limited success. Most data indicate that weight and(or) visual estimations of fat are at least as accurate as ultrasound predictions of carcass composition. In beef finishing programs, ultrasound has, at times, been used successfully to predict fat and muscle traits before slaughter and beef carcass chemical composition. The ability to predict marbling, however, remains unclear and requires further investigation. Ultrasound has also been used in beef finishing programs to predict days on feed to a constant body compositional end point. When summarized, these data indicate that a single ultrasonic measurement of fat can be helpful in predicting days on feed in yearling cattle. When used alone, however, a single backfat measurement does not provide adequate accuracy. Therefore, factors such as age, sex, breed type, weight, and hip height are needed to help predict days on feed more accurately.

Effect of dietary energy, body condition and calf removal on pituitary gonadotropins, gonadotropin-releasing hormone (GnRH) and hypothalamic opioids in beef cows.

Beef cows (n = 64) were slaughtered to evaluate effects of dietary energy and calf removal (CR) on hypothalamic and adenohypophysial endocrine characteristics. From d 190 of gestation until parturition, cows received maintenance (ME; n = 32) or low (LE; n = 32) energy diets (ME = 100%, LE = 70% NRC recommendations). After parturition, half (n = 16) of each prepartum diet group received low (LE; n = 32) or high (HE = 130% NRC; n = 32) energy diets. At 30 d postpartum, cows were slaughtered 0 or 48 hr after CR. Hypothalami [preoptic area (POA), hypothalamus (HYP), stalk-median eminence (SME)] and pituitaries were collected. Basal and K(+)-induced release of GnRH from SME, and pituitary luteinizing hormone (LH) and follicle stimulating hormone (FSH) did not differ among groups (P greater than .05). Hypophyseal LH was correlated (P less than .01) with body condition score (BCS) at parturition and slaughter (r = .36 and .47, respectively). Prepartum LE diet increased (P less than .05) met-enkephalin in POA compared to prepartum ME (.59 +/- .05 vs. .44 +/- .04 pmol/mg) regardless of postpartum diet or suckling status. Concentrations of beta-endorphin in combined HYP + POA were decreased (P less than .05) by 48 hr CR (15.1 +/- 1.1 vs. 18.1 +/- 0.7 fmol/mg).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of body composition, pre- and postpartum energy level and early weaning on reproductive performance of beef cows and preweaning calf gain.

Mature Charolais x Angus rotational cross cows were adjusted to moderate body condition by d 190 of gestation then randomly blocked to a maintenance (ME) or low-energy (LE) diet. At parturition, the 128 cows were randomly allotted within prepartum (PRP) diet to a high-energy (HE) or LE diet. At d 30 postpartum (PP), cows were randomly blocked to two treatments in which calves were weaned early (EW) or normally (NW) at 7 mo of age. Cows receiving a LE PRP diet had lighter calves at birth (34.7 vs 39.0 kg) and 105 d (127.9 vs 144.6 kg). Prepartum and PP energy interacted to affect postpartum anestrous interval (PPI, d) and cycling activity (%), respectively (LE-LE = 72.6, 33.3; LE-HE = 54.3, 56.3; ME-LE = 65.7, 52.9; ME-HE = 68.4, 54.3). High PP energy averaged over PRP diet increased (P less than .10) pregnancy rate by 22.7% and 105-d calf weight by 15.1 kg. Early weaning reduced PPI by 24.3 d (P less than .01) and first service conception rate by 21.7% (P less than .10). Cycling activity within 60 d PP was affected (P less than .01) by PRP diet and suckling status (LE-EW = 62.5, LE-NW = 26.7, ME-EW = 88.9, ME-NW = 13.3%). Thin cows had a longer PPI but had a higher first service conception rate than moderate and fleshy cows. Higher pregnancy rates were observed in cows approaching or maintaining average body condition from parturition to conception than for cows moving away from moderate body condition. Results suggest that fleshy and thin cows at parturition should be managed to approach moderate body condition before the breeding season to optimize reproductive performance and preweaning calf gain.

Effects of body composition, pre- and postpartum energy intake and stage of production of energy utilization by beef cows.

Mature Charolais x Angus cows (n = 128) were adjusted to a body condition score (BCS) of 3 (1 = very thin, 3 = moderate, 5 = very fat) between 130 and 190 d of gestation. When cows averaged 190 d of gestation, they were assigned randomly to a maintenance energy diet (ME) or to a diet very low in energy (LE). Cows were allotted within these prepartum (PRP) diets to a high-energy (HE) or LE diet at parturition. At 30 d postpartum (PP), cows were allotted to four treatments: a) slaughter at 0 (n = 32) or b) 48 h after calf removal (n = 32), c) cows whose calves were early weaned at 30 d PP (n = 32) or d) normally weaned at 205 d PP (n = 32). Low energy PRP intake reduced (P less than .01) BCS, cow weight, total empty body lipid (TEBL), body energy (BE) and daily predicted maintenance energy (PME)/W.75 by parturition. Pre- and postpartum energy intake combined to affect (P less than .10) these same factors in a similar manner at 30 d PP. From 30 to 60 d PP, early weaning reduced (P less than .05) PME/W.75. Cow BCS at 190 d of gestation had little effect (P greater than .10) on PME/W.75 or PME/Mcal of BE. Body condition score at parturition, however, affected (P less than .05) delta BCS, delta BE and PME/Mcal of BE by 30 and 60 d PP, with thinner cows losing less condition and requiring more PME/Mcal of BE. Cow BCS had a similar effect from 30 to 60 d PP. Total daily PME was greater for the fat cows during both the PRP and PP periods. Body composition, PRP and PP energy intake and early weaning affect energy requirements and energetic efficiency of beef cows.

Analysis of bovine udder, plate and viscera using near infrared reflectance spectroscopy.

The objective of this study was to evaluate near infrared reflectance spectroscopy (NIRS) as an accurate and inexpensive alternative to conventional chemical analyses of nonconsumer bovine tissue. Udder, plate and visceral samples were collected from mature, Charolais-Angus and Hereford-Angus crossbred beef cows at slaughter, ground and analyzed for concentrations of lipid, protein and dry matter using standard AOAC chemical procedures. Samples were analyzed using NIRS. The collection of samples was randomly split into separate calibration and validation sets. Nine calibration equations representing each constituent and tissue combination were developed, using first- or second-order derivative mathematical transformations, and those calibration equations were validated. Correlation coefficients of calibration (R) and validation (r) ranged from .95 to .98 and from .87 to .97, respectively, for all analyses except plate dry matter (r = .77). Standard errors of calibration and prediction ranged from 1.89 to 5.81%. Results from this study are interpreted to indicate that bovine udder, plate and visceral tissue composition can be accurately, quickly and efficiently predicted using NIRS technology.