Monitoring Changes in Carcass Quality Across Time-on-Feed Using Real-Time Ultrasound to Optimize Marketing Endpoints11Research was supported by the Idaho Cattle Association

The effect of anabolic implants on intramuscular lipid deposition in finished beef cattle

Two experiments were conducted to determine the effects of anabolic implants on performance, changes in ultrasound measurements, carcass quality, cellularity of i.m. and s.c. adipose depots, and mRNA expression of acetyl CoA carboxylase (ACC), stearoyl CoA desaturase (SCD), and lipoprotein lipase (LPL) in i.m. adipose tissue of finished beef cattle. Angus heifers (experiment 1: n = 10; 411 kg of BW) and steers (experiment 2: n = 18; 279 kg of BW) were randomly allotted as control (C) or implanted with Synovex-Plus (SP) at d 0 and midway through the finishing period. The cattle were fed a high-concentrate diet and were weighed at approximately 28-d intervals. Heifers and steers were finished for 108 and 133 d, respectively. At slaughter, a section of the LM (sixth to ninth rib) was removed, and i.m. adipose tissue was dissected for mRNA analysis. Subcutaneous and i.m. adipose tissues also were collected for determination of cellularity. At 48 h postmortem, carcass data were collected, and a steak (12th rib) was removed for analysis of lipid and fatty acid composition. Body weight did not differ (P > 0.10) between treatments until after reimplanting of the heifers (d 55) or steers (d 73). Average daily gain was 36 and 16% faster (P < or = 0.01) for implanted heifers and steers, respectively, compared with their control counterparts. Implanting resulted in larger (P < or = 0.10) HCW and LM area for heifers and steers. However, implanting did not affect (P > 0.10) dressing percent, fat thickness, percentage of KPH, yield grade, or marbling score. Intramuscular lipid content and concentrations of major fatty acids did not differ (P > 0.10) between treatments. Percentage of SC adipocytes was greater at larger diameters ( > 150 microm), whereas the majority of i.m. adipocytes were at small to middle diameters (50 to 150 microm). The number of i.m. adipocytes per gram of tissue was greater (P < 0.05) for SP than C and also were greater (P < 0.05) than the number of s.c. adipocytes in SP heifers. In experiment 2, adipocytes per gram of tissue tended to be greater (P = 0.07) for SP than C and were greater (P < 0.01) for i.m. than s.c. In experiment 1, average cell diameter and volume did not differ (P > 0.10) between treatments and tissues, but in experiment 2 both cellularity traits were greater (P < 0.01) for s.c. than for i.m.. Implanting did not alter mRNA expression of ACC, SCD, or LPL in i.m. adipose tissue. This study shows that anabolic implants do not appear to have direct effects on i.m. lipid deposition.

Factors affecting carcass value and profitability in early-weaned Simmental steers: II. Days on feed endpoints and sorting strategies

In a 4-yr study, early-weaned Simmental steers (n = 192) of known genetics were individually fed to determine EPD, performance, and carcass measurements explaining variation in carcass value and profitability across incremental days on feed (DOF) when sorted by HCW, calculated yield grade (YG), or at their highest profit endpoint (BEST). Steers were weaned at 88.0 +/- 1.1 d of age, pen-fed a high-concentrate diet for 84.5 +/- 0.4 d, individually fed for 249.7 +/- 0.7 d, and slaughtered at 423.3 +/- 1.4 d of age. Carcass weight, YG, and marbling score (MS) were predicted using real-time ultrasound throughout the finishing period to calculate carcass value and profitability at 90, 60, 30 d preslaughter and under three individual sorting strategies. Sorting strategies included marketing the 25 and 50% heaviest HCW, the highest YG at d 60 and 30, or the remaining 25% at 0-d endpoints. Independent variables were year, weaning weight EPD, yearling weight EPD, marbling EPD, DMI, ADG, HCW, YG, and MS. Profit was quadratic in response to increased DOF; the greatest economic return was noted on d 30 (pre-slaughter). Final weight, DMI, HCW, MS, and YG increased (linear; P < 0.001) with additional DOF, and ADG and G:F decreased (linear; P < 0.001). Total cost of gain was quadratic (P < 0.001), and incremental cost of gain rose at an increasing rate (quadratic; P < 0.001) with increased DOF. With increasing DOF, HCW importance decreased from 58 to 21%; MS was variable, ranging from 18 to 23%; and YG and DMI were minor contributors to profit variation. Among sorting strategies, final BW and HCW were greater for BEST, whereas other measurements were similar. Sorting individuals by HCW, YG, or at BEST increased profitability 3.70 dollars, 2.52 dollars, or 30.65 dollars over the optimal group DOF endpoint (d 30). Retrospective analyses illustrated that sorting does not need to pinpoint each animal's profit optimum to result in economic gains; rather, increasing HCW and decreasing weight- and YG-related penalties improved profitability. Opportunities may exist with existing and new technology to uniformly allocate cattle into feeding and marketing groups, decrease overfeeding, and increase carcass value and profitability.

Effects of supplemental rumen-protected conjugated linoleic acid or linoleic acid on feedlot performance, carcass quality, and leptin concentrations in beef cattle1

Thirty-six Angus x Hereford heifers (365 kg) were used to determine effects of dietary lipid supplementation from two sources during the final 32 or 60 d of feeding on serum and adipose tissue leptin concentrations, animal performance, and carcass characteristics. Following an initial feeding period of 56 d, heifers were fed one of three diets in a 3 x 2 factorial arrangement: 1) basal diet, 2) basal diet plus 4% (DM basis) corn oil, or 3) basal diet plus 2% (DM basis) rumen-protected conjugated linoleic acid (a mixture of Ca-salts of palm oil fatty acids with 31% conjugated linoleic acid). Jugular blood samples were collected at 28-d intervals (d 28 to 118) and serum subsequently harvested for leptin quantification via RIA. Real-time ultrasound measurements were collected at 28-d intervals across time on feed. At slaughter, samples were obtained from various adipose depots. Data were analyzed with dietary treatment, length of supplementation, adipose depot (when appropriate), and all two- and three-way (when appropriate) interactions in the repeated measures model. Measures of feedlot performance, including ADG, DMI, and gain:feed did not differ (P > 0.23) with dietary treatment or supplementation length. Heifers supplemented with corn oil tended (P < 0.07) to have higher marbling scores following 32 d of treatment than those supplemented with rumen-protected conjugated linoleic acid, with controls intermediate. Quality grade and hot carcass weight did not differ (P > 0.15) with treatment or length of supplementation. Leptin concentrations were higher (P < 0.05) from d 57 to 118 on feed than the initial period (d 0 to 56) of dietary adaptation when all animals received the basal diet. Circulating leptin concentrations were not affected by dietary treatment. However, leptin concentrations in adipose tissues were greater (P < 0.05) for heifers supplemented with corn oil than either control or rumen-protected conjugated linoleic acid diets, which did not differ. Compared with adipose tissues from rumen-protected conjugated linoleic acid-supplemented animals, tissues from heifers fed corn oil contained 68% greater leptin concentration. Correlations between performance, carcass traits, and serum leptin concentrations were low. Serum leptin concentrations across time on feed were not associated with carcass and performance data, including ADG, DMI, and gain:feed. Based on these data, concentrations of leptin are not related to indices of feedlot performance and carcass quality in beef cattle.