T.T. Marston

Effects of early weaning on carcass and ribeye steak characteristics of bulls and steers

Crossbred Hereford × Angus calves (n = 103) were used to determine the effect of early weaning on carcass and ribeye (longissimus muscle) characteristics of bulls and steers. Treatments were: 1) early-weaned (117 days of age) bulls, 2) early-weaned steers, 3) normal-weaned (220 days of age) bulls, and 4) normal-weaned steers. Cattle were harvested at 360 and 389 days of age. At 36 hours postmortem, carcass quality and cutability were measured. Ribeye steaks were aged 14 days and scored for color, Warner-Bratzler shear force, and sensory panel evaluations. Carcasses from early-weaned cattle had greater dressing percentages, heavier weights, greater fat thicknesses, and higher numerical USDA Yield Grades (lower cutability). They also had more marbling and greater USDA quality grades, but had similar longissimus color, shear force, and sensory panel scores, compared with those of normal-weaned cattle. Bulls had greater dressing percentages, but had similar carcass weights to steers. Bull carcasses had less fat thickness and greater ribeye areas, resulting in lower numerical USDA Yield Grades (higher cutability) than steers had. They also had less marbling, darker color, and lower USDA quality grades than steers did. Longissimus muscles from bulls were darker, had greater shear forces, and had lower sensory panel tenderness scores than those from steers. For early-maturing British-type cattle, early weaning is a viable management strategy to produce heavier, higher-quality carcasses than those of normalweaned cattle. Carcasses from early-weaned cattle are fatter and have lower cutability. For a non-implant “natural” market, bulls could be an alternative for producing high-cutability carcasses. Steaks may be less tender, however, and pre-harvest management must be optimized to reduce dark-cutting carcasses.

Aging improves tenderness of longissimusmuscle steaks from fed mature cows

Introduction Steaks from cows are tougher than those from young steers and heifers. This difference is often attributed to the increased cross-linkage of collagen in muscle of mature animals that is considered very stable and more resistant to postmortem degradation. Aging steaks from young steers and heifers is a common postmortem practice used to improve tenderness of steaks from the ribeye roll and strip loin. Improvement in tenderness because of aging has been attributed to enzymatic degradation of, primarily, the myofibrillar fraction of muscle and is most beneficial for low connective tissue muscles. Because muscles from mature cows have more collagen cross-linking, postmortem tenderization methods, such as blade tenderization and enzymatic tenderization, are often used to increase tenderness of steaks from mature cows. However, few studies have investigated the effect of aging on tenderness of longissimus muscle steaks from fed mature cows. Therefore, the objective of this study was to determine effects of aging on tenderness of longissimus steaks of fed mature cows from different management strategies.

The combination of implanting with Revalor-200 and feeding Zilmax increases ribeye area of fed cows

Introduction Mature cows are typically removed from the cow herd for various reasons, such as reproductive inefficiency and poor performance. It has been estimated that as much as 15 to 25% of a ranch’s revenue may be from cull cows. When cows are culled from the herd, they are normally in thin condition and potentially can be fed to gain weight and increase income. Previous studies indicate that feeding a high-energy diet and implanting cull cows can improve performance and increase meat yield.

The combination of implanting with Revalor-200 and feeding zilmax increases subprimal meat yield of fed cows

Introduction Mature cows are culled from herds for reasons such as poor performance and failure to rebreed. When these cows are removed from the herd, they are typically in thin condition and potentially can be fed to gain weight and increase income. Previous research has shown that feeding cull cows high-energy diets can increase carcass weight, fatness, and meat yield. Management practices of implanting and feeding β-adrenergic agonists, repartitioning agents that favor protein deposition at the expense of fat deposition, have been shown to further improve performance and carcass yields. As reported elsewhere in this publication, carcasses from concentrate-fed cows implanted with Revalor-200 (Intervet Inc., Millsboro, DE) and fed Zilmax (zilpaterol hydrochloride; Intervet Inc.) had more muscling as indicated by larger ribeye areas than carcasses from grass-fed cows and both implanted and non-implanted concentrate-fed cows. These carcasses potentially would have increased subprimal meat yields. Therefore, the objective of this study was to determine the effects of concentrate feeding, implanting, and feeding Zilmax on subprimal meat yield of mature cows fed for 70 days.

Management practices affect tendernessof strip loin but not knuckle steaks fromfed mature cows

Introduction Approximately 16% of cattle slaughtered in the United States are cows. When these cows are removed from the herd, they are typically in thin condition. Steaks from these cows are considered tougher than those from young steers and heifers but could potentially be improved with alternative management practices, such as high-concentrate feeding. Feeding high-concentrate diets, implanting, and feeding β-agonists prior to harvest have been shown to improve performance and carcass meat yields. However, the effect on steak tenderness of feeding Zilmax (zilpaterol hydrochloride; Intervet Inc., Millsboro, DE) to mature cows is unknown. Therefore, the objective of this study was to determine the effects of concentrate feeding, implanting, and feeding Zilmax on tenderness of strip loin and knuckle steaks from cull cows fed for 70 days.

Aging, blade tenderization, and injection impacts tenderness of muscles from fed steers

Enhancement of steer and heifer meat has become a common practice, especially for some large retailers in the United States, because it increases the weight of salable product and decreases variability in tenderness and juiciness. Enhancement also may reduce the aging period for some muscles. Muscles for this research were identified by National Cattlemen’s Beef Association (NCBA) as possible muscles in which value could be added with some type of postmortem tenderization treatment. If muscles are enhanced, aging may become less important, thus allowing more efficient and faster processing of those cuts. Therefore, the objective of this research was to determine the influence of aging period on tenderness of enhanced muscles from three intermediate-priced steaks.

Aging, blade tenderization, and enzyme injection impacts tenderness of muscles from fed cull cows of known age

Approximately 16% of the 31 million head of cattle harvested in the United States in 2005 were aged cows. Cow meat is known to be tougher than meat from young steers and heifers, and it typically has a less desirable, darker color. It is generally assumed that cow meat needs to be ground or have some form of postmortem tenderization applied to be merchandized as a whole muscle product. The knuckle, top sirloin, and top blade muscles have been identified as muscles that potentially can be upgraded to medium-priced steaks. Most cow steaks are fabricated by food-service providers for their customers with different specifications for aging and post-mortem tenderization application. Aging, blade tenderization, and injection enhancement are commonly used on cow meat to increase tenderness. It is unknown if extended aging is needed in addition to the other two methods to improve tenderness. If shorter aging periods can be used without compromising an improvement in tenderness, then aging costs would be greatly reduced. Our objective was to determine the effects of days of aging on tenderness of cow steaks from the knuckle, top sirloin, and top blade that were blade tenderized and injected with an enhancement solution containing an enzyme tenderizer.

Effects of early weaning on feedlot performance of bulls and steers

Crossbred Hereford × Angus calves (n = 103) were used to determine the effects of early weaning on feedlot performance of bulls and steers. Treatments were: 1) early-weaned (117 days of age) bulls, 2) early-weaned steers, 3) normal-weaned (220 days of age) bulls, and 4) normal-weaned steers. Earlyweaned calves were placed on a grower ration at an average age of 134 days and on a finishing ration at 182 days of age. Normal-weaned calves were placed on a finishing ration at 242 days of age. Weight, feed intake, and ultrasound measurements were recorded during the feeding period. Three early-weaned cattle were removed due to chronic bloat, and four early-weaned cattle died in the feedlot. The feedlot period was terminated at either 358 or 387 days of age. Early-weaned cattle had greater average daily gains early in the feedlot period, but normal-weaned cattle had greater gains later in the feedlot period. Excluding the initial weight at 117 days of age, earlyweaned cattle maintained heavier weights throughout the feeding period. Bulls had greater average daily gains until feedlot entry of normal-weaned calves, but steers had greater average daily gains later in the feedlot period, resulting in similar final weights. For early-maturing British-type cattle, early weaning resulted in heavier final weights, but it may not be the most viable management strategy because of disadvantages in animal health. Overall, there was no growth-performance advantage for leaving males intact, suggesting that the implant regimen used for these steers was sufficient to compensate for the expected loss in performance when bulls are castrated. Introduction

Effect of castration time on feedlot performance, carcass characteristics, and beef tenderness

Crossbred Angus calves (n=120) were randomly assigned to early-castrated, earlycastrated plus implant, and late-castrated treatment groups. After weaning, calves were placed on feed at the Western Kansas Agricultural Research Station in Hays, Kansas, for finishing. On-feed weights and final weights were similar among treatments. During the first 132 days on feed, the steers castrated early and implanted had a lower average daily gain than earlyand latecastration treatments. Early castrates tended (P=0.08) to have a lower feed-to-gain ratio for the first 132 days on feed. Hot carcass weight, internal fat, and marbling scores were not affected by treatment. Carcasses from steers castrated late had less backfat, larger ribeye areas, and lesser yield grades (greater cutability) than carcasses from steers castrated early, with or without an implant. Carcasses from steers castrated early and implanted had a greater percentage grading USDA choice (60%) than did carcasses from steers castrated early (45%) or late (41%). Warner-Bratzler shear force and sensory-panel traits were similar for all treatment groups.

Effects of early weaning on performance of cow/calf pairs

Commercial cow/calf pairs (Angus based, n=103) were used to determine the effect of calf weaning age on cow body weight and body condition score (scale=1 to 9) and calf performance in terms of subcutaneous fat and marbling deposition. Only cows with male progeny (steers, n=52; bulls, n=51) were used in this study. Treatments were: 1) earlyweaned bulls, 2) early-weaned steers, 3) traditionally weaned bulls, and 4) traditionally weaned steers. Cow/calf pairs grazed pastures at four different locations. Calving began February 1, 2003, and ended in early April. In the early-weaned treatment group, calves were weaned June 25, with an average age of 115 days. In the late-weaned treatment group, calves were weaned October 6, with an average age of 218 days. The data indicate that the cows in the early-weaned treatment group gained 121 lb more weight (P<0.0001), had 0.13 inches more external backfat (P<0.0001), and had an average body condition score 1.2 greater (P<.0001) than their late-weaned counterparts. All steer calves were implanted before they entered the feedlot. Early weaning and subsequent feedlot placement produced heavier calves at approximately nine months of age. Ultrasound technology indicated that early-weaned calves had greater backfat and marbling scores 26 days after feedlot placement than did traditionally weaned calves. However, the early–weaned bulls had less backfat at a similar average weight to their steer contemporaries. Introduction