Genomic testing of feeder cattle is reported to be beneficial in selecting cattle for the feedlot, as well as making management and marketing decisions. The objective of this study was to determine differences in performance and efficiency of finishing steers with a range of Neogen Igenity Beef scores for average daily gain (ADG) and milk. Spring born steer calves from the Oklahoma State University Range Cow Research Center (n = 83, BW = 419 ± 31.9) of Angus ancestry were placed on feed at the Willard Sparks Beef Research Center on May 5, 2022, after grazing wheat pasture for 155 d. The steers were grouped based on Igenity ADG Score [low (1-4), medium (5-6), or high (7-10)] and Milk Score [low (1-5) or high (6-10)] based on the Igenity results. Steers were allocated into pens (n = 5 steers/pen) in heavy and light BW blocks. Steers were fed a step-up diet for 30 d before being switched to a finishing ration diet (8% prairie hay, 20% Sweet Bran and 62% dry-rolled corn). Cattle were fed ractopamine for 30 d before slaughter. The heavy block were on feed for 119 d, while the light block were on feed for 148 d. Data were analyzed as a randomized complete block design using the mixed procedure of SAS (SAS Inst. Inc., Cary NC) with pen as the experimental unit. Steers with high growth (HG) scores gained weight more rapidly during finishing and weighed more at slaughter than medium growth (MG) and low growth (LG; P < 0.01); while steers with high milk (HM) gained faster (P < 0.01) and tended (P = 0.06) to be heavier at slaughter than low milk (LM). Growth score was shown to have an effect on dry matter intake (P < 0.01) with HG consuming more feed than MG or LG. Cattle with HM scores were less efficient than LM scores (P = 0.01), but there was no difference (P = 0.37) in feed efficiency due to ADG score. Those with high growth and milk scores had a higher average daily gain (P < 0.01). These data indicate that Igenity ADG scores can be used to select cattle with higher performance and bodyweight at slaughter with no adverse effect on feed efficiency. Steers with higher Igenity Milk scores were less efficient than those with LM scores. Igenity Milk scores can be used to predict efficiency, according to these data.
The objective of this study was to rank beef heifers for residual feed intake and greenhouse gas emissions using an unprocessed, grass hay diet. Fifty yearling Angus heifers were monitored for 62 days using the SmartFeed individual intake measuring technology (C-Lock Inc., Rapid City, SD) in drylot pens at the Oklahoma State University Range Cow Research Center located in Stillwater, OK. Means ± SD for dry matter intake (DMI; 6.76 ± 1.20 kg), average daily gain (ADG; 0.51 ± 0.21 kg), body weight (BW; 338.67 ± 55.24 kg), and residual feed intake (RFI; -0.04 ± 0.80 kg) were recorded while the heifers were fed unprocessed long-stem grass hay (10.3% CP, 2.0 Mcal ME, and 56% TDN). Additionally, a subset of 29 heifers were subjected to the collection of gas flux data using an open-circuit, portable, gas-quantification system (GreenFeed, C-Lock Inc., Rapid City, SD) to measure (means ± SD) oxygen consumption (O2; 3979.51 ± 510.32 g), carbon dioxide production (CO2; 5299.65 ± 610.89 g), and methane production (CH4; 202.656 ± 28.30 g). Using R, RFI was calculated using a multiple regression equation to predict DMI using BW0.75 and ADG (P > 0.05; R2 = 0.37). To analyze forage utilization efficiency, heifers were classified into three RFI categories consisting of efficient (n = 16), average (n = 16), and inefficient (n =18). The ADG was low for all RFI classifications and similar for all three categories (P < 0.05). Heifers classified in the top third of RFI rank consumed 22% less forage per day compared to the inefficient heifers. The phenotypic correlation between DMI with CO2, CH4, and O2 was 0.66, 0.18, and 0.49, respectively. These data suggest that progress in feed efficiency can be achieved when cattle are tested using a moderate-quality, unprocessed forage diet.
The objective of the study was to evaluate if a genetic relationship exists between pulmonary arterial pressure (PAP) measured at high elevation with traits associated with moderate elevation feedlot and carcass traits. For this analysis, PAP, feed intake, and carcass data were taken from 6,898, 558, and 1,627 animals, respectively. At an elevation of 2,115 m, PAP measurements were collected, then a selective group of steers was relocated to a moderate elevation feedlot (1,500 m) where feed intake data were collected. Genetic relationships were evaluated with 5-trait animal models using REML statistical analysis. For all traits in the analysis, fixed effects and contemporary groups were assigned as well as a direct genetic random effect. For weaning weight, a maternal permanent environmental effect was applied in the analysis. For PAP, the heritability estimate was 0.29 ± 0.03. Genetic correlations between PAP with feedlot traits was positive, with estimates of 0.34 ± 0.20 (average dry matter intake) and 0.05 ± 17 (average daily gain). The strongest genetic correlation between PAP and carcass performance traits were those of rib eye area (-0.30 ± 0.12) and calculated yield grade (0.29 ± 0.13). Genetic correlations between PAP and marbling score, back fat, or hot carcass weight were 0.00 ± 0.13, -0.07 ± 0.13, and 0.14 ± 0.10, respectively. These results suggest a favorable genetic relationship exists between PAP with feedlot and carcass traits.
Forage and supplemental feed costs remain the overriding factors driving profitability in U.S. cow/calf operations. The cow/calf sector uses 74% of the total feed energy required to produce one pound of carcass weight. Methane is the second most abundant anthropogenic greenhouse gas after carbon dioxide. The cow/calf sector of beef production accounts for 77 to 81% of enteric methane emissions per unit of carcass weight produced. Reducing feed energy required and methane emissions by the cow/calf segment of the beef production system will improve economic, environmental, and social sustainability. Most of the beef production cycle occurs on land not suitable for raising crops. Of the 2.3 billion acres available in the United States, about 655 million acres (29%) are classified as grassland pasture and rangeland, and 316 million acres (14%) are identified as parks and wildlife areas, some of which are grazed. Therefore, improving forage utilization efficiency would have a wide-reaching impact on U.S. food security and profitability of cow/calf enterprises. Beef production is a critical component in U.S. and global food security because cattle upcycle poorly digestible plant components and food waste products into high-quality human edible protein. In recent years, substantial progress has been made in understanding biological variation and genetic components of feed efficiency in growing animals consuming energy-dense mixed diets during the post-weaning phase. Much less is known about within-animal variation of forage utilization efficiency for beef cows consuming moderate to low-quality forage diets common to most cow/calf production systems. Considerable evidence indicates the existence of an environment by genetic interaction for feed efficiency. More rapid progress in forage utilization efficiency and reduction in greenhouse gas emissions could be made by studying forage utilization efficiency directly.
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