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  • 1
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    272 Effect of Frame Size and Supplementation on Performance and Carcass Characteristics of Beef Cattle Finished on Novel Endophyte-infected Tall Fescue Pastures
    Oxford University Press (OUP) ; 2021
    In:  Journal of Animal Science Vol. 99, No. Supplement_3 ( 2021-10-08), p. 140-141
    Details
    In: Journal of Animal Science, Oxford University Press (OUP), Vol. 99, No. Supplement_3 ( 2021-10-08), p. 140-141
    Abstract: Objectives were to investigate the effects of frame score (FS) and supplementation on performance and carcass characteristics of cattle finished on novel endophyte-infected fescue pastures. This 2-yr experiment used 80 Angus-sired, crossbred steers and heifers bred for divergent FS. Cattle were allotted to 5 treatments: 1) non-supplemented small frame (S-NON; FS = 3.0 ± 0.9), 2) supplemented small frame (S-SUPP), 3) non-supplemented large frame (L-NON; FS = 4.7 ± 0.6), 4) supplemented large frame (L-SUPP), and 5) grain-based control feedlot ration (CON; FS = 4.2 ± 0.6; target ADG = 1.36 kg/day). Daily rations were delivered individually using Calan gates. Pasture supplement contained corn gluten feed, a commercially available rumen-protected prilled vegetable fat, and dried molasses fed at 0.5% of BW. Treatments started on 7/8/2019 and 5/21/2020, and ended in November of each yr when cattle were slaughtered at a commercial abattoir. Results were analyzed using PROC MIXED of SAS with main effects of treatment, sire, sex, yr, and yr x treatment, with contrast statements comparing large vs. small frame, pasture supplemented vs. non-supplemented, and control vs. pasture groups. As expected, CON had greater (P & lt; 0.001) growth performance (final BW and ADG) and carcass characteristics (HCW, subcutaneous fat, marbling, dressing percentage (DRESS%) than pasture groups, and tended to have greater (P=0.053) REA. Relative to pasture groups, CON had greater (P & lt; 0.001) Minolta L* and a* lean tissue values, and decreased (P & lt; 0.001) b* values for fat tissue. While non-supplemented cattle had decreased (P = 0.016) yield grades (YG), supplemented cattle had greater (P & lt; 0.050) final BW, ADG, subcutaneous fat, HCW, marbling, and DRESS% compared to non-supplemented cattle. Small framed cattle tender to have decreased (P = 0.056) YG; but, large framed cattle had greater (P = 0.006) HCW, and tended (P = 0.060) to have greater ultrasound subcutaneous fat. Results support low-level supplementation in pasture-finishing systems to improve carcass value.
    Type of Medium: Online Resource
    ISSN: 0021-8812 , 1525-3163
    URL: Article
    DOI: 10.1093/jas/skab235.257
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2021
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  • 2
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    133 Ranking Mature Beef Cows for Residual Intake Using an Unprocessed Grass Hay Diet and Its Relationship to Greenhouse Gas Exchange
    Oxford University Press (OUP) ; 2022
    In:  Journal of Animal Science Vol. 100, No. Supplement_1 ( 2022-03-08), p. 35-35
    Details
    In: Journal of Animal Science, Oxford University Press (OUP), Vol. 100, No. Supplement_1 ( 2022-03-08), p. 35-35
    Abstract: The objective of this study was to compare high and low residual feed intake (RFI) beef cows when consuming an unprocessed, grass hay diet (93% DM, 8.73% CP, 2.11 Mcal ME, and 59.25% TDN). Relationships of hay intake to carbon dioxide (CO2) and methane (CH4) production were also evaluated. Thirty-six mature Angus and Angus x Hereford cows were assigned randomly to five pens (n = 6 or 9) and individual feed intakes were collected for 52-d using SmartFeed intake units (C-Lock Inc., Rapid City, SD) at a stocking rate of 3 cows per feeder. An open-circuit, gas-quantification system (GreenFeed, C-Lock Inc., Rapid City, SD) was used to collect CO2 (7611.63±714.09 g) and CH4 (283.64±37.10 g) production for 9 days of collection per pen for a minimum of 20 visits per cow (n = 22 cows, 36.18±14.24 visits). Data collection on cows included (means ± SD) dry matter intake (DMI; 13.86±2.16 kg), metabolic body weight (MBW, 111.65±9.28 kg), average daily gain (ADG, 0.77±0.29 kg), and rib eye area by ultrasound (REA, 46.62±6.34 cm).To calculate RFI (0.03±1.71), a multiple regression model was used to predict DMI (PDMI = ADG + REA + MBW; R2=0.50, P = 0.001). Cows were categorized into three RFI classes: low (n = 7), moderate (n = 6), and high (n = 9). Differences between RFI and RFI class and DMI and RFI class were analyzed using PROC MIXED in SAS (SAS, Cary, NC). Low RFI cows (-1.81 kg) consumed 12.08 kg hay DM daily and high RFI cows (1.59 kg) consumed 15.27 kg hay DM daily (P & lt; 0.001). Correlations between DMI and daily gas exchange were estimated using PROC CORR in SAS (SAS, Cary, NC). Pearson Correlation Coefficients were significant between DMI and CO2 (r=0.58, P = 0.004), and CH4 (r=0.70, P & lt; 0.001) production. Differences in feed intake for high and low RFI rankings were similar to previously reported literature when growing cattle consumed energy-dense diets.
    Type of Medium: Online Resource
    ISSN: 0021-8812 , 1525-3163
    URL: Article
    DOI: 10.1093/jas/skac028.067
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2022
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  • 3
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    137 Replacement Heifer Gain, Feed Intake and Efficiency While Consuming an Unprocessed Hay Diet Followed by a Mixed Concentrate/Forage Diet
    Oxford University Press (OUP) ; 2023
    In:  Journal of Animal Science Vol. 101, No. Supplement_1 ( 2023-05-04), p. 81-82
    Details
    In: Journal of Animal Science, Oxford University Press (OUP), Vol. 101, No. Supplement_1 ( 2023-05-04), p. 81-82
    Abstract: The objective of this study was to evaluate weight gain, feed intake, and feed efficiency in beef heifers while consuming two diets divergent in energy density. Fifty-four yearling Angus and Angus cross heifers (initial body weight = 307.5 ± 30.35 kg) were subject to sequential intake trials using SmartFeed individual intake measuring technology (C-Lock Inc., Rapid City, SD) in drylot pens at the Oklahoma State University Range Cow Research Center. The first intake period (HAY) was initiated on July 15 (d -21) with a 21-d adaptation period and a 70-d intake period. Bermudagrass hay (10.3% CP, 2.0 Mcal ME, and 56% TDN) and a salt/mineral/vitamin supplement was offered on an ad libitum basis throughout the experiment. The second intake period was initiated on d-92 and included 14 d of adaption with 42 d of data collection. A mixed diet (12.4% CP, 45% NDF, and 65% TDN) consisting of 50% chopped bermudagrass hay, concentrate feeds, and a liquid supplement containing minerals and vitamins (TMR) was offered on an ad libitum basis. In both periods, weights were recorded every 14 days, and ADG was calculated by regressing body weight over time. Dry matter intake (DMI) and residual feed intake (RFI) were calculated at the end of each feeding period. Statistical regression equations were used to predict RFI for both HAY and TMR, including average metabolic body weight and average daily gain for each of their respective trials. For RFI, cattle were classified as inefficient, average, or efficient based on 0.5 SD away from the mean RFI score. Descriptive statistics for HAY evaluated traits of DMI, ADG, and RFI (means ± SD) were 5.49 ± 0.84 kg, 0.15 ± 0.16 kg, and 0.0 ± 1.01 kg, respectively. Means ± SD for DMI, ADG, and RFI for TMR were 9.54 ±1.26 kg, 1.45 ± 0.38 kg, and 0.0 ± 0.15 kg. Spearman rank correlations for DMI, ADG, and RFI were 0.35 (P = 0.0089), 0.16 (P = 0.2367), and 0.52 (P & lt; 0.0001), respectively. This initial study suggests that intake of hay and a mixed diet may be modestly correlated, while there is no relationship of weight gain when consuming forage and weight gain consuming a mixed, processed diet.
    Type of Medium: Online Resource
    ISSN: 0021-8812 , 1525-3163
    URL: Article
    DOI: 10.1093/jas/skad068.097
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2023
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  • 4
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    320 Effect of Breed of Sire and Calving Season on Feedlot Performance and Carcass Characteristics
    Oxford University Press (OUP) ; 2022
    In:  Journal of Animal Science Vol. 100, No. Supplement_3 ( 2022-09-22), p. 153-154
    Details
    In: Journal of Animal Science, Oxford University Press (OUP), Vol. 100, No. Supplement_3 ( 2022-09-22), p. 153-154
    Abstract: Four years of feedlot performance and carcass characteristics were pooled on spring-(SPRING) and fall-(FALL) born steers (n=460) into a mixed model to evaluate the effects of calving season, sire breed (Angus [AN], Charolais [CHAR] or Hereford [HER]) and their interaction on feedlot performance and carcass traits. Initial and final BW, DOF, ADG, DMI, and G:F were evaluated as performance measures and HCW, YG, FT, REA, and MS were collected at harvest. There was no season by breed interaction for entry or final BW (P & gt;0.05). SPRING steers (400.2 kg, 686.4 kg) weighed more than FALL (350.9 kg, 668.3 kg) upon entering and leaving the feedyard (P & lt; 0.001). CHAR weighed 14.3 kg less than AN upon feedlot entry (P=0.01) although final BW did not differ by breed (P & gt;0.05). SPRING steers (21.8 kg/d) consumed more feed than FALL steers (18.8 kg/d; P=0.002), but there was no difference in gain:feed due to calving season nor sire breed (P≥0.575). A calving season by sire breed interaction was present for ADG and DOF (P≤0.014). FALL AN (1.70 kg/d) and FALL HER (1.80 kg/d) gained more than FALL CHAR (1.55 kg/d;P & lt; 0.001) and FALL AN were fed over a shorter period than FALL CHAR and FALL HER (P≤0.006). However, average daily gain of SPRING calves did not differ by breed (P & gt;0.05). There was a tendency for FALL (400.9 kg) steers to have lighter carcasses than SPRING steers (407.9 kg; P=0.068). HER carcasses were 18.0 kg heavier than AN carcasses (P & lt; 0.001), but did not differ from CHAR (P=0.13). CHAR had larger REA (93.5 cm2) than both AN (87.7 cm2) and HER steers (88.5 cm2;P≤0.001). Fall-born steers had less YG than spring-born steers (P & lt; 0.042). Feedlot performance was generally less for fall-born steers finished during the winter months. Under these conditions, numerous performance and carcass traits were influenced by the interaction of breed and season.
    Type of Medium: Online Resource
    ISSN: 0021-8812 , 1525-3163
    URL: Article
    DOI: 10.1093/jas/skac247.285
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2022
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  • 5
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    Effects of bale feeder design on hay waste, intake, and apparent diet digestibility in gestating beef cows
    Oxford University Press (OUP) ; 2021
    In:  Translational Animal Science Vol. 5, No. 3 ( 2021-07-01)
    Details
    In: Translational Animal Science, Oxford University Press (OUP), Vol. 5, No. 3 ( 2021-07-01)
    Abstract: Two experiments were conducted to determine the effects of feeder design on hay intake, apparent diet digestibility, and hay waste in gestating beef cows. Native tallgrass prairie hay and a protein supplement was fed throughout both experiments. In Exp. 1, 56 crossbred cows were used in a Latin square arrangement. Feeder design treatments included a conventional open bottom steel ring (OBSR), an open bottom polyethylene pipe ring (POLY); a sheeted bottom steel ring (RING), and a sheeted bottom steel ring with a basket (BASK). Cows were weighed and allotted based on BW to one of four previously grazed 2.0 ha paddocks equipped with a concrete feeding pad. Fourteen cows were assigned to each paddock and three round bales were fed consecutively within each treatment period. The cows acclimated to the feeders while the first bale was being consumed. Subsequently, hay waste data were collected while the second and third bale within each period were being consumed. Waste was measured for each bale at 24, 48, 72, and 96 h after each bale was introduced into the pen. Hay waste was significantly affected by hay feeder design with 19.7, 21.1, 12.4, and 5.5% of original bale weight wasted for OBSR, POLY, RING, and BASK, respectively (P & lt; 0.01). There was a feeder design × day interaction (P & lt; 0.01) with greater waste when the bale was first introduced into the pen in OBSR, POLY, and RING feeders and gradually declining thereafter, while waste from the BASK feeder was consistently low. There was a tendency (P = 0.06) for cows eating from OBSR feeders to consume less hay than cows eating from RING feeders. Feeder design did not influence apparent diet digestibility (P = 0.46). In Exp. 2, 64 crossbred cows (body weight = 590 ± 59 kg) were used to determine waste, forage intake, and apparent diet digestibility when hay was fed from a sheeted bottom steel ring (RING) or a RING feeder with a cone insert (CONE). More hay was wasted when cows were fed from RING feeders compared to CONE feeders (11.9% vs. 4.8%, P & lt; 0.01). Feeder design had no effect on DMI or apparent digestibility (P & gt; 0.45). Hay savings from adopting a more conservative feeder design can have a dramatic influence on hay utilization by beef cows and thus on cost of production.
    Type of Medium: Online Resource
    ISSN: 2573-2102
    URL: Article
    DOI: 10.1093/tas/txab104
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2021
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  • 6
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    39 Cow-calf Management Strategies and Their Influence on Environmental Sustainability
    Oxford University Press (OUP) ; 2022
    In:  Journal of Animal Science Vol. 100, No. Supplement_1 ( 2022-03-08), p. 22-23
    Details
    In: Journal of Animal Science, Oxford University Press (OUP), Vol. 100, No. Supplement_1 ( 2022-03-08), p. 22-23
    Abstract: 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.
    Type of Medium: Online Resource
    ISSN: 0021-8812 , 1525-3163
    URL: Article
    DOI: 10.1093/jas/skac028.043
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2022
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  • 7
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    136 Relationship of Mature Beef Cows on an Unprocessed Hay Diet to Residual Intake and Greenhouse Gas Exchange During Gestation and Lactation
    Oxford University Press (OUP) ; 2023
    In:  Journal of Animal Science Vol. 101, No. Supplement_1 ( 2023-05-04), p. 81-81
    Details
    In: Journal of Animal Science, Oxford University Press (OUP), Vol. 101, No. Supplement_1 ( 2023-05-04), p. 81-81
    Abstract: The objective of this study was to compare residual feed intake (RFI) and greenhouse gas exchange in mature beef cows during gestation and lactation when consuming an unprocessed, grass hay diet. Twenty-six mature Angus and Angus x Hereford cows (4.5 ± 0.0 yr) were used in two voluntary intake studies. Cows were evaluated during mid-gestation (GEST) and late lactation (LACT). Unprocessed grass hay (GEST = 8.73% CP and 59.25% TDN; LACT = 8.31% CP and 54.50% TDN) and a mineral mix were provided for ad libitum consumption. Individual animal feed intake data was collected for 52 d and 71 d for GEST and LACT respectively using SmartFeed intake units (C-Lock Inc., Rapid City, SD) and a stocking rate of 3 cows per feeder. An open-circuit, gas-quantification system (GreenFeed, C-Lock Inc., Rapid City, SD) was used to collect CH4 production for 9 days per pen for a minimum of 20 visits per cow. Hay intake averaged 13.8 ± 2.3 kg and 16.6 ± 2.0 kg during GEST and LACT, respectively. The Pearson correlation coefficient for hay intake among the two stages of production was 0.65 (P & lt; 0.01). Metabolic body weight, average daily gain, and ultrasound ribeye area explained 46% of the variation in GEST DMI (P & lt; 0.01), and milk yield, metabolic body weight, and average daily gain explained 64% of the variation in LACT DMI (P & lt; 0.01). Each one kg additional milk production resulted in 0.7 kg greater hay intake during LACT (P & lt; 0.01). There was a moderate correlation between GEST and LACT CH4 (r = 0.64) and a moderate correlation between CH4 production within each stage of production and DMI for that same stage of production (r = 0.58 and 0.63 for GEST and LACT, respectively). Hay intake was moderately correlated between stages of production although highly sensitive to milk yield.
    Type of Medium: Online Resource
    ISSN: 0021-8812 , 1525-3163
    URL: Article
    DOI: 10.1093/jas/skad068.096
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2023
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  • 8
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    341 Meta-analysis of the Performance Responses of Replacement Heifers and Beef Cows to Monensin
    Oxford University Press (OUP) ; 2021
    In:  Journal of Animal Science Vol. 99, No. Supplement_3 ( 2021-10-08), p. 191-192
    Details
    In: Journal of Animal Science, Oxford University Press (OUP), Vol. 99, No. Supplement_3 ( 2021-10-08), p. 191-192
    Abstract: Performance benefits of monensin have been extensively studied in finishing and stocker cattle, but considerably less published work is available evaluating response to monensin supplementation in cow-calf production systems. Feed additives are more difficult to study in cow-calf production systems due to unstable diet characteristics and cow physiological state throughout the production cycle. This meta-analysis investigated the impacts of monensin on performance of extensively raised beef cow-calf and developing replacement heifers. The replacement heifer analysis was conducted with a maximum of 48 treatment means in 18 experiments. The mature cow analysis included 21 publications and 26 mean comparisons. The metaphor package (version 2.4-0; Viechtbauer, 2010) for R (version 4.0.3; www.r-project.org) was used to determine the overall effect size of monensin compared to a negative control. Each study’s n, means, and SEM or P-value was used to calculate the mean difference and estimate of within study variance for responses of interest. For replacement heifers, average daily gain (+0.03 ± 0.008 kg/d), feed efficiency (+0.013 ± 0.008 gain:feed), and percentage cycling before the breeding season (+15.9 ± 5.13%) were increased (P & lt; 0.01), while dry matter intake (-4.3%) and age at puberty (-8.9 ± 1.48 d) were decreased (P & lt; 0.01). Six studies reporting ad libitum forage intake for mature cows showed that monensin decreased (P = 0.008) DMI by 0.85 ± 0.322 kg/day. Six studies showed monesin increased (P = 0.01) milk yield 0.39 ± 0.15 kg/day by mature cows in early lactation. There were no differences in artificial insemination pregnancy nor total pregnancy for either the heifer or mature cow data sets. This analysis also indicates potential for use of monensin in beef cow production systems, but further research is needed to elucidate the effects on DMI and milk production in beef cows.
    Type of Medium: Online Resource
    ISSN: 0021-8812 , 1525-3163
    URL: Article
    DOI: 10.1093/jas/skab235.345
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2021
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  • 9
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    151 Effect of Neogen Igenity Beef Index Scores on Performance of Steers During Finishing
    Oxford University Press (OUP) ; 2023
    In:  Journal of Animal Science Vol. 101, No. Supplement_1 ( 2023-05-04), p. 95-96
    Details
    In: Journal of Animal Science, Oxford University Press (OUP), Vol. 101, No. Supplement_1 ( 2023-05-04), p. 95-96
    Abstract: 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 & lt; 0.01); while steers with high milk (HM) gained faster (P & lt; 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 & lt; 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 & lt; 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.
    Type of Medium: Online Resource
    ISSN: 0021-8812 , 1525-3163
    URL: Article
    DOI: 10.1093/jas/skad068.113
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2023
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  • 10
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    321 Evaluation of Heifer Forage Efficiency Through RFI and Greenhouse gas Emissions
    Oxford University Press (OUP) ; 2022
    In:  Journal of Animal Science Vol. 100, No. Supplement_3 ( 2022-09-22), p. 153-153
    Details
    In: Journal of Animal Science, Oxford University Press (OUP), Vol. 100, No. Supplement_3 ( 2022-09-22), p. 153-153
    Abstract: The objective of this study was to evaluate the relationship between beef heifer feed efficiency and subsequent greenhouse gas emissions using an unprocessed hay diet. Fifty-four Angus and Angus Herford cross heifers were subject to a 71-day hay intake test using individual intake technology (C-Lock Inc., Rapid City, SD) with a stocking rate of 3.6 heifers per feeder. Heifers were blocked by BW into 2 drylot pens (HEAVY, n=21; LIGHT, n=33) at the Oklahoma State University Range Cow Research Center located near Stillwater, OK. Throughout the study, heifers were fed a long-stem, unprocessed, grass hay diet (10.8% CP, 2.0 Mcal ME, and 56% TDN) with 21-d adaptation. A subset of 39 heifers were used for 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 (3,118±330.9 g/d), carbon dioxide production (4,664±467.9 g/d), and methane production (169±23.4 g/d). Phenotypic measures (means±SD) for dry matter intake (DMI), average daily gain (ADG), average body weight (BW), and residual feed intake (RFI) were 6.75±1.12 kg, 0.15±0.2 kg, 312.7±30.5 kg, and 0.08±0.84 kg, respectively. Predicted DMI was calculated using a multiple regression equation (-3.11 + 0.13*BW0.75+0.76*ADG; P & lt; 0.05; R2=0.43) in R. To further evaluate forage efficiency, heifers were segregated by 0.5 SD into three RFI categories of efficient (n=13), average (n=31), and inefficient (n=10) resulting in means of 5.8, 6.76, and 7.94 kg DMI and 0.16, 0.16, and 0.15 kg ADG, respectively. There was no significant difference (p & lt; 0.05) between RFI categories for ADG, CO2, CH4, and O2. Phenotypic correlations of DMI with CO2, CH4, and O2 were 0.59, 0.45, and 0.61, respectively. Efficient heifers consumed 21% less forage compared with inefficient heifers, suggesting that improvement in forage utilization can be achieved when efficiency is evaluated using an unprocessed grass hay diet.
    Type of Medium: Online Resource
    ISSN: 0021-8812 , 1525-3163
    URL: Article
    DOI: 10.1093/jas/skac247.284
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2022
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