M. E. Drewnoski

Estimation of relationships between mineral concentration and fatty acid composition of longissimus muscle and beef palatability traits

The objective of this study was to determine the influence of beef LM nutrient components on beef palatability traits and evaluate the impact of USDA quality grade on beef palatability. Longissimus muscle samples from related Angus cattle (n = 1,737) were obtained and fabricated into steaks for trained sensory panel, Warner-Bratzler shear force (WBSF), lipid oxidation measured by thiobarbituric acid reactive substances (TBARS), fatty acid, and mineral composition analysis. Pearson phenotypic correlations were obtained by the correlation procedure of SAS. Beef palatability data were analyzed by the GLM procedure of SAS with USDA quality grade as the main effect. Specific mineral concentrations did not demonstrate strong correlations with WBSF or sensory traits (r = -0.14 to 0.16). However, minerals appeared to have a stronger relationship with flavor; all minerals evaluated except Ca and Mn were positively correlated (P < 0.05) with beef flavor. Stearic acid (C18:0), C18:2, C20:4, and PUFA were negatively correlated (P < 0.05) with all 3 panelist tenderness traits (r = -0.09 to -0.22) and were positively correlated (P < 0.05) with WBSF (r = 0.09 to 0.15). The MUFA were positively correlated (P < 0.05) with panelist tenderness ratings (r = 0.07 to 0.10) and negatively associated (P < 0.05) with WBSF (r = -0.11). The strongest correlations with juiciness were negative relationships (P < 0.05) with C18:2, C18:3, C20:4, and PUFA (r = -0.08 to -0.20). Correlations with beef flavor were weak, but the strongest was a positive relationship with MUFA (r = 0.13). Quality grade affected (P < 0.05) WBSF, TBARS, and all trained sensory panel traits, except livery/metallic flavor. As quality grade increased, steaks were more tender (P < 0.05), as evidenced by both WBSF and sensory panel tenderness ratings. Prime steaks were rated juiciest (P < 0.05) by panelists, whereas Select and Low Choice were similarly rated below Top Choice for sustained juiciness. Quality grade influenced (P < 0.05) beef flavor, but not in a linear fashion. Although there were significant correlations, these results indicate tenderness, juiciness, and flavor are not strongly influenced by individual nutrient components in beef LM. Furthermore, the positive linear relationships between USDA quality grade and beef palatability traits suggest quality grade is still one of the most valuable tools available to predict beef tenderness.

Effects of increased dietary sulfur on beef steer mineral status, performance, and meat fatty acid composition

Ninety-six crossbred yearling steers (321 ± 29 kg BW) were used to determine the effects of feeding cattle a high S diet on pasture before receiving a high S diet in the feedlot. Steers were blocked by BW, allocated to 2.4-ha bromegrass (Bromus inermis L.) pastures (n = 4 plots per treatment), and supplemented at 1% BW with either low S dried distillers grains with solubles (DDGS; 0.34% total diet S; LS) or LS DDGS with additional S (0.47% total diet S; HS) from NaSO(4) for 36 d. On d 37, steers moved into the feedlot where one-half remained on the previous S treatment and the other half switched treatments, resulting in 4 treatments (LS-LS, LS-HS, HS-LS, HS-HS; LS: 0.2 to 0.3% total diet S, HS: 0.5 to 0.6% total diet S; n = 6 feedlot pens per treatment). During the pasture period, forage mass offered, grazing residual mass, and in vitro digestible DM of forage did not differ among treatments (P > 0.40), and ADG did not differ (LS: 1.6 kg · d(-1), HS: 1.7 kg · d(-1), P = 0.54). Plasma Mg measured on d 35 was decreased by ≈ 5% in response to increased dietary S during the pasture period (P = 0.05), though no effect on plasma Mg was observed during finishing (P > 0.15). Plasma Cu concentrations on d 155 were ≈ 15% less (P = 0.02) in HS vs. LS steers, and d 155 liver Cu concentrations were ≈ 51% less in HS vs. LS steers (P = 0.01). Increased dietary S during the feedlot period decreased ADG by ≈ 10% (P = 0.01) and tended to decrease HCW by ≈ 5% (P = 0.06) compared with LS steers. Steers receiving the HS diet had increased stearic acid (C18:0) and heptadecanoic acid (C17:0; P = 0.04 and 0.01, respectively) percentages in rib facings collected at slaughter. Exposing cattle to greater S diets (0.47% S) during a forage-based diet did not influence later performance on high S feedlot diets (0.5 to 0.6% S); however, cattle fed high dietary S on pasture had greater fat cover at slaughter (P = 0.01), suggesting S may have influenced lipid metabolism.

Genome-wide association and prediction of direct genomic breeding values for composition of fatty acids in Angus beef cattlea

BackgroundAs consumers continue to request food products that have health advantages, it will be important for the livestock industry to supply a product that meet these demands. One such nutrient is fatty acids, which have been implicated as playing a role in cardiovascular disease. Therefore, the objective of this study was to determine the extent to which molecular markers could account for variation in fatty acid composition of skeletal muscle and identify genomic regions that harbor genetic variation.ResultsSubsets of markers on the Illumina 54K bovine SNPchip were able to account for up to 57% of the variance observed in fatty acid composition. In addition, these markers could be used to calculate a direct genomic breeding values (DGV) for a given fatty acids with an accuracy (measured as simple correlations between DGV and phenotype) ranging from -0.06 to 0.57. Furthermore, 57 1-Mb regions were identified that were associated with at least one fatty acid with a posterior probability of inclusion greater than 0.90. 1-Mb regions on BTA19, BTA26 and BTA29, which harbored fatty acid synthase, Sterol-CoA desaturase and thyroid hormone responsive candidate genes, respectively, explained a high percentage of genetic variance in more than one fatty acid. It was also observed that the correlation between DGV for different fatty acids at a given 1-Mb window ranged from almost 1 to -1.ConclusionsFurther investigations are needed to identify the causal variants harbored within the identified 1-Mb windows. For the first time, Angus breeders have a tool whereby they could select for altered fatty acid composition. Furthermore, these reported results could improve our understanding of the biology of fatty acid metabolism and deposition.

High-sulfur in beef cattle diets: A review

While many cattle feeding areas in the United States have long dealt with high sulfate water, increased feeding of ethanol coproducts such as distillers grains with solubles to beef cattle has led to a corresponding increase in dietary sulfur. As a result, sulfur metabolism in the ruminant has been the focus of many research studies over the past 10 yr, and advances in our knowledge have been made. Excessive sulfur in cattle diets may have implications on trace mineral absorption, dry matter intake, and overall cattle growth. This review will focus on what we have learned about the metabolism of sulfur in the ruminant, including ruminal sulfate reducing bacteria, the role of ruminally available sulfur, factors affecting the production of hydrogen sulfide in the rumen, and the potential mechanisms behind sulfur toxicity in cattle. Additionally, this review will discuss potential strategies to minimize risk of sulfur toxicity when cattle are fed high-sulfur diets, including dietary and management strategies. Further research related to high-sulfur diets including implications for carcass characteristics, meat quality, and animal health will also be discussed. As ethanol production processes continue to change, the nutrient profile of the resulting coproducts will as well. Often removal of one nutrient such as oil will result in the concentration of other nutrients such as sulfur. Therefore, it seems even more likely that a better understanding of sulfur metabolism in the ruminant will be important to beef cattle feeding in the future.

Assessment of ruminal hydrogen sulfide or urine thiosulfate as diagnostic tools for sulfur induced polioencephalomalacia in cattle

To determine if ruminal hydrogen sulfide, urine thiosulfate, or blood sulfhemoglobin could be used as diagnostic indicators for sulfur-induced polioencephalomalacia, 16 steers (8 cannulated, 368 ± 12 kg; 8 unmodified, 388 ± 10 kg; mean ± standard error) were fed 1 of 2 dietary treatments. Diets consisted of a low sulfate (0.24% S; control) wheat midd–based pellet or the control pellet with sodium sulfate added to achieve a high-sulfate (0.68% S) pellet. As designed, intake did not differ (P = 0.80) between treatments. At 8 hr postfeeding, ruminal hydrogen sulfide was not affected by cannulation (P = 0.35) but was greater (P < 0.01) in high S (6,005 ± 475 mg/l) than control (1,639 ± 472 mg/l) steers. Time of day of sampling affected (P = 0.01) ruminal hydrogen sulfide, with peak concentrations occurring 4–12 hr after feeding. Urine was collected prefeeding (AM) and 7–9 hr postfeeding (PM). Urine thiosulfate concentrations of high S steers sampled in the PM were greater (P > 0.01) than in the AM. However, there was no difference due to time of sampling for control. In both the AM and PM, urine thiosulfate concentrations of high S were greater (P > 0.01) than control. Although hydrogen sulfide and thiosulfate were elevated by increased dietary S intake, a concentration at which polioencephalomalacia is likely to occur could not be determined. Sampling urine for thiosulfate or rumen gas for hydrogen sulfide of nonsymptomatic pen mates 4–8 hr after feeding may be useful to assess sulfur exposure and differentiate between causes of polioencephalomalacia.

Performance of growing cattle grazing stockpiled Jesup tall fescue with varying endophyte status.

The objective of this study was to evaluate the performance of growing cattle when intensively grazing stockpiled endophyte-infected (E+), endophyte-free (E-), and nontoxic endophyte-infected (EN) tall fescue during the winter. The experiment was conducted over 5 consecutive winters. In each year, plots (1 ha each, 4 per treatment) were harvested for hay in August, fertilized in September, and forage was allowed to accumulate until grazing was initiated in early December. Each year, 48 Angus-cross tester cattle (4 per plot) were given a daily allotment of forage, under strip-grazing (frontal grazing) management, with a target residual height of 5 cm. Steers were used the first year, and heifers were used in subsequent years. The grazing periods for determination of pasture ADG were 86 d (yr 1), 70 d (yr 2), 86 d (yr 3), 72 d (yr 4), and 56 d (yr 5). Pasture ADG of cattle did not differ among treatments (P = 0.13) and were 0.51, 0.59, and 0.56 kg/d (SEM 0.03) for E+, E-, and EN, respectively. Serum prolactin concentrations of heifers grazing E+ were less (P < 0.05) than those grazing E- and EN during all years except yr 2. In yr 2, E+ and E- did not differ (P = 0.11). Serum prolactin of heifers grazing E- and EN did not differ (P > 0.20) except in yr 4. During yr 4, serum prolactin of heifers grazing E- was greater (P = 0.05) than that of heifers grazing EN. Serum urea-N concentrations (SUN) tended to differ among treatments (P = 0.10) and there was a treatment x year interaction (P = 0.05). During yr 1 through 3, SUN did not differ (P > 0.15) among treatments. However, as the stands aged, E- had a greater invasion of other plant species, which increased the CP content of the sward, thus causing heifers grazing E- during yr 5 to have greater (P < 0.01) SUN than heifers grazing E+ and EN, which did not differ (P = 0.89). Forage disappearance (DM basis) did not differ (P = 0.75) among treatments and was 4.7, 4.7, and 5.0 kg/animal daily (SEM 0.27) for E+, E-, and EN, respectively. Body weight gain per hectare was greater (P = 0.04) for E+ (257 kg) than for E- (220 kg) or EN (228 kg). In most years, animal grazing days on E+ were greater than those on E- or EN. However, in yr 5, animal grazing days did not differ (P > 0.20) among treatments. The use of stockpiled E+ as a source of low-cost winter feed is a viable option for producers, whereas grazing of EN may be more beneficial during the spring and fall, when more severe negative effects of ergot alkaloids have been observed.

Effects of supplementation frequency on ruminal fermentation and digestion by steers fed medium-quality hay and supplemented with a soybean hull and corn gluten feed blend

Reducing the frequency of supplementation to beef cattle would reduce labor and vehicle maintenance costs and could have the potential to increase profits if performance is not negatively affected. Six ruminally cannulated beef steers (362 ± 18 kg of BW) were used in a replicated 3 × 3 Latin square design to determine the effect of supplementation frequency (daily or on alternate days) on digestion and ruminal parameters when feeding medium-quality hay and supplementing with a mixture of soybean hulls and corn gluten feed. Dietary treatments consisted of ad libitum fescue hay (8.8% CP and 34.8% ADF) that was supplemented at 1% of BW daily (SD), supplemented at 2% of BW on alternate days (SA), or not supplemented (NS). The supplement (14.6% CP and 29.8% ADF) contained 47% soybean hull pellets, 47% corn gluten feed pellets, 2% feed grade limestone, and 4% molasses (as fed). Each period consisted of a 12-d adaptation phase followed by 6 d of total fecal, urine, and ort collection. All supplement offered was consumed within 2 h. Ruminal fluid was collected every 4 h for 2 d. Hay intake was reduced (P < 0.01) for SD and further reduced (P < 0.01) for SA. Hay intake was 1.54, 1.19, and 1.02% of BW (SEM ± 0.036) for NS, SD, and SA, respectively. There was a treatment (P < 0.01) × day interaction for mean ruminal pH. On the day of supplementation, ruminal pH for SA (6.13) was lower (P < 0.01) than those for both SD (6.29) and NS (6.52). However, on the day the SA treatment did not receive supplement, ruminal pH of SA (6.53) did not differ (P = 0.87) from ruminal pH of NS and was greater (P < 0.01) than that of SD. Ruminal pH of SD was lower (P < 0.01) than that of NS. Diet DM digestibility was increased (P < 0.01) by supplementation but did not differ (P = 0.58) because of frequency. Dry matter digestibility was 57.9, 64.1, and 64.6% (SEM ± 0.65) for NS, SD, and SA, respectively. The amount of N retained did not differ (P = 0.47) because of frequency (24.9 ± 5.61 and 22.0 ± 5.50 g/d for SD and SA, respectively) and was greater (P < 0.01) for the supplemented treatments than for NS (4.2 ± 3.30 g/d). When supplementing a blend of soybean hulls and corn gluten feed, producers can reduce the frequency of supplementation to every other day without reducing digestibility or N retention.

Determining the influence of dietary roughage concentration and source on ruminal parameters related to sulfur toxicity.

Cattle feedlot diets often include ethanol coproducts that provide excess dietary sulfate, which is reduced to sulfide by ruminal bacteria and can be converted to hydrogen sulfide, which has been correlated to S toxicity. The objective of this study was to determine the impact of feeding varying concentrations of NDF from chopped cornstalks (CS) or chopped bromegrass hay (BH) on ruminal pH, ruminal H2S concentration, and DMI of steers fed a high-S finishing diet. Five ruminally fistulated steers (595 ± 87 kg BW) were used in a 6 × 6 Latin square with 14-d periods and fed diets containing 0.45% S from a mixture of dried distillers grains and condensed corn distillers solubles. The study was a 2 × 3 factorial arrangement of treatments with 2 roughage sources--CS or BH--and 3 concentrations of added roughage NDF (rNDF)--4, 7, or 10%. Steers had individual ad libitum access to feed and adapted to each diet for the first 7 d of each period. Effective NDF linearly increased (P < 0.01) as rNDF increased and did not differ between sources (P = 0.44). There was no effect of concentration or source of rNDF on DMI (P ≥ 0.69). Steer behavior was observed on d 13 of each period for 3 h postfeeding. Source of rNDF did not affect time at bunk, DMI during observation, or rate of DMI (P ≥ 0.42). Time at bunk linearly increased as rNDF increased (P = 0.01), while rate of DMI linearly decreased (P = 0.02). Area under the curve for ruminal pH of 5.4, 5.6, and 5.8, calculated using data from d 8 to 14 via an indwelling ruminal bolus, were linearly decreased (P ≤ 0.03) as rNDF increased. Manual ruminal pH taken 6 h postfeeding on d 14 of each period did not differ by source (P = 0.12) but linearly increased (P < 0.01) as rNDF increased. Ruminal H2S concentrations measured 6 h postfeeding on d 14 of each period did not differ by source (P = 0.47) but linearly decreased (P < 0.01) as rNDF increased (0.62, 0.35, 0.31 g/m(3) for 4, 7, and 10% rNDF, respectively). A segmented linear model was found to best fit the ruminal pH and H2S relationship data, suggesting that at or below a pH of 5.6 ± 0.08 with 95% confidence intervals of 5.4 and 5.8, pH is a strong predictor of H2S (P ≤ 0.05), while above this pH range H2S concentrations are not well correlated with ruminal pH (P > 0.50). In conclusion, adding at least 7% NDF from CS or BH to high-S feedlot cattle diets will increase ruminal pH and decrease H2S concentrations, thus decreasing potential for S toxicity.

Vitamin D status of dairy cattle: Outcomes of current practices in the dairy industry

The need for vitamin D supplementation of dairy cattle has been known for the better part of the last century and is well appreciated by dairy producers and nutritionists. Whether current recommendations and practices for supplemental vitamin D are meeting the needs of dairy cattle, however, is not well known. The vitamin D status of animals is reliably indicated by the concentration of the 25-hydroxyvitamin D [25(OH)D] metabolite in serum or plasma, with a concentration of 30ng/mL proposed as a lower threshold for sufficiency. The objective of this study was to determine the typical serum 25(OH)D concentrations of dairy cattle across various dairy operations. The serum 25(OH)D concentration of 702 samples collected from cows across various stages of lactation, housing systems, and locations in the United States was 68±22ng/mL (mean ± standard deviation), with the majority of samples between 40 and 100ng/mL. Most of the 12 herds surveyed supplemented cows with 30,000 to 50,000 IU of vitamin D3/d, and average serum 25(OH)D of cows at 100 to 300 DIM in each of those herds was near or above 70ng/mL regardless of season or housing. In contrast, average serum 25(OH)D of a herd supplementing with 20,000 IU/d was 42±15ng/mL, with 22% below 30ng/mL. Cows in early lactation (0 to 30d in milk) also had lower serum 25(OH)D than did mid- to late-lactation cows (57±17 vs. 71±20ng/mL, respectively). Serum 25(OH)D of yearling heifers receiving 11,000 to 12,000 IU of vitamin D3/d was near that of cows at 76±15ng/mL. Serum 25(OH)D concentrations of calves, on the other hand, was 15±11ng/mL at birth and remained near or below 15ng/mL through 1mo of age if they were fed pasteurized waste milk with little to no summer sun exposure. In contrast, serum 25(OH)D of calves fed milk replacer containing 6,600 and 11,000 IU of vitamin D2/kg of dry matter were 59±8 and 98±33ng/mL, respectively, at 1mo of age. Experimental data from calves similarly indicated that serum 25(OH)D achieved at approximately 1mo of age would increase 6 to 7ng/mL for every 1,000 IU of vitamin D3/kg of dry matter of milk replacer. In conclusion, vitamin D status of dairy cattle supplemented with vitamin D3 according to typical practices, about 1.5 to 2.5 times the National Research Council recommendation, is sufficient as defined by serum 25(OH)D concentrations. Newborn calves and calves fed milk without supplemental vitamin D3, however, are prone to deficiency.

Reduced supplementation frequency increased insulin-like growth factor 1 in beef steers fed medium quality hay and supplemented with a soybean hull and corn gluten feed blend

Reducing supplementation frequency in calf growing programs can reduce labor and equipment operation costs. However, little is understood about the metabolic response of ruminants to large fluctuations in nutrient intake. Eighteen Angus or Angus × Simmental cross steers (287 ± 20 kg and 310 ± 3.6 d of age) were individually fed 1 of 3 dietary treatments using Calan gates. Dietary treatments consisted of ad libitum hay and no supplement (NS), ad libitum hay and 1% BW (as-fed basis) of supplement daily (DS), or ad libitum hay and 2% BW (as-fed basis) of supplement every other day (SA). The supplement was 90% DM and contained (as-fed basis) 47% corn gluten feed, 47% soybean hulls, 2% feed grade limestone, and 4% molasses. Hay intake and ADG was measured over a 52-d period. Steers were then moved to individual tie stalls. Steers were fed at 0800 h and blood samples were collected every hour from 0600 to 1400 h and at 1800, 2200, and 0200 h over a 2-d period. Gains were increased (P < 0.01) by supplementation but did not differ (P = 0.68) due to supplementation frequency. Average daily gain was 0.45, 0.90, and 0.87 kg ·hd(-1)·d(-1) (SEM ± 0.05) for steers NS, DS, and SA, respectively. Across the 2-d supplementation cycle area under the concentration time curve (AUC) for plasma glucose was increased (P < 0.01) by supplementation but did not differ (P = 0.41) due to supplementation frequency. The AUC for plasma insulin was increased by supplementation (P < 0.01) but did not differ (P = 0.67) due to supplementation frequency. Plasma IGF-1 was increased (P = 0.01) by supplementation and was greater (P = 0.04) for steers supplemented SA than DS. Gains of steers supplemented with a soybean hull and corn gluten feed blend on alternate days did not differ from those supplemented daily suggesting the steers were able to efficiently utilize large boluses of nutrients fed every other day. The effect of less frequent supplementation on IGF-1 deserves further examination as this hormone has been shown to increase protein synthesis.