Mature Beef Research Articles

Changes in ovarian function in mature beef cows grazing endophyte infected tall fescue

The objective was to examine follicular and luteal development and function in mature, lactating beef cows grazing endophyte free (E−) or endophyte infected (E+) tall fescue during the early postpartum period. Angus, Hereford, and Angus×Hereford cows were exposed to pasture for 37–39 days before synchronized estrus. Serum concentrations of prolactin were evaluated during the luteal phase before the synchronized estrus. Every Monday, Wednesday, and Friday for one estrous cycle ovaries were monitored by transrectal ultrasonography and blood was collected for determination of serum concentrations of progesterone and estradiol in cows that responded to synchronization. Signs of fescue toxicosis in E+ cows included decreased serum concentrations of prolactin (84.9±13.6 pg/ml versus 32.3±12.0 pg/ml; P<0.009) measured during the luteal phase (day 37 of grazing) and decreased body condition of cows and weight of cows and calves ( P<0.001). Neither serum concentrations of progesterone or estradiol, nor diameter of the CL differed between treatments. Diameter of the largest follicle tended to be smaller for cows grazing E+ fescue, especially between days 8 and 12 of the estrous cycle ( P<0.08). Numbers of class 1 (3–5 mm) and class 3 (≥10 mm) follicles were similar ( P>0.05) between treatments, but number of class 2 (6–9 mm) follicles was reduced in E+ cows for most of the cycle (days 10 through 20; P<0.03). Length of synchronized estrous cycle, days open, calving interval, and pregnancy rate at 30, 45, 60, and 90 days post-breeding was similar ( P>0.05) among treatment groups. Even though follicular dynamics (diameter of the largest follicle and number of class 2 follicles) were altered in cows grazing E+ tall fescue, follicular function was apparently not affected by ergot alkaloids.

Exposure to ammoniated wheat straw as suckling calves improves performance of mature beef cows wintered on ammoniated wheat straw.

We studied how exposure to ammoniated wheat straw (AWS) early in life affected the performance of 32 mature crossbred beef cows (Bos taurus) (mean BW = 615 kg) wintered on AWS. Half (16) of these cows had been exposed as suckling calves to AWS for 66 d (Exposed), while the other 16 cows had no previous exposure to AWS (Naïve). Five years after the initial exposure, cows were stratified by BW and bred into 8 groups of 4 cows each. Exposed and Naïve cows occurred in each group, and groups of 4 cows were randomly assigned to one of eight pens. Cows were fed in these pens for a 150-d wintering period from December to May for 3 consecutive years. All cows were allowed ad libitum access to AWS and supplemented with alfalfa hay, vitamins, and minerals. Cows and their calves grazed irrigated meadow pastures for the remainder of the year. Cow BW and body condition score (BCS) were monitored monthly during the 3-yr study. Milk production was measured monthly from June to November of each year using the weigh-suckle-weigh technique. For all 3 yr, yearly average BW (P = 0.06, 0.03, 0.07) and BCS (P=0.07,0.001,0.01)were higher for Exposed than Naïve cows. Postpartum interval (PPI) to rebreeding, monitored using consecutive calving dates, was shorter for Exposed than Naïve cows during yr 1 and 2 (P = 0.004 and 0.02, respectively), but similar in yr 3 (P = 0.19). Exposed cows also produced more milk than Naïve cows during yr 1 and 2 (P = 0.04 and 0.07, respectively), but milk production was similar in yr 3 (P = 0.74). Collectively, calves exposed to AWS briefly early in life performed better as cows when reexposed to AWS from 5 to 8 yr later in life. Thus, researchers and managers should consider previous exposure to low-quality forages (LQF) when assigning cattle to studies involving the use of LQF or when considering using LQF to reduce food costs.

Effect of crambe meal on performance, reproduction, and thyroid hormone levels in gestating and lactating beef cows.

Crambe meal was compared to a combination of sunflower and soybean meal as a protein supplement for mature beef cows in two experiments. In Exp. 1, cows (n = 80, average BW 651+/-14.4 kg) were fed crambe meal at 9.86% of dry matter intake (DMI) during the last trimester of gestation. No differences (P < .05) were detected due to treatment for cow weight, condition score, thyroid hormones, calf birth weight, or calving interval. In Exp. 2, cows (n = 100, average BW 566+/-6.82 kg) were fed crambe meal at 7.44% of DMI during the last trimester of gestation and at 8.33% of DMI during early lactation (53+/-6 d of lactation). Gains were greater during gestation (P = .09) and throughout the supplementation period (P = .06), and days to first estrus were reduced (P < .01) for cows fed crambe meal. During lactation, serum triiodothyronine (T3) concentrations did not decline as much (P = .03) in cows fed crambe meal as in cows fed sunflower-soybean meal-based supplements. No differences (P > .10) were apparent for condition score, birth weight, calf growth rate, weaning weight, thyroid hormones during gestation, or calving interval. These data indicate that crambe meal fed at the levels used in this experiment can be used as a protein supplement for beef cows without negatively affecting cows' performance.

Timing of realimentation of mature cows that were feed-restricted during pregnancy influences calf birth weights and growth rates.

The objective of this study was to determine the effect of feeding strategies in cows that allowed BW loss followed by BW gain on the efficiency of feed utilization for calf production. The first treatment (H-H-H) was designed to maintain body condition score of mature cows at 5.5 from the second trimester until the subsequent breeding season. The second treatment (L-H-H) was designed such that cows lost body condition during the second trimester and regained it during the third trimester and were equal in weight and body condition scores at parturition to cows assigned to the H-H-H treatment. The third treatment (L-L-H) was designed such that cows lost body condition during the second trimester and gained body condition after 28 d of lactation so that they would be equal to the other two treatments at breeding. Forty-eight cows were assigned to each treatment. Total DMI over the entire study did not differ between the H-H-H and L-H-H treatments (P = 0.23), but intake on both were higher than the L-L-H treatment (P < 0.001). Calf birth weight of the H-H-H treatment did not differ (P = 0.43) from those of L-H-H, but both groups were greater than those of the L-L-H (P < or = 0.002) treatment. At 28 d of age, H-H-H (P = 0.008) and L-H-H (P = 0.007) calves weighed more than the L-L-H calves, but at 58 d of age there was no difference in calf BW among the treatments (P = 0.81). The percentage of cows that were diagnosed pregnant at weaning with their next calf did not differ (P = 0.71) among treatments. We interpret the results of this study to suggest that weight cycling in mature beef cows may be a viable management tool for decreasing food costs.

Reduction of Pathogens Using Hot Water and Lactic Acid on Beef Trimmings

ABSTRACTBeef trimmings from young or mature beef cattle were obtained commercially. Trimmings within age type then were inoculated with about 6.0 log10 CFU/mL of rifampicin‐resistant. Escherichia coli O157:H7 and Salmonella typhimurium (ATCC 13311) were randomly assigned to 1 of 3 treatments (control; 95 °C hot water alone, or with 2% L‐lactic acid). After treatment, trimmings were ground, held for 0, 14, 28, or 42 d in chub packages at 4 °C, and total aerobic plat counts, E. coli O157:H7, and S. typhimurium counts were determined. Non‐inoculated trimmings were also treated and samples were evaluated for pH, fat, moisture, TBA, meat color by colorimeter, and meat color, and odor by trained sensory panels. Trimmings treated with water or hot water plus lactic acid reduced levels of E. coli O157:H7 and S. typhimurium and tended to be darker after treatment. Meat odor in the final product was not affected by treatment.

Influence of body condition score on carcass characteristics and subprimal yield from cull beef cows.

Mature beef cows (n = 83) were slaughtered to measure the influence of body condition score (BCS) on carcass characteristics and subprimal yields. All cows were weighed and assigned BCS, based on a 9-point scale, 24 h before slaughter. Cows were slaughtered, and, after a 48-h chilling period, quality and yield grade data were collected on the left side of each carcass. The right side was quartered, fabricated into primal cuts, and weighed. Each primal cut was further processed into boneless subprimal cuts, minor cuts, lean trim, fat, and bone. Cuts were progressively trimmed to 6.4 and 0 mm of external and visible seam fat. Weights were recorded at all stages of fabrication, and subprimal yields were calculated as a percentage of the chilled carcass weight. Live weight, carcass weight, dressing percentage, fat thickness, longissimus muscle area, muscle:bone ratio, and numerical yield grade increased linearly (P = .0001) and predicted cutability and actual muscle-to-fat ratio decreased linearly (P = .0001) as BCS increased from 2 to 8. Carcasses from BCS-8 cows had the most (P<.05) marbling. The percentage of carcasses grading U.S. Utility, or higher, was 16.7, 20.0, 63.6, 43.3, 73.3, 100.0, and 100.0% for cows assigned a BCS of 2, 3, 4, 5, 6, 7, and 8, respectively. At 6.4 mm of fat trim, carcasses from BCS-5 cows had higher (P<.05) shoulder clod yields than carcasses from cows having a BCS of 6, 7, and 8. Carcasses of BCS-2 cows had lower (P<.05) strip loin yields than carcasses from BCS-3, 4, 5, 6, and 7 cows. Top sirloin butt yields were higher (P<.05) for carcasses of BCS-2, 3, 4, and 5 cows than those of BCS-6, 7, or 8 cows. Carcasses from BCS-7 and 8 cows had lower (P<.05) tenderloin and inside round yields than carcasses of BCS-5, or less, cows. At both fat-trim levels, carcasses from BCS-5 cows had higher (P<.05) eye of round yields than cows assigned BCS of 2, 7, or 8. When subprimal cuts were trimmed to 6.4 mm of visible fat, carcasses from BCS-5 cows had higher (P<.05) total lean product yields than cows assigned a BCS of 2, 4, 7, and 8. Regardless of fat trim, total fat yields increased (P = .0001) and total bone yields decreased (P = .0001) linearly as BCS increased from 2 to 8. Although carcasses from BCS-5 and 6 cows had the highest yields of lean product, cattle producers and packers may benefit most by marketing and(or) purchasing BCS-6 cows because a higher percentage of their carcasses had quality characteristics deemed desirable for fabrication into boneless subprimal cuts.

Influence of body condition score on live and carcass value of cull beef cows.

Mature beef cows (n = 88) were slaughtered to determine the influence of body condition score (BCS) on carcass and live animal value. Cows were weighed and assigned a BCS (9-point scale), 24 h before slaughter. Hide and by-products weights were recorded during harvest. After a 48-h chill period, the right side of each carcass was fabricated into boneless subprimal cuts, minor cuts, lean trim, fat, and bone. Weights were recorded at all stages of fabrication. Carcass values (U.S.$/100 kg of hot carcass weight) were calculated for U.S. Utility and U.S. Cutter grades, as well as for the Utility/Cutter mix for each BCS. Gross value included the carcass value and the value of the hide and byproducts, whereas net value was calculated after harvest and fabrication costs and by-product value were considered. Live value (U.S.$/100 kg of live weight) was computed by dividing the net value by the animal's live weight 24 h before harvest. The value of the hide and by-products for BCS-2 cows was greater (P<.05) than for cows assigned a BCS of 3 through 8. Even though U.S. Utility carcasses from BCS-8 cows produced the least (P<.05) valuable subprimal cuts from the chuck, loin, and round, the gross and net values of BCS-8 cows were greater (P<.05) than those of BCS-3, 4, 5, and 6. Within the grade of U.S. Cutter, carcasses from BCS-6 cows had the highest (P<.05), and BCS-2 cows had the lowest (P<.05), gross and net values. Across the U.S. Utility/Cutter mix, cows designated with a BCS of 7 and 8 had greater (P<.05) gross and net values than cows assigned a BCS of 6, or lower. Live value increased linearly (P = .0002) from a low of $76.10/100 kg for BCS-2 cows to a high of $90.84/100 kg for BCS-7 cows. Carcasses from BCS-6 cows were relatively lean (8.4 mm of fat opposite of the longissimus muscle), and approximately 73% of the carcasses achieved a quality grade of U.S. Utility. Moreover, carcasses from BCS-6 cows had the highest total carcass values and live values comparable (P>.05) to BCS-7 cows. Information from this study can be used by the non-fed beef industry to establish a value-based marketing system. Data from this study would indicate that marketing cull beef cows at a BCS of 6 could optimize economic returns to both cow-calf producers and non-fed beef packers.

Low- and high-quality forage utilization by heifers and mature beef cows.

Eight cows (7 to 9 yr old, 522 kg) and six heifers (10 mo old, 169 kg) were fed either alfalfa hay (18.7% CP) or mature brome hay (5.1% CP) to determine the effect of cattle age on apparent forage utilization. Cattle were fitted with ruminal and duodenal cannulas and were individually fed once daily (ad libitum intake, 1000). The split-plot design consisted of age (whole-plot) and two sampling periods feeding alfalfa or brome hay (subplot). Each period consisted of 28 d: d 1 to 13 for adaptation, d 13 to 20 for feed intake determination, and d 20 to 28 for sampling. Nylon bags containing NDF substrate from alfalfa or brome hay were incubated ruminally for 0, 3, 6, 12, 24, 48, 96, and 192 h to determine the rate and extent of fiber degradation. Ruminal liquid dilution rate and fermentation characteristics were conducted on d 27. Ruminal fill was determined by total evacuation at 0800 on d 28. Cows consumed more feed (BW.75; P<.01) and had greater ruminal OM fill (P = .04) but had similar fluid fill (P = .88) compared with heifers. Ruminal liquid dilution rate was greater in cows than in heifers (P<.01). The rate of in situ NDF degradation was 3 and .5% per hour greater in cows than in heifers when alfalfa and brome hay were fed, respectively (age x hay, P<.01). Ruminal NDF digestibility as a percentage of intake was greater in cows than in heifers (P<.01). Numbers of ruminal cellulolytic bacteria were not affected by treatment (P>.21). These data indicate that mature cows have a smaller ruminal fluid fill that turns over more rapidly, and this may be responsible for a faster rate of ruminal fiber degradation in cows than in young heifers.

Influence of body condition score on by-product yield and value from cull beef cows.

Mature beef cows (n = 122) representing British and Continental phenotypes were slaughtered to measure the influence of body condition score (BCS) on by-product yield and value. All cows were weighed and assigned BCS, based on a 9-point scale, 24 h before slaughter. By-product weights were obtained during the slaughter process and included blood, feet (with hooves attached), oxlips, tongue, gullet, trachea, cheek meat, head meat, skull, tripe, honeycomb tripe, large and small intestines, spleen, mesenteric fat, weasand meat, kidneys, heart, lungs, and oxtail. By-product yields were calculated as a percentage of the animal's live weight taken 24 h before slaughter. By-product values were computed by multiplying the weight of each piece removed during the slaughter process by the 1997 average price. Live weight increased linearly (P<.001) as BCS increased from 2 to 8, whereas Continental cows were approximately 86 kg heavier (P<.05) at slaughter than British cows. Cows assigned a BCS of 2 or 3 had greater (P<.05) skull, feet, tongue, tripe, honeycomb tripe, trachea, and lung yields than cows assigned a BCS of 4 or higher. On the other hand, BCS-7 and 8 cows had greater (P<.05) weights and yields of large intestines and mesenteric fat than cows given a BCS of 6 or lower. The feet, trachea, lungs, and bone meal from BCS-2 cows had the greatest (P<.05) value, whereas the value of the large intestine, oxtail, and mesenteric fat was highest (P<.05) for BCS-7 and 8 cows. Weight, yield, and value of the skull, head meat, and feet were greater (P<.05) for Continental cows than British cows. Total by-product value was quadratically (P<.001) related to BCS. Cows assigned a BCS of 5 had lower (P<.05) total by-product values than either BCS-2 or BCS-7 and 8 cows. Drop credit for BCS-2 cows was greater (P<.05) than BCS-3, 4, 5, and 6 cows, with cows assigned a BCS of 7 and 8 having intermediate drop credit values. Continental cows tended to have greater (P<.10) total by-product and drop credit values than British cows. Information from this study indicated that the BCS of cows at the time of slaughter had a profound influence on by-product yields and, more importantly, values of by-products that are credited back against the cost of production to the beef cattle producer.

Effect of source of cattle and distance transported to a commercial slaughter facility on carcass bruises in mature beef cows

Objective To determine the effect of source of cattle and distance cattle were transported to a commercial slaughter facility on prevalence and severity of carcass bruises in mature beef cows. Design Epidemiologic investigation. Sample Population Carcasses from 3,955 beef cows from 11 states assembled in 89 procurement lots. Procedure Each carcass was scored for bruise severity and location. Source of cattle was categorized. Distance from source to slaughter facility was determined. An ANCOVA was used to determine effects of variables on carcass bruises. Results Mature beef cows marketed through livestock auctions conducting first-point testing for brucellosis, especially when transported longer distances (&gt; 325 km) to slaughter facilities, had a greater number and severity of carcass bruises than cows originating from ranches or livestock auctions not conducting first-point testing. There was an increase in number of rib bruises in cows originating from livestock auctions not conducting first-point testing. Prevalence and severity of bruises were not significantly affected by transportation distance between cows originating from auctions not conducting first-point testing and cows originating from ranches. Clinical Implications A strong association existed between handling for brucellosis testing prior to sale for slaughter and distance transported to slaughter facility with carcass bruises in mature beef cows. Bruises are major quality defects that decrease carcass value and slaughter-cow prices. Repeated handling and restraint as well as long-distance transport are issues to consider regarding the responsibility of the livestock industry to provide for the safety and well-being of cattle sold for slaughter. (J Am Vet Med Assoc 1998; 212:668-672)

Improving the flavor of calcium chloride and lactic acid injected mature beef top round steaks

The effect of added commercial beef flavoring on the physical and sensory characteristics of CaCl 2 and lactic acid injected cow meat was investigated. A 10% injection of 0.3 M CaCl 2 and 0.3 M lactic acid into hot-boned top rounds ( m. semimembranosus) decreased shear forces over traditional top round steaks. The addition of commercial beef flavoring (4% solution) to the CaCl 2 and lactic acid injection did not alter the resulting pH, cook loss or total aerobic plate count (APC) of injected steaks. However, beef flavoring did increase the beef/brothy and oniony aromatics and salt taste, and decreased the soured and medicinal aromatics and bitter tastes of hot-boned, CaCl 2 and lactic acid injected top round steaks.

Influence of steroid implants and concentrate feeding on carcass and longissimus muscle sensory and collagen characteristics of cull beef cows.

Sixty nonpregnant, mature beef cows were used to determine the effects of steroid implants and concentrate feeding on carcass quality, longissimus muscle (LM) collagen characteristics, and LM sensory traits. Twelve nonfed cows were slaughtered at 0 d to establish basal carcass values. The remaining 48 cows were assigned randomly in a 2 x 4 factorial arrangement to an implant treatment and fed for either 28 or 56 d. The implant treatments were 1) nonimplanted (controls), 2) a 200-mg trenbolone acetate (TBA) implant, 3) a 200-mg testosterone propionate +20 mg estradiol benzoate (TEB) implant, or 4) both implants (TBA+TEB). Carcasses from cows fed for 28 and 56 d had improved (P < .05) LM marbling, lean maturity, and quality grade; a lighter (P < .05) LM color (higher Hunter L* values); a higher (P < .05) percentage of LM soluble (heat-labile) collagen; and a lower (P < .05) LM Warner-Bratzler shear force value (more tender) than carcasses from nonfed cows. Feeding for 28 and 56 d also improved (P < .05) LM sensory panel traits of flavor intensity, connective tissue amount, myofibrillar tenderness, and overall tenderness. Feeding cows for an additional 28 d (to 56 d) improved (P < .05) LM visual lean color, texture, and firmness and carcass fat color. All LM HunterLab color measurements were higher (P < .05) for cows fed for 56 d compared to 28 d, indicating a brighter, redder, more vivid color. Implant treatments did not influence (P > .05) carcass quality or LM color. Steaks from implanted cows compared to controls had (P < .05) more soluble (heat-labile) collagen, a higher percentage of soluble collagen, and improved sensory traits of tenderness (myofibrillar and overall) and connective tissue amount. Steaks from TBA-implanted cows compared to the other implant treatments had superior (P < .05) LM sensory evaluations for myofibrillar and overall tenderness. Feeding thin cows a high-concentrate diet for 28 d improved quality grade and LM sensory traits, and feeding for 56 d improved LM lean and carcass fat color. Implanting fed cows improved LM sensory panel tenderness.

Influence of steroid implants and concentrate feeding on performance and carcass composition of cull beef cows.

Sixty nonpregnant, mature beef cows were used to evaluate the influence of steroid implants on performance and carcass composition of beef cows fed a high-concentrate diet. Twelve nonfed cows were slaughtered at 0 d. Remaining cows were stratified by weight and randomly assigned to an implant treatment and feeding period (28 or 56 d). Treatments included 1) no implant (control), 2) a 200-mg trenbolone acetate (TBA) implant, 3) a 200-mg testosterone propionate +20 mg of estradiol benzoate (TEB) implant, or 4) both implants (TBA + TEB). As days on feed increased, hot carcass weight (HCW), carcass soft tissue (CST) weight, adjusted fat thickness (AFT), longissimus muscle area (LMA), percentage of CST, and percentage of CST lipid increased (P < .05) and percentage of CST crude protein and moisture decreased (P < .05). Cows fed for 56 d accumulated (P < .05) more kilograms of lean than cows fed for 28 d, and cows fed for 28 d tended (P = .08) to have more kilograms of lean than nonfed cows. Cows fed for 56 d had (P < .05) higher dressing percentages than nonfed cows or cows fed for 28 d, and nonfed cows had (P < .05) higher dressing percentages than cows fed for 28 d. Implanted cows compared with control cows had (P < .05) heavier final weights, increased gains, improved feed efficiency, heavier hot carcass weights, larger LMA, higher cutability yield grades, compositionally leaner CST (higher percentage of moisture and protein and lower percentage of lipid), and more kilograms of lean. In addition, double-implanted (TBA + TEB) cows had (P < .05) more kilograms of CST than control and TBA-implanted cows. Furthermore, cows implanted with TBA had (P < .05) lower dressing percentages than TEB-implanted cows, less AFT than controls, and fewer kilograms of lipid than cows on the other three treatments. Full feeding of thin beef cows for 28 or 56 d increased carcass weight through an increase in CST lean as well as fat (lipid). The live performance and accretion of lean during realimentation can be enhanced by using anabolic implants.

Effects of corn vs. corn plus wheat in forage-based diets containing broiler litter on feed intake, ruminal digesta characteristics and digestion in cattle

Cattle consuming low-to moderate-quality forage were supplemented with corn or a 1:1 corn:wheat mixture with or without broiler litter to determine effects on feed intake, ruminal digesta characteristics and digestion. In the first experiment, mature beef steers (529 ± 33 kg initial body weight) with cannulas in the rumen and duodenum were fed prairie hay and soybean meal alone (control) or with (dry matter basis) 0.3% body weight (BW) of ground corn (C), 0.15% BW of corn plus 0.15% BW of ground wheat (CW), corn plus 0.3% BW of broiler litter (C-L) or the corn-wheat mixture plus 0.3% BW of broiler litter (CW-L). Ruminal fluid ammonia nitrogen (N) concentration 2 h after feeding was increased ( P < 0.05) by supplementation and was greater ( P < 0.05) for C-L than for CW-L (8.9, 9.3, 11.4, 27.6 and 21.4 mg dl −1 for control, C, CW, C-L and CW-L, respectively). Neither duodenal microbial N flow nor efficiency of microbial growth was affected by treatment. In the second experiment, Holstein steers (129 ± 11 and 219 ± 17 kg initial and final BW, respectively) consumed ad libitum bermudagrass hay alone (control) or with (dry matter basis) 0.6% BW of corn (C), 0.3% BW of corn plus 0.3% BW of wheat (CW), corn plus 0.6% BW of broiler litter (C-L) or the corn-wheat mixture plus 0.6% BW of broiler litter (CW-L). Total organic matter (OM) intake was increased ( P < 0.05) by supplementation and inclusion of broiler litter in supplements (4.34, 4.91, 5.14, 5.27 and 5.32 kg day −1 ); total tract OM digestion was increased ( P < 0.05) by supplementation and was lower ( P < 0.05) for supplement treatments with than without broiler litter (57.2, 61.8, 63.0, 59.5 and 59.9%); and digestible OM intake was increased ( P < 0.05) by supplementation and was not altered by broiler litter inclusion in supplements (2.51, 3.05, 3.25, 3.14 and 3.20 kg day −1 for control, C, CW, C-L and CW-L, respectively). In summary, supplementation of a diet containing broiler litter with a corn-wheat mixture compared with corn alone decreased ruminal ammonia N concentration early after feeding but did not change duodenal microbial N flow or efficiency of microbial growth. Grain source did not alter total feed intake by growing Holstein steers consuming diets with broiler litter, and an increase in total feed intake when broiler litter was included in diets compensated for low digestibility of broiler litter.

Effects of corn vs. corn plus wheat in forage-based diets containing broiler litter on feed intake, ruminal digesta characteristics and digestion in cattle

Cattle consuming low-to moderate-quality forage were supplemented with corn or a 1:1 corn:wheat mixture with or without broiler litter to determine effects on feed intake, ruminal digesta characteristics and digestion. In the first experiment, mature beef steers (529 ± 33 kg initial body weight) with cannulas in the rumen and duodenum were fed prairie hay and soybean meal alone (control) or with (dry matter basis) 0.3% body weight (BW) of ground corn (C), 0.15% BW of corn plus 0.15% BW of ground wheat (CW), corn plus 0.3% BW of broiler litter (C-L) or the corn-wheat mixture plus 0.3% BW of broiler litter (CW-L). Ruminal fluid ammonia nitrogen (N) concentration 2 h after feeding was increased ( P < 0.05) by supplementation and was greater ( P < 0.05) for C-L than for CW-L (8.9, 9.3, 11.4, 27.6 and 21.4 mg dl −1 for control, C, CW, C-L and CW-L, respectively). Neither duodenal microbial N flow nor efficiency of microbial growth was affected by treatment. In the second experiment, Holstein steers (129 ± 11 and 219 ± 17 kg initial and final BW, respectively) consumed ad libitum bermudagrass hay alone (control) or with (dry matter basis) 0.6% BW of corn (C), 0.3% BW of corn plus 0.3% BW of wheat (CW), corn plus 0.6% BW of broiler litter (C-L) or the corn-wheat mixture plus 0.6% BW of broiler litter (CW-L). Total organic matter (OM) intake was increased ( P < 0.05) by supplementation and inclusion of broiler litter in supplements (4.34, 4.91, 5.14, 5.27 and 5.32 kg day −1); total tract OM digestion was increased ( P < 0.05) by supplementation and was lower ( P < 0.05) for supplement treatments with than without broiler litter (57.2, 61.8, 63.0, 59.5 and 59.9%); and digestible OM intake was increased ( P < 0.05) by supplementation and was not altered by broiler litter inclusion in supplements (2.51, 3.05, 3.25, 3.14 and 3.20 kg day −1 for control, C, CW, C-L and CW-L, respectively). In summary, supplementation of a diet containing broiler litter with a corn-wheat mixture compared with corn alone decreased ruminal ammonia N concentration early after feeding but did not change duodenal microbial N flow or efficiency of microbial growth. Grain source did not alter total feed intake by growing Holstein steers consuming diets with broiler litter, and an increase in total feed intake when broiler litter was included in diets compensated for low digestibility of broiler litter.

Effects of Cubing Alfalfa Hay on Development of Yearling Beef Heifers and In Situ Rate and Extent of Disappearance

The objective of this study was to evaluate the effects of cubing alfalfa on heifer development and in situ ruminai NDF and CP disappearance. One hundred ninety-two prepuberal crossbred heifers were allotted to 16 pens with each pen randomly allotted to treatment; 1) cubed alfalfa (CA) or 2) long alfalfa (LA). Diets were consumed ad libitum. Heifers were weighed every 28 d throughout the 96-d trial. Following synchronization, heifers were bred by AI 12h after observed estrus. Hay intake by CA heifers was lower (P<.05) than LA heifers (11.6 vs 13.5kg per head per d), but ADG was faster (P<.05) for CA heifers than those fed LA (1.35 vs 1.03kg per head per d). Feed per kilogram of gain was lower (P<.05) for heifers fed CA than for heifers fed LA (8.6 vs 13.2kg:kg). No differences were observed in number of heifers bred AI (P>.25)or in total pregnancy (P>.25). Six mature beef cows fitted with ruminal cannula were used in a switchback design to determine influence of cubing on in situruminal CP and NDF disappearance. During each period animals consumed their respective diets ad libitum for 14 d of adaptation and 5 d of data collection. Nylon bags containing 5-g samples of either CA or LA were ruminally incubated for 12,24,36,48,72, and 96h. Bag residues were analyzed for DM, CP, and NDF content. The DM and NDF disappearance rate constants and extent of DM disappearance for CA (.27, .11, and 79.6%, respectively) were higher (P<.04) than LA(.16, .08, and 68.1%, respectively). Crude protein rate constants were similar (P>.05) forCA (.33) and LA (.28). Results from the heifer development trial suggest that heifers fed CA gained faster and were more efficient than heifers fed LA. No differences were detected in reproductive performance, possibly because all heifers reached the recommended weight for puberty at the beginning of the breeding season regardless of treatment (average, 409kg). Results from the in situ trial indicate ruminal DM and NDF disappearance were enhanced by cubing alfalfa, but not rate of CP disappearance.

Insulin-like growth factor-I (IGF-I) and IGF-binding proteins in bovine sera and pituitaries at different stages of the estrous cycle.

The objective of this study was to determine whether concentrations of hypophyseal and serum insulin-like growth factor-I (IGF-I) and binding activities of serum and hypophyseal IGF-binding proteins (IGFBPs) differ with stage of the estrous cycle in mature beef cows. Cows were assigned to the following stages of the estrous cycle based on serum concentrations of progesterone (P4) and ovarian structures at death: days 1-5 (day 0 = estrus; n = 18), days 6-10 (n = 24), days 11-16 (n = 39), and days 17-21 (n = 7). Serum samples collected at death and anterior pituitary homogenates were analyzed for IGF-I, LH, and FSH by RIA. Serum and pituitary IGFBPs were evaluated by ligand and immunoblot analyses. Serum samples contained IGFBP activity at 44 and 40 kilodaltons (kDa; IGFBP-3), 34 kDa (IGFBP-2), 30 kDa (IGFBP-5), 28 kDa, and 24 kDa. The intensity of binding by the different sized proteins in serum remained constant throughout the estrous cycle. IGFBPs detected in anterior pituitaries included a 36-/40-kDa doublet (IGFBP-3), a 32-kDa protein (IGFBP-2), and a 29-kDa IGFBP (IGFBP-5). The intensity of [125I]IGF-I binding to IGFBPs was greater (P < 0.05) during days 11-16 than days 1-5 or days 6-10 of the estrous cycle and was intermediate (P > 0.05) during days 17-21. Serum concentrations of LH were low (< 0.4 ng/ml) during days 1-16 of the estrous cycle, but increased (P < 0.05) approximately 3- to 4-fold during days 17-21. LH concentrations in the anterior pituitary increased (P < 0.05) from the postovulatory period (548 +/- 52 micrograms/g; days 1-5) to the late luteal phase (791 +/- 39 micrograms/g; days 11-16) and were intermediate (P > 0.05) during the preovulatory phase (707 +/- 85 micrograms/g; days 17-21). Concentrations of IGF-I and FSH in the anterior pituitary and serum did not differ (P > 0.05) by stage of the estrous cycle. A positive correlation among the different IGFBPs in the pituitary (P < 0.01) and between each pituitary IGFBP and serum P4 (P < 0.05) existed. The significance (P < 0.0002) of the correlation between pituitary IGFBP-3 and P4 was greater (P < 0.02) than that between the other pituitary IGFBPs and P4. In summary, IGFBP activity in the anterior pituitary, but not that in serum, changed with stage of the estrous cycle in association with serum concentrations of P4. The absence of similar changes in serum or anterior pituitary concentrations of IGF-I supports the hypothesis that IGFBPs may regulate the actions of IGF-I on gonadotropin release from the anterior pituitary gland during the estrous cycle of beef cattle.

Correlations of mature beef palatability with optical probing of raw meat

Organoleptically tested samples of longissimus dorsi (LD) and semitendinosus (ST) muscles from 20 beef carcasses covering a wide chronological age were tested with probes for connective tissue fluorescence (365 nm excitation) and for muscle reflectance (400–800 nm). In LD, the number of fluorescence peaks cm −1 was correlated with toughness ( r = 0·73, P ≤ 0·0005), whereas the half-width of peaks was the best single predictor for ST ( r = 0·66, P < 0·005). Measurements on initial penetration of samples were more useful for predicting meat toughness than those made as the probe was withdrawn. With the reflectance probe, negative correlations of reflectance with taste intensity were detected (for example, r = − 0·63, P ≤ 0·005 at 420 nm in ST), but stronger correlations of taste with the fluorescence signal were detected (for example, r = 83, P ≤ 0·0005 for peaks cm −1 measured coaxially). Correlations of the fluorescence signal with taste may have been fortuitous, because taste was correlated with toughness ( r = 61, P ≤ 0·005). However, ST juiciness was correlated with the height of the largest fluorescence peak in a transect ( r = 0·78, P ≤ 0·0005 for coaxial measurements damped at 10 Hz) although no significant correlation of ST juiciness with toughness was detected ( r = 0·06). These results demonstrate the UV probe to be a fairly robust predictor of toughness from connective tissue, working as well on a wide age range of carcasses as it does on a narrow age range. Further development may enable the empirical prediction of taste, juiciness and hardness.

Digestion characteristics, feed intake and live weight gain by cattle consuming forage supplemented with defatted rice bran or other feedstuffs

Effects of supplementing cattle with defatted rice bran compared with full-fat rice bran, ground corn or wheat middlings on feed intake, digestibility and live weight gain (LWG) were determined. In Experiment 1, in situ (ruminal) dry matter disappearance in two steers consuming forage was 75, 45, 77 and 53% at 12 h (standard error (SE) 4.4), and 86, 95, 83 and 82% at 48 h (SE 0.6) for full-fat rice bran, corn, wheat middlings and defatted rice bran, respectively. In Experiment 2, six Holstein steer calves (193 ± 1.3 kg average trial body weight (BW); 6 × 6 Latin square) consumed a 1:1:1 mixture of alfalfa, orchardgrass and bermudagrass hay ad libitum without supplementation (Control), or with 0.80% of BW of full-fat rice bran (FR), 0.62% of BW of corn (C), 0.81% of BW of wheat middlings (W), 0.80% of BW of defatted rice bran (L-DR) or 1.10% of BW of defatted rice bran (H-DR). Total organic matter intake was lower ( P < 0.05) for FR than for C, W, L-DR and H-DR (5.65, 5.48, 5.96, 5.90, 6.03 and 5.86 kg per day; SE 0.127), digestibility of neutral detergent fiber was 53.3, 49.5, 53.7, 51.4, 50.9 and 49.8% (SE 1.13), and digestible organic matter intake was 2.96, 2.98, 3.35, 3.32, 3.17 and 3.11 kg per day (SE 0.088) for Control, FR, C, W, L-DR and H-DR, respectively (C and W greater than Control and FR; P < 0.05). In Experiment 3, six mature beef cows (564 ± 37 kg BW) with cannulae in the rumen and duodenum (6 × 6 Latin square) were fed the same hays with similar dietary proportions of supplement. True ruminal nitrogen disappearance was greatest ( P < 0.05) for W (62.5, 60.2, 63.0, 79.6, 68.1 and 65.7% for Control, FR, C, W, L-DR and H-DR, respectively; SE 3.24), microbial efficiency was similar among treatments ( P > 0.10), and acetate: propionate in ruminal fluid was decreased ( P < 0.05) by FR, L-DR and H-DR relative to Control (4.06, 3.69, 4.00, 4.09, 3.89 and 3.80 for Control, FR, C, W, L-DR, and H-DR, respectively; SE 0.053). In Experiment 4, crossbred beef calves (48 steers and 48 heifers; 232 ± 2.1 kg initial BW) grazed paddocks with fescue, clover and bermudagrass in the spring for 84 days and were supplemented as in Experiment 2. LWG was lower ( P < 0.05) for W, L-DR and H-DR than for FR and C (1.06, 1.18, 1.14, 0.99, 1.04 and 0.98 kg per day for Control, FR, C, W, L-DR and H-DR, respectively; SE 0.027).

Using hormone-treated pregnant cows as a potential source of oocytes for in vitro fertilization

In vivo collection of oocytes during pregnancy may be alternative method of obtaining gametes for in vitro fertilization (IVF) from genetically superior gestating cattle. The objectives of this experiment were to induce follicular growth in mature beef cows during each trimester of pregnancy, and then to collect oocytes and verify oocyte competency by IVF and subsequent embryo culture in vitro. Cyclic beef cows in Treatment A and pregnant cows in Treatment B were administered a total dose of 40 mg of FSH in descending dose levels (6, 5, 4, 3 and 2 mg) twice daily for 5 consecutive days. Cows in Treatment A were administered 25 mg of PGF 2α and in Treatment B an equal volume of 0.9% saline at the seventh FSH injection. Pregnant cows in Treatment C were administered neither FSH nor PGF 2α and served as a control group. Following a gonadotropin treatment, the ovaries of each female were evaluated for follicular development by ultrasonography. Oocytes were collected by follicle aspiration from cows in the first trimester. Following IVF procedures, the embryos were co-cultured on caprine oviductal cells, or in the chicken embryo co-culture system, or were placed in goat oviducts in vivo. The mean number of follicles per ovary 12 hours after FSH treatment was not different for cows in Treatments A and B, (8.1 vs 7.7) and both numbers were greater (P<0.05) than the 1.1 follicles per ovary for the control cows in Treatment C. Oocytes collected in vivo and exposed to IVF, resulted in 20% cleaving, and of these embryos 50% developed to the morula stage in culture. In summary, stimulating supplemental follicular development with FSH treatment during pregnancy and collecting the oocytes for IVF may be an alternative method for obtaining supplemental gametes from valuable donor cattle.