Technical note: Digital quantification of eye pigmentation of cattle with white faces.

Cancer of the eye in cattle with white faces occurs less frequently in cattle with pigmented eyelids. Corneoscleral pigmentation is related to eyelid pigmentation and occurrence of lesions that may precede cancer. Objectives of this study were to assess 1) variation in the proportion of eyelid and corneoscleral pigmentation in Hereford, Bos taurus, and Bos indicus crossbreds and 2) the occurrence of lesions with the presence of pigmentation in those areas. Hereford and Bos indicus crosses (Brahman or Nellore with Angus and Hereford and straightbred Brafords) and Bos taurus crosses (Angus-Hereford) were included in the study (n = 1,083). Eyelid pigmentation proportions were estimated by pixel quantification and were evaluated as total proportions and for upper and lower eyelids distinctly for each eye. Fixed effects included breed type, age categories, and sex of the animal. Lesion presence (1) or absence (0) was obtained by visual appraisal of image and was assumed to be binomially distributed. Eyelid pigmentation proportions (overall, upper, and lower eyelids) for Hereford ranged from 0.65 ± 0.03 to 0.68 ± 0.03 and were significantly lower than Bos indicus (range from 0.93 ± 0.02 to 0.95 ± 0.02) or Bos taurus (ranged from 0.88 ± 0.02 to 0.92 ± 0.02) crosses. Corneoscleral pigmentation in Hereford cows (0.17 ± 0.06) did not differ (P = 0.91) from Hereford calves and yearlings (0.16 ± 0.07). Bos indicus and Bos taurus crossbred cows had larger corneoscleral pigmentation (0.38 ± 0.05 and 0.48 ± 0.04 for left eyes and 0.37 ± 0.05 and 0.53 ± 0.04 for right eyes, respectively) than all calves (P < 0.001), and their corneoscleral pigmentations were greater than that of Hereford cows (P < 0.003). Bos indicus and Bos taurus cows had greater proportions of left eye corneoscleral pigmentation (0.38 ± 0.05 and 0.48 ± 0.04, respectively) than Hereford cows (0.17 ± 0.06) and all young animal breed types (P < 0.05). Right eye proportions differed for all cow groups (P < 0.05; 0.53 ± 0.04, 0.37 ± 0.05, and 0.17 ± 0.06). Among calves and yearlings, Hereford had a lower right eye corneoscleral pigmentation proportion (0.16 ± 0.07) than Bos taurus (P = 0.02). The lesion proportion for Hereford (0.08 ± 0.03) was significantly greater than that of either Bos indicus (0.01 ± 0.005) or Bos taurus (0.01 ± 0.003). Crossbreeding with Bos taurus or Bos indicus animals appears to increase eye pigmentation, which may help reduce the occurrence of cancer in eyes of cattle with white faces.

In vivo ruminal degradation characteristics and apparent digestibility of low-quality prairie hay for steers consuming monensin and Optimase.

Seven ruminally cannulated crossbred steers (BW = 720 ± 62 kg) were used in a randomized crossover design (4 periods, each 18 d) to evaluate in vivo rumen characteristics and apparent digestibility of steers consuming low-quality prairie hay and 1 of 4 isonitrogenous protein supplements. Treatments included 1) 40% CP (DM basis) cottonseed meal and wheat middlings-based supplement (Control), 2) a cottonseed meal and wheat middlings-based supplement with slow-release urea and a fibrolytic feed enzyme (Optimase; Alltech, Inc., Nicholasville, KY) designed to replace 30% of plant-based CP provided in the Control (OPT), 3) the Control plus 0.40 mg∙kg BW∙d monensin (Rumensin 90; Elanco Animal Health, Greenfield, IN; MON), and 4) the OPT plus 0.40 mg∙kg BW∙d monensin (COMBO). Steers were allowed ad libitum access to prairie hay (5.0% CP and 76% NDF) and were provided each respective supplement at 0800 h daily at a rate of 1.0 g/kg of BW. Steers were adapted to diets for 10 d before sample collection. Beginning on d 11, DMI was measured and samples were collected to determine apparent digestibility. On d 15 of the 18-d period, rumen fluid was collected 10 times over a 24-h period. Forage DMI was greater ( ≤ 0.02) for steers consuming the OPT compared with steers consuming the MON or COMBO, although forage DMI was not different ( = 0.10) among steers consuming the Control compared with steers consuming the OPT, MON, or COMBO. Steers fed the MON and COMBO had lower ( ≤ 0.05) passage rate compared with steers fed the Control and the OPT. The MON-fed steers had lower ( = 0.01) ruminal pH and increased ( = 0.03) propionate as a percentage of total VFA production. A time × treatment ( = 0.01) interaction was observed for ruminal NH-N due to a rapid (0 to 1 h after feeding) increase followed by a quick (1 to 4 h after feeding) decline in NH-N by steers consuming the OPT and COMBO that was not observed for steers consuming all other treatments. Apparent digestibility of DM ( = 0.01) and NDF ( = 0.03) were improved for steers fed the COMBO supplement compared with steers consuming all other experimental supplements. This work suggests that the OPT may be an effective replacement for a portion of supplemental degradable intake protein in low-quality forage. Further research is necessary to determine if the combination of monensin and the Optimase consistently improves low-quality forage utilization.

Supplementation of monensin and Optimase to beef cows consuming low-quality forage during late gestation and early lactation.

Two experiments were designed to investigate the effects of feeding monensin and/or slow release urea with a fibrolytic feed enzyme (Optimase; Alltech, Inc., Nicholasville, KY) on performance, milk production, calf growth performance, and blood metabolites in beef cows. Spring-calving cows and heifers were used in a completely randomized design in Exp. 1 (N = 84; 534 ± 68 kg initial BW) and Exp. 2 (N = 107; 508 ± 72 kg initial BW). Exp. 1 supplements were formulated to meet cow protein requirements and fed daily and included 1) cottonseed meal with no monensin (control); or 2) monensin added to control to supply 200 mg per head per d (MON). In Exp. 2, experimental supplements included 1) cottonseed meal/wheat middlings (CS) fed at a rate to provide adequate DIP and CP according to , 2) the CS plus soybean hulls and 61 g per cow per d Optimase (OPT), 3) the CS plus monensin to supply 200 mg per cow per d (MON2), and 4) OPT plus MON2 (Combo). Cows were fed in last trimester through early lactation in Exp. 1 and during 2nd trimester in Exp. 2. Data were analyzed using the Mixed procedure in SAS with animal as the experimental unit. In Exp. 1, treatment did not affect cow BW or BCS change (P > 0.19). Calf birth BW was not affected by dam treatment (P = 0.24); however, calves from dams consuming MON weighed more (P < 0.04) at d 45 and at trial end. Calves also had greater (P = 0.04) ADG from birth to trial end. Milk production did not significantly differ among treatments (P > 0.41). In Exp. 2, mean cow BW and BCS were similar (P > 0.35) among treatments on d 90. However, from d 0 to 54, cows assigned to the OPT supplement gained less BCS (P = 0.02) compared with cows assigned to the CS supplement. Cumulative BCS gain was greater (P < 0.01) for CS-fed cows than for cows fed the OPT and MON2 supplements, although it was not significantly different for cows fed the Combo supplement. These studies indicate that the influence of monensin on cow BW and BCS change is inconsistent. The potential for monensin supplementation to positively impact calf performance during early lactation seems to be clearer. Replacing a portion of oilseed N in the supplement with Optimase may marginally reduce cow performance. Further research is needed to determine both the effects of monensin and the implications of combining monensin with Optimase on forage intake and cow performance at various stages of production.

Supplementation of dried distillers grains with solubles to beef cows consuming low-quality forage during late gestation and early lactation.

Three experiments were conducted to evaluate supplementation of dried distillers grains with solubles (DGS) to spring-calving beef cows (n = 120; 541 kg of initial BW; 5.1 initial BCS) consuming low-quality forage during late gestation and early lactation. Supplemental treatments included (DM basis) 1) 0.77 kg/d DGS (DGSL); 2) 1.54 kg/d DGS (DGSI); 3) 2.31 kg/d DGS (DGSH); 4) 1.54 kg/d of a blend of 49% wheat middlings and 51% cottonseed meal (POS); and 5) 0.23 kg/d of a cottonseed hull-based pellet (NEG). Feeding rate and CP intake were similar for DGSI and POS. In Exp. 1, cows were individually fed 3 d/wk until calving and 4 d/wk during lactation; total supplementation period was 119 d, encompassing 106 d of gestation and 13 d of lactation. Tall-grass prairie hay (5.6% CP, 50% TDN, 73% NDF; DM basis) was fed for ad libitum intake throughout the supplementation period. Change in cow BW and BCS during gestation was similar for DGSI and POS (-5.0 kg, P = 0.61 and -0.13, P = 0.25, respectively) and linearly increased with increasing DGS level (P < 0.01). Likewise, during the 119-d supplementation period, BW and BCS change were similar for DGSI and POS (-72 kg, P = 0.22 and -0.60, P = 0.10) and increased linearly with respect to increasing DGS (P < 0.01). The percentage of cows exhibiting luteal activity at the beginning of breeding season (56%, P = 0.31), AI conception rate (57%, P = 0.62), or pregnancy rate at weaning (88%, P = 0.74) were not influenced by supplementation. In Exp. 2, 30 cows from a separate herd were used to evaluate the effect of DGS on hay intake and digestion. Supplementation improved all digestibility measures compared with NEG. Hay intake was not influenced by DGS (P > 0.10); digestibility of NDF, ADF, CP, and fat linearly increased with increasing DGS. In Exp. 3, milk production and composition were determined for cows (n = 16/treatment) of similar days postpartum from Exp. 1. Daily milk production was not influenced by supplementation (6.3 kg/d, P = 0.25). Milk fat (2.1%) and lactose (5.0%) were not different (P > 0.10). Milk protein linearly increased as DGS increased (P < 0.05) and was greater for DGSI compared with POS. Similar cow performance was achieved when cows were fed DGS at the same rate and level of CP as a traditional cottonseed meal-based supplement. Increasing amounts of DGS did not negatively influence forage intake or diet digestibility.

Effect of muscle type, sire breed, and time of weaning on fatty acid composition of finishing steers.

Thirty-three steer calves were used to determine the effect of sire breed (Angus or Charolais), time of weaning [normal weaned at approximately 210 d of age (NW) or late weaned at approximately 300 d of age (LW)], and muscle type [LM and semitendinosus muscle (STN)] on fatty acid composition. The whole plot consisted of a 2 (sire breed) × 2 (time of weaning) treatment arrangement, and the subplot treatment was muscle type. Body weights were recorded at 28-d intervals to determine animal performance. Muscle biopsies were collected on d 127 and 128 of finishing. All calves were slaughtered on d 138, and carcass data were collected. Angus-sired steers had lighter initial BW (271 vs. 298 kg; P = 0.02), and LW steers were heavier (351 vs. 323 kg; P = 0.03) on d 28, but no other differences in BW were noted. Charolais-sired steers had larger LM area (P = 0.03), reduced yield grades (P = 0.01), less 12th-rib fat (P < 0.01), and less marbling (P < 0.01) than Angus-sired steers. Carcass measures overall indicate Angus-sired steers were fatter. Hot carcass weight was heavier (348 vs. 324 kg; P = 0.04) in LW steers than NW steers. No other differences (P > 0.05) were observed for feedlot performance or carcass characteristics. Total lipids were extracted from muscle biopsies, derivatized to their methyl esters, and analyzed using gas chromatography. The LM had greater SFA (43.94 vs. 35.76%; P < 0.01) and decreased unsaturated fatty acids (UFA; 56.90 vs. 66.19%; P < 0.01) compared with the STN. Percent total MUFA was greater in STN than LM (51.05 vs. 41.98%; P < 0.01). Total SFA, UFA, and MUFA did not differ due to sire breed or time of weaning. Total PUFA differed (P = 0.04) due to a sire breed × time of weaning interaction but did not differ due to muscle type, with greater PUFA in NW Charolais than any other sire breed × time of weaning combination. Observed changes in percent MUFA may be a result of greater Δ(9)-desaturase activity. The calculated desaturase index suggests STN has a greater Δ(9)-desaturase activity than LM, but no differences (P > 0.05) between sire breed or time of weaning were observed. These results indicate that sire breed, time of weaning, and muscle type all affect fatty acid composition in beef. This information provides insight into factors for manipulation of beef fatty acids. More research is needed to identify beef cuts based on fatty acid profile and healthfulness.

Effects of prepartum supplementation of linoleic and mid-oleic sunflower seed on cow performance, cow reproduction, and calf performance from birth through slaughter, and effects on intake and digestion in steers.

Two experiments were conducted to determine the effects of sunflower seed supplements with varying fatty acid profiles on performance, reproduction, intake, and digestion in beef cattle. In Exp. 1, 127 multiparous spring-calving beef cows with free-choice access to bermudagrass hay were individually fed 1 of 3 supplements for an average of 83 d during mid to late gestation. Supplements (DM basis) included 1) 1.23 kg/d of a soybean hull-based supplement (control treatment); 2) 0.68 kg/d of linoleic sunflower seed plus 0.23 kg/d of the control supplement (linoleic treatment); and 3) 0.64 kg/d of mid-oleic sunflower seed plus 0.23 kg/d of the control supplement (oleic treatment). During the first 62 d of supplementation, the BW change was 11, 3, and -3 kg for cows fed the control, linoleic, and oleic supplements, respectively (P < 0.001). No difference in BW change was observed during the subsequent period (-65 kg, P = 0.83) or during the entire 303-d experiment (-31 kg, P = 0.49). During the first 62 d of supplementation, cows fed sunflower supplements tended (P = 0.08) to lose more body condition than cows fed the control diet, but BCS was not different (P > 0.22) for any subsequent measurement. At the beginning of the breeding season, the percentage of cows exhibiting luteal activity was greater for cows fed the control diet (43%; P = 0.02) than for cows fed either linoleic (20%) or oleic (16%) supplementation; however, first-service conception rate (67%; P = 0.22) and pregnancy rate at weaning (92%; P = 0.18) were not different among supplements. No differences were detected in calf birth (P = 0.46) or weaning BW (P = 0.74). In Exp. 2, 8 ruminally cannulated steers were used to determine the effects of sunflower seed supplementation on forage intake and digestion. Treatments (DM basis) included 1) no supplement; 2) a soybean hull-based supplement fed at 0.29% of BW/d; 3) whole linoleic sunflower seed fed at 0.16% of BW/d; and 4) whole high-oleic sunflower seed fed at 0.16% of BW/d. Hay intake was not influenced (P = 0.25) by supplement (1.51% of BW/d); however, DMI was greatest (P < 0.01) for steers fed the soybean hull-based supplement (1.93% of BW/d). Sunflower seed supplementation reduced (P < 0.01) NDF and ADF digestibility while increasing (P < 0.01) apparent CP and apparent lipid digestibility. In conclusion, whole sunflower seed supplementation resulted in reduced cow BW gain during mid to late gestation, but this reduction did not influence subsequent cow BW change, pregnancy rate, or calf performance.

Effect of weaning date (normal vs. late) on performance of young and mature beef cows and their progeny in a fall calving system in the Southern Great Plains.

Data from 158 predominantly Angus fall-calving beef cows were used in 4 consecutive years to determine the effects of weaning date and cow age class on cow and calf performance. Treatments were arranged in a 2 x 2 factorial with 2 weaning dates and 2 age classes (young cows or=4 yr). Weaning dates were 1) normal weaning in mid-April at 210 d of age (NW) and 2) late weaning in mid-July at 300 d of age (LW). Mature cows were heavier (P < 0.01) than young cows throughout the trial, although BCS was similar (P >or= 0.10) among cow age classes. Cow BW (P = 0.58) and BCS (P = 0.40) were similar among weaning treatments at NW; however, at the beginning of the calving season, NW cows were heavier (585 vs. 562 kg; P = 0.02) and had greater BCS (6.57 vs. 5.95; P < 0.0001) than LW cows. Postpartum BW and BCS losses were greater (P < 0.0001) for NW cows, resulting in similar BW (P = 0.56) and BCS (P = 0.07) at the beginning of the breeding season and until April. Progeny of NW cows were 2.4 kg heavier (P < 0.01) at birth and grew faster before the April weaning date, resulting in increased BW (8 kg; P < 0.05) at the time of normal weaning. This increase in BW gain may be partially explained by the increased milk production of NW cows (0.59 kg/d as measured in February; P < 0.05). Although NW calves had increased BW in April, LW calves were heavier in July because of increased ADG during the weaning interval (1.13 vs. 0.8 kg; P < 0.0001). A cow age class x weaning date interaction (P = 0.007) was detected for pregnancy rate. Pregnancy rates were greater (P < 0.10) for LW-mature cows (96.7%) and NW-young cows (98.4%) than for LW-young cows (89.3%). However, pregnancy rate of NW-mature cows (90.2%) did not differ (P = 0.12) from that of LW-mature or LW-young cows, but was less than that of NW-young cows. These findings indicate that producers may benefit from matching weaning date to cow age class. It appears more advantageous to delay weaning of calves born to dams 4 yr or older while maintaining NW for dams 3 yr or younger at the time of calving. Late weaning had no detrimental effects on the performance of mature cows.

Supplemental energy and extruded-expelled cottonseed meal as a supplemental protein source for beef cows consuming low-quality forage.

Three experiments were conducted to evaluate the efficacy of supplemental energy and extruded-expelled cottonseed meal (ECSM; 30.6% CP; 44% NDF, 10.2% fat; DM basis) as a protein supplement (SUP) to spring-calving beef cows (n = 96; 535 kg initial BW; 5.4 initial BCS) consuming low-quality forage during late gestation and early lactation. Supplementation of ECSM was compared with 2 traditional cottonseed meal-based SUP. For all experiments, SUP provided equal CP. On a DM basis, SUP included 1) a blend of 76% wheat middlings and 18% solvent-extracted cottonseed meal (WMCSM); 2) solvent-extracted cottonseed meal (CSM); and 3) delinted, extruded-expelled cottonseed meal (ECSM). In Exp. 1, cows were individually fed SUP 3 d/wk until calving and 4 d/wk during lactation; total SUP period was 95 d. Tall-grass prairie hay (4.4% CP; 74% NDF; DM basis) was provided during the SUP period. Changes in cow BW during gestation (P = 0.23), over the SUP period (P = 0.27), and over the 301-d experiment (P = 0.56) were similar. Changes in BCS were similar during gestation (P = 0.78), over the SUP period (P = 0.95) and over the 301-d experiment (P = 0.37). Calf birth weights (P = 0.21) and BW at weaning (P = 0.76) were not different. Percentage of cows exhibiting luteal activity at the beginning of breeding season (P = 0.59), AI conception rate (P = 0.71), and pregnancy rate at weaning (P = 0.88) were not different. In Exp. 2, 18 cows in early lactation from Exp. 1 were used to determine the effect of SUP on hay intake and digestion. Hay intake tended (P = 0.10) to be greater for CSM than ECSM. Intake of OM and DM was greater for WMCSM (P 0.10). Similarly, 24-h milk production was not different (P = 0.25). Neither greater energy intake of cows consuming WMCSM nor greater fat intake of cows consuming ECSM influenced cow performance measures or calf weaning weight. Cow response to SUP with ECSM compared with traditional cottonseed meal-based SUP indicates that ECSM is a viable source of supplemental protein for beef cows consuming low-quality forage.

In situ ruminal degradation characteristics of by-product feedstuffs for beef cattle consuming low-quality forage.

Eight ruminally cannulated steers (BW = 753 +/- 48 kg) were used to evaluate in situ N, NDF, and DM degradation characteristics of by-product feeds and their application for beef cows consuming low-quality forage. Experimental feedstuffs included (DM basis) 1) extruded-expelled cottonseed meal (ECSM; 33% CP and 55% NDF), 2) extruded-expelled cottonseed meal with linters (ECSML; 25% CP and 41% NDF), 3) dried distillers grains with solubles (DGS; 33% CP and 36% NDF), 4) solvent-extracted cottonseed meal (CSM; 43% CP and 29% NDF), and 5) a blend of 76% wheat middlings with 18% CSM (WMCSM; 23% CP and 40% NDF). Steers were fed chopped prairie hay (4.8% CP, 69% NDF; DM basis) ad libitum and received 0.38 kg/100 kg of BW of WMCSM daily. In situ degradation kinetics of N, NDF, and DM components included the following fractions: A (immediately soluble), B (potentially degradable), and C (undegradable). Calculated rumen degradable protein (RDP) for ECSM was the greatest among all feedstuffs (83.8%; P < 0.01), which was composed of a large A fraction of N (41%). Similar RDP values were observed for DGS and ECSML (50.7 and 50.9%, respectively, P = 0.93). The B fraction N for ECSML was large (88.9%); however, most of this was unavailable for ruminal degradation. The amount of RDP in CSM and WMCSM was similar (78.2 and 73.5%, respectively; P = 0.12) though the A fraction of N was greater for WMCSM compared with CSM (P < 0.01). Degradability of NDF was greatest (P < 0.01) for DGS (67.4%) and was similar (P = 0.48) for WMCSM and CSM (54.5 and 57.0%, respectively). The least degradability of NDF was calculated for ECSM (29.3%; P < 0.01), attributed to greater lignin content (13.3%, DM). Degradability of DM was greatest (P < 0.01) for CSM and WMCSM (63.7 and 59.4%, respectively) and least (P < 0.01) for ECSM (36.5%) and ECSML (40.6%). Ruminal N degradation characteristics of ECSM were similar to more traditional supplements containing CSM and WMCSM. The RDP for ECSML and DGS N was less compared with other feedstuffs, indicating these feeds may need to be blended with other ingredients containing greater concentrations of degradable N, particularly in situations in which forage RDP is low.

Effects of body condition score at parturition and postpartum protein supplementation on estrous behavior and size of the dominant follicle in beef cows.

The objective of this study was to determine the effects of BCS at calving and the amount of postpartum protein supplementation on the dominant follicle (DF) and behavioral characteristics at the first postpartum estrus of mature beef cows. Multiparous Angus x Hereford cows (n = 45) were fed to calve in thin (T; < 5) or moderate (M; >or=5) BCS. Cows were stratified by BCS and calving date, and randomly assigned to receive lesser (L; 1.2 kg/d) or greater (G; 2.5 kg/d) amounts of a 42% CP supplement. All cows grazed the same native grass pasture and were fed in individual stalls for 49 +/- 2 d. Beginning 20 d after calving, blood samples were collected from each cow thrice weekly, and estrous behavior was monitored continuously with a radiotelemetry system. At 4 to 16 h after the onset of estrus, size of the DF was determined by ultrasonography. Body condition score of T cows was less (P < 0.01) at calving than M cows; L and G cows had similar BCS at calving and at the end of the feeding period. Body weight gains during treatment did not differ for L or G cows. Duration from calving to first estrus was greater (P < 0.01) for T than M cows. The incidence of a short luteal phase before first estrus was not influenced by BCS or protein supplement. Concentrations of IGF-I in plasma tended (P < 0.07) to be greater and size of the DF was greater (P < 0.01) for M than T cows. Size of the DF tended (P < 0.06) to be greater for G than L cows. Duration and number of mounts received at the first estrus were not influenced by BCS or supplement. Pregnancy rate of M cows during the breeding season was greater (P < 0.05) than T cows. Postpartum protein intake and BCS at calving influenced the size of the DF at the first postpartum estrus in mature suckled beef cows. Cows should be managed to calve in moderate BCS and maintain BW after parturition to decrease the interval to first estrus, increase follicular development, and maximize pregnancy rate.

Whole soybean supplementation and cow age class: effects on intake, digestion, performance, and reproduction of beef cows.

Two experiments were conducted to determine the effects of whole soybean supplementation on intake, digestion, and performance of beef cows of varying age. Treatments were arranged in a 2 x 3 factorial with 2 supplements and 3 age classes of cows (2-yr-old, 3-yr-old, and mature cows). Supplements (DM basis) included 1) 1.36 kg/d of whole raw soybeans, and 2) 1.56 kg/d of a soybean meal/hulls supplement. Supplements were formulated to provide similar amounts of protein and energy, but a greater fat content with the whole soybeans. Supplements were individually fed on Monday, Tuesday, Thursday, and Saturday mornings. During the treatment period, cows had free choice access to bermudagrass hay [Cynodon dactylon (L.) Pers.; 8.4% CP; 72% NDF; DM basis]. In Exp. 1, 166 spring-calving Angus and Angus x Hereford crossbred beef cows were individually fed supplements for an average of 80 d during mid to late gestation. During the first 50 d of supplementation, cows fed soybean meal/hulls gained more BW (10 kg; P < 0.001) and body condition (0.18 BCS units; P = 0.004) than cows fed whole soybeans. However, BW change (P = 0.87) and BCS change (P = 0.25) during the 296-d experiment were not different between supplements. Although calves from cows fed soybean meal/hulls were 2 kg heavier at birth, there was no difference in calf BW at weaning between supplements. Additionally, first service conception rate (68%; P = 0.24) and pregnancy rate (73%; P = 0.21) were not different between supplements. In Exp. 2, 24 cows from Exp. 1 were used to determine the effect of supplement composition on forage intake and digestion; cows remained on the same supplements, hay, and feeding schedule as Exp. 1. Crude fat digestibility was the only intake or digestibility measurement influenced by supplement composition; fat digestibility was higher for cows fed whole soybeans compared with cows fed the soybean meal/hulls supplement (58.1 vs. 48.8%). Hay intake and DMI averaged 1.63 and 1.92% of BW daily, respectively. Dry matter, NDF, and CP digestibility averaged 54.1, 55.1, and 63.2%, respectively. Compared with supplementation with soybean meal/ hulls, whole soybean supplementation during mid to late gestation resulted in reduced BW weight gain during supplementation, inconsistent effects on reproduction, no effect on calf weaning weight, and no effect on forage intake or digestion.

Effect of yeast culture on in vitro fermentation of a high-concentrate or high-fiber diet using equine fecal inoculum in a Daisy II incubator.

Two experiments were conducted to evaluate the use of a closed system, fermentation apparatus (Daisy II incubator) and determine the effects of a yeast culture (YC) preparation (Saccharomyces cerevisiae) on in vitro microbial populations, diet digestion, and fermentation patterns in horses. In Exp. 1, 4 mature horses were fed a pelleted concentrate and alfalfa cubes in a 50:50 (%, as-fed) ratio. Fecal samples were taken from each horse to form the inoculum and placed in 4 separate incubation vessels. Twenty nylon bags (10 with 0.25 g and 10 with 0.50 g of the total mixed diet) were placed in each vessel, and in vitro fermentation was carried out for 48 h to determine DM, NDF, and ADF digestibility. In Exp. 2, fecal samples were taken from 4 mature horses consuming either a high-concentrate (HC) or high-fiber (HF) diet. Filter bags containing the HC or HF diet were added to the 4 incubation vessels along with their respective inoculums. Yeast culture was added to 2 of the vessels containing the HC or HF diet, whereas the other 2 vessels served as controls. Vessels were incubated as in Exp. 1 with samples taken at 24 and 48 h. Filter bags were used to determine DM, NDF, ADF, and OM digestibility, whereas vessel fluid was analyzed for lactate, ammonia, VFA, and microbial concentrations. Results of Exp. 1 indicated that DM, NDF, and ADF digestibility were greater (P < 0.05), whereas the corresponding CV was lower (P < 0.05) for the 0.25- vs. the 0.50-g sample size. In Exp. 2, YC tended (P = 0.10) to decrease ammonia concentrations in the HF diet and increased (P < 0.05) acetate production in the HC diet when compared with the control. There were no effects of YC on pH, lactate, or the measured microbial populations, as well as DM, NDF, or ADF digestibility. The results did, however, show that in vitro and in vivo DM digestibility estimates were similar within a diet. Data from Exp. 1 indicated that the 0.25-g sample size provides a more accurate estimate of DM digestibility with less variation. Although YC had little, if any, effect in Exp. 2, the results indicated that the Daisy II incubator does provide valid estimates of total tract DM digestibility in the horse. These data provide further evidence that this process would be an effective and practical means of approximating the digestibility of diets with varying concentrate to forage ratios.

Effects of interval-feeding whole sunflower seeds during mid to late gestation on performance of beef cows and their progeny.

This experiment was conducted to determine the effects of interval feeding of whole sunflower seeds on the performance of beef cows and their progeny. During mid to late gestation, 144 multiparous, spring-calving beef cows (588 kg of initial BW; 5.6 initial BCS; 4 to 13 yr old) were individually fed 1 of 3 supplements 4 d/wk for a 76-d period. Supplements (DM basis) included: 1) 0.68 kg of soybean meal/feeding (NCON); 2) 3.01 kg of a soybean hull-based supplement/feeding (PCON); and 3) 1.66 kg of whole sunflower seeds high in linoleic acid/feeding (WSUN). Supplements were formulated to provide similar amounts of CP and ruminally degraded intake protein; PCON and WSUN were also formulated to be isocaloric. During the supplementation period, cows had free-choice access to bermudagrass (Cynodon dactylon) and tall-grass prairie hay. By the end of the 76-d supplementation period, cows fed PCON (P < 0.01) and NCON (P < 0.01) had gained more BW than cows fed WSUN (33, 23, and 10 kg, respectively). However, from the end of this supplementation period to the beginning of the breeding season 84 d later, cows supplemented with PCON had lost more (P < 0.01) BW than cows supplemented with WSUN (-123 kg vs. -111 kg). Cow BW change through weaning (-50 kg, P = 0.43) and final cow BW (536 kg, P = 0.70) at weaning were not different among supplement groups. Furthermore, cow BCS was similar among supplement treatment groups at the end of the supplementation period (5.3, P = 0.09), at the beginning of the breeding season (4.8, P = 0.38), and at weaning (4.7, P = 0.08). No difference among treatments was detected for calf birth weight (36 kg, P = 0.42), calf weaning weight (235 kg, P = 0.67), percentage of cows exhibiting luteal activity at the beginning of the breeding season (57%, P = 0.29), or pregnancy rate (88%, P = 0.44). However, first service conception rate was greater (P = 0.01) for cows fed PCON (79%) and tended (P = 0.07) to be greater for cows fed WSUN (74%) than for cows fed NCON (53%). After weaning, all steer calves were placed in a feedlot and fed a high-concentrate finishing diet for an average of 188 d. Supplements fed to dams during gestation did not influence feedlot performance or carcass characteristics. Prepartum energy supplementation, regardless of energy source or prepartum energy balance, resulted in improved conception rate, but other measures of reproduction, calf and feedlot performance, and carcass characteristics were not affected.

Incidence of puberty in beef heifers fed high- or low-starch diets for different periods before breeding.

Spring-born Hereford x Angus heifers (n = 206) were used to determine effects of energy supplementation programs and amount of starch in the diet on incidence of puberty. In Exp. 1, heifers (205 +/- 5 kg; n = 68) grazing dormant native pasture were fed 0.9 kg/d (as-fed basis) of a 42% CP supplement from November until February 14. Heifers were stratified by weaning weight and allotted randomly to treatment before breeding (May to July). Treatments were 1) 0.9 kg (as-fed basis) of a 42% CP supplement/d and pasture (control); 2) a high-starch (HS) diet (73% corn; 53% starch) fed in a drylot for 60 d (HS-60); 3) a HS diet fed in drylot for 30 d (HS-30); or 4) a low-starch (LS) diet (49% corn; 37% starch) self-fed on pasture for 30 d (LS-30). The HS-60 and HS-30 heifers were limited-fed to gain 0.9 kg/d, and the LS-30 heifers had ad libitum access to the diet. High-starch-60 and LS-30 heifers were heavier (P < 0.05) than control and HS-30 heifers at the beginning of the breeding season. Thirty-one, 25, and 26% more HS-60 heifers were pubertal (P < 0.05) on May 1 compared with LS-30, HS-30, and control heifers, respectively. At puberty, HS-60 heifers were 24 and 22 d younger (P < 0.05) than LS-30 and control heifers, and 31 kg lighter (P < 0.01) than LS-30 heifers. In Exp. 2, heifers grazed dormant pasture and were fed 0.9 kg (as-fed basis) of a 42% CP supplement/d from weaning in October to late February; then heifers were assigned randomly to treatments for 60 d before the breeding season. In two years, control heifers (n = 46) grazed pasture and received 0.9 kg of SBM supplement/d; LS (n = 46) heifers were self-fed a distiller's grain and soybean hull-based diet in drylot; and HS heifers (n = 46) were limited-fed a corn-based diet in drylot. During treatment, HS and LS heifers had greater weight gains than control heifers. Pubertal BW (313 +/- 6 kg) was not influenced by treatment, but HS and LS heifers were younger (P < 0.03) than control heifers at puberty. During a 60-d breeding period, the incidence of puberty was greater (P < 0.05) for HS and LS heifers than for control heifers and was greater (P < 0.05) in HS than in LS heifers in Year 1. Feeding a LS or a HS diet for 30 d before breeding may be inadequate to stimulate puberty in beef heifers, but feeding a diet with a greater amount of starch for 60 d before breeding may increase the incidence of puberty during breeding of heifers that have inadequate yearling weight.

Vitamin E supplementation of newly arrived feedlot calves.

Seven hundred fifteen crossbred (primarily British) calves purchased in southern Oklahoma and northern Texas auction barns were received at the Willard Sparks Beef Research Center, Stillwater, OK, and used to study effects of duration (days) of vitamin E feeding during a 42-d receiving period on animal performance, health, and serum cholesterol and vitamin E concentrations. Upon arrival, calves were blocked by load (seven loads), sorted by BW (light, n = 4 pens per load; and heavy, n = 4 pens per load), and assigned randomly to one of four dietary treatments (n = 2 pens per load; 14 pens per treatment). Experimental diets were formulated to provide 2,000 IU.calf(-1).d(-1) of supplemental vitamin E (dl-alpha-tocopherol acetate) for 0 (CON), 7 (E7), 14 (E14), or 28 (E28) d. Vitamin E was delivered in a pelleted supplement that was added to the basal diet in decreasing concentrations as DMI increased (2.0 kg of DMI = 6%; 4.0 kg of DMI = 4%; and 6.0 kg of DMI = 2%). Serum samples were collected on d 0, 14, 28, and 42 for determination of cholesterol, alpha-tocopherol (d 0, 28, and 42), and antibody (IgG) concentrations. Duration of vitamin E supplementation did not affect ADG (0.98 kg/d; P = 0.56) or G:F (0.189; P = 0.87). Serum cholesterol concentrations decreased (day effect; P < 0.001) for all treatments from d 0 (average = 127 mg/100 mL) to 14 (average = 62 mg/100 mL). Serum alpha-tocopherol decreased (day effect; P < 0.001) from d 0 (5.2 microg/mL) to 28 (1.8 microg/mL); however, on d 28, a greater (P < 0.001) serum alpha-tocopherol concentration was observed for E28 (3.4 microg/mL) calves than for CON (1.1 microg/mL), E7 (1.2 microg/mL), or E14 (1.5 microg/mL) calves. Respiratory disease was diagnosed in 64.6% of calves in this study. Medical costs were less (P = 0.08) for calves fed vitamin E for 28 d (4.88 dollars/calf) than for calves fed the control diet (6.29 dollars/calf). Carcass characteristics were not affected (P = 0.19 to 0.88) by dietary treatments. Supplemental vitamin E formulated for 2,000 IU.calf(-1).d(-1) had little influence on performance and overall health status of calves under our experimental conditions; however, the increased serum concentrations of alpha-tocopherol when vitamin E was fed for 28 d suggests that any potential effects of vitamin E on health status might be time-dependent.

Relationship of sire expected progeny differences to milk yield in Brangus cows.

Milk yield from 160 Brangus cows sired by 65 Brangus bulls was measured over a 3-yr period with a single-cow milking machine to estimate the relationship of actual milk yield of daughters and their calves' BW with cow sire EPD for milk during the preweaning period. Milk yield was measured six times per year at an average 49, 78, 109, 138, 168, and 198 d postpartum. The regression of daughters' milk yield on sire milk EPD was quadratic (P < 0.01), and the initial linear portion of the curve differed among months (P < 0.05) at an average cow BW. Similarly, the regression of 6-mo average 24-h milk yield on sire milk EPD was curvilinear (P < 0.05). When cow BW was fitted as a covariate in the regression of 6-mo average 24-h milk yield on sire milk EPD, there was an interaction of cow BW with linear sire milk EPD and quadratic sire milk EPD (P < 0.10). The associated response surface suggested that the regression was primarily linear in cows weighing < or = 520 kg and curvilinear in cows weighing >520 kg. A trend existed for the regression of calf 205-d weight on grandsire milk EPD to be curvilinear (P < 0.21); however, the regression of calf 205-d weight on milk yield of their dam was linear (P < 0.01). Results from these data suggest that genetic potential for milk yield, and possibly the associated effects on calf BW transmitted through the grandsire, may have a practical maximum because of nutritional limitations that prevent the expression of genetic potential beyond that level, particularly in heavier cows, which suggests the need to match sire milk EPD and cow BW with production environment.

Influence of milk production potential on forage dry matter intake by multiparous and primiparous Brangus females.

Brangus cows (n = 29) were used in three experiments to evaluate the effects of parity (multiparous vs. primiparous) and potential genetic merit for milk production (high vs. low) on forage intake during late gestation, early lactation, and late lactation. Cows were selected for milk production based on their sire's EPD for milk production (MEPD). Cows had ad libitum access to (130% of previous 2-d average intake) low-quality hay (5.3% CP and 76% NDF), and cottonseed meal was supplemented to ensure adequate degradable intake protein. All females were adapted to diets for at least 7 d, and individual intake data were collected for 9 d. During the lactation trials, actual milk production was determined using a portable milking machine following a 12-h separation from calves. During late gestation, multiparous cows consumed 24% more (P = 0.01) forage DM (kg/d) than primiparous cows; however, parity class did not influence forage intake when intake was expressed relative to BW. Furthermore, MEPD did not influence forage intake during late gestation. During early lactation, multiparous cows produced 66% more (P < 0.001) milk than primiparous cows, and high MEPD tended (P = 0.10) to produce more milk than low MEPD. Multiparous cows consumed 19% more (P < 0.0001) forage DM than did primiparous cows when expressed on an absolute basis, but not when expressed on a BW basis. High-MEPD cows consumed 8% more (P < 0.05) forage DM than did low-MEPD cows. During late lactation, multiparous cows produced 84% more milk than primiparous cows, although MEPD did not influence (P = 0.40) milk yield. In addition, multiparous cows consumed 17% more (P < 0.01) forage DM per day than primiparous cows, but when intake was expressed relative to BW, neither parity nor MEPD influenced forage DMI during late lactation. Milk yield and BW explained significant proportions of the variation in forage DMI during early and late lactation. Each kilogram increase in milk yield was associated with a 0.33- and 0.37-kg increase in forage DMI for early and late lactation, respectively. Results suggest that multiand primiparous cows consume similar amounts of low-quality forage DM, expressed per unit of BW, during late gestation and lactation. Selecting beef cows for increased genetic merit for milk production increases forage DMI during early lactation.

Effects of supplementation on intake, digestion, and performance of beef cattle consuming fertilized, stockpiled bermudagrass forage.

Experiments were conducted to determine the effects of increasing supplement protein concentration on performance and forage intake of beef cows and forage utilization of steers consuming stockpiled bermudagrass forage. Bermudagrass pastures were fertilized with 56 kg of N/ha in late August. Grazing was initiated during early November and continued through the end of January each year. Treatments for the cow performance trials were: no supplement or daily equivalents of 0.2, 0.4, and 0.6 g of supplemental protein per kilogram of BW. Supplements were formulated to be isocaloric, fed at the equivalent of 0.91 kg/d, and prorated for 4 d/wk feeding. Varying the concentration of soybean hulls and soybean meal in the supplements created incremental increases in protein. During yr 1, supplemented cows lost less weight and condition compared to unsupplemented animals (P < 0.05). During yr 2, supplemented cows gained more weight (P = 0.06) and lost less condition (P < 0.05) compared to unsupplemented cows. Increasing supplement protein concentration had no affect on cumulative cow weight change or cumulative body condition score change. Forage intake tended to increase (P = 0.13, yr 1 and P = 0.07, yr 2) in supplemented cows. Supplement protein concentration did not alter forage intake. In a digestion trial, four crossbred steers were used in a Latin square design to determine the effects of supplement protein concentration on intake and digestibility of hay harvested from stockpiled bermudagrass pasture. Treatments were no supplement; or 0.23, 0.46, and 0.69 g of supplemental protein per kilogram of BW. Forage intake increased (P < 0.05) 16% and OM intake increased (P < 0.01) 30% in supplemented compared to unsupplemented steers. Diet OM digestibility increased (P = 0.08) 14.5% and total digestible OM intake increased (P < 0.05) 49% in supplemented compared to unsupplemented steers. Supplement protein concentration did not alter forage intake, total digestible OM intake, or apparent digestibility of OM or NDF. During the initial 30 d after first killing frost, beef cows did not respond to supplementation. However, later in the winter, supplementation improved utilization of stockpiled bermudagrass forage.

Effects of supplement type on animal performance, forage intake, digestion, and ruminal measurements of growing beef cattle.

Two experiments were conducted to determine the effects of supplement type on the rate of gain by heifers grazing bermudagrass and on the intake, apparent total-tract OM digestibility, ruminal fermentation, digesta kinetics, in situ DM digestibility, and forage protein degradation by steers fed prairie hay. In Exp. 1, 45 heifers (284+/-24 kg) grazed a bermudagrass pasture for 91 d in the late summer to determine the effects of no supplement (CON), or one of four individually fed monensin-containing (150 mg/[heifer x d]) supplements (MINCS; 0.1 kg of mineral mix with 0.2 kg [DM] of cottonseed hulls as a carrier/[heifer x d]), a pelleted protein supplement (PROT; 1 kg of DM, 242 g of degradable intake protein [DIP]/[heifer x d]), or high-fiber (HF) and high-grain (HG) (2 kg of DM, 243 and 257 g of DIP, respectively/[heifer x d]) pelleted energy supplements. In Exp. 2, four ruminally cannulated steers (311+/-22 kg) with ad libitum access to low-quality (4% DIP, 73% NDF, 40% ADF) prairie hay were individually fed monensin-containing (200 mg/[steer x d]) treatments consisting of 1) mineral mix + corn (MINCR; 0.1 kg of mineral and 0.4 kg of cracked corn [DM] as a carrier, 19 g of DIP/[steer x d]), 2) PROT (1.4 kg of DM, 335 g of DIP/[steer x d]), 3) HF, or 4) HG (2.9 kg of DM, 340 and 360 g of DIP, respectively/[steer x d]) in a 4 x 4 Latin square with 14-d adaptation and 6-d sampling periods. In Exp. 1, the HF-, HG-, and PROT-supplemented heifers had greater (P < 0.01) rates of gain than CON heifers, and the HF- and HG-supplemented heifers tended (P < 0.11) to gain more weight than those fed PROT. In Exp. 2, steers fed PROT consumed more (P < 0.05) hay OM than HF and HG, or MINCR. Total OM intake was greater (P < 0.01) by supplemented steers than MINCR-fed cattle. Hay OM digestibility was not affected (P = 0.19) by treatment, but total diet OM digestibility was greater (P < 0.01) for HF- and HG- than for MINCR- or PROT-fed steers. The rate of in situ DM digestibility was greater (P < 0.01) for HF, HG, and PROT than for MINCR. Results from these studies indicate that feeding milo- vs fiber-based energy supplements formulated to provide adequate DIP did not result in different forage intake, OM digestibility, or in situ DM digestibility, whereas both increased ADG in heifers consuming low-quality forages compared with unsupplemented or mineral- or protein-supplemented cattle. An adequate DIP:TDN balance decreased the negative associative effects often observed when large quantities of high-starch supplements are fed with low-quality hay.