Twenty-eight Hereford x Angus cows (4 yr of age) were used to determine the effects of pre- and postpartum dietary energy on performance and reproductive function in suckled beef cows. The experiment was designed as a 2 x 2 factorial with cows receiving either 70 (L) or 150% (H) of NRC recommended level of dietary energy before and(or) after parturition, resulting in four treatment combinations (L-L, L-H, H-L, H-H). Prepartum diets were fed for approximately 110 d, and postpartum diets were fed until either 10 d after the second postpartum ovulation or 150 d postpartum for those cows that failed to ovulate. Cows receiving low compared with high levels of energy before calving lost more (P less than .01) weight, body condition, subcutaneous fat, and longissimus muscle area before parturition and had calves with lighter (P less than .01) birth weights. Cows receiving low compared with high levels of energy postpartum lost more (P less than .01) weight, body condition, and longissimus muscle area after parturition. Low levels of energy before and after parturition decreased (P less than .01) milk production and calf weight at 70 d of age. Rates of cervical and uterine involution were unaffected by dietary energy treatments. Cows receiving high levels of energy prepartum had increased (P less than .01) mean concentrations and pulse frequency of LH in serum after parturition, and cows receiving high levels of energy postpartum had increased (P less than .05) pulse frequency of LH. Low levels of energy postpartum decreased (P less than .01) appearance rate of small (5.0 to 7.9 mm) and large (greater than or equal to 10 mm) follicles, and low levels of energy prepartum decreased (P less than .02) appearance rate of large follicles based on transrectal ultrasonography. Cows receiving high levels of energy prepartum had shorter (P less than .02) intervals from parturition to ovulation, and a higher (P less than .01) percentage of the cows that received high levels of energy postpartum ovulated by 150 d postpartum. In summary, prepartum level of dietary energy influenced birth weight and weight gain of calves, milk production, concentrations and pulse frequency of LH in serum, appearance rate of large follicles, and the interval to first ovulation. Postpartum level of dietary energy influenced milk production, weight gain of calves, pulse frequency of LH, appearance rate of small and large follicles, and the percentage of cows that ovulated after parturition.

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.

Milk EPD, used to predict the milk production potential of a parent's daughters, have been reported by all major cattle breed associations. Our objectives were to determine the relationship of milk EPD of a dam to actual milk production (both fluid and components) and offspring weaning weight. Angus (AN; n = 114) and Simmental (SM; n = 82) cows were machine-milked at approximately 60, 104, and 196 d postpartum after overnight calf removal. In addition, one herd of AN was also milked at approximately 35 and 145 d postpartum. A lactation curve was fitted to these measurements to estimate total milk production during lactation. Simple correlations between 205-d total milk yields (TMY) and adjusted 205-d calf weaning weight (WW) were .30 (P < .001) and .47 (P < .001) for AN and SM, respectively. Furthermore, milk EPD was positively correlated to adjusted WW (r = .38 P < .001; r = .39, P < .001) and TMY (r = .32, P < .001; r = .44, P < .001) for AN and SM cows, respectively. A 1-kg change in TMY changed WW by .014 +/- .006 kg (P < .001) in AN and by .032 +/- .009 kg (P < .001) in SM. A 1-kg change in milk EPD resulted in a 4.85 +/- 1.14 kg change in WW (P < .001) in AN and a 3.74 +/- 1.73 kg (P < .05) change in SM. Corresponding changes in TMY were 42.1 +/- 16.6 kg (P < .01) and 69.3 +/- 16.0 kg (P < .001) for AN and SM, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Two experiments were conducted to quantify the impact on forage use and performance of varying supplementation frequency of cattle consuming forage diets across a range of frequencies. In both experiments, a common supplement was used that contained a relatively high concentration of CP (43%) and was fed at the following frequencies: 1) 2 d/wk; 2) 3 d/wk; 3) 5 d/wk; and 4) 7 d/wk. In Exp. 1, 120 Hereford x Angus cows (BW = 537 kg) grazing winter tallgrass-prairie range were supplemented at the various frequencies from December 7 until calving (average calving date = 3/7/99). All treatments provided the same quantity of supplement on a weekly basis (12.74 kg, as-fed) but divided the amount delivered on a given day equally among the number of supplementation events for that treatment. Less BW was lost from December 7 through calving (linear effect, P = 0.02) as frequency of supplementation increased, but the magnitude of difference in weight change was relatively small. Body condition responded similarly through early February (linear effect, P = 0.02), although treatment effects were not as distinct at calving (cubic effect, P = 0.11). In Exp. 2, 16 ruminally fistulated Hereford x Angus steers (BW = 257 kg) were blocked by weight and assigned to one of the four frequencies of supplementation. Steers were offered tallgrass prairie hay (73.5% NDF, 4.8% CP) ad libitum and were supplemented at a rate (relative to BW) similar to that of the cows in Exp. 1. Increasing frequency of supplementation increased (linear effect, P < or = 0.02) forage OM intake, OM and NDF digestion, and digestible OM intake. However, the most prominent differences in forage OM intake tended (cubic effect, P = 0.07) to occur with the two extreme frequencies of supplementation. In conclusion, forage use was improved with an increased frequency of supplementation, but the impact on performance is not likely to be large unless extreme differences in frequency occur.

Seventy-two Holstein steers averaging 182 kg were assigned randomly to one of six treatment groups: 1) nonimplanted controls (C); 2) implanted with 36 mg of zeranol (Z); 3) implanted with 20 mg of estradiol benzoate and 200 mg of progesterone (EP); 4) implanted with 140 mg of trenbolone acetate (TBA); 5) implanted with 140 mg of trenbolone acetate plus 20 mg of estradiol benzoate and 200 mg of progesterone (TBA + EP); and 6) implanted with 140 mg of trenbolone acetate plus 36 mg of zeranol (TBA + Z). Each treatment group consisted of three replications of four animals per pen, which were implanted on d 0, 56, 112, and 168. Masculinity and muscling scores were assigned at 24 h preslaughter. Hide removal difficulty was scored by a plant supervisor. Quality and yield grade data were obtained at 24 h postmortem. Longissimus muscle (LM) steaks were removed and cooked for Warner-Bratzler shear (WBS) determinations and sensory panel (SP) evaluations. Over the entire feeding period (249 d), TBA + EP steers had higher (P less than .05) ADG than TBA + Z, TBA, and C steers. All treatments had higher (P less than .05) ADG than C, with the exception of TBA. The only feed efficiency differences were those following the 168-d implant time, when TBA steers were more (P less than .05) efficient than TBA + Z or C steers. The TBA + EP and TBA + Z steers were more (P less than .05) masculine and their hides were more (P less than .05) difficult to remove than those of EP and C steers. Carcass weights of TBA + EP steers were heavier (P less than .05) than those of TBA or C steers. The TBA + EP steers had larger (P less than .05) LM areas than Z, TBA, and C steers. Also, TBA + EP steers tended (P = .07) to have lower numerical yield grades than EP, Z, or C steers. Even though mean marbling scores and quality grades were similar (P greater than .05) among treatment groups, only 50% of TBA + EP carcasses graded low Choice or higher, compared with 100, 75, 82, 90, and 83% for C, TBA, Z, EP, and TBA + Z carcasses, respectively. The only meat palatability differences were that myofibrillar and overall tenderness scores tended to be lower (P = .07) for steaks from EP and TBA + Z than for steaks from Z and C groups.