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As perennial warm-season grasses mature in late summer, dry matter intake (DMI) of growing heifers may be limited due to low protein (7.2 ± 2.5 %) and increased NDF content (67.5 ± 2.7%), which may compromise growth potential. Cottonseed meal (CSM) supplementation may improve forage digestibility by increasing rumen degradable protein offered, but research regarding the specific effects of CSM supplementation on gain performance and composition of gain in heifers is limited. It was hypothesized that supplementation of CSM to heifers grazing mature forage would have greater growth performance compared with heifers not receiving CSM. Objectives for this experiment were to compare the effects of two CSM supplementation strategies on the growth performance of heifers grazing mature summer forage. In two consecutive summers, commercial Angus cross heifers (n = 63) weighing 266.08 ± 32.74 kg were blocked by BW (light, medium, and heavy) and allocated to 9 paddocks (1.64 ha) of WW-B. Dahl Bluestem (Bothriochloa bladhii) for 67 to 70 d. This was a RCBD with a factorial arrangement of 3 treatments by 3 BW blocks, with paddock and year as random effects. Heifers received one of three supplementation strategies: no cottonseed meal (CON), 454 g/animal of CSM daily (CSM1), or 908 g/animal of CSM every other day (CSM2). Initial and final shrunk BW were measured; ADG and percent of BW gained were calculated. Ultrasound of initial and final longissimus muscle area (LMA), backfat (BF), and intramuscular fat (IMF) were measured; percent gained was calculated, respectively. There were no treatment by block interactions for any measured variable. Heifers receiving CSM1 and CSM2 had greater final BW than heifers receiving CON (317 and 320.8 vs 302.6 kg, respectively; (P = 0.01). Likewise, percent of BW gained was greater (P = 0.02) for CSM1 and CSM2 supplemented heifers compared with CON heifers (19.4 and 20.2 vs 14.6%, respectively). The ADG of CSM1 and CSM2 supplemented heifers was greater (P = 0.01) than CON (0.74 and 0.78 vs 0.54 kg/d, respectively). Treatment did not affect the percent of BF (P = 0.24) or IMF gained (P = 0.39). Heifers receiving CSM1 and CSM2 tended to gain proportionally more LMA than heifers receiving CON (13.58 and 13.77 % vs 7.24%, respectively; P = 0.07). As anticipated, BW block affected final BW (P < 0.001) and percent BW gained (P = 0.02), as well as percent LMA gained (P = 0.02). In conclusion, CSM supplementation significantly affected growth performance of heifers grazing late summer WW-B. Dahl Bluestem forage versus no supplementation. In addition, there was no difference in growth performance between heifers receiving 454 g/d of CSM supplementation or 908 g/animal every other day, indicating flexibility for feeding strategy. [ABSTRACT FROM AUTHOR]

Nutritive quality of perennial warm-season grasses during summer may limit the DMI of growing calves due to low protein and increased NDF content. Cottonseed meal (CSM) supplementation may improve forage utilization by increasing rumen degradable protein, but research in calves is limited. It was hypothesized that supplementation of CSM to heifers grazing mature forage would have improved performance due to greater forage DMI and fiber digestibility. Objectives were to compare the effects of CSM supplementation on calf gain performance, estimated forage intake, and in vitro true digestibility (IVTD) and neutral detergent digestibility (IVNDFD) of low-quality, warm-season forage. Angus heifers (n = 18) weighing 232.7 ± 12.6 kg were blocked by BW (light, medium, and heavy) and allocated to 6 paddocks (1.64 ha) of W.W. B-Dahl Bluestem (Bothriochloa bladhii) for 67 d. Heifers were supplemented daily with a mineral mix and either no cottonseed meal (CON) or 454 g/animal of CSM (CSM1) in a RCBD with a 2×3 factorial arrangement of treatments and BW blocks, respectively. Initial and final shrunk BW was measured to calculate total gain, ADG, and percent of BW gained. Forage samples were collected weekly and composited into 3 periods for chemical analysis and in vitro incubations. Forage DMI was estimated using a double sampling technique for each paddock within period. Forage IVTD and IVNDFD were analyzed using batch fermentation with and without CSM in a CRD (2 treatments by 3 periods). Mean forage CP during periods 1 and 2 were 5.75% and increased to 10.3% in period 3 (P < 0.01). Forage NDF content increased over time (64.1 vs. 69.3%; P < 0.01) and estimated forage DMI of heifers tended (P = 0.07) to decrease from 2.9 to 2.1% of BW. Treatment did not affect estimated forage DMI (P = 0.40). Heifers receiving CSM1 gained 28.3% more BW than heifers receiving CON (47.27 vs. 36.82 kg, respectively; P = 0.02). Percent of BW gained was greater for heifers receiving CSM1 than CON (16.9 vs. 13.8% of initial BW, respectively, P = 0.029). There were no treatment by period interactions on IVTD or IVNDFD. The IVTD of forage from period 1 was greater than periods 2 and 3 (49.9 vs. 47.1 and 46.6%, respectively; P = 0.005). The IVTD of forage incubated with CSM tended (P = 0.06) to be greater than forage without CSM (52.1% vs. 47.8%, respectively). The IVNDFD was not affected by period but tended to be greater with CSM inclusion (P = 0.09) relative to CON (24.83% vs. 18.95%, respectively). In conclusion, 454 g/d of CSM supplemented to heifers grazing latesummer W. W. B-Dahl Bluestem forage likely provided sufficient protein to alter ruminal fiber digestibility, without affecting forage intake, and had measurable effects on gain. [ABSTRACT FROM AUTHOR]

Summer stocker calves grazing perennial warm-season grasses may benefit from protein supplementation due to the low protein content typically observed in these forages. Cottonseed meal (CSM) is an excellent protein supplement that is readily available in the south and is competitively priced per unit of protein in early summer. However, research regarding the effects of CSM supplementation level and frequency on calf gain and composition of gain is limited. It was hypothesized that supplementing CSM to grazing heifers would improve ADG and perhaps alter composition of gain when compared with non-supplemented heifers. Objectives for this experiment were to 1) compare gain and composition of gain between calves supplemented with CSM to non-supplemented calves, and 2) compare the effect of daily vs. alternating days of CSM supplementation. A total of 27 commercial Angus beef heifers weighing 234.1 ± 4.18 kg were blocked by BW (light, medium, and heavy) and allocated to 9 paddocks of W.W. B-Dahl Bluestem (Bothriochloa bladhii) for 67 d. The experimental was designed as a RCBD with 3×3 factorial arrangement of 3 treatments and 3 weight blocks. Heifers were supplemented daily with a mineral mix and either no cottonseed meal (CON), 454 g/animal of CSM daily (CSM1), or 909 g/animal of CSM every other day (CSM2). Initial and final shrunk BW was measured, and total gain, ADG, and percent of BW gained were calculated. Ultrasound of initial and final longissimus muscle area (LMA), backfat (BF), and intramuscular fat (IMF) were measured. There were no treatment by block interactions for any measured variable. Treatment significantly affected total gain and ADG (P = 0.0156), as well as percent of BW gain (P = 0.029). Heifers receiving CSM1 treatment gained 28.3% more total BW than heifers receiving CON (47.27 vs. 36.82 kg, respectively) and CSM2 was intermediate (42.73 kg). Likewise, percent of BW gained was greatest for CSM1 and least for CON (16.9 vs.3.8% of initial BW), with CSM2 not differing (15.5% of initial BW). Treatment did not affect the composition of gain (P = 0.190); however, block tended (P = 0.0812) to affect LMA % gain, with light heifers being greater than medium and heavy heifers (12.00% vs. 7.35% and 5.09% increase, respectively). As expected, heifers grazing late summer W.W. B-Dahl Bluestem forage who received 454 g of CSM daily had significantly greater ADG than heifers not receiving CSM. Heifers receiving 909 g of CSM every other day tended to gain more than heifers not receiving CSM, but replication of this experiment is needed for validation of this specific supplementation strategy. In conclusion, supplementation of CSM to calves grazing low protein summer forage within a limited period may have positive measurable effects on gain. [ABSTRACT FROM AUTHOR]