D. E. Johnson

Effect of a wide range in the ratio of supplemental rumen degradable protein to starch on utilization of low-quality, grass hay by beef steers

Hereford×Angus steers were used in a 14-treatment, 2-period, crossover design experiment to examine effects of a wide range in the ratio of supplemental starch to rumen degradable protein (RDP) on low-quality forage utilization and ruminal characteristics. Steers were given ad libitum access to grass hay (4.9% CP, 42.4% ruminally degradable) and supplemented in a 2×7 factorial arrangement of treatments. All supplements were administered directly into the rumen and delivered one of two levels of ruminally degradable starch (cornstarch grits; 0 and 0.3% of initial BW) and one of seven levels of RDP (sodium caseinate; 0, 0.015, 0.051, 0.087, 0.123, 0.159, and 0.195% of initial BW). Supplementation with RDP increased consumption of forage OM, total OM, NDF, and digestible OM in a quadratic (P<0.01) fashion (intake increased and then declined). Starch supplementation depressed (P<0.01) forage OM and NDF intakes. In general, RDP supplementation elicited a positive quadratic response on NDF digestion (P=0.02). However, an interaction between supplemental starch and RDP level was observed (P<0.01) for NDF digestion. At the four lowest levels of supplemental RDP, starch supplementation substantially reduced NDF digestion, although for steers receiving the three highest levels of supplemental RDP, starch supplementation had little effect on NDF digestion. In contrast, neither the starch×RDP interaction nor the starch main effect was significant for OM digestion, which increased linearly (P<0.01) with supplemental RDP. Supplementation with RDP altered passage rate of acid detergent insoluble ash in a quadratic (P=0.05) manner that paralleled the intake response. However, liquid passage rate was not affected significantly. A decline in ruminal pH was associated (P=0.02) with increasing supplemental RDP and tended (P=0.07) to be associated with increasing starch, but it was not requisite for starch-induced depressions in NDF digestion. Ruminal NH3 concentration increased in response to increasing RDP, although the increase when starch was supplemented was less than that observed without starch (P=0.03). Supplemental starch generally elicited negative effects on low-quality forage intake and fiber digestion, but the effects on fiber digestion were overridden by adequate supplemental RDP. Supplemental RDP exerted a highly positive effect on consumption and digestion of this low-quality forage.

A collaborative study comparing an in situ protocol with single time-point enzyme assays for estimating ruminal protein degradability of different forages☆

Abstract Seven institutions conducted a collaborative trial to compare three methods for estimating effective degradability (ED) of forage protein from alfalfa ( Medicago sativa ; 2.9% N), bermuda ( Cynodon dactylon ; 1.4% N), brome ( Bromus inermis ; 0.9% N), forage sorghum ( Sorghum bicolor ; 0.8% N), and prairie (mixture of native tallgrass prairie species; 0.9% N) hays. To facilitate the collaborative nature of this study, an adaptation of an abbreviated in situ procedure proposed by Broderick [Quantifying forage protein quality. In: Fahey, G.C., Collins, M., Mertens, D.R., Moser, L.E. (Eds.), Forage Quality, Evaluation, and Utilization. ASA, CSSA, and SSSA, Madison, WI, USA, pp. 200–228] and subsequently validated by Vanzant [J. Anim. Sci. 74 (1996) 2773] was adopted for comparison with other procedures. The abbreviated in situ procedure (conducted at four institutions) assumed first-order degradation kinetics and entailed not incubating (0xa0h) as well as ruminally incubating (2, 8, and 96xa0h) duplicate polyester bags ( 10 cm ×20 xa0cm) of each forage (5xa0g) in the rumens of two steers per location during each of two periods. Rinsing, drying, and microbial correction procedures were standardized. The in situ estimates of ED were compared with two single time-point enzyme assays (using Streptomyces griseus protease) derived from the work of Roe [Techniques for measuring protein fractions in feedstuffs. In: Proceedings of the Cornell Nutrition Conference, Department of Animal Science, Cornell University, Ithaca, NY, pp. 81–88] and Krishnamoorthy et al. [Br. J. Nutr. 50 (1983) 555] with adaptations based on the work of Abdelgadir et al. [J. Anim. Sci 75 (1997) 2215] and Coblentz et al. [J. Diary Sci. 82 (1999) 343]. For the protease assays, duplicate forage samples (15xa0mgxa0N) were incubated (at seven institutions) in 40xa0ml of a buffer solution for 1xa0h. Subsequently, 10xa0ml of a S. griseus protease solution (0.33xa0U of activity/ml) were added to the buffer plus forage and incubated for 48xa0h. In addition, a shorter procedure was evaluated (at six institutions) wherein an increased concentration (33.0xa0U of activity/ml) of S. griseus concentration was used to compensate for shorter incubation time (4xa0h). Average ED values obtained from both the 48 and 4xa0h S. griseus assays explained a large portion of the variation observed for the average ED values from the in situ technique ( r 2 =0.87 and r 2 =0.88, respectively). However, there did appear to be some evidence that the S. griseus assays tested overestimated in situ ED in forages with low degradability. The 4xa0h/high-concentration and 48xa0h/low-concentration S. griseus assays were closely related ( r 2 =0.99) with little bias evident in the relationship. These assays were also less variable than the abbreviated in situ approach. In conclusion, single time-point S. griseus assays with appropriately balanced incubation lengths and enzyme concentrations appear promising for estimating ED under routine laboratory conditions.

Effects of ractopamine and sex on serum metabolites and skeletal muscle gene expression in finishing steers and heifers

We evaluated growth-related responses to ractopamine in steers and heifers. Sixteen Angus steers (512 kg) and 16 Angus heifers (473 kg) housed in individual pens were used in a complete block design. At 90 to 97 d before the experiment, steers were implanted with 120 mg of trenbolone acetate and 24 mg of estradiol-17beta (Component TE-S) and heifers were implanted with 140 mg of trenbolone acetate and 14 mg of estradiol-17beta (Component TE-H). Treatments were arranged as a 2 x 2 factorial and included sex (steer vs. heifer) and ractopamine-HCl (0 or 200 mg/d). Cattle were fed a diet based on steam-flaked corn once daily. Blood and LM and biceps femoris (BF) biopsy samples were collected on d 0 (before ractopamine feeding) and after 14 and 28 d of ractopamine feeding. Serum insulin concentrations were not affected by ractopamine or sex. Serum IGF-I concentrations were greater in steers than heifers (P < 0.001), and steers demonstrated greater IGF-I mRNA expression in BF than heifers (P = 0.05). Ractopamine decreased serum IGF-I concentrations in heifers on d 14, but increased serum IGF-I concentrations in steers on d 28 (sex x ractopamine x day interaction; P = 0.03). Ractopamine did not affect (P >or= 0.19) mRNA expression of IGF-I, IGFBP-3, or calpastatin in BF or LM. However, ractopamine led to increases in LM expression of IGFBP-5 in heifers, but to decreases in expression in steers (ractopamine x sex interaction; P = 0.04). Ractopamine decreased myosin heavy chain IIA mRNA expression in BF (P = 0.04) but not in LM (P = 0.99). Ractopamine decreased beta(2)-receptor mRNA expression in LM of steers on d 14, but not on d 28; in contrast, expression of beta(2)-receptor mRNA in LM of heifers was not affected by ractopamine (sex x ractopamine x day interaction; P = 0.03). Although there were a few criteria for which ractopamine led to differences in response between steers and heifers, there were no striking disparities to suggest that the effectiveness of ractopamine would markedly differ between sexes.

Characterization of ruminal dynamics in Holstein dairy cows during the periparturient period

We used four pregnant Holstein cows to delineate ruminal adaptations as cows transitioned from one lactation to the next. Cows were fed typical diets through far-off and close-up dry periods and lactation. We measured ruminal characteristics on day 72 (late lactation), 51 (far-off dry), 23 and 9 (close-up dry) prepartum and on days 6, 20, 34, 48, 62, 76 and 90 postpartum (early lactation). Measurements included: ruminal fill (weight of actual contents), ruminal capacity (volume of rumen when fully filled), digestibilities and ruminal passage rates. Ruminal capacity tended to increase linearly during early lactation but was stable during dry and transition periods. Both total and liquid fill decreased linearly during the dry period, increased across parturition, and increased linearly through early lactation. Dry matter fill decreased as cows were fed the close-up diet at day 23 prepartum then increased near parturition and continued to increase across early lactation. Solid passage rate was greatest when cows were fed the close-up diet, and decreased throughout the transition period. In lactation, solid passage rate responded quadratically with peak at day 48 followed by decreases through day 90 postpartum. Liquid passage increased linearly across the transition period. Total tract organic matter digestibilities increased linearly over the dry period with significant increases prior to or immediately after parturition, then they remained relatively stable over early lactation until they increased at day 90. Fibre digestibilities demonstrated quadratic responses over early lactation, being higher on day 6 and day 90 than at other times. Starch digestibilities decreased linearly across both the dry and transition periods with decreases in lactation until day 62 followed by increases until day 90. High producing lactating dairy cows go through a multitude of ruminal adaptations, in terms of digestion, passage, capacity and fill, as they transition from one lactation to the next.

Feeding zilpaterol hydrochloride to calf-fed Holsteins has minimal effects on semimembranosus steak color

To determine the effects of feeding zilpaterol hydrochloride (ZH) for 0, 20, 30, or 40 d (ZH0, ZH20, ZH30, ZH40) on semimembranosus (SM) steak color and color stability in 3 packaging systems, SM subprimals were removed from 60 calf-fed Holstein steers 24 h postmortem. A 7.62-cm-thick portion was removed from each subprimal and stored (2 degrees C) for 21 d; then two 2.54-cm-thick steaks were cut, overwrapped with polyvinyl chloride (PVC) film, and assigned to 0 or 3 d of display. Remaining portions of the subprimals were vacuum packaged for 10 d and then enhanced (10% with a solution containing 0.3% sodium chloride, 0.35% phosphate, and 0.05% rosemary extract), cut into steaks, packaged in high-oxygen (HO-MAP) or carbon monoxide (CO-MAP) modified atmosphere packaging (MAP), and assigned to 0, 3, or 5 d (HO-MAP) or 0 or 9 d (CO-MAP) of display. Panelists evaluated the deep and superficial portions of SM steaks for initial color, display color, discoloration, pH, L*, a*, b*, hue angle, and saturation indices. Feeding duration did not affect (P > 0.05) initial color scores of steaks in PVC. Steaks displayed in PVC from ZH20 or ZH30 diets were slightly brighter and less discolored than the ZH40 treatment. For enhanced steaks in HO-MAP, ZH20 steaks were darker on d 5 (P < 0.05) and more discolored (P < 0.05) on d 3 through 5 than all other diet treatments. For enhanced steaks from steers fed ZH40 and in CO-MAP, the deep and superficial SM tended (P > 0.05) to have improved display color compared with other dietary regimens; however, steaks in CO-MAP from all feeding durations had less than 20% metmyoglobin through d 9 of display. Overall, feeding ZH20 might result in steaks with slightly less color stability when packaged in HO-MAP; however, feeding ZH20 or ZH30 to calf-fed Holstein steers will yield steaks that have equal to or more desirable color traits when packaged in PVC or CO-MAP. Regardless of ZH feeding regimen, HO-MAP and CO-MAP extended the color life of the SM. The CO-MAP system minimized color differences between the superficial and deep portions of the SM muscle and extended total case life compared with traditional and HO-MAP packaging.

Effects of zilpaterol hydrochloride feeding duration on crossbred beef semimembranosus steak color in aerobic or modified atmosphere packaging.

The objective of this research was to determine the effects of feeding zilpaterol hydrochloride (ZH) for 0, 20, 30, or 40 d before slaughter (ZH0, ZH20, ZH30, or ZH40, respectively) on semimembranosus (SM) color development and stability. A 7.62-cm-thick portion was removed from 60 beef steer SM subprimals and stored (2 degrees C) for 21 d; then two 2.54-cm-thick steaks were cut, overwrapped with polyvinyl chloride (PVC) film, and assigned to 0 or 3 d of display. Remaining portions of the subprimals were stored in a vacuum for 10 d and then enhanced 10% to a meat concentration of 0.3% sodium chloride, 0.35% phosphate, and 0.05% rosemary extract. Steaks were packaged in a high-oxygen (HO-MAP) or carbon monoxide (CO-MAP) modified atmosphere and assigned to 0, 3, or 5 d (HO-MAP) or 0 or 9 d (CO-MAP) of display. The deep (DSM) and superficial (SSM) portions of steaks were evaluated for initial color, display color, discoloration, pH, L*, a*, b*, hue angle, and saturation indices. For steaks in PVC, no differences (P > 0.05) occurred in initial or discoloration color scores because of ZH feeding duration. The enhanced SSM steaks from ZH20 in PVC were brighter red (P < 0.05) than SSM steaks from ZH40 in PVC. The DSM in PVC had less (P < 0.05) pH and paler (P < 0.05) color than the SSM. Display color scores for the DSM of PVC steaks were brighter red (P < 0.05) than the SSM initially (d 0 and 1), but the DSM discolored faster (P < 0.05) than the SSM on d 1 to 3. The SM steaks from steers fed ZH20 or ZH30 were slightly brighter and less discolored during display in PVC than the ZH40 diet. For enhanced steaks in HO-MAP, the DSM of ZH20 and ZH30 diets displayed 4 d and the DSM of ZH20 displayed 5 d was a brighter (P < 0.05) red than the DSM from ZH40. At display d 1 and 5, the SSM of ZH20 steaks in HO-MAP was a brighter (P < 0.05) red than SSM steaks from ZH40. The SSM of ZH40 HO-MAP steaks was darker (P < 0.05) red on d 3 than the SSM from other diets. For enhanced steaks in CO-MAP, ZH30 steaks were brighter (P < 0.05) red than ZH0 or ZH40 steaks on d 0 and 9 of display. Steaks in CO-MAP from all feeding durations were less than 20% discolored through d 9. The DSM was lighter (P < 0.05) than the SSM on d 0 for steaks packaged in HO-MAP and CO-MAP. Feeding cattle ZH for 20 or 30 d will yield steaks with color characteristics equal to or better than steaks from control cattle, whereas feeding ZH for 40 d will likely produce less desirable meat color traits.