Few studies have dealt with measuring individual plant defoliations in the context of intensive grazing management. In May, July, and August of 1987, grazing trials were conducted to quantify the effects of herbage allowance on defoliation patterns of big bluestem [An&opogon gem&i Vitmanl, hrdiangrass [Sorghtrum nutons(L.) Nash], and little bluestem [ScEza&yr~ scqnrrium (Michx.) Nash]. Herbage allowancea of 10, 20,30, and 40 kg AUD" were replicated twice per trial. Tiller height, relative leaf area removed, and lrequency of defoliation were measured every 2 days over loday trials. Indiangrass was the most preferred species in all trials. The rate of leaf area removal increased as herbage allowance decreased. Current guidelines which call for rest periods of 3040 days would result in light to moderate intensity defoliation for indiangrass at all herbage allowances. The maximum percentage of tillers grazed only once per trial ranged from 20 to 9g%1 depending on herbage allowance, species, and trial.Selectivity between species was reduced by decreasing herbage allowance hut this effect was not large until herbage allowance was below 20-25 kg AUD" and selectivity was never completely removed. Grazing all tillers only once in a grazing period, even within a species, is unlikely in a tallgrass prairie community. Leaf area removal was moderate the first time a tiller was defoliated and severe for later defoliations. The goal of grazing any individual tiller at no greater than moderate intensity within a grazing period would he roughly equivalent to grazing any tiller no more than once. However such a goal would require many tillers to go ungrazed.
Two experiments examined the effects of Aspergillus oryzae fermentation product (AO; Amaferm®; BioZyme Inc., St. Joseph, MO, USA) on productive variables in transition dairy cows. In experiment 1, 33 Holstein cows (22 multiparous and 11 primiparous) were enrolled from −21 to 60 days in milk (DIM). Cows were individually fed either a control total mixed ration (TMR) diet consisting of primarily alfalfa hay and steam-flaked corn [62:38 and 59:41, forage:concentrate (F:C) for prepartum and postpartum phases, respectively] or the control diet along with 15 g d−1 of AO. In experiment 2, 455 multiparous Holstein cows were enrolled from −21 to 121 DIM. Cows were group-fed either a control TMR diet (n = 228) consisting primarily of corn silage and rolled corn (44:56, F:C) or the control diet (n = 227) with 15 g d−1 of AO. In experiment 1, cows fed AO had increased (P < 0.05) milk production compared with controls (37.7 vs. 34.6 kg d−1). Milk composition, dry matter intake, body weight (BW), and BW loss both prepartum and postpartum did not differ (P > 0.10) between treatments. Cows fed AO tended to have decreased plasma nonesterified fatty acids levels (14%, P < 0.10), but plasma glucose concentration did not differ (P = 0.89). In experiment 2, cows fed AO had decreased milk yield (43.0 vs. 43.8; P < 0.05), and increased milk fat content (3.50% vs. 3.38%; P < 0.01) but similar quantities of 3.5% fat-corrected milk (42.5 vs. 42.7 kg d−1; P > 0.10). Results suggest that AO has the potential to improve aspects of milk production efficiency, but the percentage and types of forage utilized may influence the response.
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