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.     

Effect of frequency and amount of rumen-degradable intake protein supplementation on urea kinetics and microbial use of recycled urea in steers consuming low-quality forage

We evaluated the effect of frequency and amount of rumen-degradable intake protein (DIP) on urea kinetics in steers consuming prairie hay. Five ruminally and duodenally fistulated steers (366 kg of BW) were used in a 5 x 5 Latin square and provided ad libitum access to low-quality prairie hay (4.7% CP). Casein was provided daily in amounts of 61 and 183 mg of N/kg of BW (61/d and 183/d) and every third day in amounts of 61, 183, and 549 mg of N/kg of BW per supplementation event (61/3d, 183/3d, and 549/3d). Periods were 18-d long with 9 d for adaptation and 9 d for collection. Steers were in metabolism crates for total collection of urine and feces. Jugular infusion of (15)N(15)N-urea followed by determination of urinary enrichment of (15)N(15)N-urea and (14)N(15)N-urea was used to determine urea kinetics. Treatment means were separated to evaluate the effects of increasing DIP supplementation and the effects of frequency at the low (61/d vs. 183/3d) and at the high (183/d vs. 549/3d) amounts of DIP provision. Forage OM and total digestible OM intakes were linearly (P < or = 0.05) increased by increasing DIP provision but were not affected by frequency of supplementation at either the low or high amounts. Production and gut entry of urea linearly (P < or = 0.006) increased with DIP provision and tended to be greater (P < or = 0.07) for 549/3d than 183/d but were not different between 61/d and 183/3d. Microbial N flow to the duodenum was linearly (P < 0.001) increased by increasing DIP provision. Additionally, 183/d resulted in greater (P = 0.05) microbial N flow than 549/3d. Incorporation of recycled urea-N into microbial N linearly (P = 0.04) increased with increasing DIP. Microbial incorporation of recycled urea-N was greater for 549/3d than 183/d, with 42 and 23% of microbial N coming from recycled urea-N, respectively. In contrast, there was no difference due to frequency in the incorporation of recycled urea-N by ruminal microbes at the low level of supplementation (i.e., 61/d vs. 183/3d). This study demonstrates that urea recycling plays a substantial role in the N supply to the rumen and to the animal, particularly in steers supplemented infrequently with high levels of protein.     

Phosphorus mineralization in subarctic agricultural and forest soils

Summary Potential P and C mineralization rates were determined in a 12-week laboratory incubation study on subarctic forest and agricultural soil samples with and without N fertilizer added. There was no significant difference in net inorganic P produced between N fertilized and unfertilized soils. The forest soil surface horizons had the highest net inorganic P mineralized, 32 mg P kg^-1 soil for the Oie and 17 mg P kg^-1 soil for the Oa. In the cropped soils net inorganic P immobilization started after 4 weeks and lasted through 12 weeks of incubation. Cumulative CO₂–C evolution rates differed significantly among soils, and between fertilizer treatments, with the N-fertilized soils evolving lower rates of CO₂–C than the unfertilized soils. Soils from the surface horizons in the forest evolved the highest rates of CO₂–C (127.6 and 89.4 mg g^-1 soil for the Oie and Oa horizons, respectively) followed by the cleared uncropped soil (42.8 mg g^-1 soil C), and the cropped soils (25.4 and 29.0 mg g^-1 soil C). In vitro soil respiration rates, or potential soil organic matter decomposition rates, decreased with increasing time after clearing and in accord with the degree of disturbance. Only soils with high potential C mineralization rates and high organic P to total P ratios, mineralized P by the end of the study. Mineralizable P appeared to be associated with readily mineralizable organic C.     

Effects of different supplemental sugars and starch fed in combination with degradable intake protein on low-quality forage use by beef steers.

Twenty ruminally fistulated steers (Exp. 1, 448 kg and Exp. 2, 450 kg) were used in two consecutive randomized complete block experiments with five treatments in each experiment. The purpose was to evaluate the impact of feeding different supplemental sugars or starch in combination with supplemental degradable intake protein (DIP) on the utilization of low-quality tallgrass-prairie hay. In Exp. 1, steers were given ad libitum access to forage and, except for the negative control (NC), received a limited supply (insufficient to maximize forage use) of supplemental DIP (.031% BW/d, DM basis). In addition to the NC, this experiment included four supplementation treatments in which one of four carbohydrate (CHO) sources (starch, glucose, fructose, or sucrose) was fed at .30% BW of DM/d. In Exp. 2, the treatment structure was identical except that the supplemental DIP level (.122% BW, DM basis) was near the level needed to maximize forage use. Forage OM intake (FOMI) was not affected (P> or =.26) by supplementation in Exp. 1 but was increased (P = .05) in Exp. 2. However, no difference (P> or =.46) in FOMI occurred among CHO sources in either experiment. Total OM and digestible OM intakes were increased (P<.01) by supplementation in both experiments. In Exp. 1, no difference (P>.26) in OM digestion (OMD) occurred among treatments. In Exp. 2, supplementation increased (P<.01) OMD. Additionally, sugars yielded a higher (P = .04) OMD than starch, and the monosaccharides yielded a higher (P = .02) OMD than sucrose. In Exp. 1, NDF digestion (NDFD) was decreased (P = .02) by supplementation, but no differences (P> or =.21) occurred among CHO sources. In Exp. 2, NDFD was increased (P = .03) by supplementation. Additionally, sugars led to higher (P = .05) NDFD than starch, and the monosaccharides led to higher (P = .03) NDFD than sucrose. In both experiments, discernible patterns were observable with regard to the effects of supplementation and type of supplemental CHO on ruminal fermentation characteristics. In conclusion, even though some consistency in fermentation profiles for different carbohydrate sources was evident in both experiments, forage intake and digestion responses were not consistent across experiments. This raises the possibility that carbohydrate source may interact with the amount of supplemental DIP fed and, as such, deserves additional investigation.     

Effects of migratory geese on nitrogen availability and primary productivity in subarctic barley fields

 Migratory geese affect agricultural production by removing biomass and by depositing fecal nutrients. This study used ¹⁵N as a tracer to examine the quantitative effects of goose fecal N contributions on agricultural production. Barley (Hordeum vulgare cv. Datal) was grown for the production of ¹⁵N-labeled grain and straw. Two Canada geese (Branta canadensis Taverners) were fed the grain after harvest to obtain ¹⁵N-labeled and unlabeled feces. Net N mineralization and micro-plot studies both indicated that in comparison to barley grain and straw, goose feces provided the greatest amount of available N to the soil and to the subsequent crop, and consequently higher barley yields (59% and 62% increase, respectively). However, C mineralization was greater from grain, with 56% evolved compared to 49% and 26% for feces and straw, respectively. Goose feces also provided the greatest addition of N for the barley plants, with fertilizer N recovery efficiency (FNRE) of 16%, compared to FNRE of 10% from the grain amendment, and 1.2% from the straw amendment. The amount of N available in fecal material from leftover grain consumed by grazing geese is small in comparison to total crop needs, but is a potential source of mineral N during the critical early growth of crops grown in cold, high-latitude soils. Received: 16 May 1999     

Growth rate of a vesicomyid clam from the galapagos spreading center

The shell of a 19-centimeter-long vesicomyid clam, collected live at the Galápagos spreading center hydrothermal field, was sampled along growth lines and analyzed for members of the (238)U and (232)Th decay series. The growth rate, determined from the (210)Po/(210)Pb and (228)Th/(228)Ra couples, is about 4 centimeters per year along the axis of maximum growth, which is 12 centimeters long. This yields an age of 3 to 4 years for this clam.     

Effects of residues of deltamethrin in cattle faeces on the development and survival of three species of dungbreeding insect

Objective To assess the toxicity to insects of drug residues excreted in cattle faeces following treatment with deltamethrin.
Design Bioassays were performed on one species of dung-breeding fly ( Musca vetustissima ) and two species of dung beetle ( Onthophagus binodis and Euoniticellus fulvus ).
Animals Cattle on properties near Kangaroo Valley, Canberra and Gundagai were treated with pour-on formulations of deltamethrin. Untreated animals acted as controls.
Procedures Faeces from treated and untreated cattle were inoculated with newly emerged fly larvae or fed to adults of two species of dung beetle. Percentage survival and duration of development provided measures of the toxicity of deltamethrin residues in faeces.
Results Residues of deltamethrin were excreted in concentrations sufficient to inhibit survival of larvae of M vetustissima for 1 to 2 weeks after treatment. Peak concentrations of 0.4mg deltamethrin/kg dry weight of faeces occurred 3 days after treatment and were sufficient to kill adult beetles for at least twice this period. With one of two formulations tested, there was evidence of a reduction in dung beetle fecundity and an increase in the duration of juvenile development. A model of the effect of deltamethrin on the breeding success of dung beetles in the field suggests that a single treatment, applied when most of the population is in a non-parous condition, may cause up to 75% reduction in beetle acitivity by the end of the season. Multiple treatments at 10 or 21 day intervals may drive local populations towards extinction.
Conclusion Depending on the time and frequency of treatment, the effect of deltamethrin on insects in cattle faeces may range from negligible to catastrophic.