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The objective of this producer survey was to identify and estimate damage caused by bird-livestock interactions in commercial dairies. The interactions between birds and livestock have previously been implicated in causing economic damage while contributing to the environmental dissemination of microorganisms pathogenic to livestock and humans. Very little research exists to help producers understand what bird species use dairies, why they use dairies, or the scope and nature of damage created as a result of bird-livestock interactions. To better characterize these interactions, we surveyed dairy operators within Pennsylvania, New York, and Wisconsin. Survey results suggest that the most common and destructive bird species found on commercial dairies are invasive to North America, and their use of dairies is associated with the loss of cattle feed, increased operating costs, and an increase in dairies self-reporting Salmonella spp. and Mycobacterium avium ssp. paratuberculosis. Cattle feed loss estimates generated from this survey were used to parameterize an input-output (IO) economic model using data from 10 counties in the state of Pennsylvania (Bedford, Berks, Blair, Bradford, Chester, Cumberland, Franklin, Lancaster, Lebanon, and Somerset). This IO model allowed us to estimate direct, indirect, and induced economic effects of feed loss from bird damage to dairies within these counties. The IO model output suggests that feed loss costs Pennsylvania between $4.11 and $12.08 million (mean $10.6 million) in total economic damage, with approximately 43 to 128 jobs (mean 112) forgone statewide in 2009., (Copyright © 2012 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

We conducted two experiments to evaluate the effect of the ionophore laidlomycin propionate (LP) on steer performance and ruminal N metabolism. Experiment 1 was a 91-d growth study evaluating the growth and ruminal characteristics of steer calves consuming supplemental LP. Steers (n = 96; 255 +/- 3 kg; four steers/pen; six pens/treatment) were used in a randomized complete block design with a 2 x 2 factorial arrangement of treatments consisting of two levels of dietary CP (formulated to be 10.5 and 12.5% of DM) with and without LP (11 mg/kg diet DM). Ruminal fluid was collected via stomach tube on d 91 from one steer randomly selected from each pen. No CP x LP interactions were observed with performance data (P > .64). Final weight and total gain were greater (P < .07) for 12.5% CP and LP compared with 10.5% CP and control steers, respectively. Also, DMI was increased (P = .08) with 12.5% CP but not with LP supplementation (P = .36). In addition, ADG and gain:feed ratio were greater (P < .03) for both 12.5% CP and supplemental LP. Ruminal NH3 N concentration was greater (P < .09) with 12.5% CP and LP. Total VFA concentration and molar proportion of acetate were not affected by treatment (P > .11). However, propionate concentration was increased (P < .09) with 12.5% CP and LP, and acetate:propionate was lower (P = .02) with LP supplementation. In Exp. 2, six steers were used in a replicated 3 x 3 Latin square design to compare ruminal fermentation and protein degradation in steers without ionophore feeding or adapted to LP or monensin. In vitro deamination of amino acids by adapted ruminal microbes was also assessed. Ionophore supplementation decreased (P = .07) ruminal NH3 N concentration compared with control steers, and LP increased (P = .02) ruminal NH3 N compared with monensin. Molar proportion of acetate was decreased (P = .02) and propionate increased (P = .01) with ionophore treatment. Consequently, ionophore supplementation depressed the acetate:propionate ratio (P = .01). In situ degradation rate of soybean meal (SBM) CP was greater (P = .09) with ionophore treatment, but estimates of SBM undegradable intake protein were not altered by treatment (P > .25). Microbial specific activity of net NH3 N release and alpha-amino N degradation were decreased (P < .04) with ionophores. Based on this study, LP and monensin did not affect the extent of ruminal degradation of SBM CP but decreased amino acid deamination.

Two in vitro digestion experiments were conducted to evaluate the influence of the novel urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) on in vitro urea kinetics, substrate digestion, and fermentation characteristics. In Exp. 1, in vitro incubations were conducted in 50-mL test tubes containing .25 g of ground fescue hay to which 0, 6.5, 13, 26, or 52 mg of NBPT in a buffered ruminal fluid innoculum was added. Tubes were incubated in triplicate at 39 degrees C and replicated on consecutive days, with NH3 N and urea concentrations measured at 0, 10, 30, 60, 120, 240, and 360 min. Samples for VFA analysis were collected at 6 h, and incubations were continued through 48 h to estimate true digestibility (based on NDF analysis). Increasing the dose of NBPT tended (P < .12) to linearly depress the rate of urea hydrolysis and decreased (P < .0004) subsequent NH3 N formation. Although total VFA concentration at 6 h increased linearly (P < .03), acetate:propionate and estimated true digestibility decreased (P < .01) with increasing NBPT concentration. In Exp. 2, we compared in vitro urea kinetics and digestion of forage-only or mixed forage-grain substrates in response to addition of NBPT. In vitro incubations were conducted in 50-mL test tubes containing either .5 g of ground fescue hay or .5 g of a ground fescue hay and ground corn mixture (50:50, DM basis) to which 0, 6.5, 13, 26, or 52 mg of NBPT in a buffered ruminal fluid innoculum was added. Tubes were incubated in triplicate at 39 degrees C and replicated on consecutive days, with NH3 N and urea concentrations measured at 0, .5, 1, 2, 4, 8, 12, 24, and 48 h. At 48 h, samples for VFA analysis were collected and true digestibility (based on NDF analysis) was estimated. No (P > .10) NBPT dose x substrate interactions were detected. Increasing the dose of NBPT depressed (P < .003) the rate of urea hydrolysis and subsequent NH3 N formation, regardless of substrate. Although total VFA concentration was unaffected (P > .10), the acetate:propionate and estimated true digestibility decreased (P < .002) with higher NBPT addition. In both experiments, the rate of urea degradation was not different (P > .20) from zero for the 26 and 52 mg NBPT treatments, indicating that nearly complete inhibition of urease had been achieved. We conclude that NBPT can be used to reduce the rate of NH3 N release from dietary urea and, thereby, offers the potential to improve nonprotein nitrogen utilization in ruminants.

Four Angus steers (318 +/- 16 kg) fitted with ruminal, duodenal, and ileal cannulas were used in a 4 x 4 Latin square design to determine carbohydrate disappearance from the small intestine (SI). Steers were fed fescue hay at 1.8% of BW and abomasally infused with starch hydrolysate (SH) at 10, 20, or 40 g/h or glucose (G) at 30 g/h. Starch hydrolysate was raw cornstarch digested by a heat-stable alpha-amylase. Experimental periods were 10 d with 6 d of adaptation, 3 d of digesta and feces collection, and 1 d of rest. Glucose (% of infused) had greater (P < .001) apparent small intestinal and postruminal disappearance (% of infused) compared with 20 and 40 g/h SH. Starch hydrolysate infusion linearly increased (P < .001) apparent SI, large intestinal (LI), and total intestinal starch disappearance (g/d) and quadratically increased (P < .003) apparent SI and total intestinal starch disappearance (% of infused). Ileal starch flow from infusion increased quadratically (P < .03) as SH infusion increased. True SI and total intestinal starch disappearance increased linearly (P < .001; g/d) with SH infusion. However, SH infusion quadratically decreased (P < .02) efficiency of true SI starch disappearance (% of infused). True LI starch disappearance (g/d and % of infused) quadratically increased (P < .03) as SH infusion increased. These data demonstrate that, even in animals fed all-forage diets, there is a significant flow of alpha-glucosides, and these need to be considered when evaluating intestinal carbohydrate digestion.

Six Angus steers (260+/-4 kg initial BW) fitted with ruminal, duodenal, and ileal cannulas were used in a 6 x 6 Latin square design to evaluate the effect of feeding poultry by-product meal (PBM) on small intestinal flow and disappearance of amino acids. The diets were provided at 2% of BW on a DM basis, formulated to contain 11.5% CP, and consisted of 49% corn silage, 36% cottonseed hulls, and 15% supplement on a DM basis. Supplements were formulated to contain 37% CP with sources of supplemental N being soybean meal (100% SBM) and 0, 25, 50, 75, and 100% PBM, with urea used to balance for N. Duodenal flow of all amino acids increased linearly (P < .07) as PBM increased in the diet and, except for His, increased (P < .09) for 100% PBM compared with 100% SBM. Similar results were observed for duodenal flow of nonbacterial amino acids, which linearly increased (P < .05) with PBM and were greater (P < .05) for 100% PBM than for 100% SBM. Soybean meal increased (P < .09) the duodenal flow of nonbacterial Lys compared with 0% PBM, and 0% PBM increased (P < .04) flow of Val, Ala, and Pro compared with 100% SBM. Duodenal bacterial essential, nonessential, and total amino acid flows were not affected (P > .80) by PBM; however, they were greater (P < .02) for 100% SBM than for 100% PBM. In addition, nonessential and total bacterial amino acid flows were increased (P < .06) for 100% SBM compared with 0% PBM. Small intestinal disappearance of Lys and Pro increased linearly (P < .09) as PBM increased, and 100% PBM increased (P < .07) disappearance of Arg and Ala compared with 100% SBM. Supplemental N source had no effect (P > .31) on apparent small intestinal disappearance of essential, nonessential, and total amino acids. These data suggest that when PBM, SBM, and urea were used as sources of supplemental N, the daily disappearance of amino acids from the small intestine of steer calves consuming a corn silage- and cottonseed hull-based diet was similar.

We conducted three studies with steers to evaluate poultry by-product meal (PBM) as a supplemental N source for ruminants. An in situ study compared the solubility, degradation rate, and ruminal escape of PBM N with blood meal (BM), corn gluten meal (CGM), and soybean meal (SBM) N. Additionally, an 84-d growth study (n = 95, 228+/-5 kg BW) and a digestion trial (6 x 6 Latin square) were conducted. The basal diet for the growth and digestion studies consisted of 49% corn silage, 36% cottonseed hulls, and 15% supplement (DM basis). Sources of supplemental N (% of total supplemental N) were 100% SBM and 0, 25, 50, 75, and 100% PBM, with urea used to balance for N. In situ ruminal escape N (25.2, 55.3, 86.7, and 98.9% for SBM, PBM, CGM, and BM, respectively) was greater (P < .05) for PBM than for SBM; however, a greater (P < .05) proportion of BM and CGM N escaped ruminal degradation compared with PBM. Dry matter intake, ADG and gain/ feed increased linearly (P < .003) as PBM increased; however, no differences (P > .48) were observed in these variables for 100% PBM compared with 100% SBM. Duodenal N flow and small intestinal N disappearance increased linearly (P < .05) as PBM increased in the diet. Bacterial N flow to the small intestine was not affected (P > .19) by treatment; however, 100% SBM decreased (P < .04) bacterial CP synthesis (g bacterial N/kg OM disappearance from the stomach) compared with 0 and 100% PBM. In vivo ruminal escape N of PBM and SBM was 40.6 and 13.7%, respectively. Ruminal NH3 N decreased linearly (P < .001) as PBM increased. These data suggest that PBM can replace SBM as a source of supplemental N for steer calves that consume a diet based on corn silage and cottonseed hulls.

Consumption of tall fescue forage infested with the endophytic fungus Acremonium coenophialum can result in a condition termed "fescue toxicosis," which is characterized by decreased weight gains, milk production, conception, and serum prolactin and an inability to dissipate body heat by beef cattle. These decreases in productivity have been estimated to cost beef producers more than $600 million annually. The unthrifty appearance of cattle consuming endophyte-infected tall fescue (E+) is most evident during periods of environmental heat or cold stress, suggesting an interaction with environmental conditions. Without temperature stress, cows consumed similar amounts of E+ and endophyte-free tall fescue (E-). But, when temperatures exceeded 32 degrees C, cows that grazed E+ consumed less forage than cows that grazed E-. After removal of E+ from the diet of steers, compensatory growth was observed, indicating no long-term negative effects of E+. A decrease in serum prolactin but apparently little change in other hormones has been measured after consumption of E+. Under periods of heat stress, animals had reduced ability to dissipate body heat, and blood flow to peripheral (rib skin), core-body (duodenum colon), and brain (cerebellum) tissues was decreased. Due to the depressive effects of E+ on prolactin and heat dissipation, dopamine antagonist therapy has been used in an attempt to rectify these changes. Dopamine antagonists have increased serum prolactin but there is limited evidence to suggest an improvement in heat dissipation. Experiments to elucidate the effects of E+ on alpha-1 and -2 adrenergic receptors may also offer insights into developing strategies to overcome the negative effects of E+ consumption. Preliminary results suggest that injections of an alpha-1 adrenergic antagonist (prazosin) in rats fed E+ under 32 degrees C conditions increased DM intake and reduced rectal temperature.

There is a decrease in the specific activity of labeled IgG1 of serum over 3 wk following the feeding of iodine-125 labeled immunoglobulin IgG1 in colostrum to calves at birth. This decrease indicated the appearance of new IgG1 from some source. To determine if this new IgG1 came from endogenous production in the calf or from continued small amount of intestinal absorption from milk, labeled IgG1 was added to normal milk and fed to calves of various ages up to 3 wk after an initial feeding of colostrum at birth. Labeled IgG1 was also added to colostrum fed to calves at birth, and the calves were maintained on a normal milk diet or fed a synthetic milk diet. Determination of iodine-125 in the serum protein fractions of these calves indicated that there was no apparent intestinal absorption of labeled IgG1 from the milk in the period from 2 days to 3 wk. Furthermore, comparable decreases occurred in the specific activity of labeled IgG1 in serum in the calves fed the labeled IgG1 in colostrum at birth and subsequently maintained either on a diet including milk or on the synthetic milk diet devoid of IgG1. The results support the conclusion that the origin of new IgG1 in the calf after about 36 h and up to about 3 wk of age arises from endogenous production at a rate of about 1 g of IgG1 per day.

Blood and colostrum samples were obtained from 87 dairy cows in five lactation groups and analyzed for immunoglobulins G1, G2, M, and A. The five groups ranged from cows in first lactation, about 30 mo of age, to cows in fifth or more lactation, about 84 mo of age. Compared to older groups, blood serum of cows in first lactation contained less G1. Cows in first lactation also produced less total colostrum containing less total G1, G2, and M. Immunoglobulin G1 comprised over two-thirds of the immunoglobulins in the colostrum of all groups. Older cows had more immunoglobulin G1 in their colostrum with a tendency toward a higher ratio of G1 to G2. Amount of immunoglobulin A was constant through all lactations. After a rise in the second lactation, total amount of immunoglobulins G2 and M tended to level off. Total immunoglobulin G1 tended to reach a maximum in the third or fourth lactation, almost doubling in amount compared to the first lactation. Age and number of lactations are factors correlated with amounts of these immunoglobulins in colostrum.

Production rates (entry rate into blood plasma) and other metabolic parameters for the IgG1 and IgG2 subclasses of immunoglobulins in mammary secretions (ratio of about 7 to 1) were determined in cows around the time of parturition by both single-injection and continuous-infusion isotope-dilution techniques. Four cows were given a single dose of 150 to 200 muCi of iodine-125 labeled IgG1 and 100 to 250 muCi of iodine-131 labeled IgG2 at 2 to 1 wk before parturition. Four cows, including two of the above, were infused continuously with constant amounts of the labeled immunoglobulins starting at 11 to 4 days before parturition. All cows were maintained until 4 to 6 days after parturition for monitoring the specific activities of iodine-125 labeled IgG1 and iodine-131 labeled IgG2 in the plasma and mammary secretions. Maximum entry rates of IgG1 and IgG2 were between 3 and 1 day prepartum with means of 125 and 60 g/500 kg body weight per day. The exchangeable pool means for IgG1 and IgG2 were 619 and 643 g/500 kg body weight, and both immunoglobulins were divided almost equally between the intra- and extravascular pools. A greatly increased production and a shortened half-life or greater turnover for plasma IgG1 occurs around the time of parturition which can account for the large accumulation of IgG1 in colostrum.

In origin immunoglobulins in mammary secretions are both humoral, arising from the blood stream, and local, arising from production by plasmacytes in the mammary gland. The relative importance of each of these sources varies between species. In some species (human, rabbit, etc.), the transfer of maternal immunoglobulins to the blood stream of the neonate occurs in utero across the placenta or yolk sac membrane. In other species, including ruminants, transfer of maternal immunoglobulins to the neonate occurs exclusively via the colostrum. Both in utero and colostral routes of transfer are operative in other species. The concentration and class of immunoglobulins in the colostrum and milk of a species reflect the route and origin of the immunoglobulins. Immunoglobulins transferred in quantity in utero or via the colostrum are mainly of the IgG class. Immunoglobulins locally produced by plasmacytes located adjacent to the secretory epithelium and in the mammary secretions are largely of the IgA and IgM classes. The bovine transfers large amounts of IgG immunoglobulins, and IgG1 in particular, from the blood stream across the mammary barrier into colostrum (and milk) by a specific transport mechanism. Bovine colostrum and milk also contain much smaller amounts of locally produced IgA and IgM.

Subcellular localization of enzymes of the pyrimidine biosynthetic pathway was determined in lactating bovine mammary tissue. Aspartate transcarbamylase was associated with a membrane portion of the microsomal cell fraction. Dihydroorotate dehydrogenase w3as in the mitochondrial fraction with no evidence for a cytosolic enzyme requiring pyridine nucleotides. Orotate phosphoribosyltransferase was in the cytosol of the cell. The significance of these findings to other mammalian cells and orotic acid accumulation in bovine milk is discussed.

The ability to synthesize lactose was studied in despersed cell cultures of lactating bovine mammary tissue under conditions of varying cell density, time, glucose, and lactose concentrations. The observable rate of lactose synthesis at a given time in an adequate medium is dependent on individual animal, length of time in culture, and density of cells. Rate of loss with time in the ability to synthesize lactose followed first order kinetics (half-time 11 h). Rate of synthesis per cell at a given time was an inverse function of the cell density following a linear relationship expressed by plotting the inverse of the amount accumulated versus the inverse of the cell number. A cell density for such experimental studies of about 2.5 times 10-6 cells per ml was ideal. The medium concentration of lactose and, above a minimum, that of glucose did not affect production of lactose.