Fibrolytic enzymes to increase the nutritive value of dairy feedstuffs

In vitro studies and a lactation trial were conducted to investigate the effects of fibrolytic enzyme mixtures at different inclusion amounts. Seven enzymes in amounts designed to mimic addition of 1, 5, 15, or 30 g/d to dairy diets were incubated in vitro with either soybean hulls or alfalfa for 24 or 48 h. Enzyme treatments generally increased in vitro dry matter disappearance (IVDMD), but not volatile fatty acid production. For some enzyme mixtures, lesser amounts of enzymes led to greater increases in IVDMD, whereas for others there were no differences among the amounts tested. The enzyme mixture with the most cellulase activity was the most effective enzyme in improving IVDMD. In additional in vitro experiments, the same enzymes were used at an amount of 5 g/d, as well as at other amounts that showed promising responses in the first trial. Preincubation of substrates with enzymes before fermentation also was tested. Alfalfa, soybean hulls, corn silage, and corn gluten feed were used as substrates. Preincubation of the substrate with enzymes for 18 h before in vitro fermentation improved IVDMD. The effect on substrate solubilization of incubating substrates with the enzymes but without rumen fluid was also studied. Addition of enzymes to substrates without subsequent fermentation did not solubilize significant amounts of dry matter, indicating that the positive effect of preincubation cannot be attributed directly to hydrolysis of substrates before the in vitro fermentation with ruminal microbes. The fibrolytic enzyme that appeared most promising in vitro did not affect lactational performance when fed to dairy cows.     

Transport of Cryptosporidium oocysts in porous media: role of straining and physicochemical filtration

The transport and filtration behavior of Cryptosporidium parvum oocysts in columns packed with quartz sand was systematically examined under repulsive electrostatic conditions. An increase in solution ionic strength resulted in greater oocyst deposition rates despite theoretical predictions of a significant electrostatic energy barrier to deposition. Relatively high deposition rates obtained with both oocysts and polystyrene latex particles of comparable size at low ionic strength (1 mM) suggest that a physical mechanism may play a key role in oocyst removal. Supporting experiments conducted with latex particles of varying sizes, under very low ionic strength conditions where physicochemical filtration is negligible, clearly indicated that physical straining is an important capture mechanism. The results of this study indicate that irregularity of sand grain shape (verified by SEM imaging) contributes considerably to the straining potential of the porous medium. Hence, both straining and physicochemical filtration are expected to control the removal of C. parvum oocysts in settings typical of riverbank filtration, soil infiltration, and slow sand filtration. Because classic colloid filtration theory does not account for removal by straining, these observations have important implications with respect to predictions of oocyst transport.     

Development and application of a mobile laboratory for measuring emissions from diesel engines. 2. Sampling for toxics and particulate matter

Limited data are available on the emission rates of speciated volatile and semivolatile organic compounds, as well as the physical and chemical characteristics of fine particulate matter (PM) from mobile, in-use diesel engines operated on the road. A design for the sampling of these fractions and the first data from in-use diesel sources are presented in this paper. Emission rates for carbonyls, 1,3-butadiene, benzene, toluene, xylene, PM, and elemental and organic carbon (EC and OC) are reported for a vehicle driven while following the California Air Resources Board (ARB) four-mode heavy heavy-duty diesel truck (HHDDT) cycle and while transiting through a major transportation corridor. Results show that distance specific emission rates are substantially greater in congested traffic as compared with highway cruise conditions. Specifically, emissions of toxic compounds are 3-15 times greater, and PM is 7 times greater under these conditions. The dependence of these species on driving mode suggests that health and source apportionment studies will need to account for driving patterns in addition to emission factors. Comparison of the PM/NOx ratios obtained for the above tests provides insight into the presence and importance of "off-cycle" emissions during on-road driving. Measurements from a stationary source (operated and tested at constant engine speed) equipped with an engine similar to that in the HHDDT yielded a greater understanding of the relative dependence of emissions on load versus engine transients. These data are indicative of the type of investigations made possible by the development of this novel laboratory.     

Development and application of a mobile laboratory for measuring emissions from diesel engines. 1. Regulated gaseous emissions

Information about in-use emissions from diesel engines remains a critical issue for inventory development and policy design. Toward that end, we have developed and verified the first mobile laboratory that measures on-road or real-world emissions from engines at the quality level specified in the U.S. Congress Code of Federal Regulations. This unique mobile laboratory provides information on integrated and modal regulated gaseous emission rates and integrated emission rates for speciated volatile and semivolatile organic compounds and particulate matter during real-world operation. Total emissions are captured and collected from the HDD vehicle that is pulling the mobile laboratory. While primarily intended to accumulate data from HDD vehicles, it may also be used to measure emission rates from stationary diesel sources such as back-up generators. This paper describes the development of the mobile laboratory, its measurement capabilities, and the verification process and provides the first data on total capture gaseous on-road emission measurements following the California Air Resources Board (ARB) 4-mode driving cycle, the hot urban dynamometer driving schedule (UDDS), the modified 5-mode cycle, and a 53.2-mi highway chase experiment. NOx mass emission rates (g mi(-1)) for the ARB 4-mode driving cycle, the hot UDDS driving cycle, and the chase experimentwerefoundto exceed current emission factor estimates for the engine type tested by approximately 50%. It was determined that congested traffic flow as well as "off-Federal Test Procedure cycle" emissions can lead to significant increases in per mile NOx emission rates for HDD vehicles.     

Inclusion of psyllium in milk replacer for neonatal calves. 2. Effects on volatile fatty acid concentrations, microbial populations, and gastrointestinal tract size

Fermentable fibers such as psyllium increase volatile fatty acid (VFA) concentrations in the lower digestive tract and increase the gastrointestinal tract (GIT) mass of many mammals. We reasoned that psyllium inclusion in milk replacer might produce similar effects in neonatal dairy calves, which could lead to improved growth and health. Male Holstein calves were fed a milk replacer (22% crude protein, 20% fat) either without or with psyllium (1.1% of dry matter, DM) from 2 d through 28 d of age. Milk replacer was reconstituted to 12.5% DM and fed at 12% of calf body weight, adjusted weekly. Water was offered ad libitum but no starter was fed. Three calves per treatment were harvested weekly to sample digesta from the reticulo-rumen, abomasum, jejunum, proximal colon, and distal colon, and to determine length and mass of GIT components. Psyllium in milk replacer increased the proportion of butyrate in reticulo-rumen contents from 2.4 to 3.2% of total but did not affect total VFA concentrations. Total VFA concentrations were very low in the jejunum but psyllium tended to increase total VFA, acetate, and valerate concentrations; valerate accounted for 15.9 and 16.7% of total VFA (molar basis) for control and psyllium calves, respectively. Psyllium increased total VFA concentrations in the proximal and distal colon by 104.4 and 45.6%, respectively, but had little effect on the profile of VFA. Psyllium in milk replacer increased populations of bifidobacteria (from 9.7 to 10.3 log₁₀ cfu/g of DM) and lactobacilli (from 8.2 to 9.4 log₁₀ cfu/g of DM) in the reticulo-rumen, but did not affect populations in jejunum or colon. Calves fed psyllium had 12.0% greater total GIT mass and 9.4% greater GIT as a percentage of body weight. Psyllium tended to increase mass of the reticulo-rumen and significantly increased mass of duodenum (34.2%), jejunum (14.5%), and colon (14.6%). Density of intestinal tissues from calves fed psyllium-supplemented milk replacer was 25.9% greater in the jejunum and 25.3% greater in the ileum, and tended to be greater in duodenum and colon than tissue from control calves. Supplementation of psyllium to milk replacer increased fermentation in the colon, mass of the total GIT, and populations of bifidobacteria and lactobacilli in the reticulo-rumen.     

Effects of supranutritional dietary vitamin E levels on subcellular deposition of α-tocopherol in the muscle and on pork quality

The influence of three levels of vitamin E in the diet of pigs on the subcellular deposition of α-tocopherol in the muscle and on selected quality characteristics of pork meat (oxidative stability of lipids, colour, drip loss, microbial growth) was studied. The content of α-tocopherol in adipose tissue and L. dorsi muscle as well as in mitochondrial and microsomal fractions of the muscle significantly increased (P < 0.05) with increasing levels of dietary vitamin E. The differences in the concentrations of α-tocopherol in the subcellular fractions were evident in the enhanced stability of the membranes when exposed to metmyoglobin/hydrogen peroxide. The beneficial effect of dietary vitamin E on the oxidative stability of pork lipids during the storage of pork chops and ground pork was also demonstrated. Even though lipid oxidation increased in all cases during storage, the pork products from the pigs receiving the highest level of vitamin E (200 IU kg^?1 feed) exhibited the smallest increase in thiobarbituric acid reactive substances. In addition, increased colour stability and decreased drip loss were observed on keeping pork chops, which had been previously frozen for three months, at 4°C under fluoresent light for 10 days. The possible effect of α-tocopherol on membrane fluidity in this context is discussed.     

Relationship of early lactation and bovine somatotropin on nutrient uptake by cow mammary glands.

Twenty-one multiparous lactating dairy cows with previous 305-d milk production records varying from 5900 to 13,600 kg were used to investigate effects of bST administration and stage of lactation on nutrient plasma arterial concentrations and arterial-venous differences across the mammary glands (uptake). On d 71 and continuing until d 126 of lactation, cows were injected with 40 mg of sometribove (bST group) or bicarbonate buffer (placebo group). Arterial and venous blood plasma samples were collected over a 12-h period on d 35, 70, 105, and 126 of lactation. Plasma concentration of glucose was 7% higher in midlactation compared with early lactation cows. Plasma concentration of acetate decreased from 2.11 to 1.87 mM in placebo versus bST-treated cows. Plasma arterial concentration and uptake of D-beta-hydroxybutyrate were .52 and .18 mM higher, respectively, in early versus midlactation cows. Concentration and uptake of NEFA were elevated in both early lactation and bST-treated cows. Triacylglyceride concentrations were 24 and 19% lower in early lactation and bST-treated cows compared with midlactation cows receiving placebo. Likewise, uptake of triacylglyceride was reduced in early lactation and with bST treatment compared with midlactation. The mediation of nutrient delivery and uptake by the mammary gland appears to be markedly similar between early lactation and bST-treated cows, suggesting a similarity between these physiological states and the homeostatic and homeorhetic mechanisms regulating nutrient partitioning in the lactating dairy cow. In early compared with midlactation cows receiving placebo, uptakes of D-beta-hydroxybutyrate and NEFA were reduced, and triacylglyceride uptake increased.     

On the application of matrix generalized inverses to the design of observers for time-varying and time-invariant linear systems

A method for the design of Luenberger observers is developed utilizing the simplest generalized inverse of matrices. The method can be applied to time-invariant and to time-varying systems.     

Correlated response of udder dimensions to selection for milk yield in Holsteins

Response to selection for milk yield in Holsteins was examined by a controlled selection experiment initiated in 1964. Foundation cows were paired by sire and divided randomly into two breeding groups, selection and control. Selection group was mated to four sires each year highest for Predicted Difference milk. Twenty bulls selected in 1964 as near breed average for milk sired all control cows. Milk yield was recorded for each lactation, and height of udder from ground, distances between teats, and perimeter and area bound by the four teats were measured at 30 to 75 days postpartum on 153 selection and 202 control cows over 14 yr. Most estimates of repeatability and heritability of udder dimensions before and after milking were .45 or larger. Correlations with milk yield were negative for udder height and positive for other udder measurements. Selection cows exceeded controls for lactational milk yield. Daughters of high milk bulls had greater distances between teats, greater perimeters, and larger areas of udder floor. Selection cows did not differ from controls in udder height for first parity but were below controls in udder height and had udders that collapsed more for all parities.