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Historically, radial immunodiffusion (RID) has been the only method that directly measures IgG; however, recent studies have reported IgG concentrations in colostrum, milk, and plasma as measured using an ELISA. To our knowledge no comparison between RID and ELISA methods has been made for bovine colostrum or plasma. The objective of this study was to compare IgG concentrations measured by both methods in samples of bovine colostrum before and after heat treatment and bovine plasma. Concentration of IgG was quantified using a commercially available RID kit and a modified ELISA. Samples of bovine colostrum and plasma were collected from individual animals and colostrum was tested before and after heat treatment at 60°C for 30 min. All samples were tested using both methods. Pearson correlation coefficients were determined for RID and ELISA values from unheated colostrum, heat-treated colostrum, and plasma samples. Mixed models were used to determine the effect of assay on IgG measurement in colostrum and plasma and effect of heat treatment on IgG concentration in colostrum. A weak correlation was found between ELISA and RID results in plasma and unheated colostrum. Concentration of IgG was significantly lower in all sample types when measured by ELISA compared to RID. Thus, direct comparison of ELISA and RID results is not recommended. Colostrum IgG concentration significantly decreased after heat treatment as measured by ELISA, but means were not different when measured by RID. Correlation plots between colostrum values measured before and after heat treatment indicated changes in the colostrum protein matrix due to heat affected RID and ELISA assays differently. This investigation compared RID and ELISA results, but no conclusions could be drawn as to the accuracy of either assay.

Stimulating rumination by feeding polypropylene ribbon had no effect in alleviating milk fat depression. In two experiments with six cows in each, milk fat depression was produced by feeding a ground pelleted hay with concentrates and limited long hay. Feeding this ration resulted in a large reduction in time spent ruminating. Adding polypropylene ribbon, 5 cm long, returned rumination times to normal but had no effect on milk fat depression. Replacing ground hay with long hay returned both rumination times and milk fat to normal. The effect of long hay in preventing or reversing milk fat depression is due to factors other than its potential for stimulation of rumination.

In two reversal experiments to determine digestibility of liquid acid whey by steers and cows, trials within each experiment consisted of an adjustment period followed by 10-day preliminary and 7-day collection periods. In Experiment 1 four Jersey steers received a daily basal diet of 7000g of hay plus 800g of soybean meal. Two of the steers received 45.4kg whey in addition to the basal diet within each trial. In Experiment 2 four mature, dry, nonpregnant cows (three Jersey and one Ayrshire) were offered 9000g of hay plus 300g of soybean meal daily. Two of the cows received 45.4kg whey in addition to the basal diet within each trial. Digestion coefficients of the basal and basal-plus-whey diets were determined directly, and digestibility of whey alone was determined by the difference of the two diets. Liquid acid whey had an average digestibility of dry matter, 82.6%, 68.8% of protein, and of organic matter 84.2%.

Three experiments investigated how forages of different chemical composition affect rumination time of cattle. Three single reversal designs used four dairy heifers and two dairy steers in Experiment I and four dairy heifers in Experiments II and III. The rumination time produced by feeding a single 5-kg meal of test forage was measured with jaw motion recordings. In Experiment I the test meal was fed after 2 days of fasting; following the test meal no more was offered for an additional 2 days. In Experiments II and III only alfalfa pellets were offered during the 2 days before and after the test meal, at the rate of 2.27 kg per head per day. In Experiment I the animals which were fed straw ruminated 578 minutes following the test meal; the animals fed an excellent quality hay ruminated a shorter (P < .05) time of 369 minutes. Experiment II compared a good-quality mixed second-cutting hay with straw. The straw produced 539 minutes’ rumination time, and the second-cutting hay produced a shorter (P < .05) time of 387 minutes. In Experiment III good-quality orchardgrass produced 258 minutes’ rumination time; poor-quality orchardgrass produced a longer (P < .05) time of 449 minutes. The correlation between rumination time and cell wall constituent (CWC) content was 0.94.

Initial research showed significant differences between individual cattle in their rumination response to equal amounts of cell wall constituent intake. Two further experiments were conducted to determine if dairy cattle breeds differ in their rumination time. In Experiment 2, eight Guernseys had lower (P < .05) 24-hour rumination times than did eight Holsteins, eight Ayrshires, and eight Jerseys. When corrected for cell wall constituent intake and body weight kilogram.75 the Guernsey average rumination time was lower than the Holstein average (P < .05) and the Jersey average (P < .01). In a third experiment eight lactating Guernseys averaged lower (P < .05) total rumination times, as well as minutes rumination corrected for cell wall constituent intake and body weight kilogram.75, than did eight lactating Jerseys.