Energy balance and lactation response in Holstein cows supplemented with cottonseed with or without calcium soap.

Holstein cows (n = 58, 21 primiparous), fed corn and wilted grass silages (63:37, DM basis) for free choice consumption, were assigned to control concentrate or supplemented concentrate during wk 1 to 16 postpartum with linted whole cottonseed (15% of projected DMI) alone or with Megalac (.54 kg/d). Our objective was to examine the effects of fatty acids on energy and N balances, total tract digestibility, and milk fatty acids in wk 7 and 16 and to assess total lactation responses. During balance measurements, fatty acids constituted 4.1, 6.8, and 8.6% of DM in control, oilseed, and oilseed plus protected fatty acid diets. Fat additions reduced fiber digestion (attributed to oilseed) and, to some degree, DMI and milk yield, but enhanced fat test without affecting protein percentage. Supplementary fat increased the proportion of C18:0 in milk at the expense of short-chain fatty acids. Supplemental oilseed with or without protected fatty acids reduced total heat production by 6% and reduced heat in excess of maintenance by 8%. Best estimates of NEL in linted whole cottonseed and of fat in Megalac were 1.81 and 5.69 Mcal/kg of DM. In total lactation, primiparous cows yielded more milk and FCM when fed oilseed plus Megalac and less of each when fed oilseed alone than controls. In pluriparous cows, milk yield was reduced by 2.7 kg/d relative to other treatments when oilseed plus Megalac was fed; FCM yield increased about 2 kg/d only when oilseed was supplemented alone. Overall, data suggest that basal ration fat and oilseed supplementation were too high or that supplementation should have been delayed until feed intake was higher.

Modification of the vermont test for monitoring fat adulteration of dairy products.

The Vermont test was developed for the routine screening of dairy products for vegetable fat adulteration. A slight modification of the test procedure made it more rapid and reduced costs. Gas-liquid chromatographic analysis of saponified fatty acids in the first and second Mojonnier extractions were proportional; thus, only the first extraction was needed to determine the purity of a milk lipid sample. This modification saves about 8 min/series of four samples and conserves 48% of the volume of organic solvents necessary to perform the classical Mojonnier extraction.

Precision and sensitivity of a test for vegetable fat adulteration of milk fat.

A test for routine screening of Mozzarella cheese and butter for vegetable fat adulteration is described. Fat is extracted and saponified. The potassium salts of the fatty acids are measured through direct gas chromatographic analysis. A ratio, calculated from the concentrations of butyric and oleic acids, is used to evaluate the purity of a sample. The test offers good precision and can detect less than 10% partially hydrogenated vegetable fat.

Growth responses of Staphylococcus aureus and Streptococcus agalactiae to Corynebacterium bovis metabolites.

Staphylococcus aureus and Streptococcus agalactiae growth responses to metabolites of Corynebacterium bovis cultured in media containing polyoxyethylenesorbitan monolaurate, monooleate, or trioleate and milk were determined. Filter sterilized metabolites of 48-h C. bovis cultures in synthetic media were added to cultures of Staph. aureus and Strep. agalactiae. Staphylococcus aureus and Strep. agalactiae were inoculated into 12-h C. bovis milk cultures. Growth responses of Staph. aureus and Strep. agalactiae were not affected by C. bovis metabolites of synthetic media. Staphylococcus aureus growth was inhibited during logarithmic and stationary phases in milk containing mixed cultures of C. bovis compared with growth in pure Staph. aureus cultures. Streptococcus agalactiae growth curves were similar in pure and C. bovis mixed cultures. Fatty acid compositions were not different in sterile milk and milk containing bacterial cultures. Growth responses of Staph. aureus and Strep. agalactiae were not related to concentration of C. bovis metabolites or fatty acid content of media in which C. bovis were cultured.

Growth inhibition of mastitis pathogens by long-chain fatty acids.

Staphylococcus aureus, Staphylococcus hyicus, Streptococcus agalactiae, and Corynebacterium bovis were tested for sensitivity to long-chain fatty acids predominant in teat canal keratin. Antibacterial activity of free fatty acids on each bacterial species was measured after 12 and 24 h in chemically defined media. Polyene C18:2 and C18:3 acids were bactericidal to each species at less than or equal to 10(5) ng/ml-1. The most bacteriostatic saturated fatty acids were C12 and C14. Streptococcus agalactiae growth was inhibited more by fatty acids after 24 h than after 12 h. No incubation time effect on growth responses of other species was determined. Polyoxyethylenesorbitan monooleate had a neutralizing effect on the bactericidal activity of polyene acids on C. bovis. Corynebacterium bovis were unable to grow in synthetic media containing individual free fatty acids as the sole source of preformed fatty acids. A relationship between bacterial species commonly isolated from bovine teat canals with resistance to fatty acids predominant in keratin was not evident.

Fatty acid composition of bovine teat canal keratin.

Keratin from 507 excised teats was pooled, separated into three samples, and analyzed for fatty acid composition of extracellular and intracellular lipids. Mean weight of keratin collected per teat canal was 8.97 mg. Extracellular lipids were recovered in petroleum ether. Intracellular lipids were extracted in chloroform: methanol (2:1, vol/vol) solution. Average keratin wet weight of extracellular and intracellular lipid fractions were 37.1 and 21.9 mg/g, respectively. Polar and nonpolar lipids were present in both fractions. Predominant fatty acids in extracellular and intracellular lipids were C16, C18:1, and C18. Extracellular lipids contained greater concentrations of C4 to C18:1 fatty acids than did intracellular lipids. Percent of total fatty acid weight comprised by each of C4, C10, C12 and C14 was also significantly greater in extracellular than intracellular fractions. Intracellular lipids contained a greater concentration and percent total fatty acid content comprised by C18:2 than extracellular lipids. Data suggest lipids accessible at the keratin interface are in part of milk fat origin.

Detection of penicillin, cephapirin, and cloxacillin in commingled raw milk by the Spot test.

The objective of this study was to compare Spot Test results with the results of the Bacillus stearothermophilus disc assay. Commingled raw milk samples were subdivided and spiked with penicillin, cephapirin, or cloxacillin. All subsamples, including unspiked subsamples, were analyzed by the Spot Test (3 or 9 replicates) and disc assay (9 replicates). Mean zone diameter for every subsample was calculated; subsamples having a mean zone diameter greater than or equal to 16 mm were considered positive. At penicillin concentrations less than or equal to 3.7 ng/ml, agreement between the Spot Test and disc assay was 83.4%, and false positive and negative percentages were 14.4 and 2.2%, respectively. Above 3.7 ng/ml, agreement was 100%. At cephapirin concentrations less than or equal to 12 ng/ml, agreement between the two tests was 67.9%, and false positive and negative percentages were 28.8 and 3.3%, respectively. Above 15 ng/ml, agreement was 99.3% with .7% false negatives. At cloxacillin concentrations less than or equal to 50 mg/ml agreement between the two tests was 54.5 with 45.5% false positives. At cloxacillin concentrations greater than or equal to 62.5 ng/ml, agreement between the two tests was 87.2% and false positive and negative percentages were 12.6 and .2%, respectively. In a field trial consisting of 823 bulk samples, Spot Test and disc assay agreement was 100%. The Spot Test is a rapid and reliable method for detecting penicillin, cephapirin, and cloxacillin residues in raw milk at concentrations that will produce a 16-mm zone.

Whey Ricotta Cheese Manufactured from Fluid and Condensed Whey.

Twenty-four different supplies of fresh Mozzarella cheese whey were pasteurized. Twenty-one were evaporated into seven condensed whey product (CWP) categories; three were not evaporated. Each whey and whey product was subsequently manufactured into Ricotta cheese. Average total solids (TS) content ranged from 6.70 to 35.90%. The Ricotta cheeses manufactured from five of the eight categories were judged to be acceptable for the market. Average TS (%) of the acceptable categories were 6.70, 10.31, 14.87, 18.02 and 20.86. Ricotta cheeses manufactured with CWP of average TS contents of 25.10, 28.67 and 35.90% were not acceptable. Flavor defects for Ricotta cheeses that were unacceptable included coarse, unnatural and unclean; body and texture defects included grainy and mealy. We recommend the manufacture of whey Ricotta cheese with approximately 21% CWP. Yield based on total weight for CWP with 20.86 TS averaged 21.32%, more than four times greater than the noncondensed whey. Ricotta cheese from CWP of 20.86% TS tested 69.75% moisture, 7.55% protein, 13.37% lactose, 4.30% fat and 0.72% salt. Large amounts of protein and lactose remained in the Ricotta cheese whey and must be handled properly to prevent pollution.

Consumers Can Detect Light-Induced Flavor in Milk.

Two-thousand consumers were surveyed at three county fairs in Vermont to determine their taste preference for samples of good milk and milk with light-induced flavor defect. More than 73% of the people surveyed preferred the good milk sample. More females than males could taste a difference between the two samples, had a preference for one sample, and preferred the good sample. The data suggest strongly that it is in the best interests of the dairy industry to prevent light-induced flavor of milk.