Thirty-four mature Holstein cows were blocked into two groups on their 305-day, twice daily milked, mature equivalent milk production of the previous lactation; groups were assigned at random to a twice or thrice daily milking frequency. In addition, six pairs of paternal half-sisters and one pair of nonsibling heifers also were assigned to twice daily or thrice daily milking frequency. Half-sisters were assigned to milking frequency on alternate calvings, and the nonsibling pair was assigned at random. Milk production peaked at 6 wk lactation in mature cows in both treatments, at 7 wk for cows in first lactation milked twice daily, and at 9 wk for cows in first lactation milked thrice daily. Cows milked thrice daily reached higher peak milk production and were more persistent in milk production. Multiparous and first-lactation cows milked thrice daily produced 18.5 and 25.2% more milk than their counterparts milked twice daily, and after 15 wk heifers milked thrice daily were producing more milk per day than mature cows milked twice daily. The combined increased average production for cows and heifers milked thrice daily, 1299 kg, required only 92 kg more dry matter intake and resulted in an apparent preferential utilization of feed nutrients for milk production or higher rate of tissue catabolism in cows milked thrice daily. Milk composition was not influenced by milking frequency; total milk fat was 36 kg more for cows milked thrice daily. Reproductive performance measured as days to first estrus, days open, or services per conception also was not influenced by milking frequency.

This research was designed to test the reliability of modified Association of Official Analytical Chemists methods for quantitation of thiamine, riboflavin, and ascorbic acid in milk; to ascertain the extent of destruction of those vitamins by modern heat processing; and to determine if it is truthful to report that heat processing does not reduce milk's nutritional properties insofar as those vitamins are concerned. Milk was processed continuously at four time-temperature treatments, including that used for modern commercial sterilization. Both raw and heated milks were analyzed immediately for content of heat labile vitamins; subsamples were packaged in amber plastic bottles, frozen, and subsequently analyzed for vitamin content after 14 days storage. Analyses were by modified Association of Official Analytical Chemists fluorometric techniques.

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Compositional analysis data for 47 whey powders (including sweet whey, acid whey, demineralized delactosed whey and whey protein concentrates) were correlated with near infrared reflectance (NIR) measurements. The most useful wavelengths for determining constituent concentrations were chosen from 19 pre-selected wavelengths by using linear regression analysis. Results indicate that samples to be used for NIR calibrations should be similar in composition and should represent a limited range of constituent concentrations. Individual NIR calibrations need to be developed for each type of whey powder to be analyzed.

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