The objective of the experiment was to determine the contribution of red blood cells to transport of individual amino acids to lactating bovine mammary glands. Blood samples were collected from coccygeal and subcutaneous abdominal veins of 21 lactating Holstein cows on d 35, 70, 105, and 126 of lactation. Samples were collected every 20 min for 12 h. Subsamples of whole blood and plasma were pooled by hour and day. Hourly plasma samples and daily whole blood and plasma samples were analyzed for amino acid concentration. Plasma glutamate concentration was stable throughout the 12-h collection period, indicating that sample collection did not perturb amino acid homeostasis. Therefore, data from pooled daily samples were used for subsequent comparisons. Whole blood arteriovenous differences of phosphoserine, aspartate, glutamate, hydroxyproline, phosphoethanolamine, serine, asparagine, glycine, glutamine, taurine, histidine, citrulline, threonine, alanine, beta-aminoisobutyrate, carnosine, arginine, proline, alpha-aminobutyrate, tyrosine, valine, methionine, cystine, isoleucine, leucine, phenylalanine, tryptophan, ornithine, and lysine differed significantly from plasma arteriovenous differences. Uptakes of individual amino acids from plasma were poorly correlated with uptake from whole blood. These data clearly indicate that uptake data derived from plasma do not adequately represent whole blood amino acid uptake.

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Seven laboratories participated in a collaborative study to extend the applicability of the AOAC generic combustion method for determination of crude protein in animal feed (990.03) to include determination in cereal grains and oilseeds. In the study, method 990.03 was compared with the AOAC mercury catalyst Kjeldahl method for determination of protein in grains (979.09) and crude protein in animal feed (954.01). The study also evaluated the effect on the results of fineness of grind. For determination of crude protein in grains and oilseeds by the combustion method, standard deviations for repeatability and reproducibility ranged from 0.10 to 0.37 and from 0.25 to 0.54, respectively, and relative standard deviations for repeatability and reproducibility ranged from 0.77 to 2.57% and from 1.24 to 3.15%, respectively. The combustion method was adopted first action by AOAC International for determination of crude protein in cereal grains and oilseeds containing 0.2- 20% nitrogen.

California is the leading state for the production of almonds, with more than 400,000 bearing hectares of orchards that produced approximately 1 billion kg of shelled nuts in 2017. Almond hulls (AH) are a regional by-product feedstuff fed predominately to dairy cattle in California. A 2012 study surveyed 40 dairy farms in California and found that 39 out of 104 total mixed rations contained AH, with a mean daily feeding rate of 1.45 kg/cow. In 2017, approximately 2 billion kg of AH was produced. At a feeding rate of 1.45 kg/cow daily, even if all 1.7 million lactating cows in California are consuming AH, there will be a surplus of AH on the market as the approximately 130,000 nonbearing hectares come into nut production. Therefore, the potential of feeding varying amounts of AH to lactating dairy cows was investigated using 12 Holstein cows with 4 primiparous and 8 multiparous cows. The dietary treatments were 4 total mixed rations containing 0, 7, 13, or 20% AH. The AH used contained 12.8% crude fiber (as-is basis), which was below the 15% legal limit set by state feed regulations. Diets were formulated so that as the inclusion rate of AH increased, the amount of steam-flaked corn and soyhull pellets decreased and soybean meal inclusion increased. Experimental design was a replicated 4 × 4 Latin square. Diet had a cubic effect on actual milk yield, energy-corrected milk yield, and dry matter intake, with the 7% AH diet having the highest values and the 13% AH diet having the lowest. The percent and yield of total solids and the yields of lactose and fat did not differ with diet, but percent and yield of protein declined linearly with increased AH inclusion, and fat percent increased linearly. Apparent total-tract digestibilities of dry matter and organic matter were higher with the inclusion of AH in the diet. Total percentage of the day spent ruminating increased linearly with higher amounts of AH. Overall, this work demonstrated that AH can be fed at vary-ing amounts, up to 20% of the diet, to lactating dairy cows to support high levels of milk production and that increasing amounts of AH (up to 20%) in the diet could lead to improved digestibility and milk fat percentage but decreased milk protein production.

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