Four lactating Holstein cows (average milk yield: 20±3 l/d) were used to develop and validate a method for estimating the size of udder cisterns (Sinus lactiferi) using ultrasonography. A sectorial transducer probe of 5 MHz, placed in contact with the teat in a parallel cranial position, was used to obtain vertical scans of the udder in two perpendicular planes with the teat canal axis as reference. Udder scans for each udder quarter were taken randomly at intervals of 4, 8, 12, 16, 20 and 24 h after milking. Glandular parenchyma (echogenic) and lumen of the cisterns full of milk (anechogenic) were evident in the scans, the calculated area of the anechogenic portion being defined as cistern area. Cistern areas measured in perpendicular scans were highly correlated. Immediately after each measurement, cisternal milk was removed from each quarter using a teat cannula after i.v. injection of an oxytocin-receptor blocking agent. Alveolar milk from each quarter was then obtained by machine milking after i.m. injection of oxytocin. Cistern area and cisternal milk volume increased with length of milking interval showing a curvilinear pattern with a plateau after 16 h. Correlations between cistern area and cisternal milk volume were positive and significant (P<0·001) at all intervals but showed the highest values with the smallest residual standard deviations at 8 h (r=0·88) and 12 h (r=0·84). Since 8 h has previously been identified as a suitable time at which to determine cisternal milk volume for the purposes of defining suitability for different milking strategies, we conclude that ultrasonography provides a satisfactory, non-invasive method for determination of milk storage characteristics in dairy cows.

Effects of six different milking intervals on the distribution of milk between cistern and alveoli were studied in a randomized, incomplete Latin Square experiment with four lactating Holstein cows. Cisternal and alveolar milk was measured by udder quarter at 4, 8, 12, 16, 20 and 24-h intervals with a 3-d interperiod of regular milking. Cisternal milk was evacuated using a cannula after injection of an oxytocin-receptor blocking agent, followed by an injection of oxytocin to remove the alveolar fraction. Milk samples from each fraction and quarter were collected for analysis. Cisternal and alveolar milk increased with milking interval and represented on average 30 and 70% of the milk stored in the udder, respectively. Fat content in alveolar milk remained constant during the first 16 h, increasing rapidly thereafter, reaching its maximum at 24 h (6·95%). Fat content in cisternal milk decreased with milking interval and reached its minimum at 24 h (0·96%). Total fat yield tended to increase for cisternal milk with longer milking intervals, but it increased markedly for alveolar milk, showing that fat globules did not pass freely from alveoli to cistern between milkings. Milk protein content was greater in rear quarters than in front quarters for both milk fractions. Milk protein content increased in the cisternal milk fraction and tended to increase in the alveolar milk fraction with longer milking intervals, but values did not differ between cisternal and alveolar fractions or between front and rear quarters. Total protein yield increased with milking interval in both fractions, indicating that casein micelles passed more freely than fat globules from the alveolar to the cisternal compartment. In conclusion, the short-term effects of milking intervals in milk composition were explained by the changes observed in alveolar and cisternal milk ratio.

The response of dairy cows to omitting one milking weekly was investigated in two successive experiments conducted with Holstein cows milked twice daily. Experiment 1 compared the lactational performances and udder changes in eight cows (31.2 L/d, 201 d in milk) in the 5 wk before and the 5 wk after introducing the suppression of one milking weekly. Milk yield was recorded daily and milk composition twice weekly. Milk partitioning in the udder (alveolar and cisternal milk) and cisternal size (ultrasonography), 8 h after milking, were also measured at the start and the end of the experiment. Although daily milk yield decreased 32% during the experiment (10 wk), linear regression analysis revealed a loss of milk yield of 1.1 L/d (3.7%) as a consequence of the omission of one milking weekly. Milk composition, lactation persistency, and somatic cell count (SCC) were unaffected by milking omission. Milk partitioning in the udder decreased by 38% in alveolar milk volume and showed a tendency to decrease in cisternal milk volume (15%) and cisternal size (7%), as a result of milking omission and advancing lactation. Loss in total milk yield was negatively related with cisternal milk volume (r = -0.77) and cisternal size (r = -0.70) indicating smaller losses in the udders with large cisterns. In Experiment 2, five cows (21.0 L/d, 227 d in milk) previously adapted to the milking omission schedule were used to study the daily effects of milking omission on milk yield, milk composition and udder health during 10 wk. Milk yield and milk composition were approximately constant but SCC increased with lactation stage. The omission of one milking caused an important decrease in milk yield, fat content and SCC on the omission day and a compensatory increase over the following 2 d, but milk protein and lactose did not vary. All variables reached the average weekly value three days after the milking omission (six milkings). In conclusion, under the conditions used, omitting one milking weekly slightly reduced milk yield and did not affect milk composition when healthy cows were used. Milk losses by milking omission depend on udder cistern characteristics; evaluating cistern size by ultrasonography may be a useful tool for choosing cows that are better adapted to a reduced milking frequency.

The effects of semolina enrichment with blue-green algae (Arthrospira platensis) at three different levels (1, 2 and 3 g/100 g of semolina) on the colour, cooking properties, firmness, free radical scavenging activity and sensory characteristics of pasta are reported. Microalgae addition resulted in higher swelling index and lower cooking loss than the control sample. A significant increase in pasta firmness was evidenced with an increase of added microalgae due to structural reinforcement. In addition to colouring, the use of A. platensis (2 g/100 g of semolina) can enhance the sensory quality and nutraceutical potential as evaluated by free radical scavenging activity of pasta.

No abstract