The objective was to evaluate the effects of feeding ground canola seed on the fatty acid profile, yield, and composition of milk from dairy cows. Twenty-four multiparous Holstein cows (548.3 +/- 11.9 kg body weight and 28 +/- 9 d in lactation) were randomly assigned to 1 of 2 treatments: Control (CON) or ground canola seed treatment (GCS) with 14% [of diet dry matter (DM)] of the total ration as ground canola seed containing 34% lipid. Diets contained 20% crude protein, but varied in net energy as a result of fat content differences of 2.5% and 6.4% (DM) for CON and GCS, respectively. Diets were composed of corn, corn silage, alfalfa (50:50 ground hay and haylage, DM basis), soybean and blood meal, and vitamins and minerals. Mechanically extruded canola meal was used in the CON diet to adjust for the protein from canola seed in the GCS diet. Cows were housed in tie-stalls and fed and milked twice daily for 10 wk. The inclusion of ground canola seed did not alter DM intake, weight gain, or body condition score of cows. Milk fat from GCS cows had greater proportions of long-chain fatty acids (> or = 18 carbons) and a lower ratio of n-6 to n-3 fatty acids. Feeding GCS reduced the proportion of short- and medium-chain fatty acids. Milk fat from cows fed GCS had a greater proportion of vaccenic acid and tended to have a higher proportion of cis-9,trans-11 conjugated linoleic acid. Actual and 3.5% fat-corrected milk yields were similar between treatments. The milk fat and protein percentages were lower for GCS cows, but total yield of these components was similar between treatments. Milk urea nitrogen was lower and serum urea nitrogen tended to be lower in cows fed canola seed. Serum glucose, insulin, and nonesterified fatty acids were not altered, but serum triglycerides were higher in GCS cows. Ammonia and total volatile fatty acids tended to be lower in ruminal fluid from GCS cows; rumen pH was unchanged. Feeding canola seed to lactating dairy cows resulted in milk fat with higher proportions of healthful fatty acids without affecting milk yield or composition of milk.

The objectives of this study were 1) to examine the interactive influence of a compensatory nutrition regimen and lasalocid supplementation on dairy heifer growth performance and 2) to document the extent to which compensatory growth sustains lactation potential over the first two lactation cycles. Twelve Holstein heifers, weighing an average of 160 kg (about 6 mo of age) were randomly assigned to treatments arranged in a 2 x 2 factorial design. Treatment variables were two dietary regimens (control and stair-step compensatory nutrition) and two levels of lasalocid (0 and 200 mg/d). The control heifers were fed a diet containing 12% crude protein (CP) and 2.35 Mcal of metabolizable energy (ME) per kilogram of dry matter. The stair-step compensatory nutrition heifers were subjected to a phased nutrition regimen and reared according to an alternating 3-2-4-3-4-2-mo schedule. The first stair-step (prepubertal phase) consisted of energy restriction [17% CP and 2.35 Mcal/kg of ME] for 3 mo followed by realimentation (12% CP and 3.05 Mcal/kg of ME) for 2 mo. The second step (puberty and breeding) consisted of energy restriction for 4 mo followed by realimentation for 3 mo. The third step (gestation period) was energy restriction for 4 mo concluding with realimentation for 2 mo. Dry matter intake of heifers during the restriction phase was limited to 70% of the control intake. Heifers were given ad libitum access to a high energy density diet during realimentation to allow compensatory development. Stair-step heifers supplemented with lasalocid had the highest efficiency of growth (body weight gain/dry matter intake), suggesting synergistic metabolism of lasalocid with compensatory growth action. Compensatory growth induced during the last trimester enhanced metabolic status by increasing circulating insulin and decreasing triglyceride levels. Heifers on the stair-step regimen had a significant increase in milk yield during the first (21%) and second (15%) lactation cycles. These results support our thesis that compensatory growth induced during an allometric growth phase improves mammary development and energy and protein metabolic status of dairy heifers.

No abstract

Our objective was to determine the extent to which a stair-step compensatory nutrition regimen regulated the growth and subsequent lactation performance of developing beef heifers. Forty crossbred beef (Angus x Gelbvieh) heifer calves were assigned to either a control or stair-step compensatory nutrition regimen. Heifers fed the stair-step compensatory nutrition regimen were fed according to an alternating schedule beginning with a high energy diet (130% of the metabolizable energy recommended by the National Research Council) for 2 mo, followed by an energy restricted diet (70% of the recommended metabolizable energy) for 3 mo, and concluding with the high energy diet again for 2 mo. Thereafter, all heifers received the control diet. The average daily gain of heifers fed the stair-step compensatory nutrition regimen was 2-fold higher than that of control heifers during the final high energy phase. The RNA and protein contents in the mammary tissues of heifers fed the experimental regimen in early lactation were greater than those of control heifers. Lipid content was significantly reduced in the mammary tissues of heifers fed the experimental regimen. The expression of beta-casein in the mammary tissues of heifers fed the experimental regimen was higher than that of the control heifers. Heifers fed the stair-step regimen yielded 6% more milk than did those fed the control regimen. Total protein and casein in milk of heifers fed the experimental regimen were higher than those in milk of control heifers. These results indicate that the stair-step compensatory nutrition regimen enhanced mammary development and subsequent lactation performance.

Bovine casein gene cluster belongs to the best studied regions of the bovine genome. However, molecular basis of the regulation of casein gene expression is still of great interest for the advancement of milk production. Identification of crucial regulatory regions governing casein gene expression would provide valuable information for marker assisted selection in dairy cattle. In our study we performed comparative analysis of the bovine beta-and kappa casein gene promoter sequences with the regulatory sequences from some other species. In addition, we used homologous mammary gland derived cell culture and luciferase reporter gene system to confirm the functionality of the proximal beta and kappa casein promoters. The longer kappa casein promoter (2064 bp) showed the highest expression level, followed by the short kappa casein promoter (925 bp) and beta casein promoter (1692 bp). Here we demonstrate the suitability of the bovine mammary gland derived cell line BME UV1 for transient gene expression under transcriptional control of the bovine casein gene promoters and compare functionality of different fragments of bovine beta-and kappa casein gene promoters using homologous in vitro system. Zusammenfassung Titel der Arbeit: Funktionsanalyse der Rinder β-und κ-Kaseingenpromotoren mit Hilfe der homologen Euterzelllinie Kasein Gen Cluster beim Rind gehören zu den am besten untersuchten Teilen des Rindergenoms. Trotzdem herrscht noch immer groβes Interesse an detaillierten Studien über die molekulare Basis der Regulation der Kaseingen-Expression zur Steigerung der Milchproduktion. Die Entdeckung der Hauptregulationsmechanismen der Kaseingen-Expression wäre von groβer Bedeutung für die markergestützte Selektion der Milchkühe. In unserer Studie haben wir die Promotorsequenzen der Rinder beta-und kappa-Kaseingene im Vergleich zu einigen anderen Säugetierarten untersucht. Die Rinder-Euterzellen BME UV1 und das Luziferase Reportergen System wurden für die Bestätigung der Funktionalität der Rinder β-und κ-Kaseingenpromoters in vitro eingesetzt. Der längere κ-Kaseingen Promoter (2064 bp) hat die stärkste Expression gezeigt, gefolgt von dem kurzen κ-Kaseingen Promoter (925 bp) und dem β-Kaseingen Promoter (1692 bp). Hier können wir demonstrieren, dass die Rindereuterzelllinie BME UV1 für die vorübergehende Genexpression unter der Kontrolle der Rinderkaseingenpromotoren geeignet ist. Die Funktion von verschiedenen Teilen der Rinder β− und κ-Kaseingenpromotern wurde in einem homologen in vitro System verglichen.