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The aim of the study was to determine the effect of a Bacillus -based direct-fed microbial on performance of mid-lactating Holstein dairy cows and on their milk fatty acid composition. Six multiparous cows fitted with a rumen cannula were used in a randomized replicated crossover design. Cows received 200 g/d of either whey powder as a control or BioPlus 2B (Chr. Hansen), a commercial direct-fed microbial providing Bacillus subtilis and Bacillus licheniformis , representing a daily dose of 6.4 × 1011 cfu, and using whey powder as a carrier. The 2 experimental periods lasted 14 d and were separated by a 7-d washout interval. Samples were collected on d 0, 13, and 14 of each period. Data from d 0 were used as covariate. Significance was declared at P ≤ 0.05 and tendency at 0.05 < P ≤ 0.10. There was a 10-fold increase in the relative concentration of bacteria from the Bacillus subtilis group in the rumen when feeding direct-fed Bacillus compared with control. Treatment did not affect ruminal pH, NH 3 -N, or concentrations of acetate, propionate, and butyrate. However, direct-fed Bacillus increased ruminal concentrations of isovalerate and isobutyrate (tendency). Treatments did not affect lactation performance. Supplying direct-fed Bacillus enhanced milk relative concentration of anteiso 13:0 by 27.3% and of anteiso 15:0 by 6.5% and tended to increase concentrations of iso 14:0 (+41.8%) relative to control. When expressed on a yield basis, direct-fed Bacillus increased the secretion of anteiso 13:0 and decreased that of 11:0, 15:0, 17:0 (tendency), and cis -9 17:1. These variations, although limited in magnitude, indicate that milk branched-chain fatty acid composition is sensitive to ruminal microbiota modifications without changes in chemical composition of the diet. [ABSTRACT FROM AUTHOR]

This study investigated the use of K 2 CO 3 as dietary buffer to prevent or to recover from low milk fat production when early-lactating dairy goats are fed a high-starch, low-fiber (HSLF) diet. At kidding, 30 Alpine goats housed in pens with Calan gate feeders received a total mixed ration with a forage-to-concentrate ratio of 55:45 on a dry matter (DM) basis for a baseline period of 27 ± 4 d. Goats (milk yield, 4.14 ± 0.88 kg/d; milk fat, 4.28 ± 0.52%; mean ± SD) were then assigned to 1 of 10 blocks according to parity (first vs. second or more) and milk fat concentration, and fed a HSLF diet containing 45% forages and 55% concentrates for 2 experimental periods of 28 d. Treatments were identified as (1) control, in which the HSLF diet was fed throughout both periods; (2) preventive, in which the HSLF diet supplemented with K 2 CO 3 (1.6% of DM) was fed during both periods; and (3) recovery, in which the HSLF diet was fed during the first period (P1) and the HSLF diet supplemented with K 2 CO 3 was fed during the second period (P2). Data from P1 and P2 were analyzed separately. In P1, preplanned contrasts were used to evaluate the preventive effect of K 2 CO 3 (control and recovery, both groups receiving the same diet during this period, vs. preventive), and in P2, to assess the potential of K 2 CO 3 to alleviate an already existing state of low milk fat (control vs. recovery and preventive vs. recovery). Feeding the HSLF diet in P1 moderately decreased milk fat concentration (−16%) and yield (−13%) as compared with baseline. Dietary addition of K 2 CO 3 decreased DM intake by 12 and 14% in P1 and P2, respectively. Ruminal pH was not different among treatments. There was also no significant difference in milk yield (4.13 and 3.71 kg/d on average in P1 and P2, respectively) for any tested contrasts. In P1, milk fat concentration and yield did not differ among goats fed control (3.58% and 151 g/d, respectively) and preventive (3.67% and 148 g/d, respectively) diets. In P2, milk fat concentration and yield did not differ among goats fed the control diet (3.38% and 137 g/d, respectively), and diets where K 2 CO 3 was used as preventive (3.44% and 126 g/d, respectively) or recovery treatment (3.25% and 113 g/d, respectively). Supplementing a high-concentrate diet with 1.6% K 2 CO 3 was therefore not effective in either preventing or suppressing already existing conditions of low milk fat production in dairy goats. [ABSTRACT FROM AUTHOR]

The objective of the current study was first to characterize lipid raft microdomains isolated as detergent-resistant membranes (DRM) from mammary gland tissue, and second to determine how dietary fatty acids (FA) such as conjugated linoleic acid (CLA), 19:1 cyclo, and long-chain n-3 polyunsaturated FA affect lipid raft markers of mammary cells, and to finally establish relationships between these markers and lactation performance in dairy cows. Eight Holstein cows were used in a replicated 4 × 4 Latin square design with periods of 28 d. For the first 14 d, cows received daily an abomasal infusion of (1) 406 g of a saturated FA supplement (112 g of 16:0 + 230 g of 18:0) used as a control; (2) 36 g of a CLA supplement (13.9 g of trans- 10, cis- 12 18:2) + 370 g of saturated FA; (3) 7 g of Sterculia fetida oil (3.1 g of 19:1 cyclo, STO) + 399 g of saturated FA; or (4) 406 g of fish oil (55.2 g of cis- 5, cis- 8, cis- 11, cis- 14, cis- 17 20:5 + 59.3 g of cis- 4, cis- 7, cis- 10, cis- 13, cis- 16, cis- 19 22:6, FO). Mammary biopsies were harvested on d 14 of each infusion period and were followed by a 14-d washout interval. Cholera toxin subunit B, which specifically binds to ganglioside M-1 (GM-1), a lipid raft marker, was used to assess its distribution in DRM. Infusions of CLA, STO, and FO were individually compared with the control, and significance was declared at P ≤ 0.05. Milk fat yield was decreased with CLA and FO, but was not affected by STO. Milk lactose yield was decreased with CLA and STO, but was not affected by FO. Mammary tissue shows a strong GM-1-signal enrichment in isolated DRM from mammary gland tissue. Caveolin (CAV) and flotillin (FLOT) are 2 proteins considered as lipid raft markers and they are present in DRM from mammary gland tissue. Distributions of GM-1, CAV-1, and FLOT-1 showed an effect of treatments determined by their subcellular distributions in sucrose gradient fractions. Regardless of treatments, data showed positive relationships between the yield of milk fat, protein, and lactose, and the abundance GM-1 in DRM fraction. Milk protein yield was positively correlated with relative proportion of FLOT-1 in the soluble fraction, whereas lactose yield was positively correlated with relative proportion of CAV-1 in the DRM fractions. Infusion of CLA decreased mRNA abundance of CAV-1, FLOT-1, and FLOT-2. Regardless of treatments, a positive relationship was observed between fat yield and mRNA abundance of FLOT-2. In conclusion, although limited to a few markers, results of the current experiment raised potential links between variation in specific biologically active component of raft microdomains in bovine mammary gland and lactation performances in dairy cows. [ABSTRACT FROM AUTHOR]

• Camelina expeller, as a source of readily available oil, altered ruminal lipid metabolism and reduced milk fat yield in dairy cows. • Lactation performance was similar between cows fed whole camelina and flax seeds. • The transfer efficiency of n -3 fatty acids from the diet to milk fat was not different between whole camelina and flax seeds. • Erucic acid from whole camelina seeds and camelina expeller was transferred from the diet to milk fat with and efficiency of 10–20 %. The objective of the current study was to compare the effects of feeding corn dried distillers' grains with solubles (DDGS), camelina expeller (CE), whole camelina seeds (WCS), or whole flax seeds (WFS) on milk yield and composition of lactating dairy cows. Four Holstein cows were used in a 4 × 4 Latin square design with 21-d periods, including 14 d of adaptation followed by 7 d of sampling. Four isoproteic and isolipidic dietary treatments were formulated as follows: 1) 18 % DDGS; 2) 9.5 % CE; 3) 4.2 % WCS; and 4) 4.7 % WFS (dry matter basis). Pre-planned contrasts were established to compare: 1) the two by-products (DDGS rich in cis -9, cis -12 18:2 vs. CE rich in cis -9, cis -12, cis -15 18:3); 2) the two forms of camelina (CE vs. WCS); and 3) the two whole seeds (WCS vs. WFS). Differences were declared at P ≤ 0.05. Contrasts did not reveal any significant differences in dry matter intake (x ¯ =24.6 kg/d). Actual milk yield was greater for cows fed WCS (36.5 kg/d) compared with WFS (35.6 kg/d). Moreover, yield of fat-corrected milk was lower with CE (29.8 kg/d) than with DDGS (35.3 kg/d) or WCS (33.5 kg/d). These effects are in line with lower milk fat concentration when cows received CE (27.1 g/kg) as compared with DDGS (36.3 g/kg) or WCS (34.8 g/kg). Lower milk fat observed with CE could be explained by a shift from the trans -11 to the trans -10 pathway of biohydrogenation, leading to the production of more intermediates known to inhibit milk fat synthesis, i.e. , milk fat concentration of trans -10, cis -12 18:2 was greater with CE (0.078 mg/g) than with DDGS (0.045 mg/g) or WCS (0.041 mg/g). The transfer efficiency, from the diet to milk fat (g secreted/g consumed), of total n -3 fatty acids was lower with CE (0.082 g/g) compared with DDGS (0.109 g/g) or WCS (0.106 g/g), but was not different between WCS and WFS (0.110 g/g). Finally, the transfer efficiency of cis -13 22:1 was twice greater with CE than with WCS (0.198 vs. 0.105 g/g). In conclusion, feeding CE had a negative impact on lactation performance, and more specifically on milk fat yield; an effect that could be explained by the great accessibility of the residual oil contained in this by-product and its consequent interference with lipid metabolism in the rumen. Comparison of WCS with WFS reveals that both oilseeds support similar production efficiency and gross milk composition. [ABSTRACT FROM AUTHOR]