Regulation of Volatile Fatty Acid Uptake by Mitochondrial Acyl CoA Synthetases of Bovine Liver,

Mitochondria of bovine liver contain acyl CoA synthetases necessary for the uptake of propionate, butyrate, and valerate whereas acetate is bound only weakly. Purification of these enzymes separated a distinct propionyl CoA synthetase highly specific for propionate and acrylate and a butyrate-activating fraction with broad substrate specificity for short and medium chain fatty acids. Evidence from kinetic studies and sucrose density centrifugation suggested that this latter fraction was composed of two enzymes, a butyryl CoA synthetase and a valeryl CoA synthetase. The apparent molecular weights of the propionyl, butyryl, and valeryl CoA synthetases were 72,000, 67,000, and 65,000. The Michaelis-Menten constants of propionyl CoA synthetase for propionate, adenosine 5’-triphosphate, and coenzyme A were 1.3 × 10^?3M, 1.3 × 10^?3M, and 6.3 × 10^?4M. Enzyme activity is regulated by the concentration of propionate in portal blood. Relative to propionyl, butyryl, or valeryl CoA synthetases little acetyl CoA synthetase could be demonstrated.In ruminants hepatic metabolism is such that use of acetate as an energy source is minimum. This ensures that an alternative energy source to glucose, as acetate units, will reach the extrahepatic tissues. Separation of a distinct propionyl CoA synthetase regulated by the concentration of propionate in portal blood is significant because a primary role of ruminant liver is to synthesize glucose from ruminally derived propionate.     

Effects of the dose and viability of Saccharomyces cerevisiae. 1. Diversity of ruminal microbes as analyzed by Illumina MiSeq sequencing and quantitative PCR

This study was conducted to examine effects of the dose and viability of supplemental Saccharomyces cerevisiae on the ruminal fermentation and bacteria population and the performance of lactating dairy cows. Four ruminally cannulated lactating cows averaging 284 ± 18 d in milk were assigned to 4 treatments arranged in a 4 × 4 Latin square design with four 21-d periods. Cows were fed a total mixed ration containing 41.7% corn silage, 12.1% brewer’s grains, and 46.2% concentrate on a dry matter basis. The diet was supplemented with no yeast (control) or with a low dose of live yeast (5.7 × 10⁷ cfu/cow per day; LLY), a high dose of live yeast (6.0 × 10⁸ cfu/cow per day; HLY), or a high dose of killed yeast (6.0 × 10⁸ cfu/cow per day; HDY). Microbial diversity was examined by high-throughput Illumina MiSeq sequencing (Illumina Inc., San Diego, CA) of the V4 region of the 16S rRNA gene. The relative abundance of select ruminal bacteria was also quantified by quantitative PCR (qPCR). Adding LLY to the diet increased the relative abundance of some ruminal cellulolytic bacteria (Ruminococcus and Fibrobacter succinogenes) and amylolytic bacteria (Ruminobacter, Bifidobacterium, and Selenomonas ruminantium). Adding live instead of killed yeast increased the relative abundance of Ruminococcus and F. succinogenes; adding HDY increased the relative abundance of Ruminobacter, Bifidobacterium, Streptococcus bovis, and Selenomonas ruminantium. The most dominant (≥1% of total sequences) bacteria that responded to LLY addition whose functions are among the least understood in relation to the mode of action of yeast include Paraprevotellaceae, CF231, Treponema, and Lachnospiraceae. Future studies should aim to speciate, culture, and examine the function of these bacteria to better understand their roles in the mode of action of yeast. A relatively precise relationship was detected between the relative abundance of F. succinogenes (R² = 0.67) from qPCR and MiSeq sequencing, but weak relationships were detected for Megasphaera elsdenii, Ruminococcus flavefaciens, and S. ruminantium (R² ≤ 0.19).     

Purification and Characterization of Four Extracellular Proteases Isolated from Raw Milk Psychrotrophs

Extracellular proteases from psychrotrophic strains of Bacillus coagulans (LY 9), Bacillus sp. (LY 10), Bacillus subtilis (LY 11), and Pseudomonas fluorescens (LY 13) were purified and characterized. The molecular weight of the purified protease from Pseudomonas fluorescens LY 13 was 4.50 × 10⁴, and from the three Bacillus species ranged from 3.35 × 10⁴ to 3.90 × 10⁴. The proteases from LY 10 and LY 13 were monomeric proteins, whereas the protease from LY 9 was in a polymeric form that contained up to 14 subunits. Only the protease from Pseudomonas fluorescens LY 13 showed trypsin-like activity. All four proteases were inhibited by ethylenediaminetetraacetate and would be classified as metallo proteases. Casein was the preferred substrate for these proteases. Susceptibility of casein fractions to attack by these proteases varied with the enzyme source. Maximum enzyme activity was between pH 6.5 and 7.5. The protease from Pseudomonas fluorescens LY 13 retained more activity after heating at 63°C for 30 min than the proteases from the three Bacillus species. Calcium ion showed a protective effect by decreasing heat denaturation of the proteases from LY 9 and LY 11. This protective effect tended to be greater in the presence of Tris-HC1 buffer (.05 M, pH 7.5) plus 10% skim milk than in buffer only.     

alpha-Amylase activity in rumen fluid of cows producing milk of low and normal fat content

α-Amylase activity in cell-free rumen fluid from lactating cows was measured by Phadebas amylase test. Effects of handling and storage of rumen fluid on α-amylase activity were determined. Assays of 35,000 × g centrifuged rumen fluid stored at ?18 °C showed good reproducibility, while reproducibility of assays of samples uncentrifuged prior to freezing was poor. In frozen stored samples of rumen fluid centrifuged at 35,000 × g or 3,200 × g, α-amylase activity decreased, whereas in frozen uncentrifuged samples α-amylase activity increased with storage time. α-Amylase activity was high and showed wide variations in one cow with experimentally induced low milk fat syndrome. Enzymatic activity was correlated negatively with rumen pH and positively with total concentration of volatile fatty acids. α-Amylase activity was significantly higher in rumen fluid samples from cows with low milk fat in conventional herds compared to cows with normal milk fat in the same herds. Enzymatic activity showed negative correlation coefficients with milk fat percentage and positive with total viable counts of rumen bacteria and mole percent of rumen propionic acid in the low milk fat cows but not in the cows with normal milk fat. α-Amylase activity in cell-free rumen fluid may be a useful indicator of activity of starch-hydrolyzing rumen microorganisms.     

Regulation of Cortisol Uptake in Mammary Tissue of Cows

Mammary tissue explants from four nonlactating, nonpregnant cows were placed into culture with media containing various combinations of insulin, prolactin, growth hormone, 17β-estradiol, dexamethasone, and progesterone. Combinations of insulin, prolactin, growth hormone, or 17β-estradiol had no effect on cytoplasmic or nuclear uptake of tritiated cortisol compared with values at zero time. Combinations containing dexamethasone or progesterone reduced cytoplasmic and nuclear uptake of tritiated cortisol. To examine inhibition by progesterone of binding of tritiated cortisol, mammary tissue from each of four lactating, nonpregnant and four nonlactating, nonpregnant cows were placed in flasks containing tissue culture medium 199, tritiated cortisol (2 ng/ml), and progesterone at concentrations of 0, 10^?12, 10^?11, 10^?10, 10^?9, 10^?8, 10^?7, 10^?6, or 10^?5 × 6.4 M. Cytoplasmic uptake of tritiated cortisol into nonlactating tissue decreased linearly as progesterone increased, whereas tritiated cortisol uptake in lactating tissue did not decrease until progesterone exceeded 10^?7 M. We postulated progesterone is sequestered in milk fat of cytoplasm of lactating tissue whereas in nonlactating tissue progesterone is available to compete with cortisol at sites of cortisol binding.     

Effect of Masonex and Forms of Cottonseed Hulls on Dairy Cows

Thirty-six lactating Holstein cows were in a 5 × 3 factorial partially balanced incomplete block design with three missing categories to study effects of different forms of cottonseed hulls and liquid supplements on milk production and composition. Roughages were regular cottonseed hulls, pelleted cottonseed hulls, pelleted cottonseed hulls with 9% fat, pelleted undelinted cottonseed hulls, and pelleted undelinted cottonseed hulls with 9% fat. Liquid supplements were 8% Masonex² (hemicellulose extract) and 8% cane molasses. Control had no supplement. All rations were adjusted to contain 30% cottonseed hulls. Roughages with added fat gave total rations of 2.5% added fat (air dry).Least square means for daily intake of dry matter, milk yield, and fat percent were regular cottonseed hulls 21.6 kg, 20.3 kg, 3.37%; pelleted cottonseed hulls 20.3 kg, 21.4 kg, 3.06%; pelleted cottonseed hulls plus fat 20.1 kg, 21.2 kg, 2.51%; pelleted undelinted cottonseed plus fat 19.4 kg, 20.9 kg, 2.73%. Pelleted cottonseed hulls increased milk yield, decreased dry matter intake and milk fat percent, but did not affect milk fat yields. Rations with pelleted undelinted cottonseed hulls resulted in higher milk fat percent and body weight than pelleted cottonseed hulls. Added fat decreased milk fat percent and yield because of high degree of unsaturation. Liquid treatments produced no detectable effects on dry matter intake, milk yield, or fat percent.     

Lipolytic Enzyme Activity of Macrophages in Bovine Mammary Gland Secretions

The ability of macrophages isolated from the involuted bovine mammary gland and pooled raw milk to secrete lipolytic enzymes was investigated. Macrophages obtained from the involuted gland and maintained in cell culture secreted lipolytic enzymes into culture medium for up to 120 h. Leukocytes in pooled raw milk were separated using Ficoll discontinuous density gradients. Macro-phages secreted lipolytic enzymes into the gradient while fractions containing polymorphonuclear leukocytes and lymphocytes did not possess lipolytic activity. Enzyme activity of macrophages from pooled raw milk averaged .1% of the total milk lipoprotein lipase activity present in the original milk samples. Fresh raw milk with a macrophage concentration increased to 2.5 × 10⁶ cells/ml contained 11.6% higher milk lipoprotein lipase activity after storage for 48 h at 4°C. These results indicate that macrophages isolated from bovine mammary secretions produce lipolytic enzymes that could influence milk lipoprotein lipase activity in raw milk over storage.     

Persistence of chlorpyrifos-methyl in corn silage and effects of feeding dairy cows the treated silage

Corn was sprayed in the field at dent stage of maturity with chlorpyrifos-methyl [O, O,-dimethyl O-(3, 5, 6-trichloro-2-pyridyl) phosphorothioate] at .56, 1.12, and 2.24 kg per hectare, ensiled 1 day later, and methodology for detection of residues was developed. Losses of total residues (chlorpyrifos-methyl and its pyridinol hydrolysis product) through 83 days of ensiling were equivalent to 55, 71, and 76% of that applied. Beginning 83 days post ensiling, control and treated silages were fed to 16 cows, 4 per treatment, for 42 days during which chlorpyrifos-methyl averaged .35, .87, and 1.85 ppm, and was stable. The pyridinol averaged .44, .79, and 1.75 ppm but continued to decline and during the last week of feeding averaged only 32% of that in silage fed the 1st wk. Residue intakes amounted to .009, .022, and .054 mg chlorpyrifos-methyl and .012, .020, and .051 mg of pyridinolk/g body weight and failed to affect silage intake, milk production, blood cholinesterase activity, or body weight gains. Traces of chlorpyrifos-methyl (.003 ppm or less) were only in milk from cows on the 2.24 kg treatment. Milk from all cows fed treated silage contained traces of the pyridinol (.011 ppm or less). No trace of the O-analog of chlorpyrifos-methyl was in any sample, and all milk, urine, and feces were free of residues within 1 wk after the cows were withdrawn from treated silage.     

Behavior, milk yield, and leucocytes of dairy cows in reduced space and isolation

Space was reduced from 9.3 to 2.3 m²/cow during wk 2 and 4 for a group of 17 cows in a 4 wk study. Dominance rank was estimated from observation during 9 previous and 4 current wk. Leucocytes were determined from weekly quarter samples. The lot was marked into 5.9 m² squares. Cows were observed during three 1 h periods following feeding for each lot size. Cows with 2.3 m²/cow entered fewer squares and had fewer herdmate encounters. Cows low in dominance rank moved about more than dominant herdmates as the correlation between dominance rank and squares entered was .33. Lot size did not affect daily milk yield. Cows at 9.3 m²/cow had higher leucocytes than at 2.3 m²/cow. At the end of this study six cows were singly isolated 24 h in a holding pen 1.8 × 2.3 m. Feed and water were provided. Milk yield was not affected. Leucocytes in samples taken initially and at 6 h intervals during isolation increased generally but not significantly above the mean for 13 wk previous.     

Milk Somatic Cells and Lactation in Small Ruminants

The milk somatic cell count (MSCC) is the basis for abnormal milk control programs. The current legal MSCC limit for bulk tank milk for goats and sheep in the United States is 1000 and 750 × 10³/ml, respectively. Milk somatic cell counts for goats are higher than MSCC for cows and sheep. The MSCC for goats free from intramammary infection (IMI) range from 270 to 2,000 × 10³/ml. Cell counts for sheep are similar to cows and range from 10 to 200 × 10³/ml. Neutro-phils comprise the major cell type in milk from uninfected goats and constitute 45 to 74% of the MSCC, compared with 2 to 28% for sheep and cows. The macrophage is the major cell type in milk from cows and sheep. Milk secretion in goats and sheep is largely apocrine in nature and cytoplasmic particles, similar in size to milk somatic cells, are normal constituents of their milk. Concentrations of cytoplasmic particles in sheep milk average 15 × 10³/ml, while goat milk averages 150 × 10³/ml. Therefore, to obtain accurate MSCC for goats, only cell counting procedures specific for DNA should be used. While IMI significantly increases MSCC for goats and sheep, noninfectious factors such as parity, stage of lactation, season and milk yield have been related to increased MSCC. An increase in MSCC for goats has been shown to decrease milk and fat yields. Intramammary infusion of antibiotics at dry-off and postmilking teat dipping in goats decreased the rate of new IMI and MSCC. Thus, mastitis control practices shown to be efficacious in cows are also effective in goats.     

Short communication: Effects of prill size of a palmitic acid–enriched fat supplement on the yield of milk and milk components,and nutrient digestibility of dairy cows

The objective of our experiment was to evaluate the effects of prill size of a palmitic acid–enriched fatty acid supplement (PA; 85% C16:0) on feed intake, nutrient digestibility, and production responses of dairy cows. Twenty-four primiparous and multiparous Holstein cows were assigned based on parity and production level to replicated 4 × 4 Latin squares balanced for carryover effects with 21-d periods. Treatments were a control diet (no added PA), or 2.0% PA added as a small prill size (PA-SM; 284 ± 12.4 µm), a medium prill size (PA-MD; 325 ± 14.7 µm), or a large prill size (PA-LG; 600 ± 17.4 µm) supplement. Overall, PA treatments increased milk fat content (4.25 vs. 3.99%), milk fat yield (1.48 vs. 1.39 kg/d), 3.5% fat-corrected milk (39.2 vs. 37.7 kg/d), and improved feed efficiency (fat-corrected milk:dry matter intake; 1.51 vs. 1.42) compared with control. Compared with control, PA treatments did not affect dry matter intake, body weight, body condition score, or yields of milk, protein, and lactose. The PA treatments increased neutral detergent fiber digestibility (44.8 vs. 42.4%) and reduced the digestibility of 16-carbon fatty acids (72.3 vs. 79.1%) and total fatty acids (76.6 vs. 80.3%). Compared with control, PA treatments reduced the contents of de novo synthesized milk fatty acids (23.0 vs. 25.8 g/100 g of fatty acids) and preformed milk fatty acids (36.3 vs. 39.1 g/100 g of fatty acids), but did not affect their yields. In contrast, PA treatments increased the content (40.8 vs. 35.1 g/100 g of fatty acids) and yield (570 vs. 436 g/d) of 16-carbon milk fatty acids compared with control. The PA prill size had no effect on dry matter intake, yield of milk and milk components, or feed efficiency. However, PA-LG tended to increase milk fat content compared with PA-SM (4.28 vs. 4.22%), and it increased 16-carbon fatty acid digestibility compared with PA-MD (74.2 vs. 71.0%) and PA-SM (74.2 vs. 71.7%). Additionally, PA-LG increased total fatty acid digestibility compared with PA-MD (78.1 vs. 75.6%) and PA-SM (78.1 vs. 76.0%). Results demonstrate that PA increased milk fat content and yield, and feed efficiency. Reducing prill size decreased fatty acid digestibility, but it had no effect on animal performance under the dietary conditions and prill sizes evaluated.     

Chymotrypsin from the hepatopancreas of cuttlefish (Sepia officinalis) with high activity in the hydrolysis of long chain peptide substrates: Purification and biochemical characterisation

Chymotrypsin from the hepatopancreas of cuttlefish (Sepia officinalis) was purified to homogeneity, with a 120-fold increase in specific activity and 23% recovery. The molecular weight of the purified chymotrypsin was estimated to be 28 kDa by sodium dodecyl sulphate–polyacrylamide gel electrophoresis. The optimum pH and temperature for the chymotrypsin activity were pH 8.5 and 55 °C, respectively, using succinyl-l-ala-ala-pro-l-phenylalanine-p-nitroanilide (SAAPFpNA) as a substrate. The enzyme was extremely stable in the pH range of 7.0–10.0 and highly stable up to 50 °C after 1 h incubation. This proteinase was strongly inhibited by chymostatin, soybean trypsin inhibitor, diisopropylfluorophosphate and phenylmethylsulfonyl fluoride, but was not inhibited by tosyl-l-phenylalanine chloromethyl ketone, N-carbobenzoxy-phenylalanine chloromethyl ketone or N_α-tosyl-l-lysine chloromethyl ketone. The enzyme hydrolysed long chymotrypsin peptide substrates SAAPFpNA, SAAPLpNA and ZAALpNA and did not hydrolyse short chymotrypsin substrates. Kinetic parameters of the enzymatic reaction demonstrated that the best substrate was SAAPFpNA, with k_cat 18 s^?1 and K_m 22 μM. However, the enzyme had a lower K_m for SAAPLpNA, 54 μM.The N-terminal amino acid sequence of the first 20 amino acids of the purified chymotrypsin was IVGGQEATIGEYPWQAALQV.     

Exogenous β-mannanase improves feed conversion efficiency and reduces somatic cell count in dairy cattle

Exogenous fibrolytic enzymes have been shown to be a promising way to improve feed conversion efficiency (FCE). β-Mannanase is an important enzyme digesting the polysaccharide β-mannan in hemicellulose. Supplementation of diets with β-mannanase to improve FCE has been more extensively studied in nonruminants than in ruminants. The objective of this study was to investigate the effects of β-mannanase supplementation on nutrient digestibility, FCE, and nitrogen utilization in lactating Holstein dairy cows. Twelve post-peak-lactation multiparous Holstein cows producing 45.5 ± 6.6 kg/d of milk at 116 ± 19.0 d in milk were randomly allotted to 1 of 3 treatments in a 3 × 3 Latin square design with 3 periods of 18 d (15 d for adaptation plus 3 d for sample collection). All cows were fed the same basal diet and the 3 treatments differed only by the β-mannanase dose: 0% dry matter (DM; control), 0.1% of DM (low supplement, LS), and 0.2% of DM (high supplement, HS) supplemented to the basal diet. Supplementation of β-mannanase enzyme at the LS dose reduced dry matter intake (DMI) but did not affect milk yield or milk composition. Cows receiving LS produced 90 g more milk per kg of DMI compared with control cows. Somatic cell count (SCC) in milk was lower for cows fed the LS diet compared with cows fed control diets. Cows fed LS diet had lower DM, organic matter and crude protein digestibility compared with cows fed control diets. Starch, neutral detergent fiber, and acid detergent fiber digestibility were not affected by LS. Milk yield, DMI, SCC, and nutrient digestibility did not change for HS. Despite the reduced crude protein digestibility, reduced N intake led to similar fecal N excretions in LS cows and control cows (234 vs. 235 g/cow per day). Urinary N excretions remained similar between enzyme-fed and control cows (~190 g/cow per day), although the percentage of N intake partitioned to urinary N tended to be greater in LS than in control cows (31 vs. 27%). Cows fed LS significantly improved the percentage of apparently absorbed N partitioned to milk protein N (42 vs. 38%). When supplemented at 0.1% of dietary DM, β-mannanase can improve FCE and lower the SCC of dairy cows without affecting milk yield, milk composition, or total manure N excretions of dairy cows.     

Estimation of Residual Pepsin and Chymosin Activity in Curd,

Pasteurized milk (225 g) adjusted to pH 6.2 was set with 3.5 milk clotting units of chymosin (EC 3.4.23.4). The same amount of milk at pH 5.8 was set with 3.5 milk clotting units of porcine pepsin (EC 3.4.23.1). Fifteen minutes after clotting, the curd was broken, and curd and whey were separated by centrifugation at 3500 × g for 20 min. The curd (30 g) was extracted at pH 6.8 in 450 ml water or at pH 6.2 (chymosin) or 5.8 (pepsin) in 450 ml 1 M sodium chloride.Chymosin was completely released from the curd and accounted for by both methods of extraction. Pepsin was completely released and accounted for after extraction in 1 M sodium chloride at pH 5.8 but was partly inactivated during extraction at pH 6.8.Assay of curd extracts and whey by a linear agar diffusion test accounted for 102 ± 6% of the pepsin activity added to milk when the curd was extracted in 1 M sodium chloride. Extraction at pH 6.8 allowed recovery of only 63% of the activity. Chymosin recovery was 100 ± 5% by both methods of curd extraction.     

By-Product Feeds for Lactating Dairy Cows: Effects of Cottonseed Hulls,Sunflower Hulls,Corrugated Paper,Peanut Hulls,Sugarcane Bagasse,and Whole Cottonseed with Additives of Fat,Sodium Bicarbonate,and Aspergillus oryzae Product on Milk Production

In Experiment 1, Holstein cows (32) fed diets in three 28-day periods were used to evaluate a 3 × 2 × 2 factorial arrangement of fiber sources (sunflower hulls, pelleted cottonseed hulls, and pelleted undelinted cottonseed hulls at 35% of dry matter), fat (0 or 2.5%). and sodium bicarbonate (0 or 1.0%). Sixteen cows also received Aspergillus oryzae product (56.7 g/day) continuously. Sunflower hulls decreased daily intake (19.4 versus 25.1 kg), milk (23.3 versus 26.5 kg), milk protein (2.85 versus 2.95%), and body weight change (?.08 versus .90 kg), but milk fat percent was higher (3.54 versus 3.32%). Sunflower hulls depressed digestibility of dry matter, organic matter, and acid detergent fiber. Added fat reduced milk fat and protein percents. Experiment 2 evaluated fiber sources (20% ground corrugated cardboard boxes, combination of 10% cardboard and 10% peanut hulls, or 30% cottonseed hulls), animal fat (0 or 2.5%), sodium bicarbonate (0 or .75%), and condensed molasses solubles by-product from rum distilling (0 or 10%). Corrugated boxes effected lowest intake (18.0 kg/day), cottonseed hulls highest intake (23.5 kg/day), and combination intermediate (20.2 kg/day). Added fat depressed fat percent. Condensed molasses solubles lowered milk yield but increased milk fat percent (3.76 versus 3.30), molar percent of acetic acid, and ratio of acetic to propionic. In two other experiments whole cottonseed (12.5 or 15% of dry matter) with corn silage, pelleted steam pressure treated sugarcane bagasse, or cottonseed hulls increased milk yield but decreased milk fat percent, especially with pelleted bagasse.     

A Naturally Buffered Bulk Retentate Starter from Ultrafiltered Milk

Whole milk was ultrafiltered to approximately 4:1 protein concentration, heated to 85°C for 30 min, and cooled to 22°C. It was inoculated with a commercial frozen concentrated lactic starter to give approximately 10⁷ cfu/ml and incubated at 22°C for 12 h. A commercial phage inhibitory medium and 11% nonfat dry milk were used as controls. After 12 h, retentate had significantly higher colony forming units per milliliter (3.2 × 10⁹) and pH (5.21) than phage inhibitory medium (2.5 × 10⁹ and pH 5.02) and nonfat dry milk (2.4 × 10⁹ and pH 4.58). Retentate starter and phage inhibitory medium starter had equal activity in skim milk (.3% developed acidity in 4 h at 32°C) whereas nonfat dry milk starter had significantly lower activity (.26% developed acidity). After a further 8 h incubation at 22°C, retentate starter had the highest pH (4.95) compared with phage inhibitory medium (4.76) and nonfat dry milk (4.51). At this time retentate starter activity was higher (.3%) than phage inhibitory medium (.27%) and nonfat dry milk (.19%). In highly concentrated retentates (3.5:1 and 5:1), retentate starter lowered pH considerably quicker than nonfat dry milk starter.     

Effect of incremental amounts of camelina oil on milk fatty acid composition in lactating cows fed diets based on a mixture of grass and red clover silage and concentrates containing camelina expeller

Camelina is an ancient oilseed crop that produces an oil rich in cis-9,cis-12 18:2 (linoleic acid, LA) and cis-9,cis-12,cis-15 18:3 (α-linolenic acid, ALA); however, reports on the use of camelina oil (CO) for ruminants are limited. The present study investigated the effects of incremental CO supplementation on animal performance, milk fatty acid (FA) composition, and milk sensory quality. Eight Finnish Ayrshire cows (91 d in milk) were used in replicated 4 × 4 Latin squares with 21-d periods. Treatments comprised 4 concentrates (12 kg/d on an air-dry basis) based on cereals and camelina expeller containing 0 (control), 2, 4, or 6% CO on an air-dry basis. Cows were offered a mixture of grass and red clover silage (RCS; 1:1 on a dry matter basis) ad libitum. Incremental CO supplementation linearly decreased silage and total dry matter intake, and linearly increased LA, ALA, and total FA intake. Treatments had no effect on whole-tract apparent organic matter or fiber digestibility and did not have a major influence on rumen fermentation. Supplements of CO quadratically decreased daily milk and lactose yields and linearly decreased milk protein yield and milk taste panel score from 4.2 to 3.6 [on a scale of 1 (poor) to 5 (excellent)], without altering milk fat yield. Inclusion of CO linearly decreased the proportions of saturated FA synthesized de novo (4:0 to 16:0), without altering milk fat 18:0, cis-9 18:1, LA, and ALA concentrations. Milk fat 18:0 was low (<5 g/100 g of FA) across all treatments. Increases in CO linearly decreased the proportions of total saturates from 58 to 45 g/100 g of FA and linearly enriched trans-11 18:1, cis-9,trans-11 18:2, and trans-11,cis-15 18:2 from 5.2, 2.6, and 1.7 to 11, 4.3, and 5.8 g/100 g of FA, respectively. Furthermore, CO quadratically decreased milk fat trans-10 18:1 and linearly decreased trans-10,cis-12 18:2 concentration. Overall, milk FA composition on all treatments suggested that one or more components in camelina seeds may inhibit the complete reduction of 18-carbon unsaturates in the rumen. In conclusion, CO decreased the secretion of saturated FA in milk and increased those of the trans-11 biohydrogenation pathway or their desaturation products. Despite increasing the intake of 18-carbon unsaturated FA, CO had no effect on the secretions of 18:0, cis-9 18:1, LA, or ALA in milk. Concentrates containing camelina expeller and 2% CO could be used for the commercial production of low-saturated milk from grass- and RCS-based diets without major adverse effects on animal performance.     

Prediction and validation of residual feed intake and dry matter intake in Danish lactating dairy cows using mid-infrared spectroscopy of milk

The present study explored the effectiveness of Fourier transform mid-infrared (FT-IR) spectral profiles as a predictor for dry matter intake (DMI) and residual feed intake (RFI). The partial least squares regression method was used to develop the prediction models. The models were validated using different external test sets, one randomly leaving out 20% of the records (validation A), the second randomly leaving out 20% of cows (validation B), and a third (for DMI prediction models) randomly leaving out one cow (validation C). The data included 1,044 records from 140 cows; 97 were Danish Holstein and 43 Danish Jersey. Results showed better accuracies for validation A compared with other validation methods. Milk yield (MY) contributed largely to DMI prediction; MY explained 59% of the variation and the validated model error root mean square error of prediction (RMSEP) was 2.24 kg. The model was improved by adding live weight (LW) as an additional predictor trait, where the accuracy R² increased from 0.59 to 0.72 and error RMSEP decreased from 2.24 to 1.83 kg. When only the milk FT-IR spectral profile was used in DMI prediction, a lower prediction ability was obtained, with R² = 0.30 and RMSEP = 2.91 kg. However, once the spectral information was added, along with MY and LW as predictors, model accuracy improved and R² increased to 0.81 and RMSEP decreased to 1.49 kg. Prediction accuracies of RFI changed throughout lactation. The RFI prediction model for the early-lactation stage was better compared with across lactation or mid- and late-lactation stages, with R² = 0.46 and RMSEP = 1.70. The most important spectral wavenumbers that contributed to DMI and RFI prediction models included fat, protein, and lactose peaks. Comparable prediction results were obtained when using infrared-predicted fat, protein, and lactose instead of full spectra, indicating that FT-IR spectral data do not add significant new information to improve DMI and RFI prediction models. Therefore, in practice, if full FT-IR spectral data are not stored, it is possible to achieve similar DMI or RFI prediction results based on standard milk control data. For DMI, the milk fat region was responsible for the major variation in milk spectra; for RFI, the major variation in milk spectra was within the milk protein region.     

Composition and Distribution of Lipids of Goats’ Milk

Fresh commercial goats’ milks were examined for their lipid contents and distribution of these lipids among milk fractions. Whole milk, skim milk (produced by centrifugation at 330 and 2,000 × g), and cream were studied. Petroleum ether (free lipids) and chloroform methanol (2:1) (bound lipids) were used successively to extract the lipids from all milk fractions. Average total lipid content for five bulk milk samples was 5.0 ± 1.2%. Lipid fractions of whole milk and cream contained 97 to 99% free lipid and 1 to 3% bound lipid, respectively. Free lipid was 96.8% triglyceride, whereas bound lipids contained neutral lipid, glycolipid, and phospholipid. In this respect, goats’ milk resembled cows’ milk. However, goats’ skim milk fractions contained significantly more free lipid than did cows’ milk. This free lipid, investigated in detail by gas chromatography, was shown similar in triglyceride distribution and fatty acid content to whole goats’ milk triglyceride. Quantitative data for the triglyceride distribution in all fractions are given and differ from published data for fresh goats’ milk.     

Predicting cutting and clotting time of coagulating goat's milk using diffuse reflectance: effect of pH,temperature and enzyme concentration

A diffuse reflectance sensor, which used optical fibres and near-infrared radiation (NIR) at 880 nm, was used to monitor goat's milk coagulation. A randomised block design replicated three times was utilized to test the effects of pH, temperature and enzyme concentration on diffuse reflectance parameters. Milk pH was adjusted to three levels (5.5, 6.0 and 6.5) and coagulated at three different temperatures (28, 32 and 36°C), using three enzyme concentrations (0.020, 0.035 and 0.050 mL kg⁻¹ of milk). A linear cutting time prediction equation, T_cut=βT_max, was found to predict visual cutting time with a standard error of prediction of 84.5 s and an R² of 0.9785. β was affected by pH, temperature and enzyme concentration. The diffuse reflectance parameter (T_max) was strongly correlated to the Berridge clotting time (R²=0.9913). Parameters generated from the diffuse reflectance profiles, with the exception of response-based parameters, were found to be a function of coagulation rate.