The effect of buffering dairy cow diets with limestone, calcareous marine algae, or sodium bicarbonate on ruminal pH profiles, production responses, and rumen fermentation.

Six ruminally cannulated Holstein cows were used to evaluate the effect of 2 dietary buffers on rumen pH, milk production, milk composition, and rumen fermentation parameters. A high concentrate total mixed ration [35.2% forage dry matter (DM)], formulated to be potentially acidotic, was used to construct 3 dietary treatments in which calcareous marine algae (calcified remains of the seaweed Lithothamnium calcareum) was compared with limestone (control) and sodium bicarbonate plus limestone. One basal diet was formulated and the treatment diets contained either 0.4% of dietary DM as Acid Buf, a calcified marine algae product (AB treatment), or 0.8% of dietary DM as sodium bicarbonate and 0.37% as limestone (BC treatment), or 0.35% of dietary DM as limestone [control (CON) treatment]. Cows were randomly allocated to treatments according to a double 3×3 Latin square design, with 3 treatments and 3 periods. The total experimental period was 66 d during which each cow received each treatment for a period of 15 d before the data collection period of 7 d. Rumen fluid was collected to determine volatile fatty acids, lactic acid, and ammonia concentrations. Rumen pH was monitored every 10min for 2 consecutive days using a portable data logging system fitted with in-dwelling electrodes. Milk samples were analyzed for solid and mineral contents. The effect of treatment on acidity was clearly visible, especially from the period from midday to midnight when rumen pH dropped below 5.5 for a longer period of time (13 h) in the CON treatment than in the BC (8.7 h) and AB (4 h) treatments. Daily milk, 4% fat-corrected milk, and energy-corrected milk yields differed among treatments, with AB being the highest, followed by BC and CON. Both buffers increased milk fat content. Treatment had no effect on milk protein content, but protein yield was increased in the AB treatment. Total rumen volatile fatty acids and acetate concentrations were higher and propionate was lower in the AB treatment than in CON. The molar proportion of acetate was higher in AB than in CON, but that of propionate was lower in both buffer treatments than in CON. The acetate:propionate ratio was increased in the AB and BC treatments compared with CON. Lactic acid concentration was higher in the CON treatment than in the buffer treatments. Treatment had no effect on rumen ammonia concentrations. Results indicated that buffer inclusion in high concentrate diets for lactating dairy cows had a positive effect on milk production and milk composition. Calcareous marine algae, at a level of 90 g/cow per day, had a greater effect on rumen pH, milk production and milk composition, and efficiency of feed conversion into milk than sodium bicarbonate at a level of 180 g/cow per day.

pH dynamics and bacterial community composition in the rumen of lactating dairy cows.

The influence of pH dynamics on ruminal bacterial community composition was studied in 8 ruminally cannulated Holstein cows fitted with indwelling electrodes that recorded pH at 10-min intervals over a 54-h period. Cows were fed a silage-based total mixed ration supplemented with monensin. Ruminal samples were collected each day just before feeding and at 3 and 6h after feeding. Solid and liquid phases were separated at collection, and extracted DNA was subjected to PCR amplification followed by automated ribosomal intergenic spacer analysis (ARISA). Although cows displayed widely different pH profiles (mean pH=6.11 to 6.51, diurnal pH range=0.45 to 1.39), correspondence analysis of the ARISA profiles revealed that 6 of the 8 cows showed very similar bacterial community compositions. The 2 cows having substantially different community compositions had intermediate mean pH values (6.30 and 6.33) and intermediate diurnal pH ranges (averaging 0.89 and 0.81 pH units). Fortuitously, these 2 cows alone also displayed milk fat depression, along with markedly higher ruminal populations of 1 bacterial operational taxonomic unit (OTU) and reduced populations of another ARISA amplicon. Cloning and sequencing of the elevated OTU revealed phylogenetic similarity to Megasphaera elsdenii, a species reportedly associated with milk fat depression. The higher populations of both M. elsdenii and OTU246 in these 2 cows were confirmed using quantitative real-time PCR (qPCR) with species-specific primers, and the fraction of total bacterial rDNA copies contributed by these 2 taxa were very highly correlated within individual cows. By contrast, the fraction of total bacterial rDNA copies contributed by Streptococcus bovis and genus Ruminococcus, 2 taxa expected to respond to ruminal pH, did not differ among cows (mean= <0.01 and 10.6%, respectively, of rRNA gene copies, determined by qPCR). The data indicate that cows with widely differing pH profiles can have similar ruminal bacterial community compositions, and that milk fat depression can occur at intermediate ruminal pH. The results support recent reports that milk fat depression is associated with shifts in bacterial community composition in rumine and is specifically related to the relative abundance of Megasphaera elsdenii.

Transfer of melamine from feed to milk and from milk to cheese and whey in lactating dairy cows fed single oral doses.

A study was conducted to evaluate the excretion pattern, after a single oral dose, of melamine from feed into milk, and the subsequent transfer to cheese and whey. The transfer of cyanuric acid was also investigated. Twenty-four lactating Holstein cows were randomly allocated to 4 treatments and received single doses of melamine as follows: 0.05, 0.50, 5.00, and 50.00 g/cow for groups D1, D2, D3, and D4, respectively. Individual milk samples were collected for melamine and cyanuric acid analyses on d 1, 2, 3, 4, 5, and 7. Milk collected individually from the second milking after melamine ingestion was used to make cheese on a laboratory scale. Melamine and cyanuric acid were extracted using a solid-phase extraction cartridge, and analyses were carried out by liquid chromatography-mass spectrometry/mass spectrometry. Maximal melamine concentrations occurred between 6 and 18 h after treatment and increased with log dose (linear and quadratic), ranging from 0.019 to 35.105 mg/kg. More than 60% of the melamine that was transferred to the milk was observed within 30 h after melamine ingestion. Melamine was not detected (limit of detection was 0.002 mg/kg) in milk 5 d after treatment in group D1, and 7 d after treatment in groups D2, D3, and D4. Blood urea nitrogen was not influenced by melamine ingestion. During cheese making, melamine was transferred mainly to the whey fraction. Cyanuric acid was not detected in any of the samples (milk, cheese, or whey). The excretion pattern of melamine in milk and whey may represent a health concern when cows ingest more than 0.50 g of melamine/d. However, only at intake levels of 5 and 50 g/d did cheese exceed the limits as set forth by the European Union. The results confirmed that melamine contamination of milk and milk products may be related not only to direct contamination, but also to adulteration of animal feeds.

Hot topic: pathway confirmed for the transmission of melamine from feed to cow's milk.

Eight lactating Holstein cows were randomly allotted to 2 groups in a trial to establish whether a pathway exists for the transmission of melamine from feed to milk. All cows received oat hay ad libitum and 15 kg of concentrate pellets per cow daily. The concentrate pellets contained either melamine-contaminated corn gluten meal of Chinese origin (melamine treatment) or locally produced melamine-free corn gluten meal (control treatment). Cows in the melamine treatment ingested 17.1 g of melamine per day. Cows were milked twice daily, and milk samples were taken once daily during the afternoon milking for melamine and milk component analyses. Melamine appeared in the milk within 8 h after first ingestion of the melamine containing pellets. Melamine concentration reached a maximum of 15.7 mg/kg within 56 h after first ingestion, with an excretion efficiency of approximately 2%. Milk solids and milk urea nitrogen were not affected by treatment. The melamine concentration dropped rapidly after changing all cows back to the control pellets, but melamine only declined to undetectable levels in the milk more than 6 d (152 h) after last ingestion of melamine. Results from the current trial are important to the feed and dairy industries because, until now, any melamine found in milk and milk products was attributed only to the deliberate external addition of melamine to these products, not to adulterated ingredients in animal feeds.

Technical note: A method to facilitate retrieval of polyester bags used in in sacco trials in ruminants.

A method is described to facilitate the retrieval of polyester bags from ruminally cannulated cattle. The system consists of 2 major components, i) an accommodation vessel for multiple polyester bags in the form of an opaque nylon stocking, referred to as the "receptacle," and ii) a shorter stocking, knotted with a loop on one end to attach to the receptacle, referred to as the "catcher." The catcher is tied on the other end to the inside of the cannula plug. Sample bags are inserted in tandem into the receptacle, separated from each other by a tight knot. The receptacle is tied to the catcher and subsequently inserted into the rumen. Upon retrieval, receptacles are pulled out only far enough to expose the first bag to be removed. This procedure ensures easy bag retrieval without exposing the remaining bags (intended for further incubation) to air.

Quantification of melamine absorption, distribution to tissues, and excretion by sheep.

Eight Döhne Merino rams were used to quantify apparent absorption, distribution to tissues, and excretion of dietary melamine in sheep. Two batches of concentrate pellets were made; one (CON) contained corn gluten meal with no detectable melamine and the other (MEL) contained corn gluten meal that was previously found to be highly contaminated with melamine at 15,117 mg/kg. The MEL pellets contained 1,149 mg/kg of melamine. During a 10-d adaptation period, all the animals received a forage-based diet supplemented with 600 g/d of the CON pellets. This was followed by an 8-d collection period during which 6 of the animals received MEL pellets and 2 received CON pellets. Melamine intake of sheep that received MEL pellets was 0.69 g/d. Blood samples were taken before first ingestion of MEL pellets on d 1 and again on d 3, 6, and 8 of the collection period for melamine and serum creatinine analyses. Feces and urine were collected quantitatively over the 8 d for proximate and melamine analyses. All the animals were slaughtered at the end of the trial, and samples of the LM, liver, kidneys, and abdominal fat were taken for melamine analysis. Data of the 2 sheep that received CON pellets for the duration of the trial confirmed that no melamine was detected in any of the samples, and no statistical analyses were performed on these data. The apparent digestibility or efficiency of absorption of ingested melamine was 76.7%. Melamine was detected in the urine, blood, muscle (LM), and fat tissue of all the sheep that received MEL pellets. Serum melamine concentrations reached 5.4 mg/kg on d 8 of the collection period, and the meat (LM) contained 9.6 mg/kg of melamine. Calculations on the partitioning of ingested melamine suggested that urine is the major excretion route accounting for 53.2%, whereas feces accounted for 23.3% of ingested melamine. Approximately 3.5% of the ingested melamine was detected in muscle. It was concluded that ingested melamine is highly absorbable from the small intestine and that a pathway exists for the distribution of dietary melamine to meat.

Effect of curd forming of colostrum on absorption of immunoglobulin G in newborn calves.

Pooled colostrum from the first three milkings postpartum was used in two trials to determine the effect of abomasal curd forming on absorption of IgG in newborn calves. In Experiment 1, two groups of seven Friesland calves each received 1 h postpartum 1 L of untreated colostrum or colostrum treated with an oxalic acid-sodium hydroxide buffer to prevent coagulation. Calves were not allowed to suckle their dams and received colostrum in teat bottles. The same treatments were applied for Experiment 2, except that eight calves per group were used, and each calf received 2 L colostrum. Blood samples were taken from the jugular vein 6 h postfeeding, and plasma IgG concentration was determined by a radial immunodiffusion technique. Plasma IgG concentration, estimated IgG absorption, and apparent efficiency of absorption 6 h postfeeding for the coagulable and noncoagulable treatments, respectively, were 11.6 and 6.6 mg/ml, 28.1 and 15.8 g/d, and 87.8 and 49.3% for Experiment 1; and 21.2 and 12.9 mg/ml, 48.6 and 34.2 g/d, and 60.8 and 42.8% for Experiment 2. It was concluded that the curd-forming ability of colostrum is an important factor in effective absorption of IgG by calves during the first 6 h postfeeding.

Effect of Lactobacillus acidophilus supplementation of milk replacer on preweaning performance of calves.

Forty Holstein-Friesian calves were used to evaluate the effect on young calves of daily dietary supplementation with Lactobacillus acidophilus. Calves were randomly assigned at 2 d of age to one of two treatments; 1) milk replacer with no additives or 2) milk replacer supplemented with 1 ml (5 x 10(7)) of viable L. acidophilus bacteria at each of two feedings per day. Milk replacer was reconstituted to 12% DM and fed at 10% of BW/d for the duration of the 6-wk trial. A commercial starter pellet was offered for ad libitum intake from 7 d of age. Treatment had no effect on actual BW at any stage or on total BW gain; however, average daily gain during wk 2 was affected by L. acidophilus supplementation. Calves receiving L. acidophilus maintained initial BW, and the control calves lost BW until 2 wk of age, at an average rate of 112 g/d. Starter intake, total DMI, feed efficiency, and occurrence of diarrhea were unaffected by treatment. Therefore, L. acidophilus supplementation for calves fed milk replacer may be beneficial during the first 2 wk of life.

Amino acid profile and intestinal digestibility in dairy cows of rumen-undegradable protein from various feedstuffs.

Three lactating cows fitted with rumen cannulas and three cows fitted with proximal duodenal cannulas were used to determine the effect of in situ rumen degradation on the AA profile of rumen-undegraded protein of 12 feedstuffs. Intestinal digestibility of rumen-undegraded protein was determined using the mobile bag technique. The absorbable AA profile of rumen-undegraded protein for each feedstuff was compared with profiles of the original feedstuff and the rumen-exposed undegraded protein. Branched-chain AA in particular seemed to be rather resistant to degradation in the rumen, as was Phe. Lysine concentrations decreased in the undegraded protein fraction in 9 of 12 feedstuffs; the degradation of Met depended on the feedstuff. The absorbable AA profiles of undegraded protein, in general, closely reflected the AA profiles of the rumen-exposed residues, which suggests that rumen degradation had a greater influence than postruminal digestion on the postruminal provision of specific absorbable AA. Intestinal digestibility of undegraded protein varied from 37.8% for Eragrostis curvula hay to 98% for soybean meal; the constant digestibility factor used by most protein systems should be reconsidered.