Design and use of 16S ribosomal DNA-directed primers in competitive PCRs to enumerate proteolytic bacteria in the rumen.

Competitive Polymerase Chain Reaction primers were designed for Streptococcus, B. fibrisolvens, P. bryantii, Eubacterium sp., Prevotella, and a universal primer for the eubacteria. DNA was extracted from rumen contents collected from eight dairy cows fed four diets: adequate nitrogen, adequate nitrogen plus carbohydrate, low nitrogen, and low nitrogen plus carbohydrate. B. fibrisolvens was significantly higher on the adequate nitrogen plus carbohydrate and the low nitrogen plus carbohydrate diets compared with the other diets, while P. bryantii was significantly higher on the low nitrogen plus carbohydrate diet compared with the adequate nitrogen diet. The population of Eubacterium sp. was significantly lower on both the adequate nitrogen plus carbohydrate and low nitrogen plus carbohydrate diets. Streptococcus populations were significantly lower on the low nitrogen plus carbohydrate diet compared with all three other diets, whereas there were no significant differences in populations of Prevotella or total eubacteria on any of the diets.

Partitioning of milk accumulation between cisternal and alveolar compartments of the bovine udder: relationship to production loss during once daily milking.

Experiments were undertaken to validate a method (using adrenaline injection) for determination of the size of cisternal and alveolar compartments in the udder, to use this method to determine the pattern of milk accumulation in the udder over time and to determine the relationship between the size of the alveolar and cisternal compartments and tolerance of once daily milking. Cows received intrajugular injections of adrenaline (3 mg) immediately before milking, to block milk ejection and allow harvesting of the cisternal milk fraction. This was followed by removal of the alveolar fraction 30 min later after intrajugular oxytocin (5 i.u.) injection. Results obtained were similar to those obtained by catheter drainage. The alveolar compartment was 90% full at 16 h post milking while the cisternal compartment filled more slowly and was only 70% full at 24 h post milking. At full capacity (measured at 40 h), the volumes of milk contained in the cisternal and alveolar compartments were similar. In a further experiment involving identical twin cows, it was shown that the greater the degree of filling of the cisternal compartment at 24 h, the lower was the production loss on once daily milking. This suggests that the freedom of the alveoli to drain was an important factor in the production loss on once daily milking. Although there were significant correlations within twin sets for milk yield and the size of udder compartments, the relationship within twin sets for yield loss on once daily milking was not statistically significant.

Use of a breath test to determine the fate of swallowed fluids in cattle.

OBJECTIVE: To investigate a [13C]octanoic acid breath test as a means of detecting reticular groove contraction in cattle. ANIMALS: 19 adult dairy cows with fistulated rumen, 10 yearling bulls, and 6 yearling steers. PROCEDURE: Cows were given 200 mg of [13C]octanoic acid in the caudal portion of the rumen, reticulum, or omasum/abomasum through the reticulo-omasal orifice, or were given the same dose of label with a drench of water or sodium bicarbonate. Collected breath was analyzed for 13C in CO2 for up to 3 hours. Breath of yearlings was analyzed for 13C in CO2 over 20 minutes after drenching with 200 mg of [13C]octanoic acid with water or sodium chloride and after sucking 200 mg of [13C]octanoic acid with molasses and water. RESULTS: In cows, enrichment of 13C in breath CO2 peaked at 20 to 30 minutes after placement of [13C]octanoic acid through the orifice, compared with a lower peak at 60 and 90 minutes after placement in the reticulum and rumen, respectively. The maximal increase in enrichment after placement of [13C]octanoic acid in the reticulum did not overlap with the minimal increase when placed through the reticulo-omasal orifice. Enrichment values in cows after drenching were consistent with values obtained after direct placement of [13C]octanoic acid. In yearlings, the inclusion of sodium chloride in the drench greatly increased enrichment, compared with water, but enrichment was greatest after sucking of the molasses, water, and [13C]octanoic acid combination. CONCLUSIONS AND CLINICAL RELEVANCE: This breath test provides a simple, repeatable, nonradioactive, and noninvasive means of detecting the fate of swallowed fluids in cattle, thus revealing the route taken of orally administered therapeutic agents or nutrients.

The relative abundance of a salivary protein, bSP30, is correlated with susceptibility to bloat in cattle herds selected for high or low bloat susceptibility.

Pasture bloat is a serious economic and animal welfare problem in cattle grazed on legumes in New Zealand. Analysis of salivary proteins from dairy cattle in herds bred for either low or high susceptibility to bloat has resulted in the identification of a 30 kilodalton protein, which we term bSP30, whose relative abundance is negatively correlated with bloat score (r = -0.40 +/- 0.12). From 74 animals sampled, relative abundance of bSP30 was 66 +/- 15% higher in the low-susceptibility herd than in the high-susceptibility herd. Relative abundance of bSP30 also varied significantly within individuals, according to feeding or time of day, and from day to day. A sequence homology search of 38 amino acids derived from three tryptic fragments of the protein suggests that the amino acid sequence of bSP30 has not been described previously. Amino acid analysis indicates that bSP30 is not a member of the proline-rich family of salivary proteins. The function of bSP30 is unknown but it is conceivable that it plays a role in the aetiology of bloat.

Effects of oxytocin, machine stripping and milking rate on production loss of cows milked once a day.

The effect of treatments designed to improve the efficiency of milk removal and minimize loss of production in cows milked once a day (OAD) was assessed in short-term trials involving Friesian and Jersey cows. Trial 1 involved 80 cows and compared twice a day (TAD) milking with OAD milking with the administration of 20 i.u. of oxytocin (OX), OAD milking with udder massage before and during milking (OS) and no treatment during OAD milking (OC). The OX and OS groups had increased yields of milk and milk solids when treatments were applied, though yields were not restored to previous TAD levels. The percentage increase shown by OX cows was greater than that of OS cows for fat yield. The level of residual milk in the udder after milking was lower for the OX group than for the OAD and TAD controls. In Trial 2, 12 cows were subjected to fast or slow rates of milking OAD in each of two periods. Losses in milk, fat and protein yields averaged 9.1, 9.9 and 1.0% respectively. Increased rate of milking reduced milking time and time to let-down but did not affect response to OAD milking. The results showed that treatments that increased the evacuation of the udder during milking and decreased the level of residual milk reduced losses in production that occur on OAD milking. Increasing the rate of milking was ineffective in reducing losses on OAD milking.

Monensin controlled-release intraruminal capsule for control of bloat in pastured dairy cows.

Monensin, a polyether ionophore antibiotic, is potentially an important agent for bloat relief in dairy cows grazing temperate legume-based pasture. A series of studies was undertaken to determine the effect of monensin, when delivered continuously in the rumen of lactating dairy cows by means of controlled-release capsules (monensin CRC). Such devices release approximately 300 mg/head/day for 100 d. A short-term pilot study made at Ruakura, New Zealand, tested monensin CRC in cows selected for high susceptibility to bloat and grazing lucerne (Medicago sativa) or red clover (Trifolium pratense). Treatment significantly reduced the incidence of bloat, while milk yield and protein yield were increased. There was no effect on fat yield. Following the pilot study, 6 large-scale field experiments involving a total of 368 lactating dairy cows, were made in Australia and New Zealand to confirm the effectiveness of monensin CRC for bloat control and to measure the effect of such treatment on milk production and composition. A severe bloat problem occurred in 2 experiments, mild bloat occurred in 2 others, while no visual signs of bloat were observed in the remaining 2 experiments. Bloat was significantly (P less than 0.05) reduced by monensin CRC treatment when data was pooled over the 4 experiments in which bloat occurred. Daily milk yield was increased in all experiments from a mean of 17.7 in untreated groups to 18.8 kg/head/day (P less than 0.05) in monensin CRC-treated cows. Protein percentage was not affected by treatment, while there was a decrease from 4.29 to 4.10% fat, although total fat yield was not affected.(ABSTRACT TRUNCATED AT 250 WORDS)