Changing adrenergic sensitivity of the caruncular arterial vasculature supplying the bovine placentome

With the advancement of gestation, blood flow increases preferentially to the caruncular bed of the gravid uterus in association with a decreasing sensitivity of the uterus to the vasoconstrictive effects of circulating catecholamines. This study directly compared the sensitivity of the caruncular artery (CA) of the isolated bovine placentome to phenylephrine (PE), a specific alpha 1-adrenergic receptor (AR) agonist, with that to norepinephrine (NE) and epinephrine (E), both of which are alpha 1-, alpha 2-, and beta-AR agonists, at two stages of gestation (140 to 170 d, mid-pregnant; 210 to 270 d, late pregnant). The CA of each placentome was perfused with oxygenated Krebs Ringer solution into which PE, NE or E were administered; increases in intra-arterial pressure were recorded. Further, NE content and numbers of alpha 1- and alpha 2-AR in the CA, intercaruncular arteries (ICA) and uterine arteries (UA) were quantitated. The CA from mid-pregnant cows exhibited greater (P less than .05) contractile responses to NE and E than did the CA from late pregnant cows, whereas responsiveness to PE remained constant. No difference in NE content, alpha 1-AR or alpha 2-AR numbers were observed in the UA, ICA or CA between mid-pregnant or late pregnant cows. Alpha 1-AR numbers were similar in CA, ICA and UA. However, CA contained threefold greater alpha 2-AR numbers than either the ICA or UA (50.2 +/- 6.1 vs 14.6 +/- 1.6 and 14.8 +/- 2.4 fmol/mg protein, respectively; P less than .01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Aspects of reproduction in female Bos indicus cattle: a review

SUMMARY Differences occur between female Bos indicus and Bos taurus cattle in various aspects of reproductive physiology and behaviour. These may be associated with different natural and human selection pressures, compounded by strong genotype-environment interactions. B indicus cattle are better adapted for tropical environments (despite overall poor cattle reproductive rates in these regions) which tend to be more stressful for B taurus genotypes. Conversely, B taurus cattle generally show superior reproductive and productive traits under more favoured, temperate conditions. Despite genotype-environment effects, B indicus females are generally considered to take longer to achieve puberty and to have longer gestation lengths, exhibit prolonged postpartum anoestrus, show greater seasonality of reproductive traits (tending to be long-day breeders), display a shorter, less overt oestrus as well as less tendency to allow riding behaviour by subordinate females. Some groups appear to have increased losses both during pregnancy and in the neonatal period. On the positive side, B indicus females respond well to managerial and nutritional interventions, tend to have greater reproductive longevity and they generally exhibit strong maternal traits. Culling of infertile females and selection for greater male scrotal circumference and sex-drive, in conjunction with the use of target weights, body condition scoring and weaning stratagems can improve reproductive rates in B indicus females.     

Cardiac lesions in rats fed rapeseed oils.

Fully refined rapeseed oils containing different amounts of erucic acid (1.6%, 4.3% and 22.3%) were fed, at 20% by weight of diet, to weanling male and female Sprague-Dawley rats for periods up to 112 days. Transient myocardial lipidosis characterized by accumulation of fat droplets in myocardial fibers was marked in male and female rats fed oxidized and unoxidized rapeseed oil containing 22.3% erucic acid, moderate with rapeseed oil containing 4.3% erucic acid and very slight in rats fed rapeseed oil containing 1.6% erucic acid. Peak intensity of myocardial lipidosis occurred at three to seven days and regressed thereafter. Focal myocardial necrosis and fibrosis occurred in male rats fed rapeseed oils containing different levels of erucic acid for 112 days. The incidence of myocardial necrosis and fibrosis was markedly lower in female rats, and the incidence of these lesions in either sex was not affected by the state of oxidation of these oils. In a second experiment, male rats were fed diets containing crude, partially refined or fully refined rapeseed oils. There was no correlation between the number of foci of myocardial necrosis and fibrosis and the state of refinement of the oils, but there were generally fewer lesions in rats fed those oils having the lowest levels of erucic acid.     

Prickly paddy melon (Cucumis myriocarpus) poisoning of cattle

Twenty-six Hereford heifers died after eating mostly ripe fruit of Cucumis myriocarpus growing in a fallowed cultivation paddock. Four affected cattle were dehydrated and apparently had abdominal pain. Necropsy of three revealed intense congestion with haemorrhage of the alimentary tract, numerous C. myriocarpus seeds in ruminal contents, pulmonary congestion and oedema and, in two, swollen livers. Midzonal swelling and vacuolation of hepatocytes occurred in these two. C. myriocarpus fruit (83% by weight ripe) were dosed to two calves at 60 g wet weight/kg live weight. Both collapsed with tachycardia and dyspnoea and died within 6 h. Their packed cell volumes just before death had increased to 0.7. They had hydropic degeneration and necrosis of the ruminal mucosa, intense congestion and oedema of the rumen, abomasum and intestines, swollen and vacuolated hepatocytes and foci of myocardial degeneration and necrosis. Two other calves were dosed daily with 20 g fruit/kg for three days, then 40 g/kg for three days. One calf received a further 40 g/kg next day. Both calves developed persistent diarrhoea and neutrophilia, and their plasma gamma glutamyltransferase and bilirubin concentrations increased. Necropsy revealed necrosis and oedema of the rumen and swollen degenerate hepatocytes.     

Effect of phytase supplementation to a low- and a high-phytate diet for growing pigs on the digestibilities of crude protein, amino acids, and energy

Supplementation of microbial phytase usually improves the digestibility and utilization of phosphorus in feedstuffs of plant origin. The effect of phytase supplementation on the digestibilities of AA also has been examined, but the results have been inconsistent. This study was carried out to determine the effect of phytase (Natuphos) supplementation, at a rate of 2,000 phytase units/kg, to two basal diets on the apparent ileal digestibilities (AID) of GE, CP, and AA, and on the apparent total-tract digestibilities (ATTD) of CP and GE. The basal diets contained 18% CP and were formulated (as-fed basis) to contain either a low (0.22%) or high content (0.48%) of phytate P. The high-phytate diet contained 20% rice bran, which is a rich source of phytate and has low intrinsic phytase activity. Eight barrows (average initial BW = 40.6 kg), fitted with a simple T-cannula at the distal ileum, were fed the four diets according to a replicated 4 x 4 Latin square design. The pigs were fed twice daily at 0800 and 2000, equal amounts each meal, at a rate of 2.4 times the daily maintenance requirement for ME. Each experimental period comprised 14 d. Ileal digesta were collected from 0800 to 2000 on d 12, 13, and 14. Feces were collected from 0800 on d 8 until 0800 on d 12. Chromic oxide was used as the digestibility marker. The AID of GE, CP, and AA and the ATTD of CP and GE were less in the high- than in the low-phytate diet (P < 0.01). With the exception of glutamic acid, phytase supplementation did not affect (P > 0.10) the AID of CP and AA. There was no effect (P > 0.05) of phytase on the ATTD of CP and GE. These results show that if a response occurs to phytase supplementation, it is independent of the dietary phytate content.     

Supplementation of xylanase and phospholipase to wheat-based diets for weaner pigs

The effects of supplementing a wheat-based diet for weaner pigs with exogenous xylanase and phospholipase on ileal and faecal nutrient digestibilities and on the level of microbial metabolites in ileal digesta were examined. Fourteen piglets, weaned at 11 days, were fitted with a simple T-cannula at the distal ileum. The pigs were offered a control diet or diets supplemented with xylanase and phospholipase individually or in combination, in a two period crossover design. The combination of xylanase and phospholipase tended to increase the ileal recovery of the amino sugar galactosamine, whereas the concentration expressed in mg/kg dry matter intake of glucosamine was slightly decreased (p < 0.10). There was neither an effect of enzyme supplementation on ileal and faecal digestibility of the other nutrients and energy, nor was there an effect on pH and on the level of microbial metabolites in ileal digesta. However, an increase in ileal and faecal nutrient and energy digestibility with increasing age was observed. The ileal and faecal digestibility coefficients (except for ether extract) were significantly (p < 0.05) higher in experimental period I than in period II. These higher values may be attributed to a lower feed intake during period I. Since a lower level of feed intake is generally associated with a slower rate of passage and a longer retention time of digesta, a positive impact on digestion and absorption of nutrients can be assumed, which, on the other hand, limits the potential of additional enzyme effects.