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ABSTRACT: L-methionine is a sulphur-containing nutritionally essential amino acid. It has a number of important roles in epidermal and dermal tissues of the integument of animals. Failure of normal function of these tissues in the hoof (claw) is a cause of lameness in cattle. Little is known about quantitative relationships between post-absorptive concentrations of nutrients including sulphur-containing amino acids and uptake and utilization by epidermis and dermis of the bovine claw. These parameters were studied at the tissue level by use of an established in vitro claw explant system using tissue from cattle of beef or dairy origin and L-[35S]-labelled methionine as tracer. The results showed that uptake of L-methionine by freshly prepared solear explants in Dulbecco's Modified Eagle Medium/F-12 Nutrient Mix (DMEM/F12) (1:1) medium containing 1·0 mmol L-methionine/litre was concentrative after 5–8 min, essentially linear for up to 10 min and became curvilinear thereafter. Maximum uptake and steady state conditions were obtained at approximately 30 min. Further measurements were made following 21 h incubation in culture medium. Under conditions of varying concentrations of L-methionine and measurement of uptake after 30 min, the presence of a saturable curve, that obeyed Michaelis–Menten kinetics, was demonstrated. Values of 3·61 mmol/litre and 5·84 mmol/kg intracellular water/30 min were obtained for KM and Vmax, respectively. Uptake was not influenced by L-cysteine and L-cystine concentrations in the culture media.Similar culture and incubation conditions were used in subsequent studies of DNA and protein synthesis. These showed that rates of incorporation of L-methionine into protein fractions and stimulation of DNA synthesis measured by methyl-thymidine incorporation were dependent on L-methionine concentrations in the medium. Maximal rates occurred at approximately 50 μmol/litre, which is in the normal physiological range, and at 1% of maximum uptake capacity. Examination of histological sections by autoradiography showed localization of L-[35S]-labelled methionine in basal and suprabasal epidermal cells with limited retention in dermis. Measurement, by a range of histological, immunohistochemical, electrophoretic, western blotting and autoradiographic techniques, provided further evidence of L-methionine-dependent regulation of proliferation, differentiation and synthesis of proteins under physiological concentrations, by epidermal horn-forming cells.A key role for L-methionine is suggested in the production of horn in bovine claw. The extrapolation of these in vitro data provides guidance for strategies to optimize methionine supply to claw tissues in vivo. Such extrapolation suggests the appropriateness of delivery of systemic concentrations of 50 μmol L-methionine/litre to maximize proliferative and protein depositional activity in solear epidermis and dermis in vivo.
The Journal of Agricultural Science 01/2008; 146(01):103 - 115. · 2.04 Impact Factor
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The Journal of Agricultural Science 11/2007; 145(06):623 - 633. · 2.04 Impact Factor
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ABSTRACT: The objectives were to establish the origin of 2 acute phase proteins in milk during subclinical bovine mastitis and to characterize the relationship between those proteins in milk and blood. Haptoglobin (Hp) and mammary-associated serum amyloid A (M-SAA3) appear in milk during mastitis, whereas Hp and serum amyloid A increase in serum during mastitis. The concentrations of these proteins were determined in an experimental model using a field strain of Staphylococcus aureus to induce subclinical mastitis in dairy cows. The expression of mRNA coding for these proteins was assessed and the presence of M-SAA3 in mammary tissues was determined using immunocytochemistry. Increases of M-SAA3 and Hp in milk occurred within 12 h of Staphylococcus aureus infusion, with peak concentrations occurring 3 d after infusion of the bacteria. The increase of acute phase proteins in milk (15 h) preceded the increase in serum concentrations of both proteins (24 h). Expression of mRNA for M-SAA3 and Hp increased in both mammary and hepatic tissues 48 h after infusion of the mammary glands. In mammary tissue, the increase of M-SAA3 mRNA was greater than the increase in Hp mRNA expression, whereas in hepatic tissue, the increase in M-SAA3 mRNA was less than that for Hp mRNA. Immunocytochemistry demonstrated that M-SAA3 protein was present within secretory epithelial cells at significantly higher levels in infected mammary glands than in control tissues. These proteins, which have host defense and antibacterial activities, may play a significant role in the early response to invasion of mammary tissues by pathogenic bacteria.
Journal of Dairy Science 06/2006; 89(5):1488-501. · 2.56 Impact Factor
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ABSTRACT: Three groups of four primiparous Holstein-Friesian heifers were fed throughout pregnancy either a control diet or that diet supplemented with either 5 to 6 g per day of rumen-protected intestinally available methionine or 25 mg melatonin. They were euthanased three days after calving. The dietary supplements had no effect on the impression hardness or the concentrations of cysteine and methionine in samples of claw horn collected from a range of sites, or on the areas of erosion in the sole and heel. Significant differences were recorded for the hardness of the horn in the order wall >sole >heel. These differences were associated with higher concentrations of cysteine and lower concentrations of methionine in samples of horn from the dorsal wall than in samples from the prebulbar region of the sole. There were no significant differences attributable to the dietary supplements in the soft tissue anatomy of the solear dermis and epidermis.
The Veterinary record 01/2006; 158(1):21. · 1.25 Impact Factor
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ABSTRACT: Two experiments were conducted to study changes induced by stage of lactation and milk ejection in the cisternal compartment of the udder in dairy cows. In experiment 1, 18 cows grouped according to stage of lactation were used 12 h after milking for measuring alveolar and cisternal milk volumes (by cannula) and cisternal area (by ultrasonography) in the front quarters. Cisternal milk and cisternal area were correlated (r = 0.74 to 0.82) for all stages of lactation. As lactation advanced, volumes of alveolar and cisternal milk and cisternal area decreased. Proportion of cisternal milk varied between stages (early, 33.2%; mid, 23.1%; and late, 42.6%). In experiment 2, 7 cows were used to show return of milk from cisternal to alveolar compartments when milk ejection was induced without milking. Cisternal area was measured before (0 min) and after (3, 15, 30, and 60 min) an i.v. oxytocin (OT) injection administered immediately before normal a.m. and p.m. milking times. Cisternal area increased dramatically from 0 to 3 min (98%) and decreased slowly thereafter. The 0- and 3-min data provide clear evidence of milk ejection, and their difference indicated cistern elasticity. Maximum cisternal area in each cow was similar for the 8- and 16-h milking intervals, indicating that in both cases the cistern was completely full of milk. Decrease in cisternal area after 3 min was significant at 15, 30, and 60 min. Decreased cisternal area was interpreted as the reflux of cisternal milk to the alveolar compartment. We termed this 'cisternal recoil.' In conclusion, ultrasonography was a useful method to evaluate dynamic changes in cisternal milk throughout lactation and after udder stimulation in dairy cows. Evidence exists that udder cisterns decrease when lactation advances and milk returns to the alveolar compartment when cows remain unmilked after milk ejection.
Journal of Dairy Science 09/2004; 87(8):2409-15. · 2.56 Impact Factor
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ABSTRACT: Fourteen Murciano-Granadina dairy goats were used to evaluate udder compartments (cisternal and alveolar) and cisternal recoil after an oxytocin (OT) challenge at different milking intervals (8, 16, and 24 h) during wk 7 of lactation. Goats were milked once (1x; n = 7) or twice (2x; n = 7) daily from wk 2 of lactation. Average milk yields for wk 4 and 8 were 1.76 and 2.24 L/d, for goats milked 1x and 2x, respectively. For each half udder, cisternal area was measured by ultrasonography and cisternal milk was measured by machine milking after i.v. injection of an OT receptor blocking agent. Alveolar milk was then obtained after i.v. injection of OT. Regardless of milking frequency, alveolar milk increased from 8 to 16 h after milking, but did not change thereafter. Cisternal area and cisternal milk increased linearly (R2 = 0.96 to 0.99) up to 24 h, indicating continuous milk storage in the cistern at any alveoli filling degree. Cisternal to alveolar ratio increased with milking interval (from 57:43 to 75:25), but differences between milking intervals were significant at 8 h only, at which time goats milked 2x showed a greater ratio (1x = 51:49; 2x = 62:38). Despite extended milking intervals, cisterns of goats milked 1x did not become larger than cisterns of goats milked 2x after 5 wk of treatment. The highest correlation between cisternal area and cisternal milk was detected at 8 h after milking (r = 0.74). Primiparous goats had smaller cisternal areas and less cisternal milk than multiparous goats at all milking intervals. Cisternal recoil was studied in a sample of multiparous goats milked 1x (n = 4) and 2x (n = 4) by scanning cisterns by ultrasonography at 0, 5, 15, and 30 min after an OT challenge for each milking interval. Cisternal area increased after OT injection for the 8- and 16-h milking intervals, but no differences were observed for the 24-h interval. Unlike cows, no changes in cisternal area were observed after OT injection, indicating the absence of cisternal recoil in goats. We conclude that goats show a large cisternal compartment that increases linearly after milking. Nevertheless, cisternal size did not increased after 1x milking, probably because of lesser milk yield. Multiparous goats had larger cisterns than primiparous goats and were able to store more milk in their cisterns at all milking intervals. Because of the high capacity of goat cisterns, no milk return from cistern to alveoli is expected if milking is delayed after milk letdown.
Journal of Dairy Science 06/2004; 87(5):1181-7. · 2.56 Impact Factor
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ABSTRACT: Two experiments were conducted to study changes induced by stage of lactation and milk ejection in the cisternal compartment of the udder in dairy cows. In experiment 1, 18 cows grouped according to stage of lactation were used 12 h after milking for measuring alveolar and cisternal milk volumes (by cannula) and cisternal area (by ultrasonography) in the front quarters. Cisternal milk and cisternal area were correlated (r = 0.74 to 0.82) for all stages of lactation. As lactation advanced, volumes of alveolar and cisternal milk and cisternal area decreased. Proportion of cisternal milk varied between stages (early, 33.2%; mid, 23.1%; and late, 42.6%). In experiment 2, 7 cows were used to show return of milk from cisternal to alveolar compartments when milk ejection was induced without milking. Cisternal area was measured before (0 min) and after (3, 15, 30, and 60 min) an i.v. oxytocin (OT) injection administered immediately before normal a.m. and p.m. milking times. Cisternal area increased dramatically from 0 to 3 min (98%) and decreased slowly thereafter. The 0- and 3-min data provide clear evidence of milk ejection, and their difference indicated cistern elasticity. Maximum cisternal area in each cow was similar for the 8- and 16-h milking intervals, indicating that in both cases the cistern was completely full of milk. Decrease in cisternal area after 3 min was significant at 15, 30, and 60 min. Decreased cisternal area was interpreted as the reflux of cisternal milk to the alveolar compartment. We termed this ‘cisternal recoil.’ In conclusion, ultrasonography was a useful method to evaluate dynamic changes in cisternal milk throughout lactation and after udder stimulation in dairy cows. Evidence exists that udder cisterns decrease when lactation advances and milk returns to the alveolar compartment when cows remain unmilked after milk ejection.
Journal of Dairy Science. 01/2004; 87:2409-2415.
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ABSTRACT: An experiment was conducted to examine how the response of dairy cows to a change from twice to three times-daily milking is affected by deficiencies in the dietary supplies of three amino acids, His, Met, and Lys. Six cows were used in a 6 x 6 Latin square with 14-d periods. The three dietary treatments were: grass silage and a cereal-based supplement containing feather meal as the sole protein supplement; the same silage-cereal diet supplying similar amounts of metabolizable and rumen-undegradable protein but with additional amounts of His, Met, and Lys in the form of fish meal; and the fish meal diet with additional metabolizable energy in the form of an additional 2 kg/d of sugar beet pulp. Within each of these dietary treatments, the cows were milked twice and three times daily, making a total of six treatments. When cows were given the feather meal diet, even though dietary metabolizable energy was in considerable excess, a deficiency of specific amino acids prevented any increase in milk yield in response to increasing the frequency of milking from twice to three times daily. In contrast, when cows consumed a similar level of excess metabolizable energy and a similar level of rumen-undegradable protein for which the protein was of better amino acid balance (fish meal), the increased frequency of milking led to increased yield of milk and milk protein.
Journal of Dairy Science 11/2003; 86(10):3309-12. · 2.56 Impact Factor
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ABSTRACT: The influence of amino acid nutrition on the response to milking more frequently, with or without injection of growth hormone, was examined in eight dairy cows in two 4 x 4 Latin squares with 28-d periods. The four treatments were a diet adequate in amino acids with or without injection of growth hormone and a diet inadequate in amino acids with or without injection of growth hormone. For all four treatments, during the last 14 d of each period, one half of the mammary gland was milked three times a day (3x), while the other half remained on twice-daily milking (2x). Both diets were based on grass silage given ad libitum and 4 kg/d of sugar beet pulp together with a supplement containing either fish meal (adequate diet) or feather meal (inadequate diet) as the only protein feeds. The diet containing feather meal is known to be deficient in His, Met, and Lys. On the fish meal diet, the cows responded positively to growth hormone and to milking more frequently and the responses to both treatments were additive. On the feather meal diet, however, even though injection of growth hormone increased the yield of milk protein by around 10%, milking more frequently did not affect milk production. It is concluded that milking more frequently has a weaker effect on the partitioning of amino acid use between body and udder than does growth hormone treatment.
Journal of Dairy Science 08/2003; 86(7):2409-15. · 2.56 Impact Factor
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ABSTRACT: The response of dairy cows to omitting one milking weekly was investigated in two successive experiments conducted with Holstein cows milked twice daily. Experiment 1 compared the lactational performances and udder changes in eight cows (31.2 L/d, 201 d in milk) in the 5 wk before and the 5 wk after introducing the suppression of one milking weekly. Milk yield was recorded daily and milk composition twice weekly. Milk partitioning in the udder (alveolar and cisternal milk) and cisternal size (ultrasonography), 8 h after milking, were also measured at the start and the end of the experiment. Although daily milk yield decreased 32% during the experiment (10 wk), linear regression analysis revealed a loss of milk yield of 1.1 L/d (3.7%) as a consequence of the omission of one milking weekly. Milk composition, lactation persistency, and somatic cell count (SCC) were unaffected by milking omission. Milk partitioning in the udder decreased by 38% in alveolar milk volume and showed a tendency to decrease in cisternal milk volume (15%) and cisternal size (7%), as a result of milking omission and advancing lactation. Loss in total milk yield was negatively related with cisternal milk volume (r = -0.77) and cisternal size (r = -0.70) indicating smaller losses in the udders with large cisterns. In Experiment 2, five cows (21.0 L/d, 227 d in milk) previously adapted to the milking omission schedule were used to study the daily effects of milking omission on milk yield, milk composition and udder health during 10 wk. Milk yield and milk composition were approximately constant but SCC increased with lactation stage. The omission of one milking caused an important decrease in milk yield, fat content and SCC on the omission day and a compensatory increase over the following 2 d, but milk protein and lactose did not vary. All variables reached the average weekly value three days after the milking omission (six milkings). In conclusion, under the conditions used, omitting one milking weekly slightly reduced milk yield and did not affect milk composition when healthy cows were used. Milk losses by milking omission depend on udder cistern characteristics; evaluating cistern size by ultrasonography may be a useful tool for choosing cows that are better adapted to a reduced milking frequency.
Journal of Dairy Science 08/2003; 86(7):2352-8. · 2.56 Impact Factor
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ABSTRACT: Two experiments were conducted to determine whether longer-term deficiencies in the supply of limiting amino acids would be accompanied by a decline in mammary function (total DNA, cell proliferation rate and activities of key enzymes), and whether this would adversely affect the cow's ability to respond to a return to a nutritionally adequate diet. The first experiment was performed in early/mid lactation, and the second, using the same cows, was carried out in mid/late lactation. A control group of six cows were given a grass silage-cereal diet containing fish meal as the sole protein supplement (amino acid adequate) throughout the experiments, whereas another group of six cows in treatment received the control diet for 2 wk (lactation wk 5 and 6) and then were changed to a diet in which the fish meal was replaced by an equivalent amount of protein as feather meal (amino acid deficient) for 6 wk before returning to the fish meal diet for 4 wk (Experiment 1). After a rest period of 5 wk, the experimental procedure was repeated (Experiment 2). Although there was a fall in milk yield as lactation advanced, leading to lower milk yields in Experiment 2, the marked difference in milk yield between treatments was similar for the two stages of lactation (21% vs 16% in Experiment 1 and 2, respectively). In both experiments, the marked fall of milk yield in cows given the feather meal diet was completely recovered by a return to the fish meal diet. Despite the markedly lower milk yield with the amino acid-deficient diet, however, there was no clear evidence of corresponding changes in measurements of mammary function.
Journal of Dairy Science 05/2003; 86(4):1436-44. · 2.56 Impact Factor
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ABSTRACT: Cell proliferation and protein synthesis (keratinisation) were measured in vitro in hoof biopsy samples taken from two groups of seven heifers, the first calving in the winter and the second in the summer. Both parameters were significantly higher in summer than in winter irrespective of the heifers' reproductive state. The mean (se) measure of the rate of protein synthesis was 199 (27) dpm/microg DNA/hour in summer and 4 (1) dpm/microg DNA/hour in winter, and the equivalent values for cell proliferation (measured as DNA synthesis) were 375 (56) dpm/microg DNA/hour and 17 (4) dpm/microg DNA/hour. Changes around parturition depended on the time of the year. In the winter-calving heifers, the rates of proliferation and keratinisation increased significantly after calving from 22.3 (7.2) to 70.4 (16.6) and from 2.1 (0.7) to 12.4 (2.8) dpm/microg DNA/hour, respectively. In the summer-calving heifers, proliferation decreased from 388.2 (91.0) to 66.7 (9.6) dpm/microg DNA/hour but the rate of keratinisation did not change. Lesion scores and locomotion scores deteriorated after parturition, especially in the winter-calving group. The hooves were harder in summer than winter but their hardness was not affected by the heifers' reproductive state.
The Veterinary record 10/2002; 151(10):285-9. · 1.25 Impact Factor
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ABSTRACT: We conducted an experiment in dairy cows investigating the effects of calving season, milking frequency and nutrition on lactation persistency. Cows calved in the Spring (n=12) or Winter (n=12). Commencing in lactation week 9 one udder-half of each cow was milked thrice-daily and half of each calving group received additional concentrate at a fixed rate of 3kg per day above that of the control cows. As reported elsewhere, between lactation weeks 9 and 33 persistency (measured as the slope of decline in milk yield) was significantly improved by frequent milking (P<0.001), by calving in the Winter (P<0.001) and by additional concentrate (P<0.05). The cows were rebred after week 33. When analysis of persistency was extended up to week 20 of the recurring pregnancy only the frequency effect remained significant. Persistency was unaffected by the pregnancy up until pregnancy week 20 but was then greatly reduced (P<0.001). In this paper we report hormone concentrations. GH was unaffected by nutrition but was consistently elevated in the Winter calving group relative to the Spring. IGF1 and prolactin were both unaffected by nutrition and calving season, IGF1 tended to increase as lactation progressed but changes in prolactin were related to time of year more than stage of lactation. Insulin was not affected by nutrition and was lower in Winter calvers, but only during early lactation. Prior to rebreeding, lactation persistency was correlated (slightly) with [GH] but not with [IGF1] or [insulin] and was correlated significantly with changes in GH, IGF1 (both positive) and insulin (negative). In conclusion, whilst bovine lactation persistency is plastic and amenable to beneficial manipulation, the details of its endocrine control remain to be elucidated.
Domestic Animal Endocrinology 07/2002; 23(1-2):111-23. · 2.06 Impact Factor
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ABSTRACT: Keratinization of the epidermal cells of the bovine claw generates the horn that gives the tissue its mechanical strength. Disruption of keratinization is likely to have a detrimental effect on the strength and integrity of the horn, and could lead to solar lesions and lameness. As part of a wider investigation of the cell biological causes of lameness in dairy animals, we have compared keratin synthesis and distribution in healthy bovine claw tissue with those in hooves with solar ulcers. Protein synthesis was measured by [35S]-labelled amino acid incorporation in claw tissue explant cultures. [35S]-labelled protein synthesis was higher in tissue from diseased claws than in healthy claws, and highest at the ulcer site. The identity of proteins synthesised in vitro did not differ between healthy and diseased tissue. DNA synthesis indicative of cell proliferation was also elevated in diseased tissue. Immunoblotting after one- or two-dimensional electrophoresis showed cytokeratins (CK) 4, 5/6, 10 and 14 to be amongst those expressed in healthy claw tissue. The relative abundance of these keratins was not altered in healthy regions of ulcerated hooves, nor at the ulcer site, but CK16, not usually found in healthy tissue, was detected in the sole of diseased claws. CK5/6 and CK14 were shown by immunohistochemistry to be present in the basal epidermis of healthy tissue, whereas CK10 was found in supra-basal layers. In healthy tissue from ulcerated claws, this distribution was unaltered, but at the site of solar ulcers, CK5/6 and CK14 were each found in both basal and supra-basal epidermis. The study suggests that solar ulceration of the bovine claw is not associated with gross alteration in the keratin composition of the tissue, but causes abnormal distribution of cytokeratins, perhaps as a result of loss of positional cues from the basement membrane. Ulceration did, however, stimulate cell repair involving epidermal protein synthesis (including keratins), and keratinocyte proliferation.
J Dairy Res 12/2001; 68(4):525-37. · 1.57 Impact Factor
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C H Knight
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ABSTRACT: The modern dairy cow has been selectively bred to produce large amounts of milk. Partly as a result, food consumption is considerably less than milk energy output in early lactation. It is only at 2 months or more postpartum that intake increases to the point where positive energy balance is regained, the initial production being achieved by a substantial mobilisation of body reserves. These reserves are laid down before parturition, but it is certainly not the case that the pregnant cow will accumulate adipose tissue recklessly; in the last third of pregnancy well-fed cows in good body condition exhibit reduced, not increased, appetite. There is a fine balancing act to perform. Excessive body condition at parturition quickly leads to metabolic problems such as ketosis, but cows who subsequently become too thin have increased risk of metabolic diseases such as mastitis and lameness. The biological mechanisms regulating output of milk are reasonably well understood, those controlling appetite less well so, and there has been little attempt at systematic integration of the two. The transition from pregnancy to lactation represents a major challenge to homeostasis, made more complicated in multiparous cows by the fact that much of gestation is concurrent with lactation. Herein lies the potential for nutritionally-entrained flexibility. In the wild, concurrent pregnancy and lactation only occur when nutritional conditions are favourable. If conditions are poor, rebreeding will be delayed and lactation will continue, at an energetically-sustainable level, for much longer than its 'normal' duration. In this way the twin energetic burdens of pregnancy and lactation are separated, and extremes are avoided. Given the increasing public concern about stresses suffered by intensively-managed dairy cows, this case may be one where commercial dairying could learn useful lessons from nature.
Proceedings of The Nutrition Society 12/2001; 60(4):527-37. · 2.77 Impact Factor
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ABSTRACT: Two critical windows in mammary development have been proposed. The first arises from observations in rodents that nutrition during fetal and neonatal periods can affect mammary ductular outgrowth, subsequent proliferative activity and, eventually, tumorigenesis, that is, potentially it could have a long-term effect on pathological outcome (breast cancer) in women. The second similarly involves early diet, but in this case the outcome is phenotypic, in that dairy heifers reared too quickly during the peripubertal period subsequently show impaired udder development and reduced milk yield persisting throughout life. Most mammary development occurs during pregnancy, but this period is usually thought of only in terms of the immediate outcome for the subsequent lactation; it is not believed to be a critical window, at least in terms of lifetime mammary productivity. This review examines the evidence underlying these various claims and attempts to define the mechanisms involved, and also considers whether derangements occurring earlier in life (prenatally) could also have long-term consequences for physiological or pathological mammary development.
Reproduction (Cambridge, England) 10/2001; 122(3):337-45. · 3.09 Impact Factor
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ABSTRACT: Milk producers in Malaysia make extensive use of crossbred Sahiwal Friesian dairy cattle. These animals have, however, been found susceptible to lactation failure. A survey of cows in an experimental herd of F1 Sahiwal Friesian animals indicated that, in 30% of animals, milk yield decreased to negligible levels within the first 8 weeks post partum. Lactation failure was associated with a progressive increase in the amount of residual milk left in the udder after normal milking. By week 3 of lactation, residual milk volume was significantly greater than that in animals that, based on previous lactation history were not susceptible to lactation failure, and accounted for up to 30% of milk available at the morning milking. The cellular consequences of residual milk accumulation were evident in the activities of acetyl-CoA carboxylase, fatty acid synthetase and galactosyltransferase, key enzyme markers of cellular differentiation, which decreased in glands undergoing lactation failure and were lower than values measured in tissue of control cows. Mammary cell number, estimated by tissue DNA content, was also reduced in animals undergoing lactation failure. These indices of mammary development indicate that lactation failure is the result of premature involution in susceptible animals. Premature involution is a predictable consequence of progressive milk stasis in failing lactation, and attributable to an increase in autocrine feedback by inhibitory milk constituents. The progressive increase in residual milk is, on the other hand, unlikely to be attributable to impaired mammary development. Measurements of milk storage during milk accumulation showed no differences between control and lactation failure cows in the distribution of milk between alveolar and cisternal storage compartments. We conclude that lactation failure in Sahiwal Friesian cows is due to a failure of milk removal, and probably the result of an impaired milk ejection reflex rather than to the glands' milk storage characteristics.
J Dairy Res 06/2001; 68(2):165-74. · 1.57 Impact Factor
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ABSTRACT: Cows managed for extended lactations of 16 months duration were milked on a half-udder basis twice or thrice daily, commencing in lactation week 9. Mammary epithelial integrity (assessed by milk sodium : potassium ratio) was greater in the half-udder which was milked thrice daily. This difference was evident throughout the lactation but became greater after week 41. Milk protein composition was assessed during late lactation (52+/-3 weeks). Casein number (casein as a proportion of total protein) was significantly higher in half-udders milked thrice daily, as were the relative amounts of alpha- and beta-caseins, whilst those of kappa- and- caseins were reduced. Two days of inverted milking frequency (i.e. thrice-milked udder halves now milked twice, and vice versa) only partly reversed these differences. We concluded that thrice-daily milking will help to prevent or ameliorate the usual decline in milk processing quality associated with late lactation. Part of this effect is due simply to reduced exposure to proteolytic enzymes as a result of decreased storage time in the udder, but part is due to a better maintenance of epithelial tight junction integrity as lactation advances, which restricts leakage of proteolytic enzymes from serum into milk.
J Dairy Res 03/2001; 68(1):15-25. · 1.57 Impact Factor
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ABSTRACT: Lameness, hoof lesion development and behaviour were compared for two groups of 10 heifers: one in early pregnancy (PH), the other in early lactation (LH). Both groups were housed in the summer in cubicles under identical conditions. Behavioural observations commenced immediately after housing, and then at 2, 4 and 6 weeks post-housing. Locomotion scores were assessed weekly, and feet were examined for lesions at approximately -1, 0, 1 and 2 months after housing. All four feet were photographed, lesions were scored subjectively for severity, and lesion size and position were estimated using image analysis techniques. LH already had greater total lesion scores before housing. More severe linear lesions in the LH group were associated with reduced lying, and less idling, increased standing in cubicles and more disturbed lying behaviour.
The Veterinary Journal 04/2000; 159(2):147-53. · 2.24 Impact Factor
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ABSTRACT: Eight cows were challenged by a single quarter intramammary infusion of a relatively low-virulence strain of Staphylococcus aureus on four occasions five weeks apart and, after each challenge, each cow received one of four treatments, according to a duplicated Latin-square design. The treatments were massage alone (negative control), massage with a proprietary liniment, oxytocin, and a single course of a proprietary intramammary antibiotic. The massage treatments were applied at every milking for three weeks, oxytocin was given for one week, and the antibiotic was given after three successive milkings. Milk samples were collected immediately before and for three weeks after each challenge, and a scoring system was used to quantify the presence of bacteria during the whole of the period. None of the treatments completely eliminated bacteria from all the cows. Relative to the negative control, the liniment had no significant effect, but both oxytocin and the antibiotic reduced the numbers of bacteria significantly and did not differ significantly in efficacy.
The Veterinary record 04/2000; 146(11):311-6. · 1.25 Impact Factor
