Characterization of ruminal dynamics in Holstein dairy cows during the periparturient period

We used four pregnant Holstein cows to delineate ruminal adaptations as cows transitioned from one lactation to the next. Cows were fed typical diets through far-off and close-up dry periods and lactation. We measured ruminal characteristics on day 72 (late lactation), 51 (far-off dry), 23 and 9 (close-up dry) prepartum and on days 6, 20, 34, 48, 62, 76 and 90 postpartum (early lactation). Measurements included: ruminal fill (weight of actual contents), ruminal capacity (volume of rumen when fully filled), digestibilities and ruminal passage rates. Ruminal capacity tended to increase linearly during early lactation but was stable during dry and transition periods. Both total and liquid fill decreased linearly during the dry period, increased across parturition, and increased linearly through early lactation. Dry matter fill decreased as cows were fed the close-up diet at day 23 prepartum then increased near parturition and continued to increase across early lactation. Solid passage rate was greatest when cows were fed the close-up diet, and decreased throughout the transition period. In lactation, solid passage rate responded quadratically with peak at day 48 followed by decreases through day 90 postpartum. Liquid passage increased linearly across the transition period. Total tract organic matter digestibilities increased linearly over the dry period with significant increases prior to or immediately after parturition, then they remained relatively stable over early lactation until they increased at day 90. Fibre digestibilities demonstrated quadratic responses over early lactation, being higher on day 6 and day 90 than at other times. Starch digestibilities decreased linearly across both the dry and transition periods with decreases in lactation until day 62 followed by increases until day 90. High producing lactating dairy cows go through a multitude of ruminal adaptations, in terms of digestion, passage, capacity and fill, as they transition from one lactation to the next.     

Daily rhythm of total activity pattern in domestic cats (Felis silvestris catus) maintained in two different housing conditions

Housing conditions and human presence have been shown to have an influence on daily amount of activity in herbivores. Only few studies on the behavior of cats and interactions between cat and human were conducted, and these few works are referred to cats housed in laboratories. At the same way, only few and conflicting reports about the presence of circadian rhythms in cats are present. In view of this incomplete literature, the main aim of our study was to investigate the influence of different housing conditions on daily rhythm of total locomotor activity (TLA) in cats.For this purpose, 10 clinically healthy adult domestic cats were used. They were divided into 2 equal groups living with their owner in their home. Group A lived in 80-100 m² house and had free daily access to 20-40 m² garden from 08:00 to 9:00. Group B lived in 200-250 m² house, had free access to 2000-2500 m² garden all day, and from 21:00 to 08:00 they were kept outside. Our results showed that in group A, that live in strong symbiosis with owners respect to group B, the amount of activity was higher during the photophase. This supporting the view that domestic cats adapt their lifestyle with their owners. Group B exhibited the highest level of locomotor activity during the scotophase. Moreover, a robust daily rhythmicity of TLA was observed in group B; on the contrary, in group A, TLA showed no daily rhythmicity. Our findings underline the high influence of human presence and care on the amount of activity and daily rhythm in cats.     

Influence of time of food administration on daily rhythm of total locomotor activity in ponies

The activity rhythm can be entrained by nonphotic cues, especially food availability. Daily feeding schedules can act as “Zeitgeber” to synchronize the circadian system. In this study, the authors evaluated the influence of different feeding schedules on the daily rhythm of total locomotor activity in ponies. Six clinically healthy Shetland ponies were kept under natural 12/12-h light/dark cycle and monitored during 4 different feeding schedules: fed twice (at 8 am and 8 pm), fasted, fed at 8 pm, fed at 8 am, and fed twice a day again. Water was available ad libitum. To record total activity, we equipped the animals with actigraphy-based data loggers (Actiwatch-Mini). Two-way analysis of variance revealed a significant main effect of the time of day and no effect of feeding schedules on the amount of total locomotor activity. Locomotor activity showed daily rhythmicity in all experimental conditions, with diurnal acrophase. The amplitude of the rhythms and their robustness statistically changed across all experimental conditions. Our findings support the theory that when given essentially free choice hay, the time of feeding did not entrain activity, and suggest that feeding behavior can influence the distribution of locomotor activity during a 24-hour period in ponies, with changes in the amplitude and robustness of the rhythm.     

Effect of prepartum compensatory nutrition regimen on metabolism and performance of dairy cows

The impact of closely controlled energy management during the dry period upon general peripartum metabolism and the subsequent lactation was evaluated in multiparous dairy cows. Eight lactating, pregnant Holstein cows were paired according to current milk production and body condition score and assigned to either the control or the stair-step compensatory nutrition (SSCN) regimen 16 weeks prior to expected calving date. Control cows were fed according to National Research Council [National Research Council., 2001. Nutrient Requirements of Dairy Cattle. 7th rev. ed. Natl. Acad. Sci., Washington, DC.] recommendations and for ad libitum intake during late lactation and the far-off dry period. The SSCN cows were subjected to dietary energy restriction [80% of net energy for lactation requirements (NE_L)] during late lactation in order to maintain body weight, followed by realimentation (130% of NE_L) during the far-off dry period to induce a compensatory response. A common diet was fed thereafter. The SSCN cows gained less body condition during late lactation and tended to gain more body condition during the far-off dry and transition periods than control cows. There was no difference in dry matter intake during the prepartum transition period and early lactation. Milk yield was not affected by treatment. Serum nonesterified fatty acids (NEFA) were not altered by dietary treatment during late lactation and the dry period; however NEFA were lower in SSCN cows at week 4 of the subsequent lactation. Serum insulin was higher in SSCN cows 8 weeks prior to parturition (end of restriction), tended to be higher at 4 weeks (end of realimentation) before calving, and was also higher at week 12 of early lactation. An SSCN regimen stimulated body condition gain of mature dairy cows during the dry period, did not affect periparturient nutrient metabolism, and led to modest improvements in metabolic parameters later in the subsequent lactation.     

Study on some risk factors and effects of bovine ketosis on dairy cows from the Galicia region (Spain)

The study was designed to determine the relation between β‐hydroxybutyrate (BHB) concentrations in milk from dairy cows after calving and the length of the previous lactation, the dry period and the 305‐day normalized production, and to assess the influence of BHB concentrations on culling and test‐day milk productions and somatic cell counts (SCC) throughout the lactation that followed the BHB measurement. The data used in the study were obtained from 59 187 cows in the Galicia region (Spain). BHB determination was performed using Fourier‐transformed infrared spectrometry from the milk samples collected from each cow on the first post‐partum test day. For statistical analysis, the following methods were applied: (i) ordinal regression to assess the effect of the length of the previous lactation, the dry period and the 305‐day normalized milk production on milk BHB, (ii) a Cox model to estimate the influence of the BHB concentration on risk of culling (overall and for a variety of reasons) and (iii) linear regression to assess the link between BHB and the milk yield and SCC obtained from each of the tests day performed throughout lactation. The probability of having higher BHB concentrations increased when the length of the previous lactation (p = 0.006), the dry period (p = 0.003) and the 305‐day normalized milk yield (p = 0.005) increased. However, the slight increase observed (especially for the case of the dry period and the 305‐day milk yield) would not justify that measures be implemented to reduce these traits. Higher concentrations of BHB led to an increased risk of culling due to ‘death’ (p ≤ 0.001) and ‘urgent slaughter’ (p ≤ 0.002) (both causes of involuntary culling). It also led to a reduction in milk production (p < 0.001) and an increase in SCC (p < 0.001) in the post‐partum; from that moment onward (including peak lactation), there were no differences in those two parameters depending on the BHB levels.     

不同采食量对妊娠期和泌乳期新西兰母兔水平衡影响的研究

本研究为对母兔妊娠期和哺乳期两个生理阶段水平衡的测定。选用的16只经产妊娠期新西兰母兔,随机分成四组,每组4只。试兔采食同一营养密度日粮。对照组为充分饲养组,日采食量为260克;其余三组的采食量各为对照组的90、80和70％(即各为230克、210克和190克)。结果表明:处于同一生理阶段试兔的水平衡不受饲料采食量多少的影响。母兔妊娠期每公斤体重每天的水平衡为18.9克;泌乳期为42.0克,差异极显著(P<0.01)。可见兔的生理状态是影响兔水平衡的重要因素。测得母兔妊娠期饮水占总摄水量的68.9％,泌乳期饮水占总摄水量的84.7％。母兔妊娠期每公斤体重饮水需112.7克,泌乳期需167.0克,饮水与饲料水之比各为1.49∶1和2.11∶1。由此表明:加强繁殖母兔的饲养管理不应忽视对其供给充足、洁净的饮水。     

Body temperature,activity patterns and hunting in free‐living cheetah: biologging reveals new insights

As one of the few felids that is predominantly diurnal, cheetahs (Acinonyx jubatus) can be exposed to high heat loads in their natural habitat. Little is known about long‐term patterns of body temperature and activity (including hunting) in cheetahs because long‐term concurrent measurements of body temperature and activity have never been reported for cheetahs, or, indeed, for any free‐living felid. We report here body temperature and locomotor activity measured with implanted data loggers over 7 months in 5 free‐living cheetahs in Namibia. Air temperature ranged from a maximum of 39 °C in summer to ?2 °C in winter. Cheetahs had higher (～0.4 °C) maximum 24‐h body temperatures, later acrophase (～1 h), with larger fluctuations in the range of the 24‐h body temperature rhythm (approximately 0.4 °C) during a hot‐dry period than during a cool‐dry period, but maintained homeothermy irrespective of the climatic conditions. As ambient temperatures increased, the cheetahs shifted from a diurnal to a crepuscular activity pattern, with reduced activity between 900 and 1500 hours and increased nocturnal activity. The timing of hunts followed the general pattern of activity; the cheetahs hunted when they were on the move. Cheetahs hunted if an opportunity presented itself; on occasion they hunted in the midday heat or in total darkness (new moon). Biologging revealed insights into cheetah biology that are not accessible by traditional observer‐based techniques.     

Comparison of productive and reproductive performance and hair cortisol levels between Brown Swiss cross‐bred and Holstein cows housed in the same barn

The productive and reproductive characteristics of Brown Swiss (B) cross‐bred cows were investigated by comparing with those of Holstein (H) cows housed in the same barn. Additionally, their hair cortisol levels were analyzed to evaluate the extent of stress experienced during dry and lactation periods. B cross‐bred cows had lower milk yields and higher milk fat rates than H cows. Reproductive records showed that days from parturition to first artificial insemination (AI) in B cross‐bred (n = 16) and H (n = 27) cows were not significantly different, but conception rate at first AI of B cross‐bred cows tended to be higher than that of H cows. Percentage of B cross‐bred cows that resumed ovarian cyclic activity within 45 days after parturition was higher than that of H cows (6/6 (100%) and 5/11 (45.5%), P < 0.05), and B cross‐bred cows had higher body condition scores at that time. Hair cortisol level at 60 to 90 days after parturition in H cows increased significantly compared with in the dry period, and it was higher than that of B cows during the same period. These results suggest that B cross‐bred cows experience less metabolic stress during early lactation, which may result in earlier resumption of reproductive function.     

A Comparison of Daily Rhythm of Creatinine and Creatine Kinase in the Sedentary and Athlete Horse

The goal of this study was to investigate the existence of a daily rhythm of creatinine or creatine kinase (CK) and the influence of physical exercise on these rhythms. Blood samples from 20 Sella Italiana horses were collected every 4 hours for 48 consecutive hours via an intravenous cannula inserted into the jugular vein. The horses were divided into two equal groups (Sedentary [S] and Athlete [A]). After 2 weeks of rest, athletes (AR) were subjected again to sample collection every 4 hours for 48 consecutive hours, and sera creatinine and CK were assessed. Statistical analysis of the data was performed by one-way repeated analysis of variance (ANOVA), paired Student's t-test, unpaired Student's t-test, and analysis of single cosinor method. Cosinor analysis identified the periodic parameters and their acrophases (expressed in hours) during the 2 days of monitoring. In all horses, we found a highly significant effect of time of the day on the studied parameters (P < .01). Statistically significant differences were observed for mean serum CK values between sedentary and athlete horses. The application of the periodic model showed a daily rhythm of the parameters studied in all experimental conditions. The results obtained during the experimental period indicated a daily rhythm of creatinine and CK in sedentary and athlete horses and also indicated that physical exercise was able to influence amplitude, acrophase, and robustness of the creatinine and CK circadian rhythm.     

Follicular turnover and hormonal association in postpartum goats during early and late lactation

To clarify the effect of lactation period on ovarian follicular activity and associated hormonal levels in goats, six goats were monitored daily by ultrasonographic examination with blood sampling during early (Days 5 to 25; Day 0 was the day of kidding) and late (Days 40 to 60) lactation. While the presence of a corpus luteum of pregnancy retarded follicular growth in the ipsilateral ovary until Days 11-13 postpartum, the total follicular number (TFN) and area (TFA) increased during late lactation due to the significant increase in the number of medium- and large-sized follicles and decrease in the number of small follicles. Four goats showed a similar pattern of follicular development during the period studied characterized by the emergence of five and six waves during the early and late lactation, respectively. The largest follicle diameter of the first three waves monitored during early lactation was significantly smaller as compared with the diameter of those existing during late lactation. TFN showed a positive correlation with FSH but showed a negative correlation with immunoreactive (ir-) inhibin and estradiol during the postpartum period. TFA was positively correlated with ir-inhibin, estradiol and PRL and negatively correlated with FSH during the monitored periods. The plasma levels of ir-inhibin and progesterone were significantly higher during late lactation compared with the levels recorded during early lactation. Ir-inhibin levels showed a significant positive correlation with LH and estradiol during early and late lactation but showed a negative correlation with FSH during the whole lactation period. LH was positively correlated with estradiol and PRL during early and late lactation, respectively. These results suggest that the lactation period has a detrimental effect on ovarian activity during the early postpartum period in goats.     

Benchmarks for evaluation and comparison of udder health status using monthly individual somatic cell count

The objectives of this study were to propose benchmarks for the interpretation of herd udder health using monthly individual somatic cell counts (SCC) from dairy herds in Quebec, Canada and to evaluate the association of risk factors with intramammary infection (IMI) dynamics relative to these benchmarks. The mean and percentiles of indices related to udder infection status [e.g., proportion of healthy or chronically infected cows, cows cured and new IMI (NIMI) rate] during lactation and over the dry period were calculated using a threshold of ≥ 200 000 cells/mL at test day. Mean NIMI proportion and proportion of cows cured during lactation were 0.11 and 0.27. Benchmarks of 0.70 and 0.03 for healthy and chronically infected cows over the dry period were proposed. Season and herd mean SCC were risk factors influencing IMI dynamics during lactation and over the dry period.     

The prophylactic effect of a teat sealer on bovine mastitis during the dry period and the following lactation

AIM: To determine the prophylactic efficacy of a teat sealer, administered at drying off, in reducing new intramammary infections in the dry period and the following lactation. METHODS: A total of 528 cows with late lactation somatic cell counts <2 00,000 cells/ml was identified in three commercial herds. Of these, bacteriological examination showed 482 cows were uninfected in all four quarters and 46 were infected in only one quarter. At drying off, uninfected quarters were randomly allocated to the following treatments: no infusion (negative controls), infusion with a bismuth subnitrate based teat sealer, infusion with teat sealer + antibiotic, or infusion with a cephalonium-based dry cow antibiotic (positive control). New infections were identified during the dry period by periodic udder palpations and at calving by bacteriological culture. RESULTS: All three infused treatments reduced the incidence of new intramammary infections due to Streptococcus uberis, both during the dry period and at calving, by about 90% (p <0.01). The majority of the infections were due to Streptococcus uberis. For all treatments, a 50% lower incidence of clinical mastitis over the first 5 months of the ensuing lactation was reported by farmers. X-ray imaging of 19 teats showed that the teat sealer material was retained, at least in part, in the lower teat sinus over about 100 days of the dry period. CONCLUSIONS: Closure of the teat canal from day one of the dry period as achieved by the teat sealer was as effective in reducing new dry period infections as the infusion of a long-acting dry cow antibiotic formulation. The lower incidence of new infections in the ensuing lactation among the infused quarters implies that fewer subclinical infections persisted from the dry period. Use of teat sealers at drying off appears to offer the same prophylactic efficacy as the dry cow antibiotic approach.     

In vitro phagocytic activity of milk neutrophils during lactation cycle in Murrah buffaloes of different parity

Milk samples were collected from 34 lactating Murrah buffaloes on days 0, 5, 15, 30, 45, 60, 90, 120, 150, 180, 210, 240, 270 and day 300 after calving. Milk somatic cell counts (SCC) were highest in multiparous buffaloes . Milk SCC were significantly lower in buffaloes of third and fourth parity during early lactation and than increased significantly (p < 0.01) by the end of lactation. Milk neutrophils were significantly lower in all the buffaloes during early lactation, but increased significantly (p < 0.01) afterwards. Milk lymphocytes were significantly higher during early lactation, but decreased significantly (p < 0.01) by the end of lactation. Phagocytic activity (PA) was highest in day 1 colostrum and then decreased significantly (p < 0.01) by the fourth milking in buffaloes of second, third and fourth parity . Phagocytic index (PI) was also highest in colostrums of primiparous buffaloes. Irrespective of parity, maximum PA and PI was observed during mid lactation. In terms of in vitro phagocytic activity, early lactation is the most critical period followed by late and mid lactation.     

The effect of gestation and lactation on bone calcium, phosphorus and magnesium in dairy cows

A study was conducted to monitor changes in cortical bone mineral in the dairy cow in response to demands of lactation and pregnancy using rib bone biopsies in serial sampling. Sixteen Friesian cows from the University dairy herd were used to collect 9 samples during the lactation period and 5 samples during the dry period. The data were analysed using a split-plot design analysis of variance. There were no significant (P > 0.05) differences in cortical bone phosphorus concentrations in rib bone during the lactation period, but calcium concentrations in cortical bone were significantly (P < 0.05) higher at parturition and during the first 30 days of lactation compared to the next 30 days and between 90 and 120 days. Results reported here indicate that the cow resorbs cortical bone during the middle of the lactation period and not during the periparturient period as previously thought. Magnesium concentrations were also significantly (P < 0.05) higher at the beginning of lactation compared to some of the other sampling times, but cortical bone was significantly (P < 0.05) thinner at the beginning of lactation compared to several of the other sampling times. There were no significant (P > 0.05) differences in cortical bone Ca or Mg concentrations during the gestation period. Cortical bone P concentrations significantly (P < 0.05) decreased during the first 180 days, but significantly (P < 0.05) increased at 181-230 days and significantly (P < 0.05) decreased again at 231 days to term. Cortical bone thickness decreased significantly (P < 0.05) from the beginning of gestation to term. There were no significant (P > 0.05) differences in cortical bone thickness or Ca or Mg concentrations in cortical bone during the dry period, but cortical bone P concentrations were significantly (P < 0.05) greater at the end of the dry period compared to the first 30 days of the period. In general, cortical bone Ca and Mg values decreased as milk production increased up to 20 kg/day and cortical bone P values and bone thickness increased. In animals producing over 20 kg/day, however, cortical bone mineral values were greater and cortical bone thickness was lower compared to those animals producing less than 20 kg.     

A comparison of the effects of parenteral and oral administration of supplementary vitamin E on plasma vitamin E concentrations in dairy cows at different stages of lactation

As a result of research conducted in the US, recommendations for dry cow vitamin E intakes have increased seven fold there, however there has been no change to recommendations in the UK. As part of a larger study comparing the impact of existing UK and new US recommended vitamin E intakes on the health and fertility of commercial dairy cows in the UK, a study was set up to investigate the effect of route of supplementation and stage of lactation, over a 21 day period, on the response to mega-supplementation of cattle receiving supposedly adequate vitamin E. The study assessed the response of dry, peak lactation and mid lactation cows to in-feed or parenteral vitamin E supplementation (7 animals per treatment/lactation stage group) by measuring plasma and milk vitamin E concentrations, blood glutathione peroxidase (GSH-Px) activity and milk yields over a 21 day period. Plasma vitamin E concentrations were significantly influenced by a time, stage and treatment interaction (P = 0.046). Both dry and lactating animals had significantly higher plasma vitamin E concentrations at some time points in the parenteral supplemented cows compared to the in-feed supplementated animals (P ≤ 0.011 and P < 0.01, respectively). Milk vitamin E concentrations did not significantly differ between lactation stages but treatment had a significant effect on concentrations (P < 0.008) when lactation stage was removed from the model. There was no significant difference in milk yield between treatment groups. A significant relationship between plasma and milk vitamin E concentrations was only found in the parenterally supplemented cows (r = 0.435, P < 0.001). In cattle with intakes greater than the ARC recommendations, measurement of plasma vitamin E concentration may be of limited value in determining whether there has been a response to supplementation. The relationship between plasma and milk vitamin E concentrations is too poor for milk vitamin E concentrations to be used as a proxy for plasma vitamin E.     

Dependence of the lactation duration and efficiency on the season of lambing in relation to the prolactin and melatonin secretion in ewes

Changes in day length and the related secretion of melatonin and prolactin are of particular significance in sheep, as they determine reproductive processes, the last stage of which is lactation. The aim of the present study was to examine the dependence of the lactation duration and efficiency on the season of lambing (January—Group I/June—Group II) in relation to the hormonal status of milking ewes (Polish Longwool). The possibility of artificial extension of the milking period in late-lambing ewes by application of prolonged day length, 16 h of light–8 h of darkness (16L:8D), was introduced additionally (Group III). Measurements of plasma levels of prolactin and melatonin were used as parameters of season-dependent hormonal regulation of milk production in this seasonally breeding species. Although during the first 28 days of lactation sheep of all groups produced similar amounts of milk (based on the weight gains of the lambs), our results clearly showed that during the period of machine milking (from weaning at 56 day to the dry period) the level of milk production in Group I was almost twice that noted in Group II. Thus, the highest milk yield was obtained from sheep during the period when the days became longer, i.e. from March to May, which was accompanied by an increase in prolactin secretion. In both groups, melatonin secretion was found to increase while milk performance parameters and prolactin secretion decreased during the shortening photoperiod. The sustained decreases in milk production and prolactin secretion were also observed during the autumn months in sheep from Group III, despite the low level of melatonin. The present study showed that time of lambing and related photoperiod length could significantly affect the milk production of sheep that have a clear season of sexual activity. Maintenance of June-lambing sheep under the 16L:8D regime failed to extend the high prolactin level and lactation considerably into the autumn months. The spontaneous decrease in prolactin secretion observed under the long artificial photoperiod indicated for a development of refractoriness, which could also limit the lactation period.     

Influence of low phosphorus intake during early lactation on apparent digestibility of phosphorus and bone metabolism in dairy cows

In this study, the effects of reducing the dietary phosphorus (P) supply during the first 4 months of lactation on P balance and bone metabolism were investigated in dairy cows during a full lactation, including the dry period. Twenty-two multiparous cows of the Swedish Red and White Breed were included in the experiment. Eleven cows received a dietary P concentration of 0.43% of DM during the whole lactation (NP), and 11 cows received a dietary P concentration of 0.32% of DM during the first 4 months of lactation, followed by 0.43% of DM during the rest of lactation (LP). Total collection of faeces was carried out during five different stages of lactation, for 5 consecutive days at each occasion. The dynamics of bone metabolism was investigated by monitoring one bone-formation marker, identifying osteocalcin (OC), and one bone-resorption marker identifying C-telopeptide fragments of collagen type I (CTx) in blood plasma. At the two first collection periods, 3–7 and 11–15 weeks after parturition, the apparent digestibility of P was higher in the LP cows (52%) than in the NP cows (42%). During the following collection periods, no difference in the apparent digestibility could be noted between the two groups of cows. Phosphorus retention did not differ between treatments at any collection period. The highest retention was observed during late lactation and during the dry period. The profiles of the bone metabolism markers indicated a net resorption of bone during early lactation, but there were no differences in marker concentrations between the groups during early lactation, indicating that the LP diet did not induce a further elevated net bone resorption.     

Dry cow therapy with a non-antibiotic intramammary teat seal - a review

: Dry cow antibiotic therapy is used to eliminate existing intramammary infections and to prevent new infections in the dry period. It is implemented as part of a total management system known as the 'Five-Point Plan' for mastitis control. Recent public concerns over the widespread prophylactic use of antibiotics, coupled with an increasing interest in organic farming, have lead to a re-evaluation of the treatment of cows at drying-off. As a result, attention has focussed on the use of novel alternatives to antibiotic therapy at the end of lactation. One such therapy involves the application of a non-antibiotic bismuth-based intramammary teat seal designed for use in cows with low cell counts at the end of lactation. Like the keratin plug that forms naturally in teats of cows that have been dried-off, teat seal forms a physical barrier to invading pathogens. To date, a number of independent studies have shown that teat seal is as effective as traditional dry cow antibiotic products in preventing the occurrence of new infection during the dry period in cows with somatic cell counts of ≤200,000 cells ml-1 at drying-off. This paper reviews the efficacy of teat seal in preventing dry period mastitis in both conventional and organic dairying systems.     

Management of photoperiod in the dairy herd for improved production and health

Environmental influences on lactation efficiency are frequently associated with reductions in milk output. Heat stress, for example, leads to depressed feed intake and, subsequently, losses in production. Conversely, cold stress may limit nutrients available for milk synthesis. Fortunately, one environmental factor, photoperiod, can exert a positive effect on dairy performance when managed properly. Long days have consistently been shown to improve milk yield during established lactation. In addition, photoperiod management can be used to improve heifer growth and maximize accretion of lean tissue, including mammary parenchyma. There is, however, evidence of refractoriness to long day stimulation. Recent work has focused on the dry period as a time when photoperiod manipulation can influence subsequent milk production. In contrast to lactating cows, multiparous cows benefit from exposure to short days when the dry period is followed by long days or natural photoperiod after calving. Similarly, primiparous animals also respond positively to short days late in pregnancy when subsequently exposed to long days during lactation. Furthermore, emerging evidence suggests that short days positively influence immune function in cattle. Mechanistically, it appears that prolactin has a causal relationship with the observed dairy performance effects during the dry period and on immune function, via altered sensitivity to prolactin through differential expression of prolactin receptor in multiple tissues. The objectives of this paper include a review of fundamental aspects of photoperiod physiology, integration of applied and basic research findings, and development of management recommendations for the entire life cycle of the dairy cow to optimize performance.     

Determination of the potassium balances in diary cows and the examination of daily and lactation period-associated variations

The objectives of this study were to evaluate a method of determining the internal and external potassium balances in dairy cows and to determine daily and lactation period-associated variations of these balances. Ingested potassium, milk potassium concentration (LK) and potassium urinary fractional clearance (FeK) defined the potassium external balance. Serum (SK) and red blood cell (CIEK) potassium concentrations defined the potassium internal balance. Whole blood, urine, and milk were collected at different times of the day from 19 cows, grouped in 5 lactation periods. Significant differences were observed for LK between lactation periods. Significant variations occurred during the day for CIEK, LK, and FeK. Thus, in order to monitor potassium balances during a time period, samples should be collected at the same time each day. This method of determining both potassium balances simultaneously could be useful in the study of the bovine hypokalemia syndrome.