Late Dry Period Research Articles

Climatic variability and human impact during the last 2000 years in western Mesoamerica: evidence of late Classic (AD 600–900) and Little Ice Age drought events

Abstract. We present results of analysis of biological (diatoms and ostracodes) and non-biological (Ti, Ca / Ti, total inorganic carbon, magnetic susceptibility) variables from an 8.8 m long, high-resolution (~ 20 yr sample−1) laminated sediment sequence from Lake Santa María del Oro (SMO), western Mexico. This lake lies at a sensitive location between the dry climates of northern Mexico, under the influence of the North Pacific subtropical high-pressure cell and the moister climates of central Mexico, under the influence of the seasonal migration of the intertropical convergence zone and the North American monsoon (NAM). The sequence covers the last 2000 years and provides evidence of two periods of human impact in the catchment, shown by increases in the diatom Achnanthidium minutissimum. The first from AD 100 to 400 (Early Classic) is related to the shaft and chamber tombs cultural tradition in western Mexico, and the second is related to Post-Classic occupation from AD 1100 to 1300. Both periods correspond to relatively wet conditions. Three dry intervals are identified from increased carbonate and the presence of ostracodes and aerophilous Eolimna minima. The first, from AD 500 to 1000 (most intense during the late Classic, from AD 600 to 800), correlates with the end of the shaft and chamber tradition in western Mexico after ca. AD 600. This late Classic dry period is the most important climatic signal in the Mesoamerican region during the last 2000 years, and has been recorded at several sites from Yucatan to the Pacific coast. In the Yucatan area, this dry interval has been related with the demise of the Maya culture at the end of the Classic (AD 850 to 950). The last two dry events (AD 1400 to 1550 and 1690 to 1770) correspond with the onset of, and the late, Little Ice Age, and follow largely the Spörer and Maunder minima in solar radiation. The first of these intervals (AD 1400 to 1550) shows the most intense signal over western Mexico; however this pattern is different at other sites. Dry/wet intervals in the SMO record are related with lower/higher intensity of the NAM over this region, respectively.

Recarga de aquífero aluvial sob uso agrícola

The core in the exploitation of groundwater is its renewal, which is not usually performed in the same proportion of the abstraction. This may result in an exploration of parts of the permanent reserves of the aquifer, with the risk of severe depletion, when the abstraction is not properly monitored. This study aims to estimate the groundwater recharge in the rural area of Pesqueira (PE) from 2002 to 2011. Alluvial aquifers are strategic for communal farming in the Brazilian semiarid. The methodology used was the water balance of Thornthwaite & Mather and variation of the water level. The first considers climatological and pedological elements for the analysis of the aquifer recharge, while the second method directly analyzes the change in the groundwater level in relation to the storage coefficient of water in the soil. It was found that all the years of the study period showed a deficit of moisture in the soil, in the “late dry period”. Results were similar for both methods, being both effective in estimating aquifer recharge in the region.

Postpartum responses of dairy cows supplemented with n-3 fatty acids for different durations during the peripartal period

The objective of this study was to determine the effect of different durations of n-3 supplementation during the peripartal period on production and reproduction performance of Holstein dairy cows. Thirty-two Holstein dry cows (16 multiparous and 16 primiparous) were blocked within parity for similar expected calving dates 8 wk before calving. Cows within blocks were assigned randomly to 1 of 4 treatments: (1) control without n-3 fatty acid (FA) supplementation during the dry period; (2) n-3 FA supplementation during the whole dry period (8 wk); and (3) n-3 FA supplementation during the early dry period (first 5 wk; far-off), or (4) n-3 FA supplementation during the late dry period (last 3 wk; close-up). All cows received the same diet without n-3 FA after calving for the first 6 wk of lactation. Ovaries of each cow were examined 10, 17, 24, and 34 d from calving (calving=d 0) by transrectal ultrasonography to determine follicular development. Blood samples were collected at 14-d intervals starting on the first day of the dry period (8 wk before expected calving) to determine plasma concentrations of glucose, β-hydroxybutyrate, nonesterified fatty acids, urea N, aspartate aminotransferase, and insulin. Blood samples were also collected on d 1, 10, 17, 24, 31, and 38 postpartum for determination of progesterone concentration. Milk yield was recorded daily throughout the experiment and samples were taken twice weekly (Monday and Thursday mornings) for analysis of fat, protein, and lactose. Yields of milk and 4% fat-corrected milk and milk composition were similar among treatments except for fat proportion, which tended to be lower in cows that were fed n-3 FA throughout the dry period. We observed no differences among treatments for plasma concentrations of metabolites and hormones. The cows that were fed in the 3 n-3 FA treatments had larger ovulatory follicles compared with those fed the controlled diet. Treatments did not differ significantly in terms of the number of days open, day to first service, or number of services per pregnancy. In conclusion, n-3 FA supplementation throughout the dry period or in the early or late prepartal period had no carryover reproductive postpartum benefits and no effect on the production of Holstein dairy cows.

Inhalable Particulate Matter Burden in Selected Day-Care Centres in Ibadan, Nigeria

The indoor air quality in day-care centres may influence the occurrence of infectious diseases and increase the risk of non-communicable diseases. The World Health Organisation (WHO) and other international agencies have considered particulate matter as an indicator of impact of air pollution on human health yet information on this from childcare centres is poorly documented in developing countries. This study therefore was designed to assess the particulate matter concentration (PM₁₀) in selected day-care centres (DCCs) in Ibadan, South western Nigeria. The study was descriptive cross sectional. PM10 load was determined 3 days a week for 16 weeks spanning the late wet season and early dry season periods from 10 locations of the selected DCCs using a digital PM counter model Met one. The ratio of indoor/outdoor PM₁₀was computed. Results obtained throughout the monitoring period for all the locations were averaged and compared with WHO PM₁₀ guideline limit of 50μg/m³.Data collected were analysed using descriptive statistics and ANOVA at 5% level of significance. Mean indoor PM₁₀ readings for wet season (73.4 ± 54.4μg/m³) and dry season (296.3 ± 61.6μg/m³)significantly exceeded guideline limit (P<0.05).The indoor/outdoor PM₁₀ ratio was 1.38 ± 0.97 and being greater than 1 indicated a possible indoor source of pollution. High particulate matter concentration observed is indicative of the poor indoor air quality condition in the day care centres. Government policies on routine air quality monitoring and stringent enforcement of environmental sanitation in day care centres are advocated.

Spatial and temporal variation of fish assemblage in two intermittent streams in north‐western Zimbabwe

AbstractThis study examined the spatial and temporal variation in fish assemblage composition within two intermittent streams in north‐western Zimbabwe. Eight sites were sampled during three different periods of flow. Twenty‐five species in eight families, dominated by cichlids and cyprinids, were collected. Redundancy analysis (RDA) was used to explore the relationship between species and their environmental correlates. According to variation partition, 68.1% of assemblage variation was explained by both habitat and temporal variables. Most species were associated with large pools, whereas small species were associated with habitats that had gravel and boulders. The temporal aspect suggested a pattern associated with high catch per unit effort (CPUE) for the mormyrids, Clarias gariepinus and Labeo altivelis, during the early rain period. By comparison, the late rain period was associated with high CPUE for Labeo cylindricus, Labeobarbus marequensis, Chiloglanis neumanni and Oreochromis mortimeri, whereas the rest of the species had high CPUE during both the late rain and dry periods. The assemblage composition was more diverse during the late rain period. Refuge availability during the dry period appeared to be essential for the assemblage of the intermittent streams. Protection of these temporal habitats is therefore important in conserving fish assemblages within intermittent streams of the Lake Kariba area.

Body phosphorus mobilization and deposition during lactation in dairy cows

Dairy cow bone phosphorus (P) mobilization and deposition and their influence on P requirements were studied over the lactation cycle. Thirty Holsteins received a common diet during the dry period and one of the following three dietary treatments that varied in P percentage during the subsequent lactation (44 weeks): (i) 0.36 throughout (constant P, 0.36-0.36-0.36), (ii) 0.36 for 30 weeks then 0.29 for 14 weeks (P changed once, 0.36-0.36-0.29), and (iii) 0.43 for 10 weeks, 0.36 for 20 weeks, and 0.29 for 14 weeks (P changed twice, 0.43-0.36-0.29). Six P balance studies were conducted during the experiment, including one during the dry period and five along lactation, based on P intake, faecal P, urinary P and milk P, when appropriate. Blood samples were taken during balance to analyse bone formation (osteocalcin) and resorption (pyridinoline) marker concentrations and rib biopsies performed to determine bone P content. Phosphorus balance was negative during weeks -4 to -1 relative to lactation for all groups and remained negative for cows fed 0.36% P during weeks 1-5, but showed a positive value for cows that received 0.43% P. The balance was close to zero for all groups at weeks 19-23 and showed a clear retention during weeks 38-42; by the end of lactation, cows re-stored most of the P mobilized earlier. The pattern in P balance was consistent with changes in blood bone metabolism marker concentrations, rib bone P content, and faecal and urinary P concentrations over the experiment, indicating that cows, irrespective of the dietary P treatments received, mobilized P from bone during the late dry period when fed a low-Ca diet and early lactation, and re-stored P in late lactation. This dynamic of P metabolism can have important implications for dietary P requirements and ration formulations.

Reevaluation of vitamin E supplementation of dairy cows: bioavailability, animal health and milk quality

Although vitamin E has been known as an essential nutrient for almost 80 years, we are far from a complete understanding of all the aspects related to bioavailability and its effects on health and milk quality in dairy cows. Vitamin E is a generic descriptor for two families of lipid-soluble compounds, the tocopherols and the tocotrienols, of which α-tocopherol has the highest biological activity. Commercially available α-tocopherol supplements for dairy cows contain either the natural RRR form or the synthetic (all-rac) form, which contains all the eight possible stereoisomers (four possessing the 2R and four possessing the 2S configuration) in equimolar amounts. Recent data clearly suggest that an almost complete discrimination against the 2S isomers occurs in dairy cows. Thus, 1 g of the all-rac form is essentially equivalent to 0.5 g of the RRR form. With respect to the effect of vitamin E supplementation of dairy cows on health and milk quality, the majority of published studies suggests that vitamin E supplementation at the level 1000 to 4000 IU/cow per day during the dry period reduces both the frequency of intramammary infection and that of clinical mastitis and improves milk quality, as shown by a reduction in the levels of somatic cell count (SCC)/ml in milk, decreased plasmin activity and increased oxidative stability of milk. However, a recent study from the Netherlands suggested that vitamin E supplementation at the 3000 IU/cow per day level during the dry period when combined with high levels of plasma vitamin E at dry-off (>14.5 μmol/l) increases the incidence of mastitis. Data from previously unpublished survey studies and those from published vitamin E feeding trials, in which high levels of blood vitamin E were observed, were reanalyzed. All farms selected for the analysis implemented oral administration of vitamin E at the 3000 IU/cow per day level throughout or during the late dry period (4 weeks before the expected day of parturition). Dairy cows were divided into three groups, depending on blood α-tocopherol levels at dry-off: high (>6.25 μg/ml), medium (between 6.25 and 4.25 μg/ml) and low (<4.25 μg/ml). Data indicate that there were no differences in the incidence of mastitis and in the level of SCC/ml of milk between the three groups. Thus, supplementation of 3000 IU vitamin E/cow per day in the late dry period remains recommended because it is generally associated with decreased risk of mastitis. Conditional or opposite effects have not been repeated and require further research before changing recommendations for vitamin E supplementation.

Electrophoretic Serum Protein Fraction Profile During the Different Physiological Phases in Comisana Ewes

The aim of this study was to evaluate the influence of different physiological phases on serum total proteins and their fractions of ten Comisana ewes housed in Mediterranean area. From each animal, blood samples were collected at different physiological phases: late pregnancy, post-partum, early, mid-, end lactation and dry period. On all samples serum total proteins were determined by the biuret method, and albumin, α-globulins, β(1) -globulins, β(2) -globulins and γ-globulins concentrations were assessed using an automated system. One-way repeated measures analysis of variance was applied to determine the significant effect of different physiological phases on the parameters studied. During the late pregnancy and post-partum, total proteins, β1- and β2-globulins and γ-globulins showed the highest values. Starting from post-partum, α-globulins increased to reach their peaks in mid-lactation. Early lactation was characterized by low γ-globulins values. The increase in serum albumin concentration and the drop in some globulin fractions determined the significant increase in albumin/globulin ratio. The obtained results contributed to improve the knowledge on electrophoretic profile during the different physiological phases in ewes, confirming that pregnancy and lactation periods affect the protein metabolism. Particularly, serum protein fractions pattern could give information about dehydration, plasma volume expansion and hepatic function, which occur during the different physiological phases. Dynamics of the protein profile - from pregnancy to dry period - which are provided by our results, could be considered as guidelines for the management strategies to guarantee the nutritional needs of these animals during the different physiological phases and to avoid a decline of productive performance and consequently an economic loss.

Investigation of ice‐wedge infilling processes using stable oxygen and hydrogen isotopes, crystallography and occluded gases (O2, N2, Ar)

AbstractThe source and mechanism of infill of ice wedges of various ages (modern to Pleistocene) were examined for sites in the western Arctic. Several techniques were employed, including stable O‐H isotope and crystallographic analyses of the ice, and gas composition (O2, N2 and Ar) analyses of air entrapped in the ice. The results indicate that climatic and site‐specific conditions may influence the source of infilling during ice‐wedge growth, so that wedge ice in wet and dry environments exhibits different characteristics. For example, Vault Creek tunnel (Alaska) ice wedges, dating from the Late Pleistocene, a cold and dry period, preserved stable O‐H isotopes and gas compositions similar to those expected for ice formed by snow densification. In contrast, ice wedges from the Old Crow region (Yukon), dating from the Late Holocene, preserved isotopic and gas compositions more comparable with those expected for ice formed by the freezing of liquid water. In both ice‐wedge types, the δ(O2/Ar) values are much lower than both dissolved and atmospheric values, which may be due to the respiration of microorganisms living within ice bubbles or interstitial water at the grain boundaries. The elevated δ18OO2 (up to 16‰) of the occluded gases supports the occurrence of microbial respiration. However, the δ(N2/Ar) values do not appear to have been affected by biological processes, and as such are reflective of the infilling processes. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Prevention of Milk fever: Nutritional Approach

The use of negatively balanced cation-anion rations during the late dry or prepartum period requires excellent monitoring and management. The cows must be separated from the remaining herd and fed a total mixed ration as a group. Lower plasma calcium (Ca) will stimulate the Parathyroid hormone (PTH) and 1-hydroxylase system to increase intestinal absorption of Ca and bone resorption –reduce incidence of milk fever. The incidence of milk fever was increased simply by increasing the potassium (K) concentration in pasture Diet high in K or sodium (Na) -alkalinize the blood - decreased bone Ca resorption and renal production of 1, 25-(OH)2 vitamin D, increase incidence of milk fever. Inadequate supply of magnesium (Mg) in dry period - reduce the ability of a cow to mobilize Ca at parturition. Anionic salts (-ve DCAD) prevents milk fever by acidifying the blood to restore tissue responsiveness to the PTH.

Continuous lactation effects on mammary remodeling during late gestation and lactation in dairy goats

The present study aimed to 1) elucidate whether continuous milking during late gestation in dairy goats negatively affects mammary remodeling and hence milk production in the subsequent lactation, and 2) identify the regulatory factors responsible for changes in cell turnover and angiogenesis in the continuously lactating mammary gland. Nine multiparous dairy goats were used. One udder half was dried off approximately 9 wk prepartum (normal lactation; NL), and the other udder half of the same goat was milked continuously (continuous lactation; CL) until parturition or until the half-udder milk yields had dropped to below 50 g/d. Mammary biopsies were obtained from each udder half just before the NL gland was dried off (before dry period), within the first 2 wk after drying-off (early dry period, samples available only for NL glands), in the mid dry period, within the last 2 wk before parturition (late dry period), and at d 1 (the day of parturition), 3, 10, 60, and 180 of lactation. Mammary morphology was characterized in biopsies by quantitative histology, and cell turnover was determined by immunohistochemistry (terminal deoxynucleotidyl transferase dUTP nick end labeling and Ki-67). Transcription of genes encoding factors involved in mammary epithelial cell (MEC) turnover and vascular function was quantified by quantitative reverse transcription PCR. Results demonstrated that omitting the dry period was possible in goats but was not as easy as claimed before. Renewal of MEC was suppressed in CL glands, which resulted in a smaller MEC population in the subsequent lactation. At the time of parturition (and throughout lactation), the mammary glands subjected to CL had smaller alveoli, more fully differentiated MEC, and a substantially larger capillary fraction compared with NL glands. The continuously lactating gland thus resembled a normally lactating gland in an advanced stage of lactation. None of the studied genomic factors could account for these treatment differences. The described characteristics in CL glands compared with NL glands indicated a gland maintained in lactation for a longer period.

Effects of Stocking Rate, Breed and Stage of Production on Energy Expenditure and Activity of Meat Goat Does on Pasture

Beker, A., Gipson, T.A., Puchala, R., Askar, A.R., Tesfai, K., Detweiler, G.D., Asmare, A. and Goetsch, A.L. 2009. Effects of stocking rate, breed and stage of production on energy expenditure and activity of meat goat does on pasture. J. Appl. Anim. Res., 36: 159–174. Sixteen Boer and 16 Spanish multiparous does were used to determine how stocking rate (SR), breed and stage of production influence energy expenditure and behavioral activities on pasture and to develop a simple method of predicting energy used for activity. The experiment began in late spring at an average of 24 d after kidding. Litter size was two and kids were Boer and Spanish. Two does of each breed resided in eight 0.5-ha grass/forb pastures. There were five periods, 56, 60, 63, 64 and 73 d in length, corresponding to mid-lactation, early post-weaning, the late dry period, early gestation and mid-gestation. During period 1 and the first part of period 2, two additional does with kids of each breed grazed in four High SR pastures, with other pastures designated as Low SR. Because of low available forage mass in period 3, grass hay was offered for ad libitum consumption in periods 3–5 and a concentrate supplement was provided in periods 4 and 5. Energy expenditure (EE) was estimated from heart rate (HR) on pasture and EE.HR for each doe determined in a calorimetry system. A leg position I movement monitoring system and a GPS collar with position and movement sensors were used to estimate distance traveled and time spent grazing/eating, resting while lying, resting while standing and walking without grazing I eating. EE attributable to activity (EEa%), expressed as a percentage of the ME requirement for maintenance plus activity in confinement, was determined based on total EE, estimated milk production and doe BW and ADG. Forage DM mass in the middle of periods was 696, 246, 125 and 196 kg/ha for the High SR and 1362, 967, 479 and 610 kg/ha for the Low SR in periods 1, 2, 3 and 4, respectively. Kid ADG at weaning after 73 d was lower (P<0.05) for the High vs. Low SR (87 vs. 112 g). Distance traveled was not influenced by SR or breed but varied among periods (3.54, 3.76, 3.09, 3.08 and 4.10 km/d in periods 1, 2, 3, 4 and 5, respectively; SE = 0.193). Time spent grazing/eating tended (P < 0.07) to be greater for Boer vs. Spanish does (7.9 vs. 6.7 h/d) and differed among periods (8.0, 7.8, 7.6, 5.3 and 8.0 h I day in periods 1, 2, 3, 4 and 5, respectively; SE = 0.72). Total EE was greater (P <0.05) for Boer than for Spanish does (13.4 vs. 11.4 MJ/d) and differed among periods (13.5, 11.6, 11.7, 11.8 and 13.4 MJ I day in periods 1, 2, 3, 4 and 5, respectively; SE = 0.41). Likewise, predicted ME intake was greater (P<0.05) for Boer vs. Spanish does (14.2 vs. 12.2 MJ/d) and varied with period (16.1, 10.6, 12.8, 12.6 and 14.0 MJ/day in periods 1, 2, 3, 4 and 5, respectively; SE = 0.47). EEa% was not influenced by SR, breed or period, averaging 49%. Behavioral activities were not highly related to EEa%, although no-intercept regressions against time spent grazing/eating and grazing/eating plus walking indicated an increase in EEa% of 5.79 and 5.05%/h, respectively. In conclusion, although EEa% was not affected by trea tments of this experiment or highly related to behavioral activities monitored, it represents a sizeable cost of energy deserved of further study.

Metabolism and lactation performance in dairy cows fed a diet containing rumen-protected fat during the last twelve weeks of gestation

Effects of dietary fat supplementation prepartum on liver lipids and metabolism in dairy cows are contradictory. Thus, we examined in 18 German Holstein cows (half-sib; first lactation 305-d milk yield >9,000kg) whether dietary fat:carbohydrate ratio during the last trimester of gestation affects lipid metabolism and milk yield. The diets were formulated to be isoenergetic and isonitrogenous but differed in rumen-protected fat (FD; 28 and 46.5g/kg of dry matter during far-off and close-up dry period; mainly C16:0 and C18:1) and starch concentration [carbohydrate diet (CD); 2.3 times as much starch as FD]. Diets were given ad libitum starting 12wk before expected parturition. After parturition all cows were fed a single lactation diet ad libitum for 14wk. With the FD treatment, dry matter intake was depressed prepartum, milk yield during first 4wk of lactation was lower (36.9 vs. 41.0kg/d), and postpartum energy balance during this period was more negative. During the first 4wk, cows in the FD group had lower lactose percentage and yield but higher milk fat, whereas milk protein and fat yield as well as energy-corrected milk did not differ. Betweenwk 5 and 14, milk fat and milk protein percentage was lower in CD than in FD. Milk fat C14:0 was lower and C16:1 was higher in the FD group. For FD cows, plasma triacylglycerol, nonesterified fatty acids, and cholesterol concentrations were higher prepartum, whereas plasma β-hydroxybutyrate and glucose concentrations were lower. During the first 10 d after parturition, plasma triacylglycerol concentration was higher in FD, and prepartum plasma glucose and cholesterol differences persisted during the first 14wk of lactation. Irrespective of prepartum nutrient composition, concentrations of plasma leptin and subcutaneous fat leptin mRNA decreased between −10 d to +10 d relative to parturition, and liver lipids and glycogen reached maximum and minimal values, respectively, 10 d after parturition. Acetyl-coenzyme A carboxylase α mRNA abundance in subcutaneous fat decreased between −10 d to +1 d relative to parturition by 97%, whereas it was generally much lower in the liver and remained at a low level until wk 14 of lactation. In conclusion, feeding a diet containing rumen-protected fat during late lactation and dry period until calving negatively affected dry matter intake, energy balance, and milk yield during subsequent lactation, did not change acetyl-coenzyme A carboxylase α mRNA abundance in subcutaneous fat, and was not beneficial for liver lipid accumulation.

Insulin-like growth factor-I (IGF-I) and thyroid hormone concentrations in colostrum of Holstein-Friesian cows before and after calving

The concentration of biologically active molecules in colostrum is strongly related to the metabolic and endocrine status of the cow during the early postpartum period. The aim of this study was to determine concentrations of insulin like growth factor-I (IGF-I), triiodothyronine (T3) and thyroxine (T4) in mammary gland secretion during the late dry and colostral period and its possible association with the energy status of the cows as represented by blood glucose concentration. Ten healthy Holstein-Friesian dairy cows were involved in this study. Two samples of colostrum were taken from each animal: one between 19 and 53 hours (mean [sd] 32.10 [9.47] hours) before calving, and the second 2 hours after calving. Concentrations of IGF-I, T3 and T4 tended to decrease at the start of lactation but the changes were not statistically significant. Linear regression of colostral IGF-I and protein concentration before calving revealed a positive relationship (R2 = 0.668, p<0.01) before calving but not post partum (R2 = 0.348, p>0.05). Blood glucose concentration was 2.88 ± 0.32 mmol/L before and 2.28 ± 0.29 mmol/L after calving and the decrease was statistically significant (p<0.001). Blood glucose levels after calving were positively correlated with colostral IGF-I concentration after calving (R2 = 0.695, p<0.01), but not before parturition (R2 = 0.383, p>0.05).

Effects of silage digestibility on intake and body reserves of dry cows and performance in the first part of the next lactation

This experiment evaluated different strategies for allocating first-cut grass silages to dry dairy cows that had low body-condition score (BCS) at drying off. A total of 48 moderately yielding Holstein-Friesian cows were used, receiving one of three dietary treatments in the dry period and a single lactation diet based on a flat-rate of concentrates and grass silage ad libitum. Throughout the dry period, one group received a low-digestibility silage (harvested 15 June 1998; LL; metabolisable energy (ME) = 10.3 MJ/kg dry matter (DM)) and a second group received a high-digestibility silage (harvested 9 May 1998, HH; ME = 11.7 MJ/kg DM). A third strategy (LH) offered the low-digestibility silage in the early dry period and the high-digestibility silage in the final 3 weeks before calving. The silages had very different crude protein concentrations (144 and 201 g/kg DM) and intakes were widely divergent (10.1 v. 13.5 kg DM/day) across the dry period. No concentrates were fed during the dry period. Silage quality had a very large effect on liveweight change, with treatment means of 0.32 and 1.75 kg/day for LL and HH, respectively. BCS changes followed a similar pattern, though no cows became over-conditioned and blood metabolites were within normal ranges. Increased silage digestibility in the late dry period led to a substantial increase in milk fat concentration and a smaller increase in milk protein concentration, the latter confined to the first full week of lactation. Depression of milk fat appears related to low blood glucose when dry cows in low body condition are fed at a low level. The LH strategy avoided the tendency for lower milk yields and fat concentration that resulted from feeding the low-digestibility silage until calving. This strategy also avoided the higher calf weights that resulted from feeding the high-digestibility silage in the early dry period.

Thyroid hormones and their correlations with serum glucose, beta hydroxybutyrate, nonesterified fatty acids, cholesterol, and lipoproteins of high-yielding dairy cows at different stages of lactation cycle

The relationships between circulating thyroid hormones and serum glucose, beta hydroxybutyrate (BHB), nonesterified fatty acid (NEFA), cholesterol and lipoproteins of high-yielding dairy cows were studied in 125 adult Holsteins at various stages of lactation cycle: early (far-off) dry period (n = 24), late (close-up) dry period (n = 10), fresh cows (n = 22), early lactation (n = 13), mid-lactation (n = 27) and late lactation (n = 29). Decreased levels of thyroxin (T4) and triiodothyronine (T3) were noted in peripartum cows which were extended to mid- and late-lactation cows, respectively. In fresh cows, glucose showed correlations with T4 (r = 0.619, P < 0.01) and T3 (r = 0.627, P < 0.01). In the same cows there were correlations between T4 and BHB (r = 0.590, P < 0.01) and NEFA (r = 0.470, P < 0.01). In late dry cows, free thyroxin (fT4) showed correlations with triglyceride (TG) and very-low-density lipoprotein (VLDL; r = −0.638, P < 0.05). Pooled data of the various stages of lactation cycle revealed correlations between glucose and T4 (r = 0.20, P < 0.05), glucose and T3 (r = 0.395, P < 0.01), cholesterol and T3 (r = −0.201, P < 0.05), and free triiodothyronine (fT3) and high-density lipoprotein (HDL; r = 0.178, P < 0.05). It appears that the time and the pattern of changes and/or correlations of serum thyroid hormones and lipid fractions may vary among dairy cows and other animals.

Influence of body condition on incidence and degree of hepatic lipidosis in cows

The aim of this study was to investigate the influence of energy status of cows, estimated by body condition score, on the incidence and the degree of hepatic lipidosis during the early stage of lactation. Cows were divided into four groups: dry, early puerperal, early lactation and late lactation period. Each group consisted of 60 cows. Body condition was scored by the method established in Elaco Animal Health Buletin Al 8478. According to this method, body condition score is represented numerically from 1 to 5 points. Liver samples for pathohistological analyses were taken by biopsy from early lactation cows (60. day of lactation). Fat content in hepatocytes was determined morphometrically and results were compared with criteria based on total lipid and triglyceride content in liver tissue. On farm A, average body condition scores were in a range from 3.31, at sixty days of lactation, to 3.86 points in the dry period. Nevertheless, the range was wider on farm B, and was from 2.18 points at sixty days of lactation to 4.15 points at the dry period. Besides, differences in average body condition scores were higher than 1 point, and in some cases (between late lactation or dry period to sixty days of lactation) were almost 2 points. The incidence and the degree of hepatic lipidosis strongly differ between the two examined farms. On farm A the incidence of hepatic lipidosis was 18.33 percent, while on farm B that percent was much higher (43.32). A significant difference was established in the degree of hepatic lipidosis between those two farms. On farm A diffuse hepatic lipidosis was determined in 5.0 percent of cows, while on farm B that percent was 18.33. According to these results, most of the cows on farm B had uncontrolled lipomobilisation and severe fatty liver during the early lactation period, probably due to the obesity of these cows in late lactation and the dry period.

Genetic variation in the marbled lungfish Protopterus aethiopicus in Lake Victoria and introduction to Lake Baringo, Kenya

Marbled lungfish Protopterus aethiopicus in Lake Victoria and two nearby smaller lakes were found to have high levels of DNA sequence variation in their mitochondrial control regions (35 haplotypes in 61 fish) but no population genetic structure (ΦST= 0·00). In contrast, marbled lungfish in Lake Baringo, Kenya, appeared to be fixed for a single control region haplotype, which occurred at low frequency in the other lakes. Using FLUCTUATE software, the female effective population size in Lake Victoria during the late Pleistocene was estimated to be c. 500 000, similar to the value estimated for the present‐day population. These observations suggest that, during the late Pleistocene dry period, a large marbled lungfish population survived either in wet refugial areas within the lake basin or in surrounding areas. Marbled lungfish were reported to have been introduced into Lake Baringo 30 years ago with a founding population of only three individuals. The lack of control region variation in the Lake Baringo population is consistent with that situation.

Evaluation of the Use of Cephapirin Sodium Intramammary Therapy in the Closeup Dry Period to Reduce Subclinical Mastitis in Adult Dairy Cattle

Subclinical mastitis and milk quality are significant economic issues among dairies. It has been estimated that clinical mastitis can cost $110 per case, and the inclusion oflosses in milk production and discarded milk among subclinically affected cattle increase this estimate to $200. The prevalence of intramammary infections (IMls) peaks in the early and late dry periods, so these times are important to mastitis control programs. This study was designed to examine the potential benefit of intramammary therapy (IMT) administered in the late dry period on the incidence of IMIs in the first 180 days of lactation.

Annual and seasonal variability in evapotranspiration and water table at a shrub‐covered bog in southern Ontario, Canada

AbstractEvapotranspiration (ET) was measured via the eddy covariance technique at a shrub bog peatland in southeastern Ontario for 5 years. For most of the study period the temperature was above normal. Precipitation was variable, but, in 2 years, late summer dry periods resulted in an extended period of deep drawdown of the water table (WT). Growing‐season (May–September) daily ET varied considerably; maximum ET rates were 4 to 5 mm day−1. Winter ET rates were an order of magnitude smaller than in summer, yet the total winter ET loss was important, accounting for 23 to 30% of the annual ET water loss. Annual precipitation exceeded annual ET by 1·55 to 1·94 times.During the growing season, daily ET was closely related to daily potential evaporation (PET); however, the slope of this relationship was statistically different in some years. In contrast, ET and WT were only weakly related in most years. When ET was sorted into 5 cm WT classes there was no difference in mean ET across most WT classes; only the two deepest WT classes had significantly smaller mean ET. The ratio ET/PET followed the same pattern. We present a conceptual model of ET that relates WT, soil hydraulic properties and moss and vascular plant processes. Copyright © 2005 John Wiley &amp; Sons, Ltd.