Early Dry Period Research Articles

The Effect of the Foresummer Drought on Carbon Exchange in Subalpine Meadows

Climate in subalpine meadows of the Rocky Mountains can be characterized by an early (foresummer) drought that occurs after snowmelt (May) and lasts until the start of the summer monsoon season (July). Climate change models predict an increase in the length and severity of this dry period due to earlier snowmelt dates, rising air temperatures, and shifts in the start and/or intensity of the North American monsoon. However, it is unknown how changes in the severity of this early season dry period will affect ecosystem carbon exchange. To address the importance of early season drought, we combined a watering manipulation with 11 years of ecosystem carbon exchange data across an elevational gradient at the Rocky Mountain Biological Laboratory in Gothic, Colorado. Long-term trends reveal that earlier snowmelt dates lead to a decrease in net ecosystem productivity (NEP), in part because of the positive effect on early growing season drought conditions. Manipulating the strength of the foresummer drought by watering revealed that the timing of growing season precipitation is more important than the total amount for determining cumulative NEP. The strength of the foresummer drought did not significantly impact ecosystem respiration rates, but plants that experienced a strong foresummer drought exhibited more water stress, and lower instantaneous rates of NEP, even during the rainy season. Our results highlight the central role of the foresummer drought in determining rates of carbon exchange throughout the growing season, and the potential for an increasingly negative balance of carbon in subalpine meadows under future climate change.

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.

English

A cross-sectional study was conducted from September 2009 to March 2010 in and around Haramaya town to determine the species composition, prevalence and seasonal variation of ixodid cattle ticks. During the study period, a total of 3117 adult ixodid cattle ticks were collected from the half body regions of 346 local breeds of cattle which were under extensive management system during early dry and early wet periods and then identified to genera and species level.  Six tick species of four genera were identified in which two species each belongs to the genus Amblyomma and Rhipicephalus and one species each belong to the genus Hyalomma and Boophilus. Of the total tick collected, Amblyomma, Boophilus, Rhipicephalus and Hyalomma constitutes (65, 26.3, 10.9 and 7.8%), respectively. The prevalence of tick species were Amblyomma varigatum (41%) Boophilus decoloratus (26.3%), Amblyomma coherence (14.9%), Hyalomma rufipes (7.8%) and Rhipicephalus evertsi (5.5%) and Rhipicephalus pulchellus (5.4%).  The present study reveals that A. varigatum was the most abundant cattle tick species in and around Haramaya town and while the R. pulchelusis the least abundant. There was no statistical significance difference (P> 0.05) in tick infestation between sex of cattle’s but tick infestation was significantly (P< 0.05) higher in adult age groups of cattle compared to caves. The favorable predilection sites of Amblyomma species were ano-vulva, udder/scrotum, but B. decoloratus preferred dewlap, perineum and udder/scrotum. The sex ratio of all tick species identified during this study period was skewed towards male except for B. decoloratus. The present study on tick species composition and seasonal variability contributes its part on how to design control strategies for ticks and tick borne diseases in the study area. Key words: Ixodid cattle tick, seasonal variation, tick species composition, prevalence, Haramaya.

Daily and seasonal courses of gas exchange and niche partitioning among coexisting tree species in a tropical montane forest

We investigated the seasonal gas exchange patterns of three different functional types of tropical afromontane trees, namely Podocarpus falcatus (Thunb.) Mirb. (evergreen gymnosperm), Prunus africana (Hook. f.) Kalkm. (broad-leaf evergreen), and Croton macrostachyus Hochst. ex Del. (broad-leaf deciduous) which grow side-by-side in the Munessa forest, southern Central Ethiopia. The hypothesis is that the trees can make different use of the environmental conditions which change seasonally and also from year to year. These changes can be understood as fluctuating niches, the utilization of which allows coexistence through balanced carbon gain. In this study, light and moisture were considered the two main fluctuating niches. Porometry was used to measure the daily and seasonal responses of the leaves to environmental variables under dry and wet season conditions in the course of the climatically differing years 2009 and 2010. Correlations of the patterns of these responses were analyzed by regression analysis. From daily integrated rates of irradiation, photosynthesis and transpiration, light and water use efficiencies of photosynthetic carbon gain and their mutual interdependences were determined. Except an extended dry season in 2009 when C. macrostachyus had shed its foliage, all three species continued photosynthetic net CO2 uptake concomitant with transpiration at all seasons, although at varying rates. Ecophysiological performance of P. falcatus leaves is mainly light-driven and responds relatively little to a change in moisture conditions. Its carbon and water relations are striving for stability rather than flexibility. As of a typically subdominant species of the forest, P. africana leaves can efficiently use low light intensities but suffer from photoinhibition at full light. Their performance, showing more dynamic response to the environment than P. falcatus, P. africana appears driven more by moisture than by light. Compared to the two evergreens C. macrostachyus exhibited the highest flexibility in its leaves’ physiological responses to environmental conditions, in particular to the light climate which is additionally potentiated by the fast turnover of its foliage. This species optimizes its carbon gain during the wet season and during the early dry period when cloud cover is minimal. Our findings thus reveal that elasticity of the response to fluctuating environmental conditions is an additional aspect in the assessment of the utilization of temporally fluctuating niches by adult tree individuals.

Levels of insulin, insulin-like growth factor-I and thyroid hormones in relation to the body condition score changes in periparturient dairy cows

The objective of this study was to determine the levels of insulin, insulin like growth factor I (IGF-I) and thyroid hormones in relation to the body condition score (BCS) of periparturient dairy cows. The study was carried out on twenty Holstein-Friesian dairy cows with average milk production of 7000 L/305 days in the previous lactation, parity ranging from 2-4. All cows were BCS scored during the early dry period, 7±3 days before and after parturition. Based on the BCS at the early dry period, cows were divided in two groups: cows with high BCS (3.75- 4.25, HBCS, n=10), and cows with moderate BCS (2.75-3.75, MBCS, n=10). Blood samples were taken at the time of BCS evaluation. Concentrations of insulin, IGF-I, triiodothyroinine (T3) and thyroxine (T4) were determined by radioimmunoassay (RIA, INEP-Zemun, Serbia). Statistical differences between mean values were determined using Student t-test (p<0.01). Mean BCS values at early dry period were significantly different compared to two other periods (p<0.01) within both groups, but BCS was similar in both groups at 7±3 days after calving (2.69±0.67:2.62± 0.27, p>0.05). IGF-I level in HBCS cows at days 7±3 before calving was significantly higher (16.28±3.07:11.76±2.28, p<0.01), with a reverse relationship after calving (3.77±1.64:8.46±2.37, p<0.01). Insulin level was significantly lower at 7±3 days before calving in HBCS cows (16.26±4.60:20.18±4.96mIU/L, p<0.05). Thyroid hormones levels were significantly lower in HBCS group et all examined periods. [Projekat Ministarstva nauke Republike Srbije, br. III 46002 i br. 31003]

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.

Measurement of internal shrinkage distribution in spaghetti during drying by X-ray μCT

With the addition of aluminum particles, shrinkage of spaghetti strands during drying was studied using X-ray microtomography (μCT). Images of spaghetti dried under a prescribed drying program were taken six times during a drying period of nearly 6h. Spaghetti initially shrank in both radial and axial directions, but expanded a little later. Radially, shrinkage was initially torsional and non-central in direction, before becoming linear, and centrally- directed. The shrinkage rate was higher radially than axially. The annular distribution of the internal shrinkage was analyzed showing that radially, the periphery shrank more in the early period of drying and less in the later period. In contrast, in the axial direction, spaghetti shrank more near the center and less on the periphery. This shrinkage distribution during drying implies that residual stresses must arise and are important in explaining cracking. This study also shows that X-ray μCT is an effective technique in tracing food shrinkage during drying, especially distributions occurring internally.

Rumination and its relationship to feeding and lying behavior in Holstein dairy cows

The objective of this study was to describe the relationship between rumination and feeding and lying behavior in dairy cows. Rumination time was monitored electronically using HR-Tags (SCR Engineers Ltd., Netanya, Israel). Feeding time and dry matter intake (DMI) were monitored using Insentec feed bins (Insentec BV, Marknesse, the Netherlands). All measures were collected in 2-h periods for 42 mature Holstein cows for a minimum of 9 d in the early dry period. Pearson correlation was used to describe associations, among 2-h periods within cow, first examining the relationship within a single period, and then modeling how this relationship changes when a lag of 2, 4, or 6h was imposed. Periods when cows spent more time ruminating were associated with lower feeding times and lower DMI (r=−0.71 and r=−0.72, respectively), likely because cows were unable to feed and ruminate simultaneously. The correlations with rumination time changed from negative to positive when lags of 2, 4, and 6h were modeled (r=−0.09, 0.24, and 0.15, and r=−0.16, 0.23, and 0.17 for feeding time and DMI at lags of 2, 4, and 6h, respectively). These results indicate that following periods of high feeding times and intakes, cows spent more time ruminating. This relationship peaks at approximately 4h after feeding. Periods of rumination were also associated with time spent lying down. Cows that spent more time ruminating per day, spent less time feeding (r=−0.34) and rumination times did not relate to DMI (r=0.11). These data indicate that rumination time can be used to estimate within-cow variation in feeding behavior and intake, but daily summaries of rumination behavior are a poor indicator of DMI.

Involvement of TNF-α and MAPK pathway in the intramammary MMP-9 release via degranulation of cow neutrophils during acute mammary gland involution

Neutrophil-derived MMP-9 activity is regulated more promptly and efficiently at the level of degranulation than at other levels of regulation. In human neutrophils, degranulation is one of the earliest responses to TNF-α stimulation, which involves protein kinase C and mitogen-activating protein kinase (MAPK) pathways. The level of MMP-9 in mammary secretion of cows increases drastically following milk-stasis, which is partially explained by increases of both neutrophil infiltration and neutrophil degranulation per se. Since MMP-9 represents one of the major remodeling capacities in the mammary gland of cows during early dry period, the current study attempted to explore the involved intracellular mechanisms in the up-regulated MMP-9 secretion. We repeatedly measured on the somatic cells of mammary secretion along the early dry period of cows the expression of TNF-α protein and the phosphorylation of p38 MAPK, ERK, and JNK. Also, cultures of bovine peripheral neutrophils were conducted to examine the mode of short-term MMP-9 secretion in response to TNF-α stimulation and the blocking effects of TNF-α antibody and inhibitors of MAPK pathways. Ex vivo measurements show that conventional cow milk has fully transformed into a neutrophil-abundant, lactoferrin-rich, and high-MMP-9 mammary secretion by d 7 in milk-stasis. No significant (P>0.05) change, however, was found in the expression of TNF-α or the phosphorylation extent of MAPK pathway intermediates on the somatic cells of mammary secretion during the first 3weeks in milk-stasis. In vitro studies indicate linear increase of short-term MMP-9 release in response to TNF-α stimulation in dosages between 0.1 and 10ng/ml. In the presence of preparations of d 7-dry secretion of cows, the short-term release of MMP-9 from bovine peripheral neutrophils was significantly (P<0.05) blocked by inhibitor of p38 MAPK but was significantly (P<0.05) promoted by ERK inhibitor while TNF-α antibody or JNK inhibitor exerted no effect. In conclusion, the current ex vivo measurements suggest no apparent association of TNF-α and MAPK pathway with long term intramammary accumulation of MMP-9 during the early dry period of cows, whereas cultures of bovine peripheral neutrophils under a simulated acute involution intramammary environment of cows suggest a role played by TNF-α and MAPK pathways in the short-term MMP-9 release via degranulation.

Incidental capture of green turtle (Chelonia mydas) in gillnets of small-scale fisheries in the Paranaguá Bay, Southern Brazil

Fishing activities are an important economic resource in the Paranaguá Bay, southern Brazil. In this area, there are reports of sea turtles interacting with small-scale fisheries. It was found that the juvenile green-turtle (Chelonia mydas) uses areas disturbed by fishing activity, which puts them at a higher risk of capture. The objective of this study was to evaluate the interactions of juvenile green-turtles with the gillnets used in small-scale fisheries, enabling a long-term understanding of those gillnet characteristics which increase the risk of turtle captures. The highest sea turtle capture rates occur in the early dry season, which is correlated with the larger displacement of individuals searching for available food sources. High levels of fishing effort also occur in this early dry period without a specific target resource. The highest levels of sea turtle mortality were observed during the coldest periods of the year (late rainy and early dry seasons) and can be related to the physiological needs of the sea turtles. The characteristics of gillnets that had the strongest relationships to turtle captures were soak time and mesh size. These results suggest that it is necessary to design new regulations governing aspects of fishing techniques such as soak time, net length or seasonal use of nets. Conservation initiatives aiming to reduce the risk of turtle capture must consider the economic importance of small-scale fishing practices and address the conflict that may exist between social concerns and environmental issues.

Changes in rumen absorption processes during transition

Transition is defined as the period from 3 weeks before parturition until 3 weeks postpartum and is characterized by changes in endocrine status and by major alterations in the requirement for nutrients, vitamins and minerals. At parturition, the dry period diet is replaced by an ad libitum offered lactation diet, which causes changes of rumen fermentation because of its higher energy density and the overall increase of dry matter intake. Hence, ruminal fermentation parameters such as pH, volatile fatty acid (VFA) concentrations and osmotic pressure are changed. This causes alterations in the rumen epithelium generally termed adaptation: the modulation of enzyme activities, an increase in the number and size of papillae and enhanced transport rates of ions. These effects are well documented when sheep or cows are experimentally and independent of parturition shifted from a low energy (roughage) to a concentrate diet. Only a few studies have been conducted in cows during transition and, thus, data on diet dependent effects on postpartum rumen acidosis are absent and information regarding number and size of papillae is inconsistent. Furthermore, investigations of gene expression related to VFA absorption or metabolism have not shown diet dependent alterations. However, evidence from in vitro and in vivo studies exists that the stimulation of fermentation before parturition enhances the transport rates of Na, Cl and VFA across bovine rumen epithelium. The underlying mechanisms for epithelial adaptation to dietary alterations are poorly understood at present. Luminal factors such as increased VFA concentrations (particularly butyrate) and the hormonal effects of insulin and of insulin like growth factor 1 have partly been confirmed to be involved in the regulation of this adaptation process. More research is needed in order to determine the factors causally inducing adaptational responses and the amount of dietary change at which the adaptational responses apparently level off. Despite these uncertainties, an increase of energy and protein intake undoubtedly improves the barrier and transport functions of the epithelium. Consequently, at least for 2 weeks before parturition, a diet should be offered that is fermented more easily and more rapidly than the diet in the early dry period. Furthermore, efforts should be directed towards an improved voluntary food intake before and after parturition, with special attention being paid to the mechanisms enabling the epithelium to adapt to and handle the regular diurnal variations in pH, VFA concentration and osmotic pressure, mechanisms that seem to fail in the pathophysiology of subacute rumen acidosis.

Modifications of the defense and remodeling functionalities of bovine neutrophils inside the mammary gland of milk stasis cows received a commercial dry-cow treatment

An appropriate length of milk stasis between two consecutive lactations of dairy cows is crucial for sustainable milk production. This dry period of cows allows extensive remodeling and sufficient cell renewal in mammary gland. Nevertheless, early dry period is one of the most risky stages in cow lactation cycle to intramammary infection. Dry-cow treatment through teats is, therefore, widely practiced at the commencement of milk stasis. Neutrophils are the most abundant cellular components in cow mammary secretion during early dry period, which in turn attribute to the meanwhile elevation of somatic cell counts and matrix metalloproteinase-9 (MMP-9) level. This study used bovine peripheral neutrophils as a cell model to examine the mode of modifications in their defense and remodeling functionalities after infiltration into mammary gland during early dry period. Results indicate a dose-dependent suppression of phorbol 12-myristate 13-acetate-stimulated free radical production and induction of MMP 9 degranulation in bovine peripheral neutrophils exposure to the d 7-dry secretion of cows received dry cow treatment at d 0 in milk stasis. Meanwhile, an enhancement of plasminogen activation and TNF-α shedding on bovine peripheral neutrophils were also observed. These two cellular events might be involved in the functional modifications on infiltrated neutrophils during early dry period. In conclusion, the opposite trend of modifications in the defense and matrix remodeling functionalities of neutrophils inside the mammary gland of cows at early dry period reflect the collaboration of infiltrated neutrophils for promoting extensive glandular remodeling at minimum compromise of local defense during the acute involution period without apparent disturbance by dry cow treatment.

Mining-related contamination of surface water and sediments of the Kafue River drainage system in the Copperbelt district, Zambia: An example of a high neutralization capacity system

Contamination of the Kafue River network in the Copperbelt, northern Zambia, was investigated using sampling and analyses of solid phases and water, speciation modeling, and multivariate statistics. Total metal contents in stream sediments show that the Kafue River and especially its tributaries downstream from the main contamination sources are highly enriched with respect to Cu and exceed the Canadian limit for freshwater sediments. Results of sequential analyses of stream sediments revealed that the amounts of Cu, Co and Mn bound to extractable/carbonate, reducible (poorly crystalline Fe- and Mn oxides and hydroxides) and oxidizable (organic matter and sulfides) fractions are higher than in the residual ( Aqua Regia) fraction. Compared to Cu, Co and Mn, Fe is bound predominantly to the residual fraction. Values of pH in the Kafue River and its tributaries are alkaline in the contaminated area and concentrations of sulfate gradually increase downstream. Water balance based on sulfate indicates that inflow from the most contaminated tributaries is less than 5% of total discharge in the Kafue River. There is a significant input of Cu and Co from multiple contamination sources close to the town of Chingola, located on the Mushishima tributary, but both metals are mostly bound to suspended particles, which settle in the Kafue River. Additional contaminant sources such as the Uchi mine tailings and Nkana smelter are located in the industrial area around Kitwe, but metals released from these sources are mostly found in suspension and are attenuated efficiently. Low Fe/Cu ratios in suspension and mineralogical composition of stream sediments downstream of contaminant sources around Chingola indicate that native copper, Cu-sulfides, and Cu carbonates are present in stream sediments in addition to Cu bound to Fe(III) oxide and hydroxides. The Nkana smelter fingerprint in stream sediments is recognized by the presence of slag glass and a Cu-Fe-S intermediate solid solution (ISS). Speciation modeling suggests a possibility of precipitation of some Cu phases in the most contaminated tributaries such as the Mushishima. In the early dry period (mid-May) dissolved and suspended Cu and Co concentrations are lower than in the advanced dry period (late June). When the scale of mining and related activities in the Copperbelt is taken into account, the environmental impact of mining and related activities on the Kafue River is relatively limited due to a high neutralizing capacity of the mining wastes which control the rapid precipitation of iron oxides and hydroxides as well as adsorption and/or co-precipitation of copper, and cobalt. The high metal content in stream sediments, however, may pose a potential environmental risk during accidental acid spikes, when significant fractions of metals in sediments can be re-mobilized.

Efficacy of a novel internal dry period teat sealant containing 0.5% chlorhexidine against experimental challenge with Streptococcus uberis in dairy cattle

The incidence of clinical mastitis and infection status at calving was assessed in quarters treated with 1 of 2 internal teat sealants at the time of dry off. Two contralateral quarters per cow (n=63 cows) were treated with a sealant that contained 0.5% chlorhexidine; the other quarters were treated with a commercial teat sealant. Ten cows were untreated (controls). On d 2, 4, and 16 after dry off, cows were challenged with Streptococcus uberis S210 strain. Cows were examined daily for 34 d after drying off and cases of clinical mastitis were recorded. Milk samples were collected for culture from any quarters that developed clinical mastitis during the first 34 d after drying-off and from all quarters on d −5 and 0 relative to treatment and at the first and twentieth milking after calving. The incidence of clinical mastitis during the examination period was lower in treated quarters (n=7/252; 1.5%; lower incidence for those treated with chlorhexidine-containing teat sealant n=3/126; 1.2%) than in untreated quarters (n=13/40; 26.8%). The protection against intramammary infection after calving, adjusted for the effect of cow, was higher in quarters treated with the novel teat sealant (89/105; 15.2%; 95% CI=9.6–23.4) than in those treated with the commercial teat sealant (71/104; 31.7%; 95% CI=23.5–41.3) and untreated controls (6/28; 78.6%; 95% CI=59.8–90.0), respectively. Quarters treated with teat sealants were less likely to have an intramammary infection after calving and had a lower incidence of clinical mastitis during the early dry period than did untreated controls in this challenge study.

Fatty liver and displaced abomasums in a TMR-fed dairy herd

A change was made to a total mixed ration (TMR) on a farm of 200 Holstein-Friesian cows. At the same time a higher proportion of maize silage to grass silage was fed. As a result, 305-day yields increased dramatically over an 18-month period from 7600 to 9100 litres. Greater problems (an increased incidence of displaced abomasums, retained fetal membranes and endometritis) were experienced on the new management system in freshly-calved cows. The underlying problem, which was diagnosed from clinical signs and blood sample results, was thought to be fatty liver caused by overfeeding in late lactation and in the early dry period.

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.

Effect of milking frequency and feeding level before and after dry off on dairy cattle behavior and udder characteristics

The effects of 2 common dry-off management procedures, feed restriction [8 vs. 16kg of dry matter (DM)/d] and reduced milking frequency (once, 1× vs. twice, 2×/d), on the behavior and udder characteristics of dairy cattle were assessed in late lactation and the early dry period. Milking cows 1× instead of 2× in the week before dry off reduced milk yield (7.0 vs. 8.9 ± 0.95 kg/d for 1× and 2×, respectively), but had little effect on behavior before or after cessation of milking. In comparison, feed restriction reduced milk yield (6.9 vs. 9.1 ± 0.95 kg/d for 8 and 16kg of DM/d, respectively), udder firmness after dry off (7.3 vs. 8.0 ± 0.24 g force for 8 and 16kg of DM/d, respectively), milk leakage (2 d after dry off, 14% of cows offered 8kg of DM/d were leaking milk compared with 42% cows offered 16kg of DM/d), and the likelihood of Streptococcus uberis intramammary infection (nonclinical mastitis; 12.5 vs. 62.5% of groups with at least 1 cow with a new intramammary infection for 8 and 16kg of DM/d, respectively). Despite these benefits, cows offered only 8kg of DM/d spent less time eating (7.3 vs. 8.3 ± 0.28 h/d for 8 and 16kg DM/d, respectively), more time lying (8.8 vs. 7.3 ± 0.24 h/d), and vocalized more before dry off than cows offered 16kg of DM/d (0.8 vs. 0.2 ± 0.15 calls/min for 8 and 16kg of DM/d, respectively). These behavioral changes indicate that this level of feed restriction may cause hunger. Information is needed about alternative dry-off procedures that maintain the health benefits and comfort associated with lower milk yield before dry off but prevent hunger, such as feeding low quality diets ad libitum.

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.

Cellular Mechanisms in Regulating Mammary Cell Turnover During Lactation and Dry Period in Dairy Cows

The mechanisms involved in regulating mammary cell turnover during the pregnancy-lactation cycle in dairy cows are unclear. The objective of present experiment was to describe expression of genes encoding proteins known to be involved in pathways regulating mammary cell proliferation, apoptosis, differentiation, cell survival, and tissue remodeling. Mammary gland biopsies were taken 7 times during the pregnancy-lactation cycle of 10 dairy cows, and samples were analyzed by immunohistochemistry and real-time PCR. Cell proliferation was greatest during the dry period and apoptosis was high in early dry period and early lactation. Based on Fas (tumor necrosis factor receptor superfamily member 6), Fas ligand, and caspase-3, caspase-8, and caspase-9 gene expression, no indication was found of a stage-dependent shift between the extrinsic and intrinsic pathways leading to apoptosis. Gene expression of microsomal glutathione S-transferase (mGST) did not vary significantly, whereas B-cell leukemia/lymphoma 2 (Bcl-2) and BCL2-associated X protein (Bax) gene expression was greatest during the dry period and early lactation and coincided with high cell turnover. Gene expression of early response genes c-Fos, c-Jun, and c-Myc correlated to neither rate of cell proliferation nor plasma concentration of insulin-like growth factor (IGF)-I and insulin. Gene expression of nuclear factor of kappa light chain gene enhancer in B-cells (NFκB) and NFκB inhibitor α was greatest in the periparturient period, and NFκB gene expression coincided with an anticipated need for cell survival factors. Expression of transforming growth factor β (TGF-β) receptor 1 and 2 mRNA was greatest in early lactation, whereas TGF-β1 did not vary significant during the pregnancy-lactation cycle. Even though our results on the TGF-β system did not comply with other studies, the gene expression pattern of the TGF-β receptors indicates a role in regulating apoptosis in early lactation. Signal transducer and activator of transcription 5 (STAT5) gene expression was high in the periparturient period, which suggests a role for STAT5 in regulation of mammary cell proliferation and differentiation in dairy cows. Expression of tissue-plasminogen activator, plasminogen activator inhibitor-1, and IGF binding protein 5 genes was greatest in early lactation, suggesting a role for IGF binding protein 5 in coordinating regulation of apoptosis and tissue remodeling.