Late Pregnant Cows Research Articles

Quantitative Relationships Between Cyclic Adenosine-3′,5′- Monophosphate and Lipolysis in Adipose Tissue During the Peripartum Period

The objective was to study the control of lipolysis and to determine kinetic relationships between subcutaneous adipose tissue cyclic AMP concentrations and rates of lipolysis in primiparous dairy cows in late pregnancy and early lactation. Adipose tissue was biopsied from primiparous cows at –30, –15, –5, 5, 15, 30, and 60 d around parturition. Tissue was incubated with the following treatments: basal, no additions; isoproterenol at 10−5M; adenosine deaminase at 1 × 106 munits/ml; combined isoproteranol and adenosine deaminase; isoproteranol, adenosine deaminase, and 1mM theophylline. Cyclic AMP was highest at .25h and remained elevated for 2h. Response of cyclic AMP at .25h was 5-, 9-, 27-, and 38-fold for the four stimulatory treatments, respectively. Glycerol release at 2h increased 3-, 2.3-, 2.7-, and 3-fold, respectively. Lipolysis was related logarithmically to cyclic AMP concentrations within and among treatments and times around parturition. Either logarithmic or Michaelis-Menten equations predicted similar maximum lipolysis but increased sensitivity to cyclic AMP in tissue from lactating compared with pregnant heifers. Thus, the sensitivity of response of lipolysis to CAMP may be increased in adipose tissue from first lactation cows. These relationships also may be useful in constructing and improving mechanistic models of adipose and whole animal metabolism.

A possible role of endotoxins in spontaneous paretic cows around parturition.

Six late pregnant old cows which had a history of parturient paresis were studied with respect to clinical and blood biochemical changes during two weeks before and after parturition. The levels of serum endotoxin were evaluated during two days before and after parturition. Three out of six animals showed signs of paresis and two animals needed treatment. The clinical and general changes of all parameters supported the idea that during parturient paresis and parturition, there is absorption of endotoxins from the gastro-intestinal tract. Most of the studied parameters changed similarly to what has been described in experimentally induced endotoxaemia. The animals showed signs of ruminal stasis, had an increase in body temperature, prostaglandin metabolite and endotoxin as well as a decrease in serum calcium, zinc, iron and bile acids levels. The changes of these parameters were also closely related to each other. Furthermore, the changes were more pronounced in paretic cows. Endotoxins absorbed from the gastro-intestinal tract can be involved in paresis and make the outcome of this disease more severe.

Effects of ingestion of ponderosa pine needles by late-pregnant cows on uterine blood flow and steroid secretion.

Consumption of Ponderosa pine needles by late-pregnant beef cows results in the premature delivery of a viable calf. We have demonstrated the presence of a factor(s) in plasma from cows fed pine needles that specifically increased uterine arterial tone (i.e., decreased arterial diameter) in vitro. This study was designed to investigate changes in uterine blood flow and steroid secretion/uptake by the gravid uterus of cows fed pine needles to induce premature parturition. Sixteen beef cows were laparotomized on d 240 of gestation, and an electromagnetic blood-flow probe was placed around the uterine artery supplying the gravid horn. Cows were randomly assigned on d 250 of gestation to a control (n = 8; 8.2 kg/d of alfalfa hay) or pine needle (n = 8; 2.7 kg/d of pine needles + 5.5 kg/d of alfalfa hay) diet. Uterine blood flow was monitored, and systemic blood (uterine arterial and[or] jugular venous) and uterine venous blood samples were collected daily between 0630 and 0800, just before feeding. Five of eight cows fed pine needles calved prematurely (average day of gestation = 260.2 +/- .6) compared with cows fed the control diet, which calved on 287.6 +/- 3.4 d of gestation. Uterine blood flow in the control cows remained constant from d 250 through the day of parturition. In contrast, uterine blood flow of cows fed pine needles that calved early decreased progressively (P less than .01), declining to 25.2% of its original value by the day of parturition.(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin responsiveness to glucose and tissue responsiveness to insulin in lactating, pregnant, and nonpregnant, nonlactating beef cows.

Insulin responsiveness to glucose and tissue responsiveness to insulin, using the hyperglycemic clamp and the hyperinsulinemic euglycemic clamp techniques, were measured in lactating, late pregnant, and nonpregnant, nonlactating (NPNL) beef cows. The glucose infusion rate (GIR) in the hyperglycemic clamp technique was higher (P less than .05). in lactating cows than in NPNL cows. The plateau in plasma insulin concentration (insulin responsiveness) was higher (P less than .05) in lactating cows than in late pregnant and NPNL cows. Pregnant cows tended to have higher GIR and lower plateau in plasma insulin concentration than NPNL cows. In the hyperinsulinemic euglycemic clamp technique, GIR (tissue responsiveness to insulin) was higher (P less than .05) in lactating cows than in late pregnant cows; values for NPNL cows were intermediate. We conclude that insulin responsiveness to glucose and tissue responsiveness to insulin were enhanced during lactation but tended to be decreased during late pregnancy in beef cows.

Pregnancy effects on carcass and meat quality attributes of cows

ABSTRACTThe effects of pregnancy status (non-pregnant, early to mid (1 to 5 months) and late (> 6 months)) and month of pregnancy on live weight, carcass weight, dressing proportion, bruising and muscle properties were examined in 237 Shorthorn and Brahman crossbred cows (mean live weight 424 kg, 62% pregnant). The cows were transported 1155 km to an abattoir and given access to food and water until slaughter. Mustering to slaughter periods were 5, 6 or 7 days.The mean gross hot carcass weights for the 89 non-pregnant, 108 early to mid pregnant and 40 late pregnant cows were 207, 199 and 187 kg (P < 0·05). Their respective dressing proportions were 487, 469 and 443 g/kg (P < 0·05). Among the pregnant cows, carcass weight and dressing proportion decreased by 2·95 kg and 6 g/kg, respectively, for each month of pregnancy (P < 0·05).Cows in late pregnancy had lower mean initial yield (IY) and peak force (PF) shear values for m.longissimus dorsi (LD) than non-pregnant cows. The late-pregnant cows also had the greatest mean pH 24 h post mortem (pH24) and ultimate pH (pHu) values (P < 0·05). They also had a greater proportion of carcasses with high pHu values than the early to mid-pregnant and non-pregnant cows (0·30 v. 0·157 v. 0·079; (P < 005). Among the pregnant cows, mean pH24 increased by proportionately 0·038 and the proportion of high pH24 carcasses by 0·055 for each month of pregnancy (P < 0·05). Pregnancy status had no significant effect on mean fat depth, bruise score, PF-IY value or cooking loss.

Liver function in dairy cows in late pregnancy and early lactation

During early lactation, the dairy cow has to contend with a variety of factors which can lead to impairment of hepatic function. Studies have shown that since the overall energy requirement is greatly increased, rates of metabolic processes within the liver have to be increased in proportion. Priority appears to be given to the nutrient requirements of the foetus during gestation and to the lactating mammary gland in early lactation. The cow may be in a state of negative energy balance as peak milk yields are reached 3 to 7 weeks after calving whereas peak voluntary food intake is not reached until 8 to 10 weeks after calving. Hormone production is such as to encourage lipid mobilization. As a result of this energy deficit, cows mobilize their tissue reserves for milk production and may lose appreciable amounts of body weight and muscle. Similar factors may also pertain in late pregnancy.
 One of the possible consequences of mobilization of body reserves is the development of a fatty liver. It was estimated that up to a third of high yielding dairy cows in the U.K. were affected by consequence of fatty liver. Substantial mortality may occur as a consequence of fatty liver in dairy cows and complications such as chronic ketosis, parturient paresis, displaced abomasum, retained placenta, endometritis, an impaired immune response and an adverse effect on fertility have been reported.
 The purpose of this investigation was to establish any changes that may occur in liver function in periparturient dairy cows, when compared with non-lactating cows, in order to aid identification of the cows which are likely to develop fatty liver.

Failure of Naloxone to Stimulate Luteinizing Hormone Secretion during Pregnancy and Steroid Treatment of Ovariectomized Beef Cows1

The response of serum luteinizing hormone (LH) to naloxone, an opiate antagonist, and gonadotropin-releasing hormone (GnRH) was measured in cows in late pregnancy to assess opioid inhibition of LH. Blood samples were collected at 15-min intervals for 7 h. In a Latin Square arrangement, each cow (n = 6) received naloxone (0, 0.5, and 1.0 mg/kg BW, i.v.; 2 cows each) at Hour 2 on 3 consecutive days (9 +/- 2 days prepartum). GnRH (7 ng/kg body weight, i.v.) was administered at Hour 5 to all cows on each day. Mean serum LH concentrations (x +/- SE) before naloxone injection were similar (0.4 +/- 0.1 ng/ml), with no serum LH pulses observed during the experiment. Mean serum LH concentrations post-naloxone were similar (0.4 +/- 0.1 ng/ml) to concentrations pre-naloxone. Mean serum LH concentrations increased (p less than 0.05) following GnRH administration (7 ng/kg) and did not differ among cows receiving different dosages of naloxone (0 mg/kg, 1.44 +/- 0.20; 0.5 mg/kg, 1.0 +/- 0.1; 1.0 mg/kg, 0.9 +/- 0.1 ng/ml). In Experiment 2, LH response to naloxone and GnRH was measured in 12 ovariectomized cows on Day 19 of estrogen and progesterone treatment (5 micrograms/kg BW estrogen: 0.2 mg/kg BW progesterone) and on Days 7 and 14 after steroid treatment. On Day 19, naloxone failed to increase serum LH concentrations (Pre: 0.4 +/- 0.1; Post: 0.4 +/- 0.1 ng/ml) after 0, 0.5, or 1.0 mg/kg BW.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of physiological state and dietary nitrogen supply on digestion in the dairy cow.

The effects of N supply on digestion were compared in cows in late pregnancy vs early lactation. Two groups of four and one group of three dairy cows received, during a digestion trial, corn silage-concentrate diets (65:35) differing in N supply. Concentrates were formulated so that diets were either insufficient (Diet 1) or sufficient (Diets 2 and 3) in ruminally fermented N and either insufficient (Diets 1 and 2) or sufficient (Diet 3) in protein digestible in the intestines. Experimental periods were 3 wk before and 3 wk after parturition. Organic matter digestibilities were 69.8, 73.1 and 72.5% in late pregnancy vs 64.9, 69.8 and 70.8% in early lactation for Diets 1, 2 and 3, respectively. Digestibility was higher (P less than .05) in late pregnancy than in early lactation. Differences between physiological states were attributed to differences in ruminal digestibility and in fiber digestibility. These differences were not explained by a reduction in large particle retention time, but in situ DM disappearance was reduced in early lactation. Ruminal protozoa concentration and the acetate: propionate ratio decreased between pregnancy and lactation. The duodenal non-ammonia N:N intake ratio was higher for Diet 1 than for Diets 2 and 3, 1.20, .97 and .94, respectively, but it did not vary between physiological states. In conclusion, some of the negative consequences of a shortage in degraded N are more dramatic in early lactation than in late pregnancy.

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

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

A farming systems study of abortion in dairy cattle on the Atherton Tableland: 3. Metabolic factors

An association with a rank correlation of 0.55 (p = 0.06) was obtained between monthly rainfall and monthly abortions for a group of 24 farms in tropical Australia where cows grazed predominantly summer rain-dependent pasture. A similar association was found among cows grazing nitrogen-fertilised, irrigated pasture in winter in the same area. On farms with irrigated pasture the first service conception and abortion rates in herds which grazed intensively during the night (abortion 8.9%; first service conception 42.9%) differed significantly from those which grazed during the day (abortion 6.4%; first service conception 52.9%), and this suggested that increased abortion rates and decreased first conception rates may be part of the one syndrome. An hypothesis was developed that the feeding of immature nitrogen-fertilised pasture, rich in protein and stimulated by rain or irrigation, is associated with an increased abortion rate and a depressed conception rate. Other evidence included an increased susceptibility of first lactation cows to abortion, a lower abortion rate in late pregnant dry cows fed more mature pasture, a 20% repeat abortion rate in the population sampled and the lack of conclusive evidence for infectious and selected non-infectious agents. There were no other observed clinical signs in most aborting cows.

Low phosphorus intakes by beef suckler cows in late pregnancy and early lactation

Two groups each of 10 suckler cows were given a basal diet of oat straw and pressed unmolassed sugar beet pulp for the last 19 weeks of pregnancy and the first 6 weeks of lactation. One group received 0·88 kg extracted soya bean meal (SBM) in pregnancy and 1·03 kg in lactation. The other was given 0·27 kg of a liquid supplement (LS) (containing inter alia urea and phosphoric acid) in pregnancy increasing to 0·33 kg in lactation. Both diets provided about the same amounts of digestible crude protein and about 10 g phosphorus (P) per day in pregnancy and 12 g P per day in lactation. Cows given SBM consumed marginally more straw but there were no differences in total diet digestibility. Cows given LS lost significantly more liveweight but their calves grew equally well. There were indications that cows given LS had slightly higher mean blood inorganic P and lower mean blood calcium (Ca) concentrations. Mean blood inorganic P concentrations were not below 1·4 mmol/l in pregnancy or 1·2 in lactation. There were no signs of reduction in voluntary straw intake or depraved appetite. When transferred to grass with a bull at the end of the experiment all cows were served within 24 days. It is concluded that these amounts of dietary P were adequate over the 25 weeks.

Liver function of dairy cows in late pregnancy and early lactation

The possibility that alterations in liver function may occur during late pregnancy as well as after calving has been investigated in healthy dairy cows and the results compared with those from non-pregnant non-lactating cows. There were significant alterations in plasma total bilirubin, glucose, total ketone body and urea concentrations, in bromsulphthalein clearance and in plasma aspartate aminotransferase and creatine kinase activities in periparturient cows compared with non-pregnant non-lactating cows. Of these, only the alterations in glucose, ketone bodies and urea concentrations and bromsulphthalein half-time and retention were markedly different before calving. The degree of fatty infiltration of the liver was significant two weeks before as well as two weeks after calving which differed from previous reports. It seems likely that the changes in the liver in dairy cows are functional and reversible and related to the metabolic demands of late pregnancy and early lactation. The results suggest that such changes in the liver occur well before calving.

Prediction of calving date in beef cows by real-time ultrasonic scanning.

Three hundred pregnant beef cows between 35 and 125 days of gestation were scanned ultrasonically and their calving dates were predicted from measurements of fetal parts. The mean difference between the actual and predicted calving dates was 0.9 day with a standard deviation of 9.0 days. The accuracy and precision of the prediction of calving date were sufficient to be of benefit in the management of cows in late pregnancy and at calving.

Masking the Taste of Rapeseed Meal in Dairy Compound Feeds

Oilseed rape meal is high in protein and available in the UK relatively cheaply. Toxic constituents limit its inclusion in feeds for pigs and poultry but this is not a problem with ruminant animals where microbial action in the rumen removes them. However, the bitter taste of rape meal has been thought to reduce its palatability for ruminant animals (Stedman and Hill, 1987) and it is recommended that its inclusion in compound feeds for cows should not exceed about 150kg/tonne; masking agents are incorporated to reduce this limitation.The question to be addressed can be summarized as “can higher rates of inclusion of rape meal in dairy compound feeds be concealed by more mask?”. Twelve dry cows in late pregnancy were offered feeds with various levels of rape meal in combination with several levels of mask and rate of consumption was monitored.

Functional differences between small and large luteal cells of the late-pregnant vs. nonpregnant cow.

This paper describes an in vitro model for the study of two types of steroidogenic luteal cells from cows in different physiological states. Two different populations of enzymatically dispersed bovine luteal cells were separated on the basis of size in a Cel-Sep Sedimentation Chamber. The separated small (12.5-23 micron in diameter) and large (greater than 23 micron in diameter) luteal cells of late-pregnant cows (Days 190-280) contained the distinct morphological characteristics previously defined for these two populations of cells. Cells were evaluated for progesterone (P4) production during a 3-h incubation with and without bovine luteinizing hormone (bLH, 10 ng/ml). Both small and large luteal cells from the late-pregnant cow were found to contain equal levels of P4 at Time 0 and increased but equal levels of P4 after a 3-h incubation. Neither cell type showed an increase in P4 production in response to the addition of bLH (p greater than 0.05). Since these results differed from earlier reports for luteal cells of the nonpregnant cow, small and large luteal cells of the mid-cycle (Day 14) were incubated, and the levels of P4 production were compared with P4 levels from the late pregnant cow. In agreement with previous reports for nonpregnant cows, progesterone content at Time 0 was 7-fold higher in large cells than in small cells (p less than 0.05), and after 3 h of incubation, 13-fold higher (p less than 0.05). Although the small cells responded to the presence of bLH in the incubation medium with a 4-fold increase in P4 production, this increase was not significant (p greater than 0.05). The large cell did not respond to bLH. However, the large cell type continued to contain and produce more P4 than did the small cells treated with bLH. This study indicates that both the small and large luteal cells of late-pregnancy are able to produce P4. However, the large luteal cell of the estrous cycle produces greater quantities of P4 than does the small luteal cell or the large luteal cell of late pregnancy.

Changes in bovine mammary insulin binding during pregnancy and lactation

1. 1. Binding of insulin to microsomes from mammary glands of pregnant and lactating dairy cows was characterized. 2. 2. Binding affinities of the insulin receptor did not change from pregnancy to lactation. 3. 3. Maximal specific binding occurred in microsomes from cows in mid-pregnancy and declined in microsomes from cows in late pregnancy. 4. 4. Insulin binding continued to decrease from early to mid-lactation and increased during late lactation. 5. 5. Results indicate that decreased sensitivity in mammary tissue from lactating dairy cows is at least in part a result of a reduction in insulin receptor number. 6. 6. Results demonstrate further physiological differences between the ruminant and non-ruminant mammary gland.

The use of body condition scoring to ration beef cows in late pregnancy

ABSTRACTForty-eight Hereford × Friesian and Blue Grey cows ranging in body condition score from 1·75 to 4·0, 12 weeks before calving, were fed to achieve three levels of body condition score at calving. Half the cows were fed on an increasing plane of nutrition as pregnancy advanced and half were fed on a flat-rate feeding system. The condition scores achieved by the three groups at calving were 2·28, 2·47 and 2·70 (s.e.d. 0·071; P < 0·001). Differences in cow body condition at calving were reflected in cow live weight and condition 6 weeks later, but there was no effect on calf performance. Hereford × Friesian cows lost more weight in early lactation, tended to produce more milk and their calves were heavier. Pattern of feeding had no effect on cow condition score or weight at calving or on subsequent performance.It was calculated that each unit of body condition-score loss in late pregnancy contributes the equivalent of 3200 MJ dietary metabolizable energy while 6600 MJ dietary metabolizable energy are required for 1 unit of condition-score gain.

Clinical evaluation of ketone bodies in body fluids of cows in late pregnancy and their fetuses.

Ketone body concentrations were determined in six body fluids of cows in late pregnancy and their fetuses (blood plasma and urine of cows, amniotic and allantoic fetal fluids, and fetal blood serum and urine) using the head-space gas chromatographic method. Physiological ratios O/T% of oxidized (acetone and acetoacetic acid) to total (acetone, isopropanol, acetoacetic and 3-hydroxybutyric acid) ketone bodies were below 10% in cow blood plasma and urine, fetal serum and urine, and allantoic fluid, and below 20% in amniotic fluid. A scheme for the evaluation of the degree and duration of ketosis based on the O/T% ratio is proposed. The existence of a renal regulatory mechanism for excretion of ketone bodies is suggested by analogy with the renal acidobasic regulation.

Arginine Infusion Stimulates Prolactin, Growth Hormone, Insulin, and Subsequent Lactation in Pregnant Dairy Cows

L-Arginine or saline was administered intravenously by rapid infusion into 16 late-pregnant Holstein cows to study changes of prolactin, growth hormone, insulin, total protein, urea nitrogen, and subsequent lactation. Arginine was infused daily at .1 g/kg body weight starting about 7 days prior to predicted calving until calving. Blood was sampled via a jugular cannula at 0700, 0715, 0730 (infusion immediately followed 0730h sample), 0745, 0815, 0845, 1100, 1300, 1500, 1700, and 1900h. Arginine infusion evoked dramatic but transient increase of concentrations of blood serum prolactin, growth hormone, and insulin. Urea nitrogen also was elevated in blood serum but not total protein. The secretory response of prolactin, growth hormone, and insulin to daily arginine infusion during the entire prepartum period was not diminished. Milk production for the first 22 wk of lactation tended to be higher (by about 10%) for cows infused with arginine as compared to cows infused with saline. Therefore, repeated arginine infusion in late-pregnant cows dramatically increased prolactin, growth hormone, and insulin and tended to increase subsequent milk yield.

Induction of Lactation in Nonpregnant Cows by Estradiol-17β and Progesterone from an Intravaginal Sponge

An intravaginal sponge impregnated with 500mg estradiol-17β and 1000mg progesterone to induce lactation in nonpregnant dairy cattle was investigated. Sponge retention (>95%) was achieved by its attachment to a nylon collar. Treatment with the sponge for 10 days resulted in lactogenesis in 25% of treated cows compared with an 89% succes rate when an adjunct injection of dexamethasone esters (20mg intramuscular) was given on day 6 or a 96% success rate when reserpine injections (2.5mg intramuscular) were given on days 6, 8, and 10 after sponge insertion.Milking was begun 12 days after sponge insertion (2 days after removal). Peak milk yield was unaffected by adjunct treatments but was greater in spring (mean 11.5 kg/day) than in autumn treated cows (mean 3 and 6 kg/day) in 2 yr of trials.Concentration of estradiol-17β in plasma rose rapidly after sponge insertion to a peak similar to that in cows in late pregnancy. Measurement of estradiol-17β concentration in milk indicated less, even at first milking than in commercially distributed pasteurized milk. Milk fat and protein content were higher in milk from induced lactations compared with that from normally calving cows on the same day.