The failure of a prostaglandin F2 alpha analogue, cloprostenol, to initiate lactation in cattle

An experiment was designed to determine if the analogue of prostaglandin F2 alpha, cloprostenol, at a dose sufficient to cause luteolysis, was lactogenic in cattle. The mammary glands of eight Friesian heifers were developed by treatment with progesterone plus oestrogen. Lactation was then initiated by administration of cloprostenol and subsequent milk production was compared to that of heifers lactating after a normal pregnancy. Injection of cloprostenol failed to initiate lactation. The level of prolactin but not cortisol in blood was substantially elevated following treatment. The results cast further doubt on the importance of prolactin in the lactogenic process but indicate the likely involvement of glucocorticoids.     

Developmental competence of oocytes from prepubertal Bos indicus crossbred cattle

The aim of the present study was to evaluate the effect of age on embryogenic competence of oocytes recovered from Bos indicus crossbred calves and heifers. Cumulus-oocyte complexes (COCs) were collected from 4- to 7-month-old calves (experiment 1) and from 9- to 14-month-old heifers (experiment 2) during processing at an abattoir. In both experiments cow COCs were used as control. COCs were in vitro matured and fertilized, and the presumptive zygotes co-cultured with cumulus cells until 224 h post insemination (hpi). In experiment 1, the development rate during the first 68-72 hpi was similar (P > 0.05) between embryos derived from calves and cows. Fewer embryos from calves developed to the blastocyst stage, resulting in a lesser blastocyst production as well as lesser hatching rate (P < 0.05). The embryo development after blastocyst stage was, nevertheless, similar (P > 0.05) between blastocysts derived from calves and cows, suggesting that the development after blastocoele formation is not compromised in embryos derived from calves. In experiment 2, there were no differences (P > 0.05) on cleavage, blastocyst and hatching rates between embryos derived from prepubertal heifers and cows. The rate of blastocyst development until hatching was also similar (P > 0.05). These results indicate that oocytes from 9- to 14-month-old B. indicus crossbred heifers have the same developmental competence as oocytes derived from cows, while ocytes derived from 4- to 7-month-old B. indicus crossbred calves are less competent in developing to the blastocyst stage in vitro. It suggests that oocyte competence in B. indicus crossbred cattle is achieved around 9-14 months of age.     

Glucose metabolism in vivo in crossbred Holstein cattle feeding on different types of roughage during late pregnancy and early lactation

An experiment was carried out to study the glucose kinetics of crossbred Holstein cattle feeding on either hay or 5% urea treated rice straw during late pregnancy (21 days prepartum) and early lactation (30 days postpartum). In all 16 pregnant heifers (23–25 months of age) were selected for the experiments, including eight animals of two breed types, Holstein Friesian×Red Sindhi (50:50=50% HF) and Holstein Friesian×Red Sindhi (87.5:12.5=87.5% HF). They were divided into four groups of four animals each. Animals from the same breed type in each group were fed with either rice straw treated with 5% urea or pangola hay (Digitaria decumbens) as the source of roughage throughout the experiments. The glucose turnover rate in both types of crossbred Holstein cattle was determined using a continuous infusion of [U-¹⁴C] and 3-[³H]glucose during late pregnancy and early lactation. Total glucose entry and utilization rates increased significantly during lactation for all groups. Recycling of [C]glucose was, approximately, 20% in both crossbred cattle fed either hay or urea treated rice straw and was unaffected by the stage of late pregnancy or early lactation. Comparing 50 and 87.5% HF animals, arterial plasma glucose concentrations were slightly higher during pregnant periods but significantly higher in lactating periods in 50% HF animals. The ratio of specific radioactivity of arterial blood bicarbonate relative to that of arterial blood [¹⁴C]glucose in the lactating period, significantly decreased in 50% HF animals fed either urea treated rice straw or hay. An increase in udder blood flow during early lactation was significantly higher in 87.5% HF animals than in 50% HF animals. The uptake, arteriovenous differences and extraction ratio for glucose across the udder, significantly increased in the lactating period for all crossbred animals. Glucose uptake by the udder of 87.5% HF animals accounted for 65% of the total glucose turnover rate compared to a value of 46% in the lactating 50% HF animals. It can be concluded that both crossbred cattle fed either urea treated rice straw or hay exhibit the same body glucose turnover rate. The 87.5% HF animal has the genetic potential for a high milk yield and has high body and udder glucose metabolisms compared with 50% HF animals.     

Effects of experimental Trypanosoma vivax infection on first-, second-, and third-trimester pregnancy in heifers

The effects of Trypanosoma vivax on pregnancy were studied in 18 heifers. The heifers were bred by a proven bull and divided into three groups of six heifers each. In the first group, four heifers were infected with T . vivax on Day 60 (first trimester) of pregnancy; two other pregnant heifers were uninfected controls. The second and third groups were similarly infected in the fourth (second trimester) and seventh (third trimester) month of pregnancy. One infected heifer in the first-trimester group aborted 39 days postinfection (p.i.); the remaining three had relatively normal gestation and parturition. In the second-trimester group, the pregnancies were carried to term with normal deliveries. In the third-trimester group, three infected heifers (75%) had premature deliveries while the fourth died about three hours after the full-term calf was pulled out. All of the control heifers had normal gestation and parturition. No gross abnormalities were seen in the placentae of the infected heifers, but histological sections of the heifers infected in the third trimester of pregnancy revealed more mononuclear cells than in those of the uninfected controls. Postmortem examination of the dead premature calves showed lymphadenopathy, splenomegaly, serous atrophy of perirenal and pelvic fat, epicardial petechiae, and blood-tinged peritoneal and pericardial fluids. Histologically, there were slight myocardial haemorrhages and edema. T. vivax was recovered from the blood of one of the premature calves. Both birth weights and PCV were affected by the experimental maternal infection in the first- and third-trimester calves. The birth weights and PCV of calves of infected dams were lower than those for the calves of the control heifers. This work therefore demonstrates transplacental transmission of T. vivax in heifers.     

Neospora caninum in cattle: experimental infection with oocysts can result in exogenous transplacental infection, but not endogenous transplacental infection in the subsequent pregnancy

Whilst it is presumed that infection of pregnant cattle with Neospora caninum oocysts can provoke abortion and is the likely cause of epidemic abortion outbreaks, only two previous experiments have involved inoculation of pregnant cows with oocysts (and only one abortion was provoked in 22 pregnancies). Here, we describe the oral oocyst challenge of 18 cows synchronously bred and inoculated precisely at 70 (n = 6), 120 (n = 6) and 210 (n = 6) days in pregnancy with a nominal dose of 40,000 oocysts. Only one abortion occurred (at the 120 days challenge) which could be definitively ascribed to N. caninum and no transplacental infection (TPI) was detected in any of the other 11 calves born in the 70 and 120 day challenge groups. In contrast, 4/5 live calves born to cattle challenged at 210 days were transplacentally infected. When cows which had transplacentally infected their calves in the first pregnancy were rebred, no TPI occurred. The results show that the timing of challenge influences clinical and parasitological outcomes and that cattle in late pregnancy are exquisitely sensitive to oocyst challenge leading to exogenous TPI and congenitally infected calves. However, cattle which were indisputably systemically infected in their first pregnancy did not induce endogenous TPI in their subsequent pregnancy. This confirms previous results with experimental tachyzoite challenge and suggests that post-natal infection does not lead to persisting infections which can recrudesce in pregnancy.     

Suppression of the immune response to Trichuris muris in lactating mice.

Mice infected with Trichuris muris during lactation were unable to expel the infection at the normal time, but expulsion occurred when lactation was terminated. Suppression of expulsion was uniform in mice suckling more than five young but variable with smaller litters. Mice exposed to a primary infection while lactating were shown to have serum antibodies capable of passively transferring immunity to recipient mice and showed near normal immunity to a secondary infection given after lactation had ceased. Acquired immunity to T. muris was also suppressed by lactation, but the worms which became established in lactating resistant mice were fewer and smaller than those in non-lactating, non-resistant controls. It is suggested that the suppressive effect of lactation in this host-parasite relationship is exerted on the second, lymphoid cell-mediated phase of worm expulsion.     

Response of nonsensitized and sensitized lactating mice to infection with Trichinella spiralis

The effect of lactation on the expulsion of adult Trichinella spiralis were studied in: (1) lactating, (2) induced agalactic post-parturient, (3) previously sensitized, and (4) mice sensitized during lactation. The results indicated that lactation was associated with an altered pattern of worm expulsion; i.e. more adult worms were recovered from nonsensitized and sensitized lactating mice than from control mice. Furthermore, neither mice sensitized before nor during lactation demonstrated an immunity to challenge infection.     

Effects of parity and periconceptional metabolic state of Holstein–Friesian dams on the glucose metabolism and conformation in their newborn calves

The metabolic state of pregnant mammals influences the offspring’s development and risk of metabolic disease in postnatal life. The metabolic state in a lactating dairy cow differs immensely from that in a non-lactating heifer around the time of conception, but consequences for their calves are poorly understood. The hypothesis of this study was that differences in metabolic state between non-lactating heifers and lactating cows during early pregnancy would affect insulin-dependent glucose metabolism and development in their neonatal calves. Using a mixed linear model, concentrations of glucose, IGF-I and non-esterified fatty acids (NEFAs) were compared between 13 non-lactating heifers and 16 high-yielding dairy cows in repeated blood samples obtained during the 1st month after successful insemination. Calves born from these dams were weighed and measured at birth, and subjected to intravenous glucose and insulin challenges between 7 and 14 days of age. Eight estimators of insulin-dependent glucose metabolism were determined: glucose and insulin peak concentration, area under the curve and elimination rate after glucose challenge, glucose reduction rate after insulin challenge, and quantitative insulin sensitivity check index. Effects of dam parity and calf sex on the metabolic and developmental traits were analysed in a two-way ANOVA. Compared with heifers, cows displayed lower glucose and IGF-I and higher NEFA concentrations during the 1st month after conception. However, these differences did not affect developmental traits and glucose homeostasis in their calves: birth weight, withers height, heart girth, and responses to glucose and insulin challenges in the calves were unaffected by their dam’s parity. In conclusion, differences in the metabolic state of heifers and cows during early gestation under field conditions could not be related to their offspring’s development and glucose homeostasis.     

Influence of the dam and sire on size at birth and subsequent growth, milk production and fertility in dairy heifers

Genetic selection has resulted in larger cows with high milk production potential but a tendency for poor fertility. In multiparous cows fetal development competes for nutrients with concurrent milk production. This study tested the hypotheses that (a) maternal age and milk yield during pregnancy alter calf birth size and (b) birth weight influences subsequent productivity and fertility. Concurrently born Holstein-Friesian heifers (n=65) with multiparous dams and three sires were monitored from birth to the end of their first lactation to assess effects of birth weight on growth, milk production and fertility. Calves were analyzed as three subgroups: low (L), average (A) and high (H) birth weight (BW) calves (n=21-22 per group). LBW calves were born 10 kg lighter than HBW calves and remained significantly lighter throughout the study. They were generally smaller in other measured indices (length, height, girth, ponderal index) between birth and 9 months and were more likely to have older dams (lactations 3-6) with higher peak yields (>42 kg/day). Milk production parameters were indistinguishable between the 3 birthweight groups and metabolic parameters (IGF-I, insulin, glucose) measured around first calving were unaffected. HBW offspring were more likely to have persistent corpora lutea following their first calving and other fertility parameters also tended to be worse. Sire influenced gestation length but not birth size. Sire heritability estimates showed that weight, IGF-I and insulin concentrations after first calving and fertility in the first lactation were all heritable. The results support the hypothesis that high milk production in the dam may predispose to birth of a smaller calf. Smaller birth size did not, however, have any subsequent adverse effects on productivity or fertility in the first lactation and sire was more influential at this stage.     

Effects of ghrelin injection on plasma concentrations of glucose, pancreatic hormones and cortisol in Holstein dairy cattle

Ghrelin affects not only growth hormone secretion but also nutrient utilization and metabolic hormone secretion in humans and experimental animals. The effects of ghrelin on plasma metabolic hormone and metabolite levels in domestic herbivores remain unclear despite the fact that the physiological characteristics of nutrient digestion and absorption imply specific responses to ghrelin. Therefore, the effects of ghrelin on plasma glucose, pancreatic hormones and cortisol concentrations were investigated in Holstein dairy cattle in various physiological states. Ghrelin (0.3 nmol/kg) or placebo (2% bovine serum albumin in saline) was intravenously injected in pre-ruminant calves (pre-rumen function), adult non-lactating (functional rumen) and lactating cows (functional rumen and lactation), and plasma glucose, insulin, glucagon and cortisol concentrations were then determined. Ghrelin injection increased plasma glucose concentrations in adult cows, especially in lactating cows. No hyperglycemic response was observed in pre-ruminant calves. A transient rise of insulin and glucagon levels was distinctively found in lactating cows in response to the ghrelin administration. Ghrelin injection decreased the insulin level in pre-ruminant calves. Ghrelin increased cortisol secretion independently of the physiological state. The results of the present study suggest that the effects of ghrelin on plasma glucose and pancreatic hormone levels may reflect differences in the physiological states of dairy cattle.     

Cryptosporidium andersoni is the predominant species in post-weaned and adult dairy cattle in China

Dairy industry plays an important role in the agricultural economy of China. To estimate the prevalence and public health significance of cryptosporidiosis in post-weaned and adult dairy cattle in China, during four consecutive years (from 2006 to 2009), a total of 1315 fecal samples from 22 dairy cattle farms in ten prefectures in Henan Province were examined for the presence of Cryptosporidium oocysts. The overall prevalence of Cryptosporidium was 7.9%, with the highest infection rate (11.3%) in 3 to 11-month-old calves and the lowest infection rate (1.0%) in >2-year-old cows (p<0.01). Cryptosporidium-positive samples (n=104) were analyzed by PCR-restriction fragment length polymorphism (RFLP) analysis of the small subunit (SSU) rRNA gene, and 25 representative samples were further analyzed by DNA sequencing of the PCR products. Cryptosporidium bovis and Cryptosporidium andersoni were identified. C. andersoni (84/104) was the predominant species and was found in all age groups, whereas C. bovis (20/104) was only detected in 3 to 11-month-old calves. Thus, C. andersoni appears to be the dominant species in weaned dairy calves and heifers in China, in contrast with its common occurrence in adult cattle in other parts of the world.     

The effect of Trypanosoma vivax infection on late pregnancy and postpartum return to cyclicity in Boran cattle

A study was designed to examine the effect of infection with Trypanosoma vivax KETRI 2501 on the maintenance of pregnancy and postpartum return to reproductive function in susceptible Galana (n = 6) and trypano-tolerant Orma Boran (n = 6) heifers during the third trimester of pregnancy. Of the 12 study animals, 3 Galana and 3 Orma Boran heifers served as controls. One of 3 Galana heifers calved prematurely with subsequent perinatal loss. Of the 2 heifers that produced live calves, 1 calf died shortly after birth, while the other survived. Two of 3 Orma heifers calved prematurely and all 3 calves died shortly after birth. The 6 control heifers produced live calves at term, all of which survived. Infection with T. vivax during the third trimester of pregnancy delayed the resumption of ovarian activity after calving, with the Ormas taking a significantly (P < 0.05) shorter time from calving to ovulation. There was no clear evidence that premature birth was associated with pathological changes in reproductive organs. Results from this study demonstrated that infection with pathogenic T. vivax during late pregnancy influenced the outcome of pregnancy in both susceptible Galana and trypano-tolerant Orma Boran heifers, resulting in premature births, perinatal loss, retained placentae, low birth weights and a prolonged period to the onset of postpartum ovarian activity.     

Influence of management factors on pregnancy attrition in dairy cattle

The present study was conducted to determine the influence of management factors on pregnancy attrition in dairy cattle. Data from 3162 diagnosed pregnancies in parous cows and 1050 in heifers at 9 commercial dairy herds in northeastern Spain were used. Pregnancy diagnosis by palpation per rectum was performed from 30 to 70 d post insemination. Pregnancy attrition was registered when pregnancy diagnosis resulted negative in a second palpation carried out between 120 and 150 d following insemination. Overall proportion of pregnancy losses was 7.9% (9.6% in parous cows and 2.8% in heifers). Data analysis was performed by multiple logistic regression methods. For all animals, effect of time of pregnancy diagnosis was shown (Odds ratio = 0.97 for 1 d increase; P = 0.0042). Conceptus loss in heifers was lower than in parous cows (Odds ratio = 0.28; P = 0.0001), and a higher proportion of pregnancy attritions was detected in animals inseminated in spring, summer and winter, compared to those inseminated in autumn (P < 0.04). Herd effect on pregnancy attrition was also significant. Similar results were observed in the subanalysis for parous cows and, furthermore, no effect of lactation number and of interval from previous calving to pregnancy was shown in this group. In heifers, no effect of time of pregnancy diagnosis and of insemination season on pregnancy attrition was shown, and only a herd effect was observed. Our data suggest that the influence of parity status (heifer vs cow) could affect the proportion of pregnancy attrition rather than early diagnosis, and, in pregnant cows, adaptation to seasonal changes associated with temperature decreases seem more efficient.     

The use of embryo transfer in the field for increased calf crops in beef and dairy cattle

Non-surgical transfer of one embryo to 63 previously synchronized inseminated recipients was performed on farms to induce twinning in beef and dairy cattle. All the transfers were done by technicians of A.I. centers. After calving, a twinning rate of 44.4% was achieved with no differences between beef Charolais heifers (45.4%), lactating Normande cows (42.8%) and dairy Friesian cows (45.4%). Compared with controls, the calving crop after a three-breeding-cycle period was significantly higher with recipients: 1.16 calf per treated recipient vs. 0.83 calf per control animal. It would seem that the possibility of obtaining about one-third more calves with embryo transfer could be of economical interest to increase meat production from cattle herds.     

Experimental infections with Cooperia oncophora (Railliet, 1918) in calves. Results of single infections with two graded dose levels of larvae.

Two experiments were carried out in which calves reared parasite-free were infected with a single dose of 3rd-stage larvae of Cooperia oncophora. In the first experiment the calves received 20 000 or 200 000 infective larvae and they were autopsied 28 or 56 days after the infection. In the second experiment the doses were the same but the animals were killed 14, 84 or 140 days after infection. If a dose of 20 000 was given, clinical signs were never observed, while at a dose level of 200 000 the weight gain was less on 56 and 84 days after the infection compared with the low-infected groups or the control animals. After 170 days the differences in weight gain were compensated. Faecal egg output was higher in the 200 000 groups only in the first period of patency, thereafter the calves in the 20 000 groups produced more. No obvious differences between the two infection levels were observed with regard to the haematological data. In the low-infected groups worm counts were only slightly lower when the results after 28 days were compared with those after 56 days. Also, the worm numbers after 14 days were almost equal to those after 84 days, while at 140 days 1 animal still had the same number, the other one had lost its worm burden. In the high-infected groups the worm loss was much quicker. After 28 days a great part of the population had already been lost. Obviously, at the 200 000 level the reaction of the host against the parasite was much stronger. Adult worms were expelled at a higher rate than early 4th-larval stages. In the first experiment worm measurements revealed differences between the length of females, males and spicules of males, these being significantly longer in the low-infected groups. Analysis of the distribution of worms over the small intestine showed that in the low-infected groups worms were mainly restricted to the first 6 metres. In the high-infected groups the worm population was distributed more evenly over the whole small intestine.     

Factors influencing heifer survival and fertility on commercial dairy farms

The average dairy cow survives only three lactations, reducing the availability of replacement heifers. Prenatal losses occur due to early embryonic mortality (about 40%), later embryo loss (up to 20% in high-yielding herds) or abortion (about 5%). A recent survey of 19 UK herds showed that 7.9% of calves were born dead and 3.4% died within 1 month. During the rearing phase, 6.7% of animals were lost before reaching first service at 15 months due to disease or accident and another 2.3% failed to conceive. Many potential replacements therefore never enter the milking herd. This severely limits opportunities for on-farm selection of breeding cows in addition to presenting a welfare issue and causing economic loss. The most profitable animals once lactation is reached combine good milk production with a regular calving pattern. Some aspects of performance are related to age at first calving (AFC), which in turn is influenced by heifer growth rates. Poorly growing animals required more services to conceive, calved later and subsequently performed badly. Optimum fertility and maximum yield in the first lactation were associated with an AFC of 24 to 25 months. However, heifers calving at 22 to 23 months performed best in terms of total milk yield and survival over the first 5 years, partly because good heifer fertility was associated with better fertility later. We have investigated some possible juvenile predictors of future performance. Low-birth-weight calves were more likely to come from either primiparous mothers or older dams (3+ lactations) with higher peak milk yields, suggesting that the uterine environment may limit prenatal calf growth due to competition for nutrients with maternal growth or milk production. Linear trait classification scores for frame size show genetic correlations with longevity. The skeletal measures of height and crown rump length in 1-month-old calves was correlated to subsequent stature, and frame size was correlated to weight at 15 months. It may thus be possible to predict performance from simple size measurements as juveniles. Neither endogenous nor stimulated growth hormone (GH) release in 6-month-old calves were related to milk yield in the first three lactations, but size of a stimulated GH peak was positively related to milk energy values in the first lactation. Cows with delayed ovulation (>45 days) in the first lactation had a higher GH pulse amplitude and lower IGF-I as a juvenile. Cows that partition excess energy into milk in their first lactation may suffer reduced longevity.     

Effectiveness of administration of gonadotropin-releasing hormone at Days 11, 14 or 15 after anticipated ovulation for increasing fertility of lactating dairy cows and non-lactating heifers

One strategy for improving fertility in cattle is mid-cycle administration of GnRH to increase progesterone secretion and delay luteolysis. This strategy might be especially useful during hot weather because heat stress increases uterine prostaglandin release and reduces development of the elongating embryo. A series of experiments was conducted to test the efficacy of GnRH for increasing fertility. There was no effect of administration of 100 microg GnRH at Day 11 after anticipated ovulation on pregnancy rates in virgin heifers subjected to timed artificial insemination (TAI) during the summer. Similarly, there was no beneficial effect of administration of GnRH at Day 11 after anticipated ovulation on pregnancy rates of lactating cows subjected to TAI in summer and winter. Three experiments tested effects of injection of GnRH at Days 14 or 15 after anticipated ovulation on pregnancy rates of lactating cows. The first experiment used 477 lactating cows subjected to TAI. Cows receiving GnRH at Day 14 had higher pregnancy rates in both summer and winter than cows receiving vehicle (20.3 versus 12.7%, P<0.02). When this experiment was repeated during summer with 137 cows, there was a negative effect of GnRH treatment at Day 14 on pregnancy rate. In the third experiment, lactating cows during summer were inseminated at detected estrus and cows were assigned to treatment with either GnRH or vehicle at Days 14 or 15 after insemination. Pregnancy rates were 25.6% (32/125) for cows receiving vehicle, 20.7% (19/92) for cows receiving GnRH at Day 14, and 20.3% (16/79) for cows receiving GnRH at Day 15. In conclusion, GnRH administration at Days 11-15 after anticipated ovulation or estrus did not consistently increase pregnancy rates in either cool or warm seasons.     

Evaluation of productivity of sexually precocious Nelore heifers

The objectives of the present study were to investigate the influence of yearling weight on the occurrence of early pregnancy and to determine differences between precocious and non-precocious heifers in terms of pre- and postnatal calf mortality, calf weight and height, mature cow weight, and stayability of the cow in the herd. Data from 26 977 females of a Nelore herd that participated in the breeding season between 1986 and 2004 were analyzed. The influence of yearling weight on sexual precocity and differences between precocious and non-precocious heifers in pre- and postnatal calf mortality and stayability were analyzed using the GENMOD procedure of the SAS program. Differences in the growth traits between precocious and non-precocious animals were estimated by contrast analysis. Three groups were analyzed for postnatal mortality: first calving of the heifers, calves born from the third calving and all offspring of the cow. In order to have a standardized calving to conception period for all females (precocious and non-precocious), calves born from the second calving were not included in the analysis. This was necessary because the first calving to conception period (days open) of precocious heifers was longer than for non-precocious due to farm reproductive management. No differences in postnatal mortality rates, from the third calving, were observed between the two groups of heifers studied. Analysis of all offspring of the dams showed a 9% higher probability of death of calves born to precocious heifers compared with calves born to non-precocious heifers. With respect to stayability, precocious heifers presented 33% greater odds to remain in the herd until 5 and 6 years of age and 28% greater odds to remain in the herd until 7 years when compared with non-precocious heifers. Precocious heifers weaned calves (205 days) significantly heavier than non-precocious ones, 1.410 and 0.797 kg considering the weaning weights of all offspring and of the third calving, respectively. With respect to sexual precocity, the results suggest that the probability of heifers to become pregnant at 16 months of age increases with increasing weight. However, heifers weighing more than 240 kg present practically the same pregnancy probability. Nevertheless, exposure of heifers during the early breeding season is recommended for beef cattle herds raised in tropical regions in view of the numerous benefits demonstrated here.     

The use of PGF2α as ovulatory stimulus for timed artificial insemination in cattle

The objective of this study was to evaluate the effect of a PGF2α-analogue (PGF) on ovulation and pregnancy rates after timed artificial insemination (TAI) in cattle. In experiment 1, crossbred dual-purpose heifers, in a crossover design (3 × 3), were given an intravaginal progesterone-releasing insert (controlled internal drug release [CIDR]) plus 1 mg estradiol benzoate (EB) intramuscularly (im) and 250 μg of a PGF-analogue im on Day 0. The CIDR inserts were removed 5 days after follicular wave emergence, and the heifers were randomly divided into three treatment groups to receive the following treatments: (1) 1 mg of EB im (EB group, n = 13); (2) 500 μg of PGF im (PG group, n = 13); or (3) saline (control group, n = 13), 24 hours after CIDR removal. Ovulation occurred earlier in EB (69.81 ± 3.23 hours) and PG groups (73.09 ± 3.23 hours) compared with control (83.07 ± 4.6 hours; P = 0.01) after CIDR removal. In experiment 2, pubertal beef heifers (n = 444), 12 to 14 months of age were used. On Day 0, the heifers were given a CIDR insert plus 2 mg EB im. On Day 9, the CIDR was removed and the heifers were given 500 μg of PGF im. Heifers were randomly assigned into one of three treatment groups: (1) 1 mg of EB (EB group; n = 145); (2) 500 μg of PGF (PG group; n = 149), both 24 hours after CIDR removal; or (3) 600 μg of estradiol cypionate (ECP group; n = 150) at CIDR removal. Timed artificial insemination occurred 48 hours after CIDR removal in the ECP group and 54 hours in the PG and EB groups. The percentage of heifers ovulating was higher in the PG group compared with the other groups (P = 0.08). However, the pregnancy rates did not differ among groups (47.6%, 45%, and 46.6%, for EB, PG, and ECP, respectively; P = 0.9). In experiment 3, 224 lactating beef cows, 40 to 50 days postpartum with 2.5 to 3.5 of body condition score were treated similarly as described in experiment 2, except for the ECP group, which was excluded. The treatments were as follows: 1 mg EB (EB group; n = 117) or 500 μg PGF (PG group; n = 107), 24 hours after CIDR removal. The calves were temporarily separated from their dams from Days 9 to 11. No difference was detected on the pregnancy rate between the EB and PG groups (58.1% vs. 47.6%, respectively; P = 0.11). Taken together, the combined results suggested that PGF2α could be successfully used to induce and synchronize ovulation in cattle undergoing TAI, with similar pregnancy rates when compared with other ovulatory stimuli (ECP and EB).     

Gastrointestinal parasitic infections in intensive dairy cattle breeding: Update on the epidemiology and associated risk factors in northern Italy

Parasitic infections such as Strongylida and Eimeria still represent a major health problem of dairy cattle impacting their health, welfare, and productivity. In view of the scarcity of data on risk factors contributing to the spread of parasitic infections in cattle breeding, an epidemiological study in intensive dairy farms in northern Italy was planned. 495 animals (lactating and dry cows, heifers, and calves) from 19 farms were enrolled in the study. Individual fecal samples were analyzed by a quantitative copromicroscopic analysis to detect the number of Strongylida eggs or Eimeria oocysts per gram of faeces (EPG/OPG). Data concerning management, sanitary and biosecurity measures were collected using a questionnaire; a management measures score (MMS) was also calculated. The possible influence of risk factors on Strongylida and Eimeria was thus assessed by statistical analysis using generalized linear mixed models (GLMMs).Eimeria spp. was the most frequently detected parasitic taxon (herd and individual prevalence: 89.5% and 46.2%, respectively), followed by Strongylida (herd and individual prevalence: 63.1% and 16.6%, respectively). The presence of Strongylida resulted associated to the productive category (p-value = 0.028), with heifers and dry cows at higher risk of infection than lactating cows and calves, and to the MMS (p-value = 0.007). Higher prevalence values were recorded in farms with intermediate or low MMS compared to those with optimal MMS. As regard Eimeria infection, a greater effect of MMS on OPG was recorded in calves when compared to those recorded in heifers (OR = 0.228, p-value = 0.003) and dry cows (OR = 0.241, p-value = 0.009).Gastrointestinal parasitic infections still remain an underestimated problem in intensive dairy cattle breeding. MMS may help in the choice of strategies aimed at minimizing the impact of parasites on animal health, thus improving the productivity of the entire herd.