جستجوی مقالات مرتبط با کلیدواژه « Dairy Cows » در نشریات گروه « دامپزشکی »

In the present study, aflatoxin M1 (AFM1) in bulk milk (n=72) and aflatoxin B1 (AFB1) in concurrent rations (TMRs; n=48) and feed ingredients (n=230) were assessed in 12 dairy farms in winter and summer. Bulk milk was sampled on days 1, 15 and 30 of the study. Feeds were sampled at days 1 and 30. Aflatoxin was measured using ELISA kits (detection ranges: 1-81 ngkg−1 for milk, 1.25-101.25 ngkg−1 for feeds). AFM1 was identified in all milk samples (range: 2.03 to >81 ngkg−1; median: 70 ngkg−1). Overall, 76% of milk samples (n=55/72) had AFM1 levels <81 ngkg−1 (Iranian limit:100 ngkg-1). Contaminations >81 ngkg−1 (n=17/72; 24%) were more frequent in winter (n=15/36 vs. 2/36). Sixty-nine percent of winter (n=25/36) and 31% of summer samples (n=11/36) had contaminations above the median. The chance of contaminations above the median was higher in winter (OR=5.33, P=0.007). All TMRs and ingredients had higher contaminations in summer. Seventy percent of summer and 30% of winter TMRs had contaminations above median (716 ngkg-1). The chance of TMR contamination above median was higher in summer (OR=5.57, P=0.002). The lower AFM1 levels in summer could be due to reduced hepatic AFB1 metabolism and lower dry matter intake induced by heat stress. Grain mix (rs=0.90; P=0.001), corn silage (rs=0.66; P=0.001) and wet beet pulp (rs=0.68; P=0.005) were the most prominent contaminants of TMRs. Due to the limitations of the diagnostic kit and different year-round nutritional conditions, higher or lower AFM1 contaminations are probable. With the current nutritional practices, higher summer contamination may happen if heat stress is efficiently controlled.

In order to prepare reductive polypeptides from the placenta of dairy cows，fresh placentas from healthy Chinese Holstein cows were obtained and homogenized. Response surface model was established to optimize the hydrolysis condition for the extraction of the placental polypeptides. Specifically, the placental tissue homogenate was treated with both trypsin and pepsin for 348 min and 329 min; at 35.00% and 35.75% of substrate concentration; with anenzyme-substrate ratio of 3.33% and 3.92%, respectively, based on the models. The treated samples were then demineralized and freeze-dried to obtain the hydrolyzed polypeptides. In order to identify the molecular mass distribution and reducibility of polypeptides, matrix-assisted laser desorption ionization (MALDI) and Prussian blue methods were used. The concentrations of placental polypeptides after hydrolysis by trypsin or pepsin were 5.52% and 5.97%, respectively; the vitamin C (Vit C) equivalents were 36.26 μg mg-1 or 61.15 μg mg-1, respectively. Both groups showed intensity peaks of MALDI patterns in the range of 300 - 400 Da, and polypeptides hydrolyzed by pepsin had higher Vit C equivalent anti-oxidant activity than trypsin hydrolyzed polypeptide, suggesting that the proteins in the placental tissues were hydrolyzed to di-peptides and tri-peptides completely. In conclusion, both trypsin and pepsin hydrolysis performed well in preparation of reductive polypeptides from the fresh placentas of dairy cows; while, pepsin is more effective than trypsin. The primary reductive ingredients may be the oligopeptides with molecular mass less than 1000 Da.

Previous studies have indicated negative association of anogenital distance (AGD) with fertility in dairy cows; however, the mechanism of inverse relationship is not completely understood. In this regard, post-partum uterine infections and their corresponding risk factors could diminish fertility of cows, yet there has been no research exploring the relationship between AGD and postpartum disorders.

The aim of this study was to investigate the relationship between AGD and postpartum reproduc-tive performance in dairy cows.

AGD of Holstein dairy cows of a commercial dairy herd (n = 290) was measured in millimeter at the first postpartum examination (days 28 to 32 postpartum). The cows were classified into three categories based on the AGD length, including short (20% of cows with lowest values), intermediate (60% of cows with moderate values) and long (20% of cows with highest values) AGDs. Additionally, data of postpartum reproductive variables were retrieved form the herd database. Data was analyzed using SAS software version 9.4.

The rate of dystocia, twinning, retention of fetal membranes, puerperal metritis and clinical endome-tritis, calf birth weight, and days to first service did not differ among the various AGD categories (P>0.05). However, proportion of male offspring was lower in the short AGD cows than intermediate and long AGD cows (P<0.05). Furthermore, the first service conception rate was greater in the intermediate anogenital distance group than short and long anogenital distance groups (P<0.05).

In conclusion, the present study showed suboptimal first postpartum conception rate in the cows with minimal and maximal length of anogenital distance and indicated that this inferior fertility was not mediated through alteration in the rate of postpartum reproductive disorders

Improving the reproductive performance of dairy cows requires estrus manipulation using estrus synchronization protocols.

The current study aimed to assess the effect of reducing the length of estrus synchronization pro-tocol by two doses of prostaglandin injection on the reproductive performance of Holstein dairy cows.

At first, all cows received GnRH (day 0) followed by PGF2α on day 7 and GnRH on day 17. Next, cows were assigned randomly to one of the three groups: Group 1) PGF2α injection on days 22 and 23, estradiol benzoate injection on day 24, Group 2) PGF2α injection on days 23 and 24, estradiol benzoate injection on day 25, and Group 3) Control group; injection of PGF2α on day 24, injection of estradiol benzoate on day 25. Estrus detec-tion was performed twice a day up to 48 h (AM/PM) based on the signs of estrus, and fixed time AI protocol was used after 48 h if not previously inseminated.

The conception rate in group 2 was significantly higher than the control group (P≤0.05) and tended to be higher than group 1 (P=0.079).

Our results confirmed the hypothesis that a decline in the period of follicle dominance by re-ducing the interval between GnRH and PGF2α through two PGF2α injections improved the fertility of lactating dairy cows.

Early resumption of ovarian activity after parturition could positively influence the fertility of dairy cows. Ovulation of the first postpartum follicular wave and formation of corpus luteum that secretes progesterone can sub-stantially benefit the resumption of ovarian cyclicity in cows. In this regard, the presence of a dominant follicle in the ovary before day 10 postpartum could enhance ovulation rate in the first postpartum follicular wave. Pregnant mare serum gon-adotropin (PMSG) is one of the hormones with the potential to improve the growth of follicles.

Accordingly, the present study was conducted to evaluate the effect of PMSG injection six days after parturition on reproductive parameters in dairy cows.

The subjects were randomly assigned to the two groups of control (N=74) and treatment (N=79). Cows in the control group received no treatment, while animals in the treatment group received 500 IU PMSG on day six postpartum. In both experimental groups, cows were subjected to Presynch-Ovsynch protocol 30-35 days postpartum. The subjects that experienced estrus during the Presynch-Ovsynch protocol were inseminated. On the other hand, the cows that were not in estrus during this period were subjected to fixed-time insemination at the end of the Presynch-Ovsynch protocol. Pregnancy was diagnosed 45 days after artificial insemination using the rectal examination.

In the control group, 66.22% of cows were inseminated based on estrus detection and 33.78% of cows were inseminated at fixed times. In the intervention group, 68.35% of cows were inseminated based on estrus detection and 31.65% of cows were inseminated at fixed times. The first-service conception rate (FSCR) was 27.03% and 48.1% in the control and treatment groups, respectively (p =0.01).

The present study showed that the injection of 500 IU PMSG six days after parturition could enhance FSCR in dairy cows.

The somatic cell count (SCC) is widely used to predict the health of cow ҆s mammary gland and the suitability of milk for human consumption. The main aim of this study was to evaluate the effects of additional supplementation of vitamin E and selenium at two intervals during late gestationon SCC and retained placenta (RP) in dairy cows. The 138 multiparous Holstein dairy cows were selected, which were randomly divided into two treatment and control groups. The cows in the control group (n=66) received a single injection of vitamin E and selenium at one dose (20 cc/cow) on day 250 of pregnancy, and in the treatment group (n=72) received two injections of vitamin E and selenium on days 250 and 270 of gestation.The SCC, milk production, RP percentage, and reproductive indices were calculated in all cows.The results showed that the SCC, milk production, RP percentage, and reproductive indices of cows in the treatment group have no significant difference from the control group. However, the calving to the first insemination interval and RP percentage in the treatment group was reduced.According to the results of the present study, it seems that more detailed studies are needed to find the effects of additional supplementation of vitamin E and selenium on the incidence of RP, milk, and SCC.

Acute-phase proteins (APPs) may be increased due to different stresses during estrus phase in farm animals.

Determining changes of APPs at different phases of non-synchronized estrous cycle group (NSEG), and Ovsynch-synchronized estrous cycle group (SEG) in Holstein cows.

Twelve non-pregnant clinically and paraclinicaly healthy Holstein cows with a body condition score (BCS) of 2.75 and 70 days in milk were chosen. Two groups including NSEG and SEG were performed. Blood sampling was carried out from NSEG at the time of diestrus, proestrus, and estrus. In SEG, blood sampling was performed on day 7 (at the time of prostaglandin injection, equivalent diestrus), day 9 (at the time of gonadotropin-releasing hormone (GnRH) injection, equivalent proestrus), and day 10 (at the time of insemination, equivalent estrus) of synchronization protocol. Concentrations of haptoglobin (Hp), serum amyloid A (SAA), ceruloplasmin (Cp), and fibrinogen (Fib) were measured.

Concentration of Hp at estrus phase was significantly higher compared with diestrus (P=0.001) and proestrus (P=0.019) in NSEG. Moreover, Hp level in the NSEG was significantly higher than SEG at estrus phase (P=0.002). Concentrations of SAA, Cp, and Fib had no significant differences during various phases of estrous cycle in each group or between equivalent phases of both groups.

It seems that unlike SAA, Fib, and Cp, concentrations of Hp may be affected by different phases of estrous cycle. Although APPs are not specific indicators, their changes besides other clinical and paraclinical indices may be helpful for more accurate heat detection in dairy cows.

Diagnosis and prognosis of inflammatory conditions based on acute phase proteins (APPs) level in blood has been exploited for a long time in human medicine and their changes in SARA condition is considered in veterinary medicine.

To evaluate the variations of serum amyloid A (SAA) and haptoglobin (Hp) as main acute phase proteins in cow with normal pH or cows that experienced rumen pH ≤5.8 during first days after parturition.

A total of 106 multiparous Holstein dairy cows were randomly selected after parturition in two different seasons of winter and summer 2017. Cows were divided into 2 groups as normal cows with pH >5.8 or rumen pH ≤5.8. Ruminal fluid samples were collected through stomach tube for rumen pH and blood samples were taken from the coccygeal vein of cows concurrently once per day at days 4, 11 and 18 post-partum. SAA and Hp were determined in blood samples. The PROC MIXED of SAS (2003) was used for all determined variables with repeated measures. BCS, parity and milk yield were included as fixed and cows as random effect. The significant level was declared at P≤0.05, and tendency toward significance was considered at 0.05<P≤0.10 by the Tukey test. Correlation between rumen pH and APPs were surveyed using PROC CORRELATION of SAS (2003).

The results of experiment showed that rumen pH was lower (P<0.05) in summer samples than winter (6.33 vs. 6.46). Rumen pH was lower (P<0.0001) in cows composed by subjects with rumen pH ≤5.8 than pH >5.8. For all examined cows, SAA concentration was greater in winter than summer (P<0.001), as well as at day 4 than days 11 and 18 after calving (P<0.05).Also, Hp concentration was greater for winter samples than summer (P<0.05), and at day 18 than days 4 and 11 after calving (333.33 vs. 299.3 and 300.1 respectively) (P<0.05). SAA and Hp concentrations were not affected by rumen pH. There was no significant correlation between rumen pH and APPs concentrations in both groups of pH ≤5.8 and pH >5.8.

Results showed that rumen pH ≤5.8 seems not to stimulate the APPs production

It was hypothesized that under apparently good management practices in dairy farms, some cows may not be metabolically perfect during the breeding period and this may affect their performance. This study was conducted to assess probable metabolic drawbacks in mid-lactation dairy cows affecting their performance. Thirty-seven clinically healthy Holstein cows were assessed for plasma concentrations of glucose, non-esterified fatty acids (NEFA), beta-hydroxybutyrate (BHB), thyroxin (T4), and tri-iodothyronine (T3) on days 60, 90 and 120 of lactation. The relationships of the measured analytes with some performance indices were also studied. Continuous declines in plasma glucose (within reference values; P<0.006), T4 (P<0.001) and T3 (0.003) were found during the study. Non-esterified fatty acids showed relatively high levels through the study with a rise at day 90 (P<0.041). Beta-hydroxybutyrate concentrations did not change significantly (P>0.05) but were higher than those reported by others in mid-lactation cows. By progress in lactation 27% of cows had glucose concentrations <2.5 mmol/L, 62% had NEFA concentrations >0.40 mmol/L and 13.5% had BHB levels above 1200 µmol/L, which are the threshold levels of peri- and post-parturient problems. Milk production had negative correlations with glucose and T4 while the correlation was positive with NEFA. The interval between calving to the 1st heat had positive correlations with BHB concentrations. The interval between calving and the 1st insemination was inversely correlated with glucose and positively correlated with NEFA levels. The changes of the studied analytes in mid-lactation cows resembled those that would happen during negative energy balance in early lactation cows and feed restriction in mid-lactation cows and may affect the general health and the performance of the cows.