Hyperthermia and body energy store effects on estrous behavior, conception rate, and corpus luteum function in dairy cows

The reproductive performance of 74 Israeli Holstein dairy cows was examined during summer. Cows were fed prepartum to reach high (3.8) and low (2.6) body condition scores by 1 mo prepartum. After calving, half of each group were cooled seven times a day for 30 min by sprinkling and ventilation. Cows were inseminated starting 60 d postpartum. Daily mean body temperatures of cooled and noncooled cows were 38.6 and 39.2 degrees C, respectively, with differences between them reaching 1 degree C and more during the hot hours. Body condition affected only the time taken postpartum to the start of ovarian activity (26 d for high and 32 d for low body condition groups). Estrous behavior lasted longer in cooled (16 h) than in noncooled (11.5 h) cows of the low body condition group only. Conception rate was higher in cooled than in noncooled cows (59 vs. 17%). Pregnancy rate at 90 d postpartum was higher in cooled (44%) than in noncooled cows (14%). Progesterone concentrations were higher in inseminated nonpregnant and in noninseminated cyclic cooled cows than in noncooled cows and were similar in pregnant cows of both cooled and non-cooled groups. The present cooling method appears to have a high potential for improvement of summer fertility.     

Dry period heat stress relief effects on prepartum progesterone, calf birth weight, and milk production

Effects of cooling high producing dairy cows during the dry period were examined in 84 pluriparous Israeli-Holstein cows. Cooling was by a combination of wetting and forced ventilation from 0600 to 1800 h until parturition and common management afterwards for both groups. Cooling maintained diurnal increase in rectal temperature within .2 degrees C as compared with .5 degrees C in control cows in warmer months, Mean rectal temperatures at 1400 h in control cows were moderate, within 39.2 degrees C. Cooling did not affect prepartum or postpartum body condition score or mean blood progesterone during the dry period. Results suggested a possible increase in blood progesterone in later pregnancy by cooling during hot weather. Cooling increased mean 150-d milk production by 3.6 kg/d (3.1 kg FCM/d). Prepartum cooling negatively affected first lactation month yield in cows calving in early summer. Prepartum cooling might prevent adaptation to heat and impair subsequent postpartum performance. Prepartum progesterone was not related to milk yield. Calves' birth weight increased by cooling, but the effect was mostly in older cows. Birth weight was related to milk yield, independently of cooling effect, mostly in older cows. Cooling during the dry period might increase milk yield as it does during lactation. Results indicate possible benefit of cooling dry cows even under mild heat stress.     

Evaluating two different evaporative cooling management systems for dairy cows in a hot, dry climate.

Milk production, rectal temperature, live weight gain, reproductive performance, and weather data were obtained on 150 Holstein cows managed under two cooling systems on a large dairy farm in Saudi Arabia during the summer months. Cows were paired at the onset of the trial according to days postpartum, lactation number, and current milk production. Females were then allocated either to a system that forced air, precooled by evaporative cooling, over the cows or to a system that alternately showered a fine mist onto the surface of the cows and then forced air at ambient temperature over them. The cows receiving evaporative cooling and those with spray and fan cooling were on sand and on slatted concrete floor, respectively, during the periods of cooling. The onset of estrus was observed during the night when the cows preferred the unshaded corral. For the 120-d trial period, 84% (62 of 75) of the cows receiving evaporative cooling and 60% (44 of 75) of the cows receiving spray and fan cooling became pregnant. In the evaporative cooling system, the pregnancy rate per insemination was 35.2% (179 inseminations) versus 23.2% (194 inseminations) for spray and fan cooling. The mean postpartum interval to pregnancy was 117.6 d for the evaporative cooling cows and 146.7 d for spray and fan cooling cows. The evaporative cooling system, with its open shades and sand bedding, enhanced reproductive performance and milk production compared with that of cows cooled with a spray and fan system with slatted flooring in this hot climate.     

The effect of strategic supplementation with trans-10,cis-12 conjugated linoleic acid on the milk production, estrous cycle characteristics, and reproductive performance of lactating dairy cattle

The objective was to determine the effects of a protected (lipid-encapsulated) conjugated linoleic acid (LE-CLA) supplement on milk production, estrous cycle characteristics, and reproductive performance in lactating dairy cows on a pasture-based diet. Spring calving dairy cows (n=409) on a single pasture-based commercial dairy farm were used in a completely randomized block design. Cows were assigned to 1 of 2 dietary supplements [LE-CLA (n=203) or no supplement (control, n=206)]. The LE-CLA cows received 51 g/d of a lipid supplement containing 5 g of both trans-10,cis-12 and cis-9,trans-11 CLA from 0 to 60 d in milk. Milk samples were collected 3 times weekly, and each sample was analyzed for progesterone to determine the interval to first ovulation and estrous cycle characteristics. Milk yield and concentrations of fat, protein, and lactose were measured every 2 wk. Cows were inseminated following visual observation of estrus. The breeding season commenced on April 8, 2009 and continued for 16 wk. Transrectal ultrasonography was carried out at 30 to 36 d and 60 to 66 d post-AI to diagnose pregnancy. The LE-CLA treatment resulted in a decrease in milk fat concentration (36.9±0.06 g/kg vs. 30.7±0.06 g/kg for control and LE-CLA, respectively) and yield (0.91±0.02 kg/d vs. 0.84±0.02 kg/d for control and LE-CLA, respectively); however, milk yield was increased by LE-CLA supplementation (24.7±0.7 kg/d vs. 27.2±0.7 kg/d for control and LE-CLA, respectively), resulting in no overall difference in milk energy output. No effect of LE-CLA was observed on any estrous cycle characteristics or measures of reproductive performance. These results support that in pasture-based systems of dairy production, where energy intake limits milk production, energy spared by CLA-induced milk fat depression is partitioned toward increasing milk yield rather than toward body reserves.     

Progesterone supplementation postinsemination improves fertility of cooled dairy cows during the summer

Reduced fertility of dairy cows during periods of elevated temperature, humidity, or both might be associated with low plasma progesterone concentration. Alleviation of thermal stress by efficient cooling is a prerequisite for improving fertility by hormonal treatment. We examined whether insertion of a controlled intravaginal drug-releasing (CIDR) insert containing progesterone following artificial insemination (AI) would improve summer conception rate. Control (n = 195) and treated (CIDR; n=165) cows, yielding on average 42.3 kg milk/d, were inseminated following estrus detection during the summer (July to October) in 2 commercial dairy herds in Israel. Mean maximal air temperature and relative humidity during the study were 30.2°C and 86%, respectively. All experimental cows were efficiently cooled throughout the study, as confirmed by measuring the body temperature of random cows. Treated cows received a CIDR insert on d 5 ± 1 post-AI for 13 d and pregnancy was confirmed by palpation 45 d post-AI. Plasma progesterone concentration in treated cows was elevated by approximately 1.5 ng/mL. Multiple logistic regressions were used to analyze conception rate. Treatment did not alter the overall conception rate; however, probability of conception increased in CIDR-treated cows with low body condition score (BCS) compared with their control counterparts (53 vs. 27%, respectively). A pronounced increase in probability of conception was recorded in CIDR-treated cows exhibiting both low BCS and postpartum reproductive disorders, compared with their control counterparts (58 vs. 14%, respectively). Exogenous progesterone supplementation on d 5 post-AI for 13 d improves summer fertility of subpopulations of cows exhibiting low BCS and postpartum reproductive disorders. Reproductive management based on specific hormonal treatment of designated subgroups of cows known to derive beneficial effects from it might improve treatment efficiency and reduce expenses.     

Cooling dairy cattle by a combination of sprinkling and forced ventilation and its implementation in the shelter system

A method for cooling dairy cattle based on repeated wetting to attain maximal water trapping in the coat, followed by its rapid evaporation by using forced ventilation has been examined. Effects examined include duration of wetting, duration of cooling, and density of the animals in the holding area. The coat was wetted by inverted static sprinklers. Also examined was the extent to which the diurnal increase in rectal temperature can be prevented. The maximal decrement of temperature was attained at 30 min after cessation of cooling in all trials. Wetting the coat for 10 s was less effective than for 20 or 30 s; the latter did not differ in their effects. Cooling animals for 15, 30, and 45 min produced decrements in temperature of .6, .7, and 1.0 degrees C, respectively. Maintaining animals at a density of 1.9 m2/cow in the holding area reduced to about half the decrement as compared with a density of 3.5 m2/cow. When cows were cooled 5 times per day for 30 min, temperatures were maintained within 38.2 to 38.9 degrees C during the day, which were significantly lower than for those not cooled.     

Technical note: A novel approach to the detection of estrus in dairy cows using ultra-wideband technology

Detection of estrus is a key determinant of profitability of dairy herds, but estrus is increasingly difficult to observe in the modern dairy cow with shorter duration and less-intense estrus. Concurrent with the unfavorable correlation between milk yield and fertility, estrus-detection rates have declined to less than 50%. We tested ultra-wideband (UWB) radio technology (Thales Research & Technology Ltd., Reading, UK) for proof of concept that estrus could be detected in dairy cows (two 1-wk-long trials; n = 16 cows, 8 in each test). The 3-dimensional positions of 12 cows with synchronized estrous cycles and 4 pregnant control cows were monitored continuously using UWB mobile units operating within a network of 8 base units for a period of 7 d. In the study, 10 cows exhibited estrus as confirmed by visual observation, activity monitoring, and milk progesterone concentrations. Automated software was developed for analysis of UWB data to detect cows in estrus and report the onset of estrus in real time. The UWB technology accurately detected 9 out of 10 cows in estrus. In addition, UWB technology accurately confirmed all 6 cows not in estrus. In conclusion, UWB technology can accurately detect estrus and hence we have demonstrated proof of concept for a novel technology that has significant potential to improve estrus-detection rates.     

Impact of heat stress and a feed supplement on hormonal and inflammatory responses of dairy cows

The aim of this trial was to evaluate the effects of an immunomodulatory supplement (OmniGen AF, OG; Phibro Animal Health Corp.) and heat stress on hormonal, inflammatory, and immunological responses of lactating dairy cows. Sixty multiparous Holstein cows were randomly assigned to 4 treatments in a 2 × 2 factorial arrangement using 2 environments: cooled using fans and misters, or noncooled, and 2 top-dressed feed supplements (56 g/d): OG or a placebo (CTL). Temperature-humidity index averaged 78 during the 8-wk trial. Blood was drawn to analyze cortisol, prolactin, and circulating tumor necrosis factor (TNF)-α and IL-10. Peripheral blood mononuclear cells (PBMC) were isolated and stimulated with hydrocortisone, prolactin, or lipopolysaccharide (LPS), individually or in several combinations, to assess induced proliferation and cytokine production. At d 52, 6 cows per treatment were injected i.v. with an LPS bolus (ivLPS) to assess hormone and cytokine responses. For cooled cows, feeding OG increased plasma cortisol concentration relative to CTL. Noncooled cows fed CTL had lower circulating TNF-α concentrations than noncooled-OG and cooled-CTL cows, with cooled-OG intermediate. Hydrocortisone+LPS-stimulated PBMC from OG cows tended to proliferate more than CTL. Relative to cooled cows, PBMC from noncooled cows produced more TNF-α and IL-10 when stimulated with LPS. Following ivLPS, cooled-OG cows had a greater cortisol response than the other treatments. In conclusion, OG supplementation enhanced cortisol release under basal condition and induced inflammation with cooling compared with CTL. This suggests that heat stress inhibits OG-mediated cortisol release. Heat stress seemed to enhance the inflammatory responses of PBMC from lactating cows. However, OG supplementation promoted PBMC proliferation under stress, or in the presence of hydrocortisone.     

Lameness, Activity Time-Budgets, and Estrus Expression in Dairy Cattle

The aim of the present study was to identify specific behavioral patterns that contribute to diminished estrus expression in lame cows. Behavioral scan and focal sampling were used to examine the effect of lameness on daily activity budgets, sexual behavior, feeding activities, and body condition score. A total of 59 milking cows (51.8 ± 1.4 d postpartum) were monitored on a commercial dairy farm for 5 d following estrus synchronization. Overall, lame cows (n = 39) spent proportionately less time elevated on their feet and more time lying down compared with nonlame cows (n = 20). This included lame cows spending less time walking or standing. Overall, the total proportion of scans in which an estrous behavior was observed was very small but tended to be smaller for lame compared with nonlame cows. Throughout a day, lame cows displayed a lower proportion of estrous behaviors in the early morning. Lameness did not affect durations of drinking, grazing, or ruminating, or how these behavioral states fluctuated throughout the day. Similarly, rumination chewing rates were the same for lame and nonlame cows, and there was no association between lameness and dominance/displacement while feeding at a feed-fence. Lame cows did, however, have a slower bite rate at pasture and had a lower body condition score. Lame cows were also nearer the rear of the herd, both as they left the field and when entering the milking parlor. In conclusion, lame cows have longer lying times and spend less time standing, walking, and expressing an estrous behavior. Lame cows also have a lower bite rate at pasture and are more likely to be of lower body condition score.     

Determinants of estrous behavior in lactating Holstein cows

The objective was to determine factors that affect the expression of estrus. Thirteen lactating Holstein cows were ovariectomized about 4 to 6 wk postpartum and then challenged repeatedly with progesterone and estradiol benzoate to induce estrus six times during the postpartum period. Each challenge included 5 d when the cow was primed with progesterone through insertion of a progesterone-impregnated, foam rubber pessary. Estradiol benzoate (1 mg) was injected intramuscularly 36 h after removal of the pessary. Groups of two to three cows each began the experiment at 3-mo intervals to avoid confounding treated simultaneously. Observations for estrous behavior were at 8-h intervals following each challenge. A minimum of three sexually active cows were always observed together to avoid differences in estrous behavior caused by having too few sexually active animals in the group. Observations for estrous behavior were at 8-h intervals following each challenge. During each observation, cows were observed for 30 min on dirt and for 30 min on concrete. Standing behavior was not influenced by postpartum interval, season of year, or milk yield. Mounting behavior increased from the first to the sixth postpartum challenge, but it was not affected by season of year or milk yield. Duration of estrus, mounting activity, and standing activity were greater on dirt than on concrete. These results indicate that the surface on which cows were observed had a profound effect on sexual behavior; however, postpartum interval, season of year, and milk yield were of minor importance.     

Effects of GnRH administered to cows at the onset of estrus on timing of ovulation,endocrine responses,and conception

Two experiments examined effects of GnRH administered within 3 h after onset of estrus (OE) on ovulation and conception in dairy cows. In experiment 1, 46 cows received either saline, 250 microg of GnRH, or 10 microg of the GnRH analogue, Buserelin. Cows were observed for estrus, blood samples were collected, and ovulations were monitored by ultrasound. In controls, 76% of cows had intervals from estrus to ovulation of < or = 30 h and 24% had intervals > 30 h. Treatment with either GnRH or GnRH analogue (data combined) increased magnitude of LH surges and decreased intervals from estrus to LH surge or to ovulation. Treated cows all ovulated < or = 30 h after OE. Among control cows, plasma estradiol concentrations before estrus correlated positively with amplitudes of LH surges. Higher plasma progesterone was observed in the subsequent estrous cycle in GnRH-treated cows compared to control cows with delayed ovulations. Experiment 2 included 152 primiparous and 211 multiparous cows in summer and winter. Injection of GnRH analogue at OE increased conception rates (CR) from 41.3 to 55.5% across seasons. In summer, GnRH treatment increased CR from 35.1 to 51.6%. Across seasons, GnRH increased CR from 36.0 to 61.5% in cows with lower body condition at insemination and GnRH increased CR (63.2 vs. 42.2%) in primiparous cows compared to controls. Use of GnRH eliminated differences in CR for cows inseminated early or late relative to OE and increased CR in cows having postpartum reproductive disorders. In conclusion, GnRH at onset of estrus increased LH surges, prevented delayed ovulation, and may increase subsequent progesterone concentrations. Treatments with GnRH increased conception in primiparous cows, during summer, and in cows with lower body condition.     

Activity monitoring and an enzyme immunoassay for milk progesterone to aid in the detection of estrus.

The accuracy and efficiency of estrus detection using an electronic activity monitor tag in conjunction with an enzyme immunoassay for milk progesterone were studied during 55 observed estrous periods in 37 cows. At approximately 30 d postpartum, cows were equipped with an activity tag and visually observed for estrus, an activity tag with a flashing light-emitting diode, or both twice daily. Milk progesterone concentrations were determined from cows observed in estrus or with an activated tag. Mean daily activity was greater on the day of estrus than during any of the 3 d preceding or 3 d following estrus. Functioning activity tags correctly identified 55% of all visually observed estrous periods that coincided with low milk progesterone levels. The overall accuracy of a flag by the tag for identifying true estrus was 21%. The enzyme immunoassay for milk progesterone was in agreement with 98% of all visually observed estrous periods and false flags committed by the tags. Although the activity tags detected some cows in estrus, a more durable and reliable tag must be developed before it is of practical value to dairy producers.     

Physiological, productive, and economic benefits of shade, spray, and fan system versus shade for Holstein cows during summer heat

During the 1984 summer, effects of spray and fan in freestall areas and feeding areas on milk yield, plasma growth hormone and prolactin, freestall utilization, and economic significance for Holstein cows were studied. Weekly milk and rectal temperatures at morning and afternoon milkings were higher for cows in shade than in shade with spray and fan cooling. Compared with rectal temperature, milk temperature measured in the clawpiece provided a more reliable indicator of heat stress than in the milk meter. Diurnal pattern of rectal temperature from 4-h measurements showed an average of 12 h in which maximal rectal temperatures of cows in shade were greater than 39 degrees C, but cows in the shade plus spray plus fan group had rectal temperatures below 39 degrees C all day. Plasma growth hormone was higher and prolactin lower for cows in shade plus spray and fan than cows in shade only. Cows cooled with spray and fan under shade produced 2 kg/cow per d more than cows in shade alone. Economic analysis showed a net income of 22 cents/cow per day for spray plus fan under shade. Results suggest that milk temperature is a practical technique to assess heat stress in dairy cattle, and the use of spray plus fan is a profitable means to maximize cow comfort and lessen stress-induced decline in milk production.     

Physiological responses in thermal stressed Jersey cows subjected to different management strategies

The effects of cooling and recombinant bovine somatotropin (rbST) on milk yield, reproductive performance, and health of Jersey cattle during summer thermal stress were measured for 2 yr. Cows were assigned to one of two groups based upon days in milk (DIM), parity, and genetic index. Year 1 and year 2 control cows (n = 143, n = 183, respectively) were housed in a pen with only shades. Cooled treatment cows each year (n = 142, n = 180) were housed with a spray and fan system for evaporative cooling. Cows were assigned at various days postpartum, not before d 63, coincident with commencement of rbST injections. One half of cows in each group received rbST on d 63 postpartum. Cows were assigned to the shade trial ranging from d 63 to 190. Cooled versus noncooled DIM were similar at the start of the trial. Trials began on July 1, 1999, and July 1, 2000, and concluded on September 30, 1999, and September 25, 2000. The ANOVA of daily milk weight data was conducted utilizing a 2 x 2 factorial design with cooling and rbST treatments as main effects. Cooling in combination with rbST increased milk yield compared with no cooling and no rbST for 1999 and 2000 (25.5 versus 21.8 kg/d, and 23.7 versus 20.5 kg/d, respectively). In general, cooling improved health and reproductive performance.     

Effect of cooling heat-stressed dairy cows during the dry period on insulin response

Heat stress (HT) during the dry period affects hepatic gene expression and adipose tissue mobilization during the transition period. In addition, it is postulated that HT may alter insulin action on peripheral tissues. Our objective was to evaluate the effect of cooling heat-stressed cows during the dry period on insulin effects on peripheral tissues during the transition period. Cows were dried off 46d before expected calving and assigned to 1 of 2 treatments: HT (n = 16) or cooling (CL, n = 16). During the dry period, the average temperature-humidity index was 78, but CL cows were cooled with sprinklers and fans, whereas HT cows were not. After calving, all cows were housed and managed under the same conditions. Rectal temperatures were measured twice daily (0730 and 1430h) and respiration rate recorded 3 times weekly during the dry period. Dry matter intake was recorded daily from dry-off to 42d relative to calving (DRC). Body weight and body condition score were measured weekly from dry-off to 42 DRC. Milk yield and composition were recorded daily to 42wk postpartum. Glucose tolerance tests (GTT) and insulin challenges (IC) were performed at dry-off, -14, 7, and 28 DRC in a subset of cows (HT, n = 8; CL, n = 8). Relative to HT, CL cows had lower rectal temperatures (39.3 vs. 39.0°C) in the afternoon and respiration rate (69 vs. 48 breath/min). Cows from the cooling treatment tended to consume more feed than HT cows prepartum and postpartum. Compared with HT, CL cows gained more weight before calving but lost more weight and body condition in early lactation. Cows from the cooling treatment produced more milk than HT cows (34.0 vs. 27.7kg/d), but treatments did not affect milk composition. Treatments did not affect circulating insulin and metabolites prepartum, but CL cows had decreased glucose, increased nonesterified fatty acid, and tended to have lower insulin concentrations in plasma postpartum compared with HT cows. Cooling prepartum HT cows did not affect the insulin responses to GTT and IC during the transition period and glucose responses to GTT and IC at -14 and 28 DRC were not affected by treatments. At 7 DRC, CL cows tended to have slower glucose clearance to GTT and weaker glucose response to IC relative to HT cows. Cows from the cooling treatment had stronger nonesterified fatty acid responses to IC postpartum but not prepartum compared with HT. In conclusion, cooling heat-stressed dairy cows in the dry period reduced insulin effects on peripheral tissues in early lactation but not in the dry period.     

Effect of dietary protein content on estrous behavior of dairy cows during early and mid lactation

One of the main contributing factors to the decline in fertility in contemporary dairy farming is the inability to detect cows in estrus. In the current study, 90 Holstein dairy cows [45 primiparous and 45 multiparous (mean parity of 3.1)] were allocated to 1 of 3 treatments at calving; 173, 144, or 114 g of crude protein/kg of dry matter. Estrous behavior was recorded for one 30-min period every 12 h from calving until all animals reached 140 d postpartum. Behavioral activities were recorded according to a scoring system developed by Van Eerdenburg et al. (1996), with 9 key estrous behavioral activities each allocated a given number of points. If the total score allocated was greater than or equal to 50 points during a single or consecutive observational periods, then the animal was deemed to be in estrus. A total of 238 estrous cycles scored 50 points or above on the Van Eerdenburg et al. (1996) scale in this experiment, with 51.7% of these cycles being characterized as standing immobile on mounting. There were no direct effects of dietary protein content on estrous behavior; however, 3 significant stage of lactation × protein treatment interactions occurred for the behavioral activities (mucous discharge, chin resting, and mounting the head side of another cow), but no consistent trends were apparent from the predicted means. There was a significant influence of parity on the frequency of mounting the head side of another cow and total number of behavior activities displayed per estrous cycle. In both cases multiparous animals displayed fewer behavioral activities than primiparous animals. An increase in the size of the sexually active group (animals in estrus at the same time, up to 5) significantly increased the expression of mounting or attempting to mount another cow, the number of cycles in which standing immobile on being mounted was observed, the total estrous score and the proportion of cyclic animals that were diagnosed as being in estrus. The most frequent behavioral activity displayed was chin resting (89.5% of cycles), and the most reliable behavior was standing immobile on mounting (when expressed 96.4% of cows were in estrus). The most dependable (function of reliability and frequency displayed) sign of estrus was mounting or attempting to mount another cow. This behavior was expressed in 83% of cycles, and when expressed, 89% of animals were in estrus.     

Short communication: Characterization of early postpartum estrous behavior and ovulation in lactating dairy cows using radiotelemetry

The objective of this study was to describe early postpartum estrous behavior and ovulation in lactating dairy cows using radiotelemetry. Cows (n=50) were continuously monitored for behavioral estrus with a radiotelemetric system, HeatWatch II (CowChips LLC, Manalapan, NJ), from d 14 to approximately d 49 postpartum. Blood collection for analysis of progesterone and ovarian ultrasonography were performed once weekly starting on d 14. First ovulation was associated with behavioral estrus in 5 cows and occurred at 28.2±10.8d (mean±SD; range 17 to 40d). The average duration of estrus was 6.0±4.9h (range 3 to 12.2h), and the mean number of standing events was 18.4±8.9 (range 4 to 26). Based on progesterone concentrations of ≥1ng/mL, estimated first postpartum ovulation occurred at 25.1±10.4d (range 10 to 49d) for 38 animals without evidence of behavioral estrus. The interval to estimated first ovulation without behavioral estrus was not different from the interval to first ovulation associated with behavioral estrus. Level of milk production and body condition score loss did not affect the interval to estimated first ovulation without estrus or first ovulation associated with estrus. Six animals did not show evidence of ovulation based on progesterone concentration, whereas 1 cow showed evidence of estrous behavior on the day before removal from the study. The majority of first postpartum ovulations (38/43; 88.4%) were not associated with behavioral estrus.     

The relationship between estrous behavioral score and time of ovulation in dairy cattle

One of the major contributors to poor fertility of a dairy herd is ineffective detection of estrus. Recently, it has become evident that cow factors contribute largely to low detection rates. Until now, standing behavior has been the symptom used to determine the right moment for insemination. However, standing behavior is not observed in over 50% of the cows in estrus in a number of herds, and no data are available to relate the moment of ovulation to other estrous symptoms. Therefore, in the present study, cows were observed for a number of visual signs of estrus, twice per day for 30 min, and the moment of ovulation was estimated by transrectal ultrasonographic scanning of the ovaries. In this study, 100 cows were detected in estrus visually, using a scoring system. Standing behavior was observed in 50% of those cows, although there was more than one cow in estrus at a time in most (85%) cases. There was no correlation between follicular size and ovulation time or estrous behavior score. Levels of 305-d milk yield and parity were also not correlated with estrous behavior scores. However, a significant correlation (0.31) was found between detection score and day of ovulation. A retrospective analysis revealed that cows that ovulated 0 to 24 h after artificial insemination (AD) scored almost three times the number of estrous behavior points compared to the ones that ovulated 24 to 48 h after AI. Ovulation more than 48 h after AI resulted in pregnancy in only 15% of the cows.     

Changes in milk characteristics and fatty acid profile during the estrous cycle in dairy cows

The relationship of the estrous cycle to milk composition and milk physical properties was assessed on Holstein (n = 10,696), Brown Swiss (n = 20,501), Simmental (n = 17,837), and Alpine Grey (n = 8,595) cows reared in northeastern Italy. The first insemination after calving for each cow was chosen to be the day of estrus and insemination. Test days surrounding the insemination date (from 10 d before to 10 d after the day of the estrus) were selected and categorized in phases relative to estrus as diestrus high-progesterone, proestrus, estrus, metestrus, and diestrus increasing-progesterone phases. Milk components and physical properties were predicted on the basis of Fourier-transform infrared spectra of milk samples and were analyzed using a linear mixed model, which included the random effects of herd, the fixed classification effects of year-month, parity number, breed, estrous cycle phase, day nested within the estrous cycle phase, conception, partial regressions on linear and quadratic effects of days in milk nested within parity number, as well as the interactions between conception outcome with estrous cycle phase and breed with estrous cycle phase. Milk composition, particularly fat, protein, and lactose, showed clear differences among the estrous cycle phases. Fat increased by 0.14% from diestrus high-progesterone to estrous phase, whereas protein concomitantly decreased by 0.03%. Lactose appeared to remain relatively constant over diestrus high-progesterone, rising 1 d before the day of estrus followed by a gradual reduction over the subsequent phases. Specific fatty acids were also affected across the estrous cycle phases: C14:0 and C16:0 decreased (?0.34 and ?0.48%) from proestrus to estrus with a concomitant increase in C18:0 and C18:1 cis-9 (0.40 and 0.73%). More general categories of fatty acids showed a similar behavior; that is, unsaturated fatty acids, monounsaturated fatty acids, polyunsaturated fatty acids, trans fatty acids, and long-chain fatty acids increased, whereas the saturated fatty acids, medium-chain fatty acids, and short-chain fatty acids decreased during the estrous phase. Finally, urea, somatic cell score, freezing point, pH, and homogenization index were also affected indicating variation associated with the hormonal and behavioral changes of cows in standing estrus. Hence, the variation in milk profiles of cows showing estrus should potentially be taken into account for precision dairy farming management.     

Changes in plasma electrolytes,minerals, and hepatic markers of health across the transition period in dairy cows divergent in genetic merit for fertility traits and postpartum anovulatory intervals

Peripartum metabolism and subsequent reproductive performance of dairy cows are linked, with maladaptation over the transition period associated with poor reproductive success. A herd of seasonal calving, grazing dairy cows was established that differed in their genetic merit for fertility traits. The heifers were produced by a customized mating program to achieve a 10-percentage point divergence in the New Zealand fertility breeding value (FertBV) as follows: +5 FertBV (POS) versus ?5% FertBV (NEG), while also limiting divergence in other breeding values, including body weight, body condition score, and milk production. In this study, we aimed to characterize differences in metabolic, mineral, and metabolic stress marker profiles during their first postpartum transition period as primiparous heifers and to examine if animals with longer postpartum anestrous intervals (PPAI; more than 66 d compared with less than 35 d) had greater metabolic dysfunction. Blood was sampled at ?21, ?14, ?7, 0, 4, 7, 10, 14, 17, 21, 28, and 35 d relative to calving in 455 primiparous cows and plasma analyzed. The NEG cows had lower concentrations of both plasma nonesterified fatty acids and β-hydroxybutyrate at d 7 compared with POS cows. Detailed temporal profiling of various metabolic, mineral, and metabolic stress markers was undertaken in a subset of cows (n = 70). Cows were selected retrospectively to create 4 groups in a 2 × 2 factorial design with either a POS or NEG FertBV and either a short (19–35 d) or long (66–131 d) PPAI. The NEG cows tended, on average, to have lower nonesterified fatty acids and β-hydroxybutyrate concentrations compared with POS cows across the transition period. Mean body weight and body condition score was greatest in NEG cows when compared with the POS cows and an interaction with day demonstrated this only occurred precalving. They also had indications of improved liver health precalving, with higher albumin-to-globulin ratios and lower bilirubin concentrations. Concentrations of aspartate aminotransferase were lower, and the Na-to-Cl ratio was greater in cows with a long versus a short PPAI at d 28 and d 35 after calving, potentially because of cows with a short PPAI (19–35 d) returning to estrous during this time. Magnesium concentrations were lower in NEG cows with a short PPAI from d 21 onwards, indicating NEG cows may metabolically respond to estrous differently than POS cows. The NEG-long PPAI cows had greater gamma-glutamyl transferase concentrations from calving until d 28 and lower bilirubin concentrations throughout the transition period. Together, the results demonstrate significant effects of FertBV on peripartum metabolic status. However, most of the markers tested returned to reference intervals within 4 d after calving or remained within those intervals for the whole transition period, indicating relatively minor biological effects of FertBV on transition period adaptation. The profound differences in reproductive performance among the groups was not explained by underlying differences in metabolic responses during the transition period.