Effects of intravenous glucose infusion and nutritional balance on serum concentrations of nonesterified fatty acids, glucose, insulin, and progesterone in nonlactating dairy cows

The objective of this study was to evaluate serum concentrations of nonesterified fatty acids, glucose, insulin, and progesterone in nonlactating dairy cows according to nutritional balance and glucose infusion. Ten nonlactating, ovariectomized Gir × Holstein cows were stratified by body weight (BW) and body condition score (BCS) on d −28 of the study, and randomly assigned to 1) negative nutrient balance (NB) or 2) positive nutrient balance (PB). From d −28 to d 0, cows were allocated according to nutritional treatment (5 cows/treatment) into 2 low-quality pastures with reduced forage availability. However, PB cows individually received, on average, 3 kg/cow per day (as-fed) of a concentrate during the study. All cows had an intravaginal progesterone releasing device inserted on d −14, which remained in cows until the end of the study. Cow BW and BCS were assessed again on d 0. On d 0, cows within nutritional treatment were randomly assigned to receive, in a crossover design containing 2 periods of 24 h each, 1) intravenous glucose infusion (GLU; 0.5 g of glucose/kg of BW, as a 5% glucose solution administered, on average, at 32 mL/min over a 3-h period), or 2) intravenous saline infusion (SAL; 0.9% solution infused on average at 32 mL/min over a 3-h period). Prior to the beginning of each period, all cows were fasted for 12 h. Blood samples were collected, relative to the beginning of the infusion, at −12 and −11.5 h (beginning of fasting), and at −0.5, 0, 0.5, 1, 2, 3, 4, 5, and 6 h. Following the last blood collection of period 1, cows received (PB) or not (NB) concentrate and were returned to their respective pastures. Changes in BCS and BW were greater in NB cows compared with PB cows (−0.60 and −0.25 ± 0.090 for BCS, respectively; −22.4 and 1.2 ± 6.58 kg for BW, respectively). Cows receiving GLUC had greater glucose concentrations from 0.5 to 3 h relative to infusion compared with SAL cows. Insulin concentrations were greater in PB cows assigned to GLUC compared with SAL cohorts at 0.5 and 3 h following infusion, whereas NB cows assigned to GLUC had greater insulin concentrations compared with SAL cohorts at 0.5, 1, 2, and 3 h. Progesterone concentrations were greater in PB cows assigned to GLUC at 2, 3, and 4 h following infusion compared with SAL cohorts. In conclusion, the effects of glucose infusion on serum concentrations of insulin and progesterone in nonlactating dairy cows were dependent on cow nutritional status.     

Effect of complementation of cattle cooling systems with feedline soakers on lactating dairy cows in a desert environment

Two experiments were conducted on a commercial dairy farm in eastern Saudi Arabia to investigate the effects of Korral Kool (KK; Korral Kool Inc., Mesa, AZ) cattle cooling systems complemented with feedline soakers on core body temperature (CBT) of dairy cows. In both experiments, cows had access to KK 24 h/d. In the first experiment, 7 primiparous and 6 multiparous lactating Holstein dairy cows were assigned to 1 of 2 pens, which were assigned randomly to treatment sequence over 4 d in a switchback design. Soakers were on (ON24) or off (OFF24) for 24 h/d. For the second experiment, 20 multiparous lactating Holstein cows were assigned randomly to 1 of 2 pens, which were assigned randomly to treatment sequence in a switchback design. This experiment lasted 4 d and feedline soakers alternately remained off or were on (ON12) for 12 h/d. In experiment 1, average ambient temperature was 30 ± 0.9°C and average relative humidity was 44 ± 14% (mean ± SD). Feedline soakers complementing KK systems for 24 h/d decreased the mean CBT of lactating dairy cows compared with KK systems alone (38.80 vs. 38.98 ± 0.061°C, respectively). A significant treatment by time interaction was found. The greatest treatment effects occurred at 2100 h; treatment means at this time were 39.26 and 38.85 ± 0.085°C for OFF24 and ON24 treatments, respectively. In experiment 2, average ambient temperature was 35 ± 1.5°C and average relative humidity was 33 ± 16%. Feedline soakers running for 12 h/d significantly decreased the mean 24-h CBT from 39.16 to 38.99 ± 0.084°C. Treatment by time interaction was also significant; the greatest treatment effects occurred at 1500 h, when ON12 reduced CBT from 39.38 to 38.81 ± 0.088°C. These results demonstrate that complementing the KK system with feedline soakers decreased the CBT of dairy cows housed in desert environments. However, the combined systems were not sufficient to lower CBT to normal temperatures in this extreme environment.     

Visceral adipose tissue mass in nonlactating dairy cows fed diets differing in energy density

Our objective was to determine dietary energy effects on feed intake, internal fat deposition, body condition score (BCS), visceral organ mass, and blood analytes in Holstein cows. Eighteen nonpregnant, nonlactating cows (BCS = 3.04 ± 0.25) were blocked based on initial BCS and were randomly assigned within each block to 2 treatments. Treatments were either high energy [HE; net energy for lactation (NE_L) = 1.62 Mcal/kg] or low energy (LE; NE_L = 1.35 Mcal/kg) diets fed as total mixed rations for 8 wk. The LE diet consisted of 81.7% forage, including 40.5% wheat straw and 28.3% corn silage, whereas the HE diet contained 73.8% forage with no straw and 49.9% corn silage (dry matter basis). Cows were fed for ad libitum intake once daily at 0800 h. Feed intake was recorded daily, blood was sampled at wk 1, 4, and 7, and BCS was assigned at wk 1, 4, and 7. Cows were killed following the 8-wk period, and visceral organs, mammary gland, and internal adipose tissues were weighed and sampled. The HE group had greater dry matter intake (15.9 vs. 11.2 ± 0.5 kg/d) and energy intakes than cows fed LE, but neutral detergent fiber intake did not differ (5.8 vs. 5.6 ± 0.25 kg/d for HE and LE). Final body weight was greater for cows fed HE (807 vs. 750 kg), but BCS did not differ between groups (3.52 vs. 3.47 for HE and LE). Omental (26.8 vs. 15.2 ± 1.6 kg/d), mesenteric (21.5 vs. 11.2 ± 1.9 kg), and perirenal (8.9 vs. 5.4 ± 0.9 kg) adipose tissue masses were larger in HE cows than in LE cows. Although subcutaneous adipose mass was not measured, carcass weight (including hide and subcutaneous fat) did not differ between HE (511 kg) and LE (496 kg). Liver weight tended to be greater for cows fed HE, but weights of gastrointestinal tract, heart, and kidney did not differ. Serum insulin tended to be greater and the glucose to insulin ratio was lower for cows fed HE. Serum concentrations of β-hydroxybutyrate and cholesterol were greater for HE cows than for LE cows but concentrations of glucose, nonesterified fatty acids, total protein, and albumin did not differ. Final BCS was correlated with masses of omental (r = 0.57), mesenteric (r = 0.59), and perirenal (r = 0.72) adipose tissue, but mesenteric adipose mass increased more as BCS increased for cows fed HE. The similar final BCS between HE and LE cows demonstrates that BCS may lack sensitivity to detect differences in visceral fat deposition that might increase risk for peripartal diseases and disorders.     

Relationships between fertility and postpartum changes in body condition and body weight in lactating dairy cows

The relationship between energy status and fertility in dairy cattle was retrospectively analyzed by comparing fertility with body condition score (BCS) near artificial insemination (AI; experiment 1), early postpartum changes in BCS (experiment 2), and postpartum changes in body weight (BW; experiment 3). To reduce the effect of cyclicity status, all cows were synchronized with Double-Ovsynch protocol before timed AI. In experiment 1, BCS of lactating dairy cows (n = 1,103) was evaluated near AI. Most cows (93%) were cycling at initiation of the breeding Ovsynch protocol (first GnRH injection). A lower percentage pregnant to AI (P/AI) was found in cows with lower (≤2.50) versus higher (≥2.75) BCS (40.4 vs. 49.2%). In experiment 2, lactating dairy cows on 2 commercial dairies (n = 1,887) were divided by BCS change from calving until the third week postpartum. Overall, P/AI at 70-d pregnancy diagnosis differed dramatically by BCS change and was least for cows that lost BCS, intermediate for cows that maintained BCS, and greatest for cows that gained BCS [22.8% (180/789), 36.0% (243/675), and 78.3% (331/423), respectively]. Surprisingly, a difference existed between farms with BCS change dramatically affecting P/AI on one farm and no effect on the other farm. In experiment 3, lactating dairy cows (n = 71) had BW measured weekly from the first to ninth week postpartum and then had superovulation induced using a modified Double-Ovsynch protocol. Cows were divided into quartiles (Q) by percentage of BW change (Q1 = least change; Q4 = most change) from calving until the third week postpartum. No effect was detected of quartile on number of ovulations, total embryos collected, or percentage of oocytes that were fertilized; however, the percentage of fertilized oocytes that were transferable embryos was greater for cows in Q1, Q2, and Q3 than Q4 (83.8, 75.2, 82.6, and 53.2%, respectively). In addition, percentage of degenerated embryos was least for cows in Q1, Q2, and Q3 and greatest for Q4 (9.6, 14.5, 12.6, and 35.2% respectively). In conclusion, for cows synchronized with a Double-Ovsynch protocol, an effect of low BCS (≤2.50) near AI on fertility was detected, but change in BCS during the first 3 wk postpartum had a more profound effect on P/AI to first timed AI. This effect could be partially explained by the reduction in embryo quality and increase in degenerate embryos by d 7 after AI in cows that lost more BW from the first to third week postpartum.     

The definition of acidosis in dairy herds predominantly fed on pasture and concentrates

This cross-sectional survey examined the prevalence of ruminal acidosis and the effects of acidosis on the production of dairy cattle. Eight fresh cows, 3 primiparous and 5 multiparous (<100 d in milk), were selected randomly from each of 100 dairy herds in 5 regions of Australia. Rumen fluid was obtained from each cow by rumenocentesis and a stomach tube, and samples were tested for pH. Stomach tube rumen fluid samples were analyzed for volatile fatty acid, ammonia, and d-lactate concentrations. On the basis of the results of all assays, cows were categorized into 3 distinct categories (categories 1, 2, and 3) by cluster analysis. The percentages of cattle in categories 1, 2, and 3 were 10.2, 29.9, and 59.9%, respectively. Mean rumen pH for categories 1, 2, and 3 were 5.74 ± 0.47, 6.18 ± 0.44, and 6.33 ± 0.43, respectively. Biochemically, categories 1, 2, and 3 were characterized, respectively, as follows: mean total VFA concentration (mM), 100.74 ± 23.22, 94.79 ± 18.13, and 62.81 ± 15.65; mean ammonia concentration (mM), 2.46 ± 2.02, 7.79 ± 3.75, and 3.64 ± 2.03; and mean d-lactate concentration (mM), 0.34 ± 0.86, 0.28 ± 0.97, and 0.12 ± 0.51. Category 1 cows had higher propionate, valerate, isovalerate, and caproate concentrations and were of lower parity than cows in other categories. Cows in category 1 had higher milk production but lower milk fat content than category 2 cows. Herds were assigned to 1 of 3 groups according to the numbers of cows assigned to each category. Herds with ≥3 of the 8 cows in category 1 were classified as acidotic. Herds with ≥3 of the 8 cows in category 2 were classified as having suboptimal rumen function, and herds with ≥3 of the 8 cows in category 3 were classified as normal. Herds that had 3 or more of the 8 cows in category 1 (acidotic herds) had diets with higher energy and nonfiber carbohydrate contents and a lower neutral detergent fiber content than herds with a high prevalence of category 2 or 3 cows. The lack of significance of a herd effect in the statistical models developed suggests that the categories were robust across production systems, in which diets varied from all pasture to total mixed rations. A point prevalence of 10% (95% credible interval, 8 to 12%) of cows with an acidotic profile indicates a high risk for acidosis in the cattle sampled. The higher nonfiber carbohydrate and lower neutral detergent fiber contents of diets for herds with a high prevalence of category 1 cows (acidotic herds) indicates that there may be opportunities to reduce the risk of acidosis by dietary manipulation.     

Management factors associated with impaired locomotion in dairy cows in England and Wales

Forty-nine farms in England and Wales were visited on 4 occasions between February 2003 and March 2004. A total of 21,693 scores of locomotion were assigned to 7,722 cattle. Locomotion was assessed on a 3-point scale by observing the posture of a cow's back while standing and walking (1 = sound, 2 = not sound, 3 = lame). Data on measurable factors potentially associated with locomotion were collected from all farms using direct observations of the farm environment and a comprehensive farmer interview. The mean herd locomotion score was 1.77 ± 0.02. There was no significant difference in mean herd locomotion scores between 5 herds housed in straw yards (1.72 ± 0.02) and 44 herds housed in free stalls (1.78 ± 0.02), possibly because of lack of power. A GLM was produced using data from the 44 herds housed in free stalls, with the mean farm locomotion score of all cows examined on all 4 visits as the outcome variable. Factors associated with an elevated locomotion score were dry cows kept in straw yards compared with free stalls (increase in locomotion score = 0.06 ± 0.03), pregnant heifers kept with milking cows in winter compared with being kept with dry cows (increase in locomotion score = 0.09 ± 0.03), aisle widths of <3 m compared with widths of ≥3 m (increase in locomotion score = 0.06 ± 0.02), a curb height of ≤15 cm compared with a height of >15 cm (increase in locomotion score = 0.07 ± 0.03), routine trimming of hooves of all cows by a hoof trimmer or by the farmer compared with no routine hoof trimming (increase in locomotion score = 0.18 ± 0.04 and 0.13 ± 0.03 respectively), feeding corn silage to milking cows compared with feeding other forage types (increase in locomotion score = 0.10 ± 0.03), and the use of automatic scrapers in the free-stall barn compared with tractor scrapers (increase in locomotion score = 0.10 ± 0.03). These variables were correlated with many other management variables. The use of automatic scrapers was correlated with the use of sawdust on rubber mats in free stalls. Curb height was negatively correlated with increasing distance of the neck rail from the front (head end) of the free stall. These putative risk factors support the hypothesis that locomotion score is linked to management factors; in particular, the combination of sawdust on rubber mats with automatic scrapers was associated with elevated locomotion scores.     

Effect of bovine somatotropin (500 mg) administered at ten-day intervals on ovulatory responses, expression of estrus, and fertility in dairy cows

The objectives of this study were to evaluate the effect of administering 500 mg of recombinant bovine somatotropin (bST) every 10 d on ovulatory responses, estrous behavior, and fertility of lactating Holstein cows. Lactating dairy cows were assigned to 1 of 2 treatments: a control with no administration of bST (73 primiparous and 120 multiparous cows) or 6 consecutive administrations of 500 mg of bST (83 primiparous and 123 multiparous cows) given subcutaneously at 10-d intervals starting 61 ± 3 d postpartum (study d 0), concurrent with the initiation of the timed artificial insemination (AI). Blood samples were collected thrice weekly from 61 ± 3 to 124 ± 3 d in milk (DIM), and plasma samples were analyzed for concentrations of estradiol, glucose, insulin, insulin-like growth factor 1, and progesterone. The estrous cycle of cows was presynchronized with 2 injections of PGF_2α at 37 ± 3 and 51 ± 3 DIM, and the Ovsynch timed AI protocol was initiated at 61 ± 3 DIM. Ovaries were scanned to determine ovulatory responses during the Ovsynch protocol. Pregnancy was diagnosed at 33 and 66 d after AI. Body condition was scored on study d 0, 10, 42, and 76. Sixty-four cows were fitted with a pressure mounting sensor with radiotelemetric transmitters to monitor estrous behavior. Treatment of lactating dairy cows with 500 mg of bST at 10-d intervals increased yields of milk and milk components in the first 2 mo after treatment. Body condition of bST-treated cows remained unaltered, whereas control cows gained BCS. Treatment with bST increased concentrations of insulin-like growth factor 1 chronically, but concentrations of insulin and glucose increased only transiently in the first 7 d after the first injection of bST. Concentrations of progesterone during and after the Ovsynch protocol remained unaltered after treatment with bST; likewise, ovulatory responses during the Ovsynch protocol were mostly unaltered by treatment. Concentration of estradiol tended to be greater for bST cows than for control cows immediately before induction of ovulation in the Ovsynch protocol. Similarly, the mean and the peak concentrations of estradiol were greater for bST cows than for control cows when monitored during spontaneous estrus. Nevertheless, duration of estrus and the median number of standing events were less for bST cows than for control cows. Pregnancies per AI after the first and second postpartum inseminations were not affected by bST treatment. Treatment of lactating dairy cows with 500 mg of bST every 10 d improved lactation performance, but it did not affect pregnancies per AI and it reduced expression of estrus.     

Effects of running time of a cattle-cooling system on core body temperature of cows on dairy farms in an arid environment

Two experiments were conducted on a commercial dairy farm to describe the effects of a reduction in Korral Kool (KK; Korral Kool Inc., Mesa, AZ) system operating time on core body temperature (CBT) of primiparous and multiparous cows. In the first experiment, KK systems were operated for 18, 21, or 24 h/d while CBT of 63 multiparous Holstein dairy cows was monitored. All treatments started at 0600 h, and KK systems were turned off at 0000 h and 0300 h for the 18-h and 21-h treatments, respectively. Animals were housed in 9 pens and assigned randomly to treatment sequences in a 3 × 3 Latin square design. In the second experiment, 21 multiparous and 21 primiparous cows were housed in 6 pens and assigned randomly to treatment sequences (KK operated for 21 or 24 h/d) in a switchback design. All treatments started at 0600 h, and KK systems were turned off at 0300 h for the 21-h treatments. In experiment 1, cows in the 24-h treatment had a lower mean CBT than cows in the 18- and 21-h treatments (38.97, 39.08, and 39.03 ± 0.04°C, respectively). The significant treatment by time interaction showed that the greatest treatment effects occurred at 0600 h; treatment means at this time were 39.43, 39.37, and 38.88 ± 0.18°C for 18-, 21-, and 24-h treatments, respectively. These results demonstrate that a reduction in KK system running time of ≥3 h/d will increase CBT. In experiment 2, a significant parity by treatment interaction was found. Multiparous cows on the 24-h treatment had lower mean CBT than cows on the 21-h treatment (39.23 and 39.45 ± 0.17°C, respectively), but treatment had no effect on mean CBT of primiparous cows (39.50 and 39.63 ± 0.20°C for 21- and 24-h treatments, respectively). A significant treatment by time interaction was observed, with the greatest treatment effects occurring at 0500 h; treatment means at this time were 39.57, 39.23, 39.89, and 39.04 ± 0.24°C for 21-h primiparous, 24-h primiparous, 21-h multiparous, and 24-h multiparous cows, respectively. These results demonstrate that multiparous and primiparous cows respond differently when KK system running time decreases from 24 to 21 h. We conclude that in desert climates, the KK system should be operated continuously to decrease heat stress of multiparous dairy cows, but that operating time could be reduced from 24 to 21 h for primiparous cows. Reducing system operation time should be done carefully, however, because CBT was elevated in all treatments.     

Somatotropic axis components and nutrient partitioning in genetically diverse dairy cows managed under different feed allowances in a pasture system

The somatotropic axis [including growth hormone (GH), GH receptor, and insulin-like growth factor (IGF)-I] is uncoupled in high-producing cows in early lactation so that the liver fails to respond to GH and produces less IGF-I. This uncoupling was implicated in the process of nutrient partitioning, enabling high milk production. Different genetic selection goals may affect functional components of the somatotropic axis. Thus, the somatotropic axis was examined in diverse genetic strains of dairy cows [North American Holstein 1990 (NA90), New Zealand Holstein-Friesian 1990 (NZ90), and New Zealand Holstein-Friesian 1970 (NZ70)] that were managed similarly within a pasture-based system but were offered feed allowances commensurate with their genetic ability to produce milk. The NA90 cows produced more milk (26.2 ± 0.3, 24.1 ± 0.3, and 20.1 ± 0.4 kg/d, for NA90, NZ90, and NZ70, respectively), but had lower milk fat percentages (4.28 ± 0.03, 4.69 ± 0.03, and 4.58 ± 0.04 kg/d for NA90, NZ90, and NZ70, respectively) compared with both NZ strains. Milk protein percentages (3.38 ± 0.02, 3.52 ± 0.02, and 3.29 ± 0.03 kg/d for NA90, NZ90, and NZ70, respectively) were greater for NZ90 cows. During early lactation (wk 2 to 6), the total net energy produced in milk was greater in NA90 compared with NZ90 or NZ70 cows, but total net energy in milk after wk 6 was equivalent for NA90 and NZ90 cows. The greater milk production in early lactation in NA90 cows was associated with lower body condition scores (BCS; 1 to 10 scale; 4.0 ± 0.1) elevated blood GH concentrations (1.6 ± 0.1 ng/mL), and low blood IGF-I concentrations (14.8 ± 1.1 ng/mL), indicating an uncoupled somatotropic axis. In comparison, the NZ70 cows retained a coupled somatotropic axis during early lactation, maintaining greater BCS (4.6 ± 0.1), lower blood GH (0.7 ± 0.1 ng/mL), and greater blood IGF-I (21.9 ± 1.2 ng/mL). The degree of uncoupling in NZ90 cows was intermediate between the other 2 strains. Additional feed allowance failed to change blood IGF-I concentrations in NA90 cows but increased IGF-I concentrations in NZ90 cows (20.9 ± 1.4 and 13.2 ± 1.4 ng/mL for the high and low feed allowance, respectively). Furthermore, additional feed allowance in NZ90 cows lessened BCS loss in early lactation, but did not affect BCS loss in NA90 cows. Functional components of the somatotropic axis differed for the respective strains and were consistent with strain differences in milk production, BCS, and feed allowance.     

Milk production of dairy cows fed wet corn gluten feed during the dry period and lactation

An experiment was conducted with 36 primiparous and 40 multiparous Holstein cows to examine the effects of feeding wet corn gluten feed (WCGF) on 305-d milk production, dry matter (DM) intake, body condition score (BCS), and health. The experimental treatments included: 1) control—WCGF not fed (n = 27); 2) WCGF-L—cows received diets containing WCGF (38% DM basis) during lactation (n = 23); and 3) WCGF-DL—cows received diets containing WCGF (38% DM basis) during the dry period and lactation (n = 26). During the dry period, cows consuming WCGF were observed to have a significant gain in BCS (0.07 ± 0.06) compared with a loss in BCS in cows fed the control diet (control = −0.11 ± 0.06 and WCGF-L = −0.04 ± 0.06). During lactation, there were no differences by treatment on BCS. Cows consuming WCGF during lactation consumed more feed compared with the control: 25.4, 23.8, and 21.2 ± 0.76 kg/d for WCGF-L, WCGF-DL, and the control, respectively. Milk production was higher for cows consuming WCGF: 35.0, 34.7, and 31.1 ± 2.1 kg/d for WCGF-L, WCGF-DL, and the control, respectively. No differences were found in either DM intake or actual milk yield between the WCGF-L and WCGF-DL treatments, indicating that prepartum diets did not influence lactational performance. The WCGF diets resulted in significant reductions in the concentration of milk fat (3.94, 3.74, and 4.15 ± 0.08% for WCGF-L, WCGF-DL, and the control, respectively), but because total milk yield was increased, there were no differences in total milk fat yield. In addition, 3.5% of fat-corrected milk tended to be affected by diet: 38.9, 36.3, and 34.7 ± 1.93 kg/d for WCGF-L, WCGF-DL, and the control, respectively. The increasing effect of DM intake and milk yield in cows consuming WCGF resulted in a similar efficiency of 3.5% fat-corrected milk production for all treatments, averaging 1.5 ± 0.09. Total protein yields were significantly higher for cows consuming WCGF diets during lactation: 1.15, 1.10, 1.00 ± 0.06 kg/d for WCGF-L, WCGF-DL, and the control, respectively. These results indicate that diets may be formulated to contain as much as 37.5% WCGF (DM basis).     

Reproductive performance of lactating dairy cows managed for first service using timed artificial insemination with or without detection of estrus using an activity-monitoring system

Lactating dairy cows (n = 1,025) on a commercial dairy farm were randomly assigned at 10 ± 3 d in milk (DIM) to 1 of 3 treatments for submitting cows to first artificial insemination (AI) and were fitted with activity-monitoring tags (Heatime; SCR Engineers Ltd., Netanya, Israel) at 24 ± 3 DIM. Cows (n = 339) in treatment 1 were inseminated based on increased activity from the end of the voluntary waiting period (50 DIM) until submission to an Ovsynch protocol; cows without increased activity from 21 to 65 DIM began an Ovsynch protocol at 65 ± 3 DIM, whereas cows without increased activity from 21 to 50 DIM but not from 51 to 79 DIM began an Ovsynch protocol at 79 ± 3 DIM. Cows (n = 340) in treatment 2 were inseminated based on activity after the second PGF_2α injection of a Presynch-Ovsynch protocol at 50 DIM, and cows without increased activity began an Ovsynch protocol at 65 ± 3 DIM. Cows (n = 346) in treatment 3 were monitored for activity after the second PGF_2α injection of a Presynch-Ovsynch protocol, but all cows received timed AI (TAI) at 75 ± 3 DIM after completing the Presynch-Ovsynch protocol. The activity-monitoring system detected increased activity in 56, 69, and 70% of cows in treatments 1, 2, and 3, respectively. Treatment-2 cows had the fewest average days to first AI (62.5), treatment-3 cows had the most average days to first AI (74.9), and treatment-1 cows had intermediate average days to first AI (67.4). Treatment-1 and -2 cows in which inseminations occurred as a combination between increased activity and TAI had fewer overall pregnancies per AI (P/AI) 35 d after AI (32% for both treatments) compared with treatment-3 cows, all of which received TAI after completing the Presynch-Ovsynch protocol (40%). Based on survival analysis, although the rate at which cows were inseminated differed among treatments, treatment did not affect the proportion of cows pregnant by 300 DIM. Thus, use of an activity-monitoring system to inseminate cows based on activity reduced days to first AI, whereas cows receiving 100% TAI after completing a Presynch-Ovsynch protocol had more P/AI. The trade-off between AI service rate and P/AI in the rate at which cows became pregnant was supported by an economic analysis in which the net present value ($/cow per year) differed by only $4 to $8 among treatments. We conclude that a variety of strategies using a combination of AI based on increased activity using an activity-monitoring system and synchronization of ovulation and TAI can be used to submit cows for first AI.     

Capturing urine while maintaining pasture intake, milk production, and animal welfare of dairy cows in early and late lactation

Capturing urine and spreading it evenly across a paddock reduces the risk of nitrogen loss to the environment. This study investigated the effect of 16 h/d removal from pasture on the capture of urination events, milk production, pasture intake, and animal welfare from cows grazing fresh pasture in early and late lactation. Forty-eight Holstein-Friesian cows in early [470 ± 47 kg of body weight (BW); 35 ± 9 days in milk] and late (498 ± 43 kg of BW; 225 ± 23 days in milk) lactation were allocated to 3 treatment groups. Cows had access to pasture for either 4 h after each milking (2 × 4), for 8 h between morning and afternoon milkings (1 × 8), or for 24 h, excluding milking times (control). When not grazing, the 2 × 4 and 1 × 8 groups were confined to a plastic-lined loafing area with a woodchip surface. In early lactation, the proportion of urinations on pasture and laneways was reduced from 89% (control) to 51% (1 × 8) and 54% (2 × 4) of total urinations. The 1 × 8 cows ate less pasture [10.9 kg of dry matter (DM)/cow per day] than the control (13.6 kg of DM/cow per day) and 2 × 4 (13.0 kg of DM/cow per day) cows, which did not differ from each other. The 1 × 8 and 2 × 4 cows produced less milk (21 and 22 kg of milk/cow per day, respectively) compared with control cows (24 kg of milk/cow per day). There were no differences in BW or body condition score (BCS) change across treatment groups, with all groups gaining BW and BCS during the experimental period. In late lactation, there was no difference in pasture intake (mean = 8.8 kg of DM/cow per day), milk production (mean = 10 kg of milk/cow per day), and BW or BCS change (mean = 3.7 kg and −0.2 U/cow per week, respectively) between treatment groups. As in early lactation, urinations on pasture and laneways were reduced from 85% (control) to 56% (1 × 8) and 50% (2 × 4) of total urinations. These findings highlight an opportunity to maintain performance and welfare of grazing cows in early and late lactation while capturing additional urine. This can subsequently be spread evenly across pasture to minimize nitrogen loss to the environment.     

Effect of monopropylene glycol on luteinizing hormone, metabolites, and postpartum anovulatory intervals in primiparous dairy cows

This study examined the effect of monopropylene glycol (MPG) supplementation on LH secretion, postpartum interval to first ovulation, and milk production in heifers calving with poor body condition score (BCS). Forty-seven heifers were allocated to 3 treatments: 1) heifers with high BCS (BCH; n = 13) that calved at a BCS of 3.4 (BCS scale of 1 to 5); 2) heifers with low BCS (BCL; n = 17) that calved at a BCS of 2.8; and 3) heifers with low BCS that calved at a BCS of 2.8 and were assigned to receive MPG supplementation (BCL + MPG; n = 17) and grazed pasture ad libitum. Monopropylene glycol was drenched (250 mL) twice daily for 16 wk after calving. Patterns of change in plasma LH were measured at 2 and 5 wk after calving. Pulsatile release of LH at 2 and 5 wk was greater in BCL + MPG and BCH cows compared with the BCL control cows. The BCL + MPG cows had lower NEFA concentrations than did the BCL cows during wk 1 to 6 after calving. At 12 wk postpartum, the proportion of cows cycling was 77, 82, and 28% for the BCH, BCL + MPG, and BCL treatments, respectively. Mean milk fat yield was greater for the BCH treatment during the first 12 wk postpartum compared with the BCL + MPG or BCL treatments, which did not differ from each other. Results of this study indicate that MPG supplementation reduced the interval from calving to first ovulation in heifers having poor body condition at calving.     

Short communication: Genetic characterization of digital cushion thickness

Dairy cow lameness is a serious animal welfare issue. It is also a significant cause of economic losses, reducing reproductive efficiency and milk production and increasing culling rates. The digital cushion is a complex structure composed mostly of adipose tissue located underneath the distal phalanx and has recently been phenotypically associated with incidence of claw horn disruption lesions (CHDL); namely, sole ulcers and white line disease. The objective of this study was to characterize digital cushion thickness genetically and to investigate its association with body condition score (BCS), locomotion score (LOCO), CHDL, and milk production. Data were collected from 1 large closely monitored commercial dairy farm located in upstate New York; 923 dairy cows were used. Before trimming, the following data were collected by a member of the research team: BCS, cow height measurement, and LOCO. Presence or not of CHDL (sole ulcer or white line disease, or both) was recorded at trimming. Immediately after the cows were hoof trimmed, they underwent digital sonographic B-mode examination for the measurement of digital cushion thickness. Factors such as parity number, stage of lactation, calving date, mature-equivalent 305-d milk yield (ME305MY), and pedigree information were obtained from the farm’s dairy management software (DairyCOMP 305; Valley Agricultural Software, Tulare, CA). Univariate animal models were used to obtain variance component estimations for each studied trait (CHDL, BCS, digital cushion thickness average, LOCO, height, and ME305MY) and a 6-variate analysis was conducted to estimate the genetic, residual, and phenotypic correlations between the studied traits. The heritability estimate of DCTA was 0.33 ± 0.09, whereas a statistically significant genetic correlation was estimated between DCTA and CHDL (−0.60 ± 0.29). Of the other genetic correlations, significant estimates were derived for BCS with LOCO (−0.49 ± 0.19) and ME305MY (−0.48 ± 0.20). Digital cushion thickness is moderately heritable and genetically strongly correlated with CHDL.     

The effect of routine hoof trimming on locomotion score,ruminating time,activity, and milk yield of dairy cows

The objective of this study was to quantify the effect of hoof trimming on cow behavior (ruminating time, activity, and locomotion score) and performance (milk yield) over time. Data were gathered from a commercial dairy farm in Israel where routine hoof trimming is done by a trained hoof trimmer twice per year on the entire herd. In total, 288 cows spread over 6 groups with varying production levels were used for the analysis. Cow behavior was measured continuously with a commercial neck activity logger and a ruminating time logger (HR-Tag, SCR Engineers Ltd., Netanya, Israel). Milk yield was recorded during each milking session with a commercial milk flow sensor (Free Flow, SCR Engineers Ltd.). A trained observer assigned on the spot 5-point locomotion scores during 19 nighttime milking occasions between 22 October 2012 and 4 February 2013. Behavioral and performance data were gathered from 1 wk before hoof trimming until 1 wk after hoof trimming. A generalized linear mixed model was used to statistically test all main and interactive effects of hoof trimming, parity, lactation stage, and hoof lesion presence on ruminating time, neck activity, milk yield, and locomotion score. The results on locomotion scores show that the proportional distribution of cows in the different locomotion score classes changes significantly after trimming. The proportion of cows with a locomotion score ≥3 increases from 14% before to 34% directly after the hoof trimming. Two months after the trimming, the number of cows with a locomotion score ≥3 reduced to 20%, which was still higher than the baseline values 2 wk before the trimming. The neck activity level was significantly reduced 1 d after trimming (380 ± 6 bits/d) compared with before trimming (389 ± 6 bits/d). Each one-unit increase in locomotion score reduced cow activity level by 4.488 bits/d. The effect of hoof trimming on ruminating time was affected by an interaction effect with parity. The effect of hoof trimming on locomotion scores was affected by an interaction effect with lactation stage and tended to be affected by interaction effects with hoof lesion presence, indicating that cows with a lesion reacted different to the trimming than cows without a lesion did. The results show that the routine hoof trimming affected dairy cow behavior and performance in this farm.     

The effects of increased milking frequency during early lactation on milk yield and milk composition on commercial dairy farms

Increased milking frequency (IMF) during early lactation has the potential for carryover responses following the return to normal herd milking frequency. The objective was to determine the consistency of response of cows in commercial dairy farms to IMF during early lactation. Cows (n = 398) were assigned randomly at calving within each of the 4 participating farms to 1 of 2 treatments. The control group was milked twice-daily (2×) during the entire lactation. The IMF group was milked 4-times daily (4×) starting on d 1 to 7, depending on farm, until d 21 postcalving and 2× thereafter. Cows in the IMF group were milked at the beginning and again at the end of the normal milking routine. Milking intervals differed across the farms for the 4× cows with a minimum interval of 3.5, 4.0, 5.0, and 6 h for each of the 4 farms, respectively. The milk yield of cows subjected to IMF increased by 2.2 ± 0.4 kg/d during the first 7 mo of lactation. Interactions of treatment with lactation group (primiparous vs. multiparous) were not significant. Although percentages of fat and protein in milk were decreased by early lactation IMF (3.69% ± 0.03 fat and 3.05% ± 0.02 true protein for control vs. 3.57% ± 0.03 fat and 2.99% ± 0.02 true protein for IMF), overall yields of protein were increased by IMF (1.02 ± 0.01 vs. 0.98 ± 0.01 kg/d). Early lactation IMF did not affect udder health as assessed by somatic cell count linear score. Cows subjected to IMF were 1.4 times more likely classified as subclinically ketotic than the control cows. Early lactation IMF has the potential to increase milk yield on commercial dairy farms. Although the direction of response was the same on all farms, the magnitude of the response was different among farms and appears influenced by management practices specific to each farm, which included, but were not limited to, housing system, stocking density, nutrition, genetics, and other covariates differing among farms.     

A comparison of the effects of 2 cattle-cooling systems on dairy cows in a desert environment

An experiment was conducted to investigate the effects of operation time and size of Korral Kool (KK; Korral Kool Inc., Mesa, AZ) systems on core body temperature (CBT) of dairy cows. Two KK systems were compared: a system with 1.29-m-diameter, 3-hp fans spaced 6 m apart (referred to as small) and a system with 1.52-m-diameter, 5-hp fans spaced 8 m apart (referred to as big). Forty-eight multiparous Holstein cows were assigned randomly to 8 pens (4 big, 4 small), and pens were assigned randomly to a sequence of treatments (KK operated for 21 or 24 h/d) in a switchback design. A complementary calorimetric analysis was developed to investigate the cooling area under the KK units of the big and small systems. Twenty-five sensors distributed equally under the KK units measured ambient temperature at 5-min intervals for 2 h. Average ambient temperature was 35.0 ± 0.6°C and relative humidity was 45 ± 8%. There were significant treatment effects on mean CBT: cows on the small 24-h treatment had a lower mean CBT than cows on the small 21-h treatment (39.22 vs. 39.36 ± 0.14°C), and cows on the big 24-h treatment had a lower mean CBT than cows on the big 21-h treatment (38.95 vs. 39.09 ± 0.13°C). A significant treatment by time interaction was observed. The greatest difference between systems occurred at 0100 h; treatment means at this time were 39.05, 39.01, 39.72, and 39.89 ± 0.16°C for the big 24-h, big 21-h, small 24-h, and small 21-h treatments, respectively. At certain times of day, the big system reduced CBT more than the small system. These results show that CBT of multiparous cows decreased when KK system operational time was increased from 21 to 24 h regardless of the size of the KK cooling system used. The calorimetric analysis showed that even though the big system resulted in lower mean ambient temperatures than the small system, the distance between units in the big system should be decreased to reduce the variation in temperature under the big units.     

Effect of lactation number, year, and season of initiation of lactation on milk yield of cows hormonally induced into lactation and treated with recombinant bovine somatotropin

Records representing data from 1,500 barren Holstein cows over an 8-yr period from a large commercial dairy farm in northern Mexico were analyzed to determine the effects of lactation number and season and year of initiation of lactation on milk production of cows induced hormonally into lactation and treated with recombinant bovine somatotropin (rbST) throughout lactation. Peak and 305-d milk yields were also assessed as predictors of total milk yield in cows induced into lactation. A significant quadratic relationship was found between 305-d milk yield and number of lactation [7,607 ± 145 and 9,548 ± 181 kg for first- and ≥6-lactation cows, respectively; mean ± standard error of the mean (SEM)] with the highest production occurring in the fifth lactation. Total milk yields of cows with ≤2 lactations were approximately 4,500 kg less than milk yields of adult cows (the overall average ± standard milk yield was 13,544 ± 5,491 kg per lactation and the average lactation length was 454 ± 154 d). Moreover, 305-d milk production was depressed in cows induced into lactation in spring (8,804 ± 153 kg; mean ± SEM) and summer (8,724 ± 163 kg) than in fall (9,079 ± 151 kg) and winter (9,085 ± 143 kg). Partial regression coefficients for 305-d milk yield and peak milk yield indicated an increment of 157 kg of milk per lactation per 1-kg increase in peak milk yield (r² = 0.69). Neither peak milk yield (r² = 0.18) nor 305-d milk yield (r² = 0.29) was accurate for predicting total milk yield per lactation. Year, parity, and season effects had significant influence on milk yield of cows induced into lactation and treated with rbST throughout lactation, and peak milk yield can assist in the prediction of 305-d milk yield but not total milk yield. This study also showed that hormonal induction of lactation in barren high-yielding cows is a reliable, practical, and affordable technique in countries where rbST treatment and prolonged steroid administration of dairy cows are legally permitted.     

Precalving effects on metabolic responses and postpartum anestrus in grazing primiparous dairy cows

The effect of increased access to pasture feeding during the last 6 wk of gestation on metabolic responses and postpartum anestrous interval was investigated. Heifers with a body condition score (BCS) of 5.0 (BC5+FF; on a 1-to-10 scale, US = 1.5 + 0.32 × New Zealand) were offered unrestricted pasture, and those with BCS 4.0 were fed either pasture unrestricted (BC4+FF) or restricted (BC4+RES) for the last 6 wk of gestation. After calving, all groups were offered unrestricted pasture. Mean BCS at calving for BC5+FF, BC4+FF, and BC4+RES were 4.7 ± 0.1, 4.3 ± 0.1, and 3.5 ± 0.1, respectively. At 35 d postpartum, LH pulse frequency was lower in BC4+RES than in BC4+FF and BC5+FF, which were similar. At 77 d after calving, 8% of BC4+RES cows had ovulated compared with 75% of BC4+FF and 69% of BC5+FF cows. Metabolic hormonal differences between BC4+FF and BC4+RES were not reflected in the differences between BC4+FF and BC5+FF for LH pulse frequency or ovulation. Unrestricted access to pasture during the final 6 wk of gestation for BC4 heifers reduced the risk of prolonged postpartum anestrus. Systemic factors, tissue sensitivity, and critical developmental set points are probably involved in the integrated control of ovulation by body condition.     

The effect of herbage allowance and concentrate supplementation on milk production performance and dry matter intake of spring-calving dairy cows in early lactation

The objective of this study was to determine the effect of daily herbage allowance (DHA) and concentrate level on milk production and dry matter intake of spring-calving dairy cows in early lactation. Seventy-two Holstein-Friesian dairy cows (mean calving date February 2) were randomly assigned across 6 treatments (n = 12) in a 2 × 3 factorial arrangement. The 6 treatments consisted of 2 DHA ( > 4 cm) and 3 concentrate levels: 13 kg of herbage dry matter/cow per d (low) or 17 kg of herbage dry matter/cow per d (high) DHA and unsupplemented, 3 kg, or 6 kg of dry matter concentrate/cow per d. The experimental period (period I) lasted 77 d and was followed by a carryover period (period II) during which animals were randomly reassigned across 2 grazing treatments offering 17 or 21 kg of herbage dry matter/cow per d. Increasing DHA significantly increased milk (+1.85 kg), solids-corrected milk, protein (+79.5 g), and lactose yields, protein concentration, and mean body weight (BW). Mean body condition score (BCS) and end-point BCS were also significantly higher with the high-DHA treatments. There was a linear response in milk yield, milk lactose concentration, and solids-corrected milk to concentrate supplementation. There was a significant difference in mean BW as concentrate increased from 0 to 3 kg (506 and 524 kg, respectively); there was no further increase in BW when 6 kg of concentrate was offered. Cows offered the low DHA had significantly lower grass dry matter intake (13.3 kg) and total dry matter intake (16.3 kg) than the high-DHA cows during period I. Concentrate supplementation significantly increased total dry matter intake. During period II, previous DHA continued to have a significant carryover effect on milk protein concentration, BW change, mean BCS, and end-point BCS. Concentrate supplementation during period I continued to have a significant carryover effect in period II on milk yield; milk fat, protein, and lactose yields; solids-corrected milk yield; BW; and mean BCS. Results from this study indicate that offering a medium level of DHA (17 kg of herbage dry matter) in early lactation will increase milk production. Offering concentrate will result in a linear increase in milk production. In an early spring feed-budgeting scenario, when grass supply is in deficit, offering 3 kg of dry matter concentrate with 17 kg of DHA has the additive effect of maintaining the grazing rotation at the target length as well as ensuring the herd is adequately fed.