Dairy cattle prefer shade over sprinklers: effects on behavior and physiology

Cattle will readily use shade in warm weather, but less is known about voluntary use of sprinklers. We examined preferences of 96 Holstein-Friesian dairy cows (milk yield: 12.7 ± 3.48 kg per day; mean ± SD) for sprinklers, shade, or ambient conditions after walking 2.0 km or 0.3 km before afternoon milking (n = 48 cows/distance). Each cow was individually tested on 3 consecutive days with a different paired choice each day: 1) shade or sprinklers, 2) shade or ambient conditions, 3) sprinklers or ambient conditions. Average air temperature during testing was 22.3°C. Cows preferred shade over sprinklers (62 vs. 38% ± 5.0%; mean ± SE) and shade over ambient conditions (65 vs. 35% ± 5.1%; mean ± SE). Cows showed no preference between sprinklers and ambient conditions (44% of the cows chose sprinklers, SE = 5.3%). The preference for shade over sprinklers and ambient conditions increased with air temperature, solar radiation, and wind speed. Walking distance did not influence the preference for any treatment. Respiration rate was decreased most by sprinklers (38% decrease) but also decreased in shade and ambient conditions (17 and 13% decrease, respectively; standard error of the difference = 4.7%). Similarly, surface temperature was decreased most by sprinklers (11.4% decrease), compared with that by shade (1.0% decrease), or that by ambient conditions (1.4% increase; standard error of the difference = 1.82%). Furthermore, sprinklers reduced insect avoidance behaviors, including number of tail flicks and hoof stamps. In conclusion, dairy cattle preferred to use shade in summer despite sprinklers being more efficient in decreasing heat load and insect avoidance behavior.     

A field study of the behavioral and physiological effects of varying amounts of shade for lactating cows at pasture

Shade reduces the negative effects of heat load, but little is known about how much is required for efficient cooling in commercial settings. The effect of the amount of shade on 8 Holstein-Friesian herds was studied for 2 consecutive summers (mean temperature: 23°C) on 6 commercial, pasture-based dairy farms. Farms varied in the amount of natural shade provided (range: 0 to 15.6 m² shade/cow). Time spent in shade, near water, eating, ruminating, lying, and standing were recorded between 1000 and 1530 h in 31 shaded and 11 unshaded paddocks using 20-min instantaneous scan observations of 15 focal cows/herd. Respiration rate and panting score (0 to 4.5) was recorded for focal animals once per hour. The total numbers of cows in shade, near water, and with panting scores ≥2 were recorded every 30 min. Cows without shade spent 4% more time lying than cows with shade (standard error of the difference, SED = 1.9%). A larger proportion of the herd had panting scores ≥2 when no shade was available (6 vs. 2% of the herd, SED = 1.2%), and respiration rates were higher by 8 breaths/min in cows without shade (SED = 4.7 breaths/min). Under the conditions tested, the maximum proportion of the herd that was observed using the shade increased by 3.1% for every 1-m² increase in shade size [standard error (SE) = 1.51%], and all cows were first seen simultaneously using shade when 2 m²/cow was provided. For every 1-m² increase in shade, 0.3% fewer cows had panting score ≥2 (SE = 0.12%). We observed no significant relationships between the amount of shade available and any other variables. Although additional work is required to make specific recommendations, these results indicate that providing more shade allowed a higher proportion of animals to use this resource and reduced respiratory signs of heat load.     

Effects of shade and sprinklers on performance, behavior, physiology, and the environment of heifers

The objective was to measure effects of cooling technique (shade vs. water sprinklers) on performance, behavior, physiology, and the environmental effect of 40 Holstein heifers housed in drylot corrals during the hot summer months. The experiment was a replicated crossover design with four 21-d periods and 2 treatments: 1) shades installed in the front half of the pen or 2) sprinklers, which applied water to the pen surface at 2-h intervals from 1100 to 1900 h. Animal performance measures were dry matter intake, average daily gain, and feed efficiency (gain:feed). Behavioral measures, elimination patterns, and corral spatial distribution were measured in 5-min scan frequencies over four 24-h periods. Physiological measures were rectal temperature, respiration rate, urinary urea N, and blood urea N. Environmental measures were corral soil surface temperature and moisture, particulate matter, and surface NH₃ volatilization; meteorological measures were also collected. Shaded compared with sprinkled heifers had increased dry matter intake (3.4%), increased average daily gain (14%), and increased feed efficiency (11%). Heifers in shaded vs. sprinkler treatments had decreased respiration rates (13%). Behavioral differences between the treatments varied by time of day. Heifers spent most time in either the shaded or sprinkled areas of their corrals (65.9 and 64.2%, respectively). Elimination behavior occurred predominantly at the front of the corral in close proximity to the feed bunks and additionally at the water trough in sprinkled corrals. Sprinkler treatment had a 31.7% greater average corral surface moisture than the shaded treatment. Corral surface temperature varied based on areas of surface moisture, shade location, and elimination concentration within the corral. Sprinkled corrals had less particulate matter emissions than shaded (25%), but NH₃ emissions were 46% greater in sprinkler vs. shaded treatment. Overall, the use of shade in heifer corrals improved heifer performance and physiological measures, but sprinkler treatment had less NH₃ emissions from corral surfaces under heat stress conditions. Both cooling techniques affected spatial distribution and behaviors of the heifers, which affected pen usage and surface characteristics.     

Effects of short-term repeated exposure to different flooring surfaces on the behavior and physiology of dairy cattle

Dairy cattle managed in some pasture-based systems such as in New Zealand are predominantly kept outdoors all year around, but are often taken off pasture for periods of time in wet weather to avoid soil damage. It is common to keep cattle on concrete surfaces during such “stand-off” practices and we investigated whether the addition of rubber matting onto concrete areas improves the welfare of dairy cattle. Sixteen groups of 5 cows (4 groups/treatment, 5 cows/group) were allocated to 1 of 4 treatments (concrete, 12-mm-thick rubber mat, 24-mm-thick rubber mat, or deep-bedded wood chips) and kept on these surfaces for 18 h/24 h for 4 consecutive days (6 h on pasture/24 h). Each 4-d stand-off period was repeated 4 times (with 7 d of recovery between periods) to study the accumulated effects of repeated stand-off. Lying behavior was recorded continuously during the experiment. Gait score, stride length, hygiene score, live weight, and blood samples for cortisol analysis were recorded immediately before and after each stand-off period. Cows on wood chips spent the most time lying, and cows on concrete spent the least time lying compared with those on other surfaces [wood chips: 10.8 h, 24-mm rubber mat: 7.3 h, 12-mm rubber mat: 6.0 h, and concrete: 2.8 h/18 h, standard error of the difference (SED): 0.71 h]. Cows on concrete spent more time lying during the 6 h on pasture, likely compensating for the reduced lying during the stand-off period. Similarly, cows on concrete spent more time lying on pasture between stand-off periods (concrete: 12.1 h, 12-mm rubber mat: 11.1 h, 24-mm rubber mat: 11.2 h, and wood chips: 10.7 h/24 h, SED: 0.28 h). Cows on concrete had higher gait score and shorter stride length after the 4-d stand-off period compared with cows on the other surface types, suggesting a change in gait pattern caused by discomfort. Cows on rubber mats were almost 3 times dirtier than cows on concrete or wood chips. Cortisol and live weight decreased for all treatment groups during the stand-off period. We observed no major effect of the repeated stand-off exposure. In summary, adding rubber matting onto concrete surfaces for stand-off purposes is beneficial for animal welfare. A well-managed wood chip surface offered the best welfare for dairy cows removed from pasture, and the findings of this study confirm that a concrete surface decreases the welfare of cows removed from pasture.     

Effect of rubber flooring in front of the feed bunk on the time budgets of dairy cattle

The objective of this experiment was to study the effect of rubber flooring in front of the feed bunk on the immediate behavioral response of dairy cattle. Four groups of 12 dairy cattle were alternately housed in sections of a free-stall barn with either 1.85 m of rubber flooring or grooved concrete in the area in front of the feed bunk. Rubber flooring did not affect time spent eating. However, animals showed a slight, but detectable, increase in time standing without eating on the rubber surface (5.5%) compared with concrete (4.8%). For reasons that are unclear, this increase in time spent standing was not limited to the area in front of the feed bunk; animals spent 11.0% of the available time standing elsewhere in the pen (outside of the free stall but not in front of the feed bunk) when they had access to the rubber flooring, compared with 9.0% when housed with access to only concrete floors. In addition, animals spent slightly less time lying in the free stall when they had access to rubber in front of the feed bunk (52.5 vs. 54.3%). Time spent engaged in behaviors such as standing elsewhere in the pen and eating were variable over time. For example, time spent eating declined from 23.1 to 17.4% over the 6-wk trial. In conclusion, dairy cattle with access to rubber flooring in front of the feeder showed small differences in where and how much time they spent standing, although the biological implications of these small changes are unclear.     

The effect of rearing substrate and space allowance on the behavior and physiology of dairy calves

The objective of this study was to investigate the effect of rearing substrate and space allowance on the behavior and physiology of dairy calves. At 1 wk of age, 72 calves were moved into 1 of 18 experimental pens (n = 4 calves/pen) where they remained until 6 wk of age. Half of the pens had floors covered with quarry stones (QS) and the other half were covered with sawdust (SW). For each substrate type, calves were reared at 1 of 3 space allowances: 1.0, 1.5, or 2.0 m²/calf. Behavior was video-recorded continuously for 24 h in the home pen at 2, 4, and 6 wk of age; the time calves spent lying, standing, walking, and running were estimated using 1-min instantaneous scan sampling. Body weight, cleanliness, fecal fluidity, and skin surface temperature were recorded at 1, 4, and 6 wk of age. Escherichia coli numbers were assessed on the skin surface of the shoulder and in feces of calves at 4 and 6 wk of age. Blood samples were taken at 1, 4, and 6 wk of age to measure cortisol, creatine kinase, immunoglobulin G, serum amyloid A, and total protein concentrations. Calves reared on QS spent less time lying and walking and more time standing at 4 and 6 wk of age compared with calves reared on SW. Furthermore, calves reared at a space allowance of 2.0 m²/calf spent less time lying and more time standing and walking compared with calves reared at a space allowance of 1.0 and 1.5 m²/calf. Calves reared on QS had lower skin surface temperatures compared with calves reared on SW. Fecal fluidity scores were lower in calves reared on QS than SW at 2 wk of age. Fewer E. coli were recovered from the shoulder of calves reared on QS than those of calves reared on SW, but fecal E. coli counts were similar between rearing substrates and space allowances. Serum amyloid A concentrations were lower in calves reared on QS than SW. We detected no effect of rearing substrate or space allowance on body weight, cleanliness, or concentrations of cortisol, creatine kinase, immunoglobulin G, and total protein. In conclusion, lower skin temperature in combination with reduced lying behavior may reflect reduced comfort of calves reared on QS. Furthermore, a space allowance of 2.0 m²/calf may provide calves with more opportunity to perform active behaviors.     

Health,physiology, and behavior of dairy calves reared on 4 different substrates

The objective of this study was to compare the health, physiology, and behavior of group-housed calves reared on wood shavings with those reared on alternative surfaces. At 1 wk of age, 80 calves were moved into 1 of 20 experimental pens (n = 4 calves/pen) where they remained until 6 wk of age. Pens had floors covered with pea gravel (PG), rubber chip (RC), sand (SA), or wood shavings (WS; n = 5 pens/substrate). Body weight, cleanliness, health, and skin surface and vaginal temperature were recorded at 1, 3, and 6 wk of age. Escherichia coli numbers were assessed on the skin surface of the shoulder and in the feces of calves at 3 and 6 wk of age. Blood samples were taken at 1, 3, and 6 wk of age to measure hematological values and cortisol, IgG, and lactate concentrations. Behaviors (lying, running, and self-grooming) were recorded in the home pen at 1, 3, and 6 wk of age using video recorders and accelerometer data loggers. At 6 wk of age, calves were tested individually in an arena test and behavior was recorded continuously for 20 min. Body weight did not differ among calves reared on PG, RC, SA, or WS, regardless of age. All calves were clean and no calves displayed any signs of lameness, leg lesions, or injuries at wk 1, 3, or 6, regardless of substrate. The number of E. coli recovered from a surface area of 100 cm² on the shoulder of each calf was affected by rearing substrate, with more E. coli recovered from calves reared on WS than PG, RC, or SA at 3 and 6 wk of age. Fecal E. coli counts were not affected by rearing substrate at 3 or 6 wk of age. Over the entire study period, calves reared on PG and SA had lower skin temperatures than calves reared on RC or WS, but skin temperature was similar between calves reared on PG and SA. However, vaginal temperature did not differ among calves reared on different substrates at 1, 3, or 6 wk of age. Hematology values and cortisol, IgG, and lactate concentrations of calves were similar among rearing substrates over the 6-wk study period. In the home pen, rearing substrate did not influence time spent lying; however, calves reared on WS performed more lying bouts than calves reared on PG or SA. In addition, rearing substrate did not influence the time calves spent running; however, calves reared on WS spent more time self-grooming than calves reared on PG, RC, and SA. During a 20-min arena test, running, bucks, jumps, and kicks performed by calves was not affected by rearing substrate. In conclusion, the physiology and behavior of calves reared on PG, RC, and SA was similar to WS, which is considered the preferred rearing substrate to use when rearing calves. Therefore, PG, RC, and SA may be acceptable substrate options when rearing group-housed dairy calves.     

Invited review: The use of distillers products in dairy cattle diets

Distillers grains with solubles (DGS) is the major coproduct of ethanol production, usually made from corn, which is fed to dairy cattle. It is a good protein (crude protein, CP) source (>30% CP) high in ruminally undegradable protein (∼55% of CP) and is a good energy source (net energy for lactation of approximately 2.25 Mcal/kg of dry matter). The intermediate fat concentration (10% of dry matter) and readily digestible fiber (∼39% neutral detergent fiber) contribute to the high energy content in DGS. Performance was usually similar when animals were fed wet or dried products, although some research results tended to favor the wet products. Diets can contain DGS as partial replacement for both concentrates and forages, but DGS usually replaces concentrates. Adequate effective fiber was needed to avoid milk fat depression when DGS replaced forages in lactating cow diets. Nutritionally balanced diets can be formulated that contain 20% or more of the diet dry matter as DGS. Such diets supported similar or higher milk production compared with when cows were fed traditional feeds. Although DGS can constitute more than 30% of diet dry matter, gut fill may limit dry matter intake and production in diets with more than 20% wet DGS and that also contain other moist feeds. The fiber in DGS, which often replaces high-starch feeds, does not eliminate acidosis but minimizes its problems. Distillers solubles, which are often blended with distillers grains to provide DGS, can be fed separately as condensed corn distillers solubles. Other distillers coproducts besides DGS such as high-protein distillers grains, corn germ, corn bran, and low-fat distillers grains are becoming available.     

Lead excretion in milk of accidentally exposed dairy cattle

Lead (Pb) exposure in dairy cattle is associated with economic losses due to mortality and treatment costs, but with production animals there is also risk to the human food chain. The first objective of this study was to quantify the Pb concentration in milk from Pb-exposed cattle. The second objective was to correlate blood and milk Pb concentrations from individual cows. The third objective was long-term monitoring to determine the duration of milk contamination after exposure ceased. A dairy herd of more than 100 cows was accidentally exposed to Pb-contaminated feed. Milk and blood were collected for Pb analysis. Serial collection of milk samples continued for 2.5 years. The initial concentration of Pb in bulk tank milk was 0.0999 mg l^–1. The highest milk Pb concentration from an individual cow was 0.4657 mg l^–1 and the highest blood Pb concentration was 1.216 mg l^–1. One milk sample collected at the end of the study (day 922) contained 0.0117 mg Pb l^–1 of Pb. The calculated relationship between milk (y) and blood (x) Pb concentration was ln(y) = 3.4(x) – 2.21 (R² = 0.98).     

Analgesics improve the gait of lame dairy cattle

Pain associated with injuries of the hoof and surrounding tissues is an important cause of lameness. The objective was to detect the attributes of impaired gait that are associated with pain. In 3 separate experiments, lactating Holstein cows (n = 20; n = 21; n = 27) diagnosed with varying degrees of gait impairment were injected i.m. (Exp. 1 and 2) or i.v. (Exp. 3) with the analgesic ketoprofen at 0, 0.3, 1.5, or 3.0 mg/kg of BW. Gait was evaluated subjectively using a numerical rating system (NRS; varying from 1 to 5) and 6 specific gait attributes (back arch, tracking up, joint flexion, asymmetric steps, head bob, and reluctance to bear weight). Each experiment was divided into 3 phases each lasting 3 d: before treatment, after treatment, and during treatment with daily injections of ketoprofen. The NRS improved by 0.25 ± 0.05 with the highest dose of ketoprofen. Although none of the specific gait attributes showed a consistent response to treatment, there was an interaction between dose and experiment for asymmetric steps and reluctance to bear weight; in Exp. 1, but not Exp. 2 and 3, cow steps were more symmetrical (improving by 7.16 ± 1.02), and cows distributed their weight more evenly (improving by 5.84 ± 1.13) at the highest doses of ketoprofen. These results indicated that the NRS was more sensitive than the specific gait attributes in assessing differences in gait associated with pain. The results showed that ketoprofen has only a modest effect on gait, indicating either that this drug has little effect on pain due to lameness or that much variation in NRS was due to factors other than pain.     

A 100-Year Review: Historical development of female reproductive physiology in dairy cattle

The objective of this historical review in female reproductive physiology is to encapsulate major advancements since the founding of the American Dairy Science Association in 1906. The emphasis is on landmark publications in the Journal of Dairy Science since its first volume in 1917. A historical perspective and inferences are made in forecasting evolution of female reproduction and links between physiology of reproduction and the mammary gland. Subsequent sections are focused into main physiological categories and the temporal advancements within these physiological windows. Time points of understanding vary considerably within categories due to various advancements in technology, biological techniques, experimental design, data collection, statistical analyses, and computational forecasting. The physiological windows examined are hypothalamic and pituitary control of the ovary related to estrous behavior and cycle; differential control of the corpus luteum and uterus as influenced by cycling and pregnancy statuses; peripartum and postpartum programing of reproduction; and scientific foundation for the next century. The importance of interdisciplinary programs and integration of reproduction, nutrition/metabolism, genetics, health, and management are emphasized. The modern dairy cow of 2017 exemplifies excellence in both reproductive and lactational performance and is the foundation biological model for the next century.     

Altered vocalization rate during the estrous cycle in dairy cattle

Correct detection of estrus is a problem in dairy herds. In practice, several procedures exist for detection of estrus besides conventional visual observation by humans. These procedures deliver very different results regarding detection of estrus. It is known that the calls of female mammals can contain information about reproductive status. It is also suspected that the vocalizations of cattle contain information about age, sex, dominance status, and stage in the estrous cycle. In the present study, a methodology for the continuous automatic recording of vocalization of heifers during the periestrous period is presented. It was shown in 10 tethered heifers that the estrous climax results in an increase in vocalization rate. Vocalization rate of heifers increased approximately 84% from d −2 to 0 (related to observed estrus) and approximately 59% from d −1 to d 0. After d 0, vocalization rate decreased about 79%. Increased vocalization was correlated with the visual observation of estrus by humans. We also found 2 different structures in the vocalization of heifers. The harmonic structure showed regular frequency bands, whereas the nonharmonic structure was noisy. The hypothesis that the disharmonic structure increases near the estrous climax was confirmed. Hence, it seems possible to get information about stage of the estrous cycle of dairy cattle by means of monitoring vocalization. The presented method of automatically detecting the rate of cattle vocalization (patent pending) could be used solely or in combination with other automated systems for detecting estrus and could considerably increase current estrus detection rates once its applicability can be demonstrated in nontethered cattle.     

Competition during the milk-feeding stage influences the development of feeding behavior of pair-housed dairy calves

This study investigated how the feeding behavior of pair-housed calves develops in response to reduced teat and feed place availability. Twenty Holstein bull calves were pair housed and provided with milk replacer (MR) and grain concentrate ad libitum via either (1) 1 teat and feed bucket/pen, such that calves could not feed simultaneously [competitive feeding (CF)] or (2) 2 teats and feed buckets/pen [noncompetitive feeding (NCF)]. The calves were weaned during wk 7 of life by incrementally diluting the MR. Postweaning, all pens were managed identically and offered a complete pelleted diet ad libitum via 2 feed buckets/pen (NCF) in period 1 (wk 8 and 9) and period 3 (wk 12 and 13) and exposed to a competitive challenge with CF in period 2 (wk 10 and 11). Feeding times and competitive interactions were recorded from video for 3 d/wk in wk 2, 4, and 6 and 2 d/wk in wk 8 to 13. Meal criteria were used to calculate daily meal frequency, meal time, and synchronized meal time (the percentage of meal time when calves within the pen were engaged in simultaneous meals). Milk replacer intake was subject to a treatment × week interaction, with calves in CF pens having lower MR intake (wk 2: 8.3 vs. 10.0 L/calf per day for CF vs. NCF), but compensating by increasing intake to a greater extent over time (wk 4–5: 13.3 vs. 11.7 L/d for CF vs. NCF). Corresponding to MR intake, meal frequencies and feeding times evolved differently over this period, increasing in CF pens and decreasing in NCF pens (wk 2: 5.8 vs. 11.1 and wk 4–6: 6.2 vs. 5.1 meals/d for CF vs. NCF). Calves in CF pens also spent less time engaged in synchronized meals (28 vs. 51% of meal time; standard error = 7.1) and displaced each other 5 times more frequently during synchronized eating. Postweaning, calves in previously CF pens maintained 5 times greater displacement frequencies and had fewer overlapping meals than calves in previously NCF pens (34.5 vs. 40.7% of meals, respectively). Postweaning, when calves were all fed noncompetitively (2 buckets/pen in periods 1 and 3), calves previously fed CF had greater intakes in period 3 (4.87 vs. 4.44 kg/d) and a tendency for greater intake in period 1 (2.80 vs. 2.63 kg/d), greater rates of intake in period 3 (87.8 vs. 72.0 g/min) and a tendency for greater rates of intake in period 1 (44.3 vs. 38.9 g/min), and greater meal frequencies in both periods (11.1 vs. 9.9 meals/d). In the competitive challenge period (1 bucket/pen in period 2), intake, rates of intake, and meal frequencies were subject to treatment × week interactions: calves in NCF pens had lower intake and meal frequencies, but increased meal frequency, intake, and rate of intake over time to a greater extent than calves previously in CF pens. These results indicate that calves are able to adapt to moderate competition by increasing meal frequency and that behavioral responses to competition persist postweaning.     

Supplementing intensively grazed late-gestation and early-lactation dairy cattle with chromium

Two hundred thirty-two primiparous and multiparous cows were assigned to a study to determine the effect of supplementing 0 or 6.25 mg/d of Cr from Cr Met on lactation and reproductive performance. Cows received treatments from 6 wk precalving through 21 wk postpartum. Precalving, treatments were incorporated into a pelleted grain mixture and group-fed. Post-calving, cows received treatments via an individual oral drench once a day after the a.m. milking. Grazed herbage was the primary diet constituent for lactating cattle. Blood was collected from a predetermined group of cows before and immediately after calving. On 4 occasions during the treatment period, milk yield was recorded and samples collected for determination of composition. Chromium supplementation had no effect on yield of milk and milk components and milk composition. Chromium supplementation decreased serum nonesterified fatty acids (NEFA) concentration (0.60 vs. 0.68 mmol/L), with chromium supplementation having the greatest impact on serum NEFA concentrations at 1 wk prepartum. Greater percentages of cows supplemented with Cr were observed to be anestrus by dairy personnel (45.5 vs. 32.0%). However, Cr supplementation tended to increase the percentage of cows pregnant in the first 28 d of the mating season (50.0 vs. 39.2%). Results indicate that Cr Met supplementation of intensely grazed, late-gestation and early-lactation dairy cattle decreased serum NEFA concentrations and tended to increase pregnancy rates in the first 28 d of the mating season.     

Estimation of genetic parameters and heterosis for longevity in crossbred Danish dairy cattle

Crossbreeding has been shown to improve the longevity of dairy cattle in countries across the world. The aim of this study was to estimate heterosis, breed effects, and genetic parameters for longevity in crossbred dairy cattle among Danish Holstein (DH), Danish Red (DR), and Danish Jersey (DJ) breeds. Data were provided from 119 Danish commercial herds that use systematic crossbreeding (i.e., rotational crossbreeding). Additional data from 11 mixed-breed herds with DH and DJ were included to estimate reliable breed effects for DJ. Survival information on 73,741 cows was analyzed with a linear animal model using the artificial insemination–REML algorithm in the DMU package. Five longevity (L) traits were defined: days from first calving until the end of first lactation or culling (L1), days from first calving until the end of second lactation or culling (L2), days from first calving until the end of third lactation or culling (L3), days from first calving until the end of fourth lactation or culling (L4), and days from first calving until the end of fifth lactation or culling (L5). Heritabilities ranged between 0.022 and 0.090. Additive breed effects in units of days were estimated relative to DH for DR as ?0.5 (L1), +10.5 (L2), +18.5 (L3), +11.9 (L4), and +28.6 (L5), and corresponding figures for DJ were +2.0, +0.5, +14.2, +27.7, and +44.0. Heterosis effects in L1 were low (1.2%) but favorable in crosses between DH and DR, whereas negative heterosis effects were estimated for crosses between DH and DJ (?2.5%) and DR and DJ (?1.2%). The largest heterosis effects for L2, L3, L4, and L5 were found in DH × DR and were favorable (+3.3, +5.7, +7.7, and +8.5%, respectively). Corresponding figures for heterosis effects in DH × DJ and DR × DJ were favorable as well: +2.3, +4.1, +5.6, and +6.2% in DH × DJ and +3.1, +7.3, +6.9, and +7.2% in DR × DJ. The favorable heterosis effects show that crossbreeding is an efficient tool for improving longevity in Danish dairy cattle.     

Using time-lapse video photography to assess dairy cattle lying behavior in a free-stall barn

The objectives of this observational study were to use time-lapse video photography to document dairy cow behavioral patterns, examine factors affecting lying behavior, and to develop guidelines for visual assessment of free-stall usage during summer conditions in a high producing dairy. Four video cameras were placed in a free-stall pen containing 144 stalls and 129 high producing cows. The videos were recorded over a 6-d period in July 1999 and then were reviewed using 60-min scan sampling techniques. Cows were counted as lying, standing in alley without eating, standing in free stalls, or eating in each of the four sections of the pen. Temperature probes were placed on the feedline, free stalls, on both ends of the pen, and at an outside location. Relationships between proportion eligible lying and ambient temperature, feeding time, and time since milking were examined. Proportion eligible lying was equal to number of cows lying divided by total number of cows lying or standing but not eating. Cattle showed a significant pattern of temporal cyclicity in their lying behavior, with the highest average proportion of eligible cows lying at 6:00 a.m. (85%) and the lowest at 9:00 p.m. (53%). Increasing environmental temperatures and time elapsed since milking negatively impacted proportion of eligible cows observed lying when evaluated using 60-min scan sampling techniques.     

Technical note: a computerized system for monitoring feeding behavior and individual feed intake of dairy cattle

The objective of this study was to develop and validate a computerized system to monitor feeding behavior and feed intake of loose-housed dairy cattle. The system consisted of 28 scales located in front of each self-locking place of a regular feedbunk. All cows had access to all scales indifferently. Each visit to the feedbunk was monitored by a transponder in the ear of each cow that was detected by a proximity reader located at the top right corner of each headlock. The data from the scales and the proximity readers were continuously recorded by a computer with an average scanning time of 3.5 s. The monitoring system was validated using all 28 feeding places and 51 lactating cows in a series of 4-h observations during 5 different d. During the observation periods, for each feeder, 2 observers recorded the cow number and the exact time of the visit. The observed data were then compared with the computer records. To validate the ability of the system to monitor feed consumption, on separate days, the amount of feed consumed by a cow during a visit was also measured manually with an external scale, and the feed that disappeared from each scale in 2 different 24-h periods was compared with the sum of feed consumed in each scale during these 2 periods. The average time spent in a given scale by each cow determined by direct observations was similar to that determined by the computer. The system was accurate and showed a high specificity (98.8%) and sensitivity (99.6%) for cow detections. Feed weights determined by the computer system were similar to those measured manually with an external scale, implying that the system was also accurate in measuring individual intake weights. In conclusion, the system provided a reasonable estimate of the number of visits per animal, length of each visit, amount of feed consumed per visit and animal, the total amount of feed consumed daily by each animal, and the rate at which animals consume feed.     

Scanning the future--ultrasonography as a reproductive management tool for dairy cattle

Application of transrectal real-time ultrasonography as a research tool to study bovine reproduction represents a technological breakthrough that has revolutionized our understanding of reproductive biology in cattle. The widespread adoption and use of ultrasonography for routine reproductive examinations of dairy cattle by bovine practitioners is the next contribution this technology will make to the dairy industry. Assessment of pregnancy status and fetal viability early postbreeding to identify cows that fail to conceive improves reproductive efficiency by decreasing the interval between artificial insemination services and increasing artificial insemination service rate. Early identification of cows carrying twin fetuses will allow for implementation of differential management strategies to abrogate negative effects of twinning during the periparturient period once such strategies have been developed. Ovarian and uterine pathologies not accurately detected via rectal palpation can easily be visualized by ultrasound, and appropriate therapies can be implemented. Determination of fetal sex in utero is useful when coupled with a management decision that justifies the expense of fetal sexing. Development of integrated reproductive management systems that combine ultrasound with new and existing reproductive technologies will further enhance the practical applications of ultrasonography. Development of Extension education programs to train bovine practitioners to use ultrasound for routine reproductive examinations is a critical step toward rapid implementation of this technology into the dairy industry.     

Imputation of genotypes from different single nucleotide polymorphism panels in dairy cattle

Imputation of missing genotypes is important to join data from animals genotyped on different single nucleotide polymorphism (SNP) panels. Because of the evolution of available technologies, economical reasons, or coexistence of several products from competing organizations, animals might be genotyped for different SNP chips. Combined analysis of all the data increases accuracy of genomic selection or fine-mapping precision. In the present study, real data from 4,738 Dutch Holstein animals genotyped with custom-made 60K Illumina panels (Illumina, San Diego, CA) were used to mimic imputation of genotypes between 2 SNP panels of approximately 27,500 markers each and with 9,265 SNP markers in common. Imputation efficiency increased with number of reference animals (genotyped for both chips), when animals genotyped on a single chip were included in the training data, with regional higher marker densities, with greater distance to chromosome ends, and with a closer relationship between imputed and reference animals. With 0 to 2,000 animals genotyped for both chips, the mean imputation error rate ranged from 2.774 to 0.415% and accuracy ranged from 0.81 to 0.96. Then, imputation was applied in the Dutch Holstein population to predict alleles from markers of the Illumina Bovine SNP50 chip with markers from a custom-made 60K Illumina panel. A cross-validation study performed on 102 bulls indicated that the mean error rate per bull was approximately equal to 1.0%. This study showed the feasibility to impute markers in dairy cattle with the current marker panels and with error rates below 1%.     

Milk coagulation ability of five dairy cattle breeds

Samples of herd milk (506) were analyzed to assess sources of variation for milk coagulation properties (MCP) for 5 different dairy cattle breeds. Data were recorded in 55 single-breed dairy herds in the Trento province, a mountain area in northeast Italy. The 5 cattle breeds were Holstein-Friesian (8 herds), Brown Swiss (16 herds), Simmental (10 herds), Rendena (13 herds), and Alpine Gray (8 herds). Herd milk samples were analyzed for the MCP traits, milk rennet coagulation time (RCT), curd-firming time, and curd firmness (a₃₀), as well as protein and fat percentages, somatic cell count, Soxhlet-Henkel acidity, and bacterial count. An ANOVA was performed to study the effect of breed, herd within breed, DIM, month of lactation, protein and fat percentages, somatic cell score, titratable acidity, and log bacterial count within breed on MCP. Breed was the most important source of variation. In particular, the Rendena breed showed the best MCP traits at 13.5 min and 27.0 mm for RCT and a₃₀, respectively. The Holstein-Friesian breed had the worst coagulation properties at 18.0 min and 17.5 mm for RCT and a₃₀, respectively. The other 3 breeds showed intermediate coagulation properties. The RCT values were better at the beginning of lactation, whereas RCT and a₃₀ values were better in September and October (14.3 min and 25.7 mm, respectively). Among the composition traits, only the titratable acidity affected MCP traits of herd milk positively.