Usefulness of an aluminized polyester film for reducing heat in polyethylene calf hutches

This study determined the efficacy of a radiant barrier material used in the construction industry to moderate summer temperatures in polyethylene calf hutches. The cover consisted of a single layer of two-sided reflective aluminized polyester film with a center polyester scrim reinforcement (reflectivity?=?95 %). At each of two dairies, six hutches containing a young calf were either uncovered (control) or had reflective covers across the top and sides of the hutch, leaving the front, back, and 1.2?×?1.8-m attached outdoor wire pen exposed. Duplicate loggers mounted 20 cm above the flooring in the center of each hutch recorded interior temperature at 30-min intervals over 22 days during late August to early September. The mean daily interior peak temperatures in each of the hutches over 21 days of observation were significantly less (P?P?=?0.77) between dairies. The mean daily interior peak temperatures in each of the hutches over the warmest 10 days of observation were significantly less (P?P?相似文献   

Physiologic responses of dairy calves to environmental heat stress

The effects of thermal stress were identified in terms of a calf's systemic response. The following physiological parameters were monitored during successive exposure of eight Holstein calves to five temperature levels ranging from 15.5°C to 37.7°C at 60% RH: stroke volume, heart rate, arterial systolic and diastolic pressures, plasma cortisol and thyroxine levels, and internal and skin temperatures. Results indicated that 3 to 4- week-old male calves respond to acute heat stress only above 32.2°C at 60% RH and do not demonstrate a marked attempt to acclimate until at least four to five hours of exposure at 37.7°C.     

Pre-weaning management of calves on commercial dairy farms and its influence on calf welfare and mortality

Welfare and management of calves is of increasing interest and also influences performance of these animals in later life. The aim of this study was to assess management and environmental conditions under which pre-weaned dairy calves are reared on commercial Irish dairy farms. We included 47 spring-calving, pasture-based herds in this study. Herd and animal-specific data, such as mortality rate, age and breed, were gathered from all participants via the HerdPlus® database. Information pertaining to management practices was collected by conducting an interview with the principal calf rearer, while an assessment of calf housing facilities was conducted to identify conditions calves were reared in. The environmental assessment included measurements of space allowance per calf, as well as feeding equipment hygiene. To assess calf behaviour video observations were used, while accounting for the number of calves present in a group and the space available per calf. Faecal samples were also collected to determine the presence of enteric pathogens among calves. To compare calf space allowance, group size and presence of enteric pathogens early and late in the calving season each farm was visited twice. Calf mortality was not associated with either herd size, space allowance per calf or post-colostrum feeding practices. Higher calf mortality was identified among herds which reported experiencing an on-set of calf pneumonia during weeks 8 to 10 of the calving season. This study demonstrates that factors associated with calf welfare on commercial Irish dairy farms (e.g. space allowance, mortality rate) are independent of herd size. Some management practices however, such as methods used for treating health issues can affect rates of calf mortality experienced. Calf mortality, for example, was lower in herds which treated diarrhoea cases by administering electrolytes, while continuing to offer milk. Behavioural observations indicate that smaller group sizes could promote expression of positive behaviours, potentially resulting from an overall improvement in welfare. Space allowance per calf was not associated with observed behaviour frequencies. We also identified that similar rates of calf mortality are experienced across herds of different sizes.     

Short term post-partum heat stress in dairy cows

Since many dairy cows calve during late summer, the objective was to determine if heat stress immediately post-partum would (1) alter metabolism, thus, increasing susceptibility to metabolic disorders, (2) affect lactation and/or (3) affect reproduction. Forty four cows, calving during late summer, were paired with one member of each pair stressed (HS) for the first 10 post-partum days in a hot barn. Controls (CC) were kept in a cooled section of the barn. Plasma drawn weekly for 7 weeks was analyzed in an autoanalyzer for calcium, inor. phosphorus, protein, glucose and cholesterol and by radioimmunoassay for cortisol and progesterone. Ovaries and uteri were palpated weekly. Rectal temperatures were significant higher for HS during the first 10 post-partum days. No significant effects on plasma constituents were observed during the 10-day treatment period. For the 7-week period, glucose and cholesterol were lower in HS, as were cyclic peaks of progesterone and cortisol. Both calcium and inorganic phosphorus remained clinically low for the 7 weeks, but no treatment effects were seen. Uteri of HS involuted more rapidly than the CC. Treatment did not affect reproductive efficiency. Lactation milk yields did not differ, but milk fat percent was lower in HS. Heat stress immediately post-partum altered lipid metabolism, but the animal's compensatory mechanisms prevented reduction in milk production or reproductive efficiency.Journal Paper No. 4227 Mississippi Agricultural and Forestry Experiment Station.Presented at the Eighth International Congress of Biometeorology, 9–14 September 1979, Shefayim, Israel.     

The effect of calf jacket usage on performance,behaviour and physiological responses of group-housed dairy calves

Poor performance and ill-health of calves in the pre-wean period can affect future productivity. Increasing numbers of producers are opting to use calf jackets as a means of mitigating the potential negative effects of low ambient temperatures, wind speed and precipitation on growth and health. This study aimed to use a range of noninvasive monitoring technologies to investigate the effects of using calf jackets in the first 3 weeks of life on calf performance and behavioural and physiological parameters. Ninety Holstein-Friesian calves were allocated to one of the two treatments: (i) Jacketed until 21 days of age and (J; n = 44) ii. Nonjacketed (NJ; n = 46). Calves were group housed and fed milk replacer (MR) and concentrate solid feed via automatic feeders. Calves were weaned at day 56, and the experiment was completed at day 63. Health assessments were conducted on a daily basis throughout the experiment using predefined faecal and respiratory scoring protocols. A range of novel, noninvasive monitoring technologies were used to examine the activity, heart rate and thermal profiles of calves on an individual basis throughout the experimental period. There were no differences in calf live weight (LWT), average daily gain (ADG) or feed conversion efficiency (FCE) in J and NJ calves between days 5 to 20. However, NJ calves consumed more MR and had more unrewarded visits to the milk feeder than J calves during this period. Although calf LWT was comparable across treatments in the week following jacket removal (days 21 to 28), both ADG and FCE tended to be greater in NJ calves. There were no treatment differences in calf LWT at the end of the study (d63). When measured over a period of 24 h and at a mean ambient temperature of 7.7°C, skin surface temperature was 6.37°C higher in J calves. Core body temperature was higher in J calves between days 5 to 20; however, there were no differences in IR eye or IR rectal temperature. No differences in lying behaviour occurred, with calves spending 18 and 17 h/day lying between days 5 to 20 and days 21 to 28, respectively. Under the climatic and management conditions described, no significant benefits to calf performance were found as a result of the provision of calf jackets to group-housed calves in the first 3 weeks of life. The higher frequency of unrewarded visits to the milk feeder in NJ calves during the first 3 weeks of life could be suggestive of a lack of satiety in these calves.     

Effect of heat stress on body temperature in healthy early postpartum dairy cows

Measurement of body temperature is the most common method for an early diagnosis of sick cows in fresh cow protocols currently used on dairy farms. Thresholds for fever range from 39.4 °C to 39.7 °C. Several studies attempted to describe normal temperature ranges for healthy dairy cows in the early puerperium. However, the definition of a healthy cow is variable within these studies. It is challenging to determine normal temperature ranges for healthy cows because body temperature is usually included in the definition. Therefore, the objectives of this study were to identify factors that influence body temperature in healthy dairy cows early postpartum and to determine normal temperature ranges for healthy cows that calved in a moderate (temperature humidity index: 59.8 ± 3.8) and a hot period (temperature humidity index: 74.1 ± 4.4), respectively, excluding body temperature from the definition of the health status. Furthermore, the prevalence of fever was calculated for both periods separately. A subset of 17 (moderate period) and 15 cows (hot period) were used for analysis. To ensure their uterine health only cows with a serum haptoglobin concentration ≤ 1.1 g/L were included in the analysis. Therefore, body temperature could be excluded from the definition. A vaginal temperature logger that measured vaginal temperature every 10 min was inserted from Day 2 to 10 after parturition. Additionally rectal temperature was measured twice daily. Day in milk (2 to 10), period (moderate and hot), and time of day had an effect on rectal and vaginal temperature. The prevalence of fever (≥ 39.5 °C) was 7.4% and 28.1% for rectal temperature in the moderate and hot period, respectively. For vaginal temperature (07.00 to 11.00 h) it was 10% and 33%, respectively, considering the same threshold and period. This study demonstrates that body temperature in the early puerperium is influenced by several factors (day in milk, climate, time of day). Therefore, these factors have to be considered when interpreting body temperature measures to identify sick cows. Furthermore, the prevalence of fever considering different thresholds is higher during hot than moderate periods. However, even in a moderate period healthy cows can exhibit a body temperature that is considered as fever. This fact clearly illustrates that fever alone should not be considered the decision criterion whether a cow is allocated to an antibiotic treatment, although it is the most important one that is objectively measurable.     

The effect of age at introduction and number of milk-portions on the behaviour of group housed dairy calves fed by a computer controlled milk feeder

This study is an investigation of the effect of age at introduction (6 days versus 14 days) and number of milk-portions (four milk-portions a day versus eight milk-portions a day) on integration into a large dynamic group of calves, fed by a computer controlled milk feeder. Forty calves (Jerseys, Danish Reds and Holstein-Friesians) were allocated equally to the two age conditions (A6 and A14) and the two milk-portion conditions (M4 and M8) in a 2 × 2 factorial design, according to sex and breed, and introduced into the group in pairs (one A6 and one A14). The behaviour of each pair was video-recorded for 8 h from 8 a.m. to 4 p.m. and 1 h from 1 to 2 a.m. on days 1, 8 and 15 after introduction.

The A6 calves performed less licking and sniffing, changed posture more often and tended to spend less time standing than the A14 calves. In the course of time A14 calves lay closer to other calves than the A6 calves.

The M8 calves, which were offered the same daily milk allowance as the M4 calves stood for a longer time in the milk feeding station and the M8 calves also sucked the empty teat more frequently than the M4 calves. Finally, the M8 calves initiated more social play behaviour than the M4 calves. On the first day after introduction the M8 calves lay closer to other calves than the M4 calves.

The results suggest that calves integrate better into a group when introduced at the age of 14 days than at the age of 6 days. Distributing the milk into eight daily milk-portions, rather than four milk-portions in the first period after introduction, increased milk feeder occupancy, which may facilitate learning to use the milk feeder. Surprisingly, more milk-portions also stimulated play behaviour, which is suggested to be due to M8 calves encountering more calves in the milk feeder area.     

Increased incidence of retained placenta associated with heat stress in dairy cows

A dairy herd experienced an increased incidence of retained placenta and postpartum metritis during late spring and summer of 1977 and 1978. The incidence of retained placenta and postpartum metritis was 24.05% during the period of May through September compared to 12.24% the rest of the year. The gestation period of cows having retained placenta and postpartum metritis was an average of 5.25 days shorter than that of cows not exhibiting these symptoms. The gestation period of cows calving during the warm season was an average of 2.82 days shorter than that of the cows calving during the cool season. Heat stress resulting in early parturition was the probable cause of this increased incidence of retained placenta and postpartum metritis. The number of days open was influenced both by abnormal postpartum period and season of calving. Cows having retained placenta and metritis were open an average of 31.69 days longer than cows with normal postpartum periods. Cows that calved during the warm season were open an average of 24.42 days longer than those calving during the cool season.     

Evaluation of timed insemination during summer heat stress in lactating dairy cattle

We wished to compare the effect of summer heat stress on pregnancy rate in cows that were inseminated at a set interval associated with a synchronized ovulation vs those inseminated upon routine estrus detection. The study was carried out on a commercial dairy farm in Florida from May to September 1995. Lactating dairy cows were given PGF2 alpha (25 mg i.m.) at 30 + 3 d postpartum and randomly assigned to be inseminated at a set time (Timed group) or when estrus was detected (Control group). Cows in the Timed group were synchronized by sequential administration of Buserelin (8 micrograms i.m.) on Day 0 at 1600 h, PGF2 alpha (25 mg i.m.) on Day 7 at 1600 h and Buserelin (8 micrograms i.m.) on Day 9 at 1600 h. They were inseminated on Day 10 between 0800 and 0900 h (Day 9 + 16 h). Cows in the Control group were given PGF2 alpha at 57 + 3 d postpartum and inseminated when detected in estrus. Estrus detection or insemination rate for control insemination cows was 18.1 +/- 2.5% versus 100% for time inseminated cows (P < 0.01). Mean interval from PGF2 alpha to insemination was shorter for time inseminated cows (3 +/- 2.1 d < 35.5 +/- 1.9 d; P < 0.01). Pregnancy rate was greater for time inseminated cows (13.9 +/- 2.6 > 4.8 +/- 2.5%; P < 0.01) as was overall pregnancy rate by 120 d postpartum (27.0 +/- 3.6 > 16.5 +/- 3.5%; P < 0.05). Number of days open for cows conceiving by 120 d postpartum was less for time inseminated cows (77.6 +/- 3.8 < 90.0 +/- 4.2 d; P < 0.05), as was interval to first service (58.7 +/- 2.1 < 91.0 +/- 1.9 d; P < 0.01). Services per conception were greater for time inseminated cows (1.63 +/- 0.10 > 1.27 +/- 0.11; P < 0.05). The timed insemination program did improve group reproductive performance. However, the timed insemination program will not protect the embryo from temperature-induced embryonic mortality, but management limitations induced by heat stress on estrus detection are eliminated. An economical evaluation of the timed insemination program indicates an increase in net revenue per cow with implementation of timed insemination for first service during the summer months.     

Dynamic cooling strategy based on individual animal response mitigated heat stress in dairy cows

Technological progress enables individual cow's temperatures to be measured in real time, using a bolus sensor inserted into the rumen (reticulorumen). However, current cooling systems often work at a constant schedule based on the ambient temperature and not on monitoring the animal itself. This study hypothesized that tailoring the cooling management to the cow's thermal reaction can mitigate heat stress. We propose a dynamic cooling system based on in vivo temperature sensors (boluses). Thus, cooling can be activated as needed and is thus most efficacious. A total of 30 lactating cows were randomly assigned to one of two groups; the groups received two different evaporative cooling regimes. A control group received cooling sessions on a preset time-based schedule, the method commonly used in farms; and an experimental group, which received the sensor-based (SB) cooling regime. Sensor-based was changed weekly according to the cow's reaction, as reflected in the changes in body temperatures from the previous week, as measured by reticulorumen boluses. The two treatment groups of cows had similar milk yields (44.7 kg/d), but those in the experimental group had higher milk fat (3.65 vs 3.43%), higher milk protein (3.23 vs 3.13%), higher energy corrected milk (ECM, 42.84 vs 41.48 kg/d), higher fat corrected milk 4%; (42.76 vs 41.34 kg/d), and shorter heat stress duration (5.03 vs 9.46 h/day) comparing to the control. Dry matter intake was higher in the experimental group. Daily visits to the feed trough were less frequent, with each visit lasting longer. The sensor-based cooling regime may be an effective tool to detect and ease heat stress in high-producing dairy cows during transitional seasons when heat load can become severe in arid and semi-arid zones.     

Genetic dissection of reproductive performance of dairy cows under heat stress

Heat stress negatively impacts the reproductive performance of dairy cows. The main objective of this study was to dissect the genetic basis underlying dairy cow fertility under heat stress conditions. Our first goal was to estimate genetic components of cow conception across lactations considering heat stress. Our second goal was to reveal individual genes and functional gene-sets that explain a cow’s ability to conceive under thermal stress. Data consisted of 74 221 insemination records on 13 704 Holstein cows. Multitrait linear repeatability test-day models with random regressions on a function of temperature–humidity index values were used for the analyses. Heritability estimates for cow conception under heat stress were around 2–3%, whereas genetic correlations between general and thermotolerance additive genetic effects were negative and ranged between −0.35 and −0.82, indicating an unfavorable relationship between cows’ ability to conceive under thermo-neutral vs. thermo-stress conditions. Whole-genome scans identified at least six genomic regions on BTA1, BTA10, BTA11, BTA17, BTA21 and BTA23 associated with conception under thermal stress. These regions harbor candidate genes such as BRWD1, EXD2, ADAM20, EPAS1, TAOK3, and NOS1, which are directly implicated in reproductive functions and cellular response to heat stress. The gene-set enrichment analysis revealed functional terms related to fertilization, developmental biology, heat shock proteins and oxidative stress, among others. Overall, our findings contribute to a better understanding of the genetics underlying the reproductive performance of dairy cattle under heat stress conditions and point out novel genomic strategies for improving thermotolerance and fertility via marker-assisted breeding.     

Daily rumination time of lactating dairy cows under heat stress conditions

The dairy industry in regions with moderate climates, such as Central Europe, will be increasingly challenged in the future by climate change. The problem of heat stress will especially affect dairy husbandry in naturally ventilated barns (NVB). The approach of the study was to determine a heat stress threshold of the average daily temperature-humidity index (THI) that results in changes in the daily rumination time (RT) of lactating, high-yielding cows. The data set was composed of a high sample size of 183 cows and long-duration measurements of 21240 daily observations over two years from June 2015 to May 2017, which were collected in an NVB in Groβ Kreutz, Germany. The THI was calculated in 5-min intervals by data from several sensors in different positions inside the barn. Additionally, every cow from the herd of an average of 53 cows in the experimental procedure was wearing a neck collar with a Lely Qwes HR system that provided the RT 24 h a day (12 2-h recordings were summarized). The study showed that heat stress also negatively influenced RT in moderate climates. The heat stress threshold of 52 THI was determined by broken-stick regression and indicated changes of RT of lactating dairy cows in Germany. During the experimental period, the heat stress threshold for RT was reached from April to September for up to 720 h per month. The changes in RT to the heat stress threshold will be affected by cows' characteristics. Therefore, we considered several cow-related factors, such as milk yield (MY), lactation number (LN), lactation stage (days in milk, or DIM) and pregnancy stage (P) to better understand cows’ individual reactions to heat stress. Multiparous, high-yielding cows in later lactation stages are potentially more strongly affected than other cows.     

Effect of heat stress on conception in a dairy herd model under South African conditions

Three regression models are proposed for predicting reproduction in a model dairy herd under South African conditions. Conception rate (CR%) was related to mean monthly temperature-humidity index (THI) by; CR% = 31.15THI - 0.25THI(2) - 890.2, and first service conception rate (FSCR%) to THI by; FSCR% = 173.45 - 1.79THI. Conception rate was related to numerical month of the year (M) by; CR% = 11.86M - 0.82M(2) + 26.36. The relation between mean monthly THI values and the conception rate of dairy cattle is significant. Further investigations to test the proposed regression models under various dairy herd conditions and to improve reproduction in South African dairy herds are needed.     

Effect of feeding yeast culture on reproduction and lameness in dairy cows under heat stress

Multiparous Holstein cows (n=717) from two dairy farms were blocked at calving by parity and previous lactation milk yield and, within each block, randomly assigned to one of two treatments: a diet containing no yeast culture (Control; n=359) or 30 g/d of a culture of Saccharomyces cerevisiae (YC; n=358) from 20 to 140 d postpartum. Only cows calving during months of heat stress, May-August were enrolled. Lameness score (1-5 scale) was evaluated at study enrollment and again at 100 d postpartum. The body condition score (BCS, 1-5 scale) was evaluated at calving, 28, 58 and 140 d postpartum. Cows received two injections of PGF(2alpha) at 37 and 51 d postpartum, and those observed in estrus were inseminated. Cows not in estrus were enrolled in a timed AI protocol at 65 d postpartum and inseminated at 75 d postpartum. Ovaries were examined by ultrasonography at 37 and 51 d postpartum to determine whether estrous cycling had been initiated by the presence of a corpus lutem (CL) in at least one of the two examinations. Pregnancy was diagnosed at 31, 38 and 66 d after the first AI and at 38 and 66 d after the second and third AI. Diet did not affect time of onset of estrous cycles postpartum, and 8.2% of the cows were anovular. Detection of estrus in the 7d after the second injection of PGF(2alpha) was similar for control and YC. For control and YC, conception rates 38 d after AI at first (30.8% and 31.4%), second (39.3% and 35.1%) and third (25.8% and 30.6%) inseminations, and pregnancy losses did not differ, which resulted in similar median days to pregnancy and proportion of pregnant cows at 140 d postpartum. Yeast culture did not affect incidence of lameness, but tended to reduce lameness score. Lame cows and anovular cows had lesser conception rates at first AI, and extended interval from calving to conception. A THI of 71 was identified as the critical point in which fertility was reduced in lactating dairy cows, although the sensitivity and specificity were minimal. Cows exposed to a THI>71 on the day of first AI had a 33% reduction in the rate of pregnancy resulting in extended interval to pregnancy. Feeding a yeast culture of S. cerevisiae had minor effects on lameness score, but no impact on reproduction of multiparous cows under heat stress.     

Identification of heat shock protein gene expression in hair follicles as a novel indicator of heat stress in beef calves

Heat shock proteins (HSPs) consist of highly preserved stress proteins that are expressed in response to stress. Two studies were carried out to investigate whether HSP genes in hair follicles from beef calves can be suggested as indicators of heat stress (HS). In study 1, hair follicles were harvested from three male Hanwoo calves (aged 172.2 ± 7.20 days) on six dates over the period of 10 April to 9 August 2017. These days provided varying temperature–humidity indices (THIs). In study 2, 16 Hanwoo male calves (aged 169.6 ± 4.60 days, with a BW of 136.9 ± 6.23 kg) were maintained (4 calves per experiment) in environmentally controlled chambers. A completely randomized design with a 2 × 4 factorial arrangement involving two periods (thermoneutral: TN; HS) and four THI treatment groups (threshold: THI = 68 to 70; mild: THI = 74 to 76; moderate THI = 81 to 83; severe: THI = 88 to 90). The calves in the different group were subjected to ambient temperature (22°C) for 7 days (TN) and subsequently to the temperature and humidity corresponding to the target THI level for 21 days (HS). Every three days (at 1400 h) during both the TN and HS periods, the heart rate (HR) and rectal temperature (RT) of each individual were measured, and hair follicles were subsequently collected from the tails of each individual. In study 1, the high variation (P < 0.0001) in THI indicated that the external environment influenced the HS to different extents. The expression levels of the HSP70 and HSP90 genes at the high-THI level were higher (P = 0.0120, P = 0.0002) than those at the low-THI level. In study 2, no differences in the THI (P = 0.2638), HR (P = 0.2181) or RT (P = 0.3846) were found among the groups during the TN period, whereas differences in these indices (P < 0.0001, P < 0.0001 and P < 0.0001, respectively) were observed during the HS period. The expression levels of the HSP70 (P = 0.0010, moderate; P = 0.0065, severe) and HSP90 (P = 0.0040, severe) genes were increased after rapid exposure to heat-stress conditions (moderate and severe levels). We conclude that HSP gene expression in hair follicles provides precise and accurate data for evaluating HS and can be considered a novel indicator of HS in Hanwoo calves maintained in both external and climatic chambers.     

Effect of experimental bedding treatments on the density of immature Musca domestica and Stomoxys calcitrans (Diptera: Muscidae) in outdoor calf hutches

Experimental bedding materials and a novel delivery method of cyromazine (Larvadex) were evaluated as replicated treatments in outdoor calf hutches for effect on the density of immature Musca domestica L. and Stomoxys calcitrans (L.). In 6-wk trials, overall density of Musca domestica L. and Stomoxys calcitrans (L.) in straw bedding averaged 36.2 and 52.6 maggots/liter, respectively, compared with respective average densities of 9.0 and 16.2 for wood chips and 10.4 and 20.0 for wood chips over a hydraulic fabric filter system. These values represent average reductions of 80 and 69% and 77 and 68%, respectively. Densities of M. domestica and S. calcitrans in ground corncob over the filter system averaged 13.3 and 4.1 maggots/liter in 3.2-mm size corncob particles, and 1.7 and 1.2 for 6.4-mm size corncob particles (average reductions of 62 and 87% and 90 and 96%, respectively) relative to straw bedding. Densities of these two species in sand bedding averaged 2.8 and 0.4 maggots/liter (average reductions of 93 and 99%), but sand became compacted and soiled with calf urine and feces after several weeks. Cyromazine excreted in calf urine limited density of both species in straw to an average of 11.0 and 15.6 maggots/liter, respectively (a 58 and 79% suppression relative to untreated straw). These data confirm that straw bedding promotes muscoid maggot growth and illustrate that alternative calf hutch bedding systems and urine delivery of cyromazine may improve muscoid fly management on dairy farms by limiting the development of muscoid maggots.     

Effects of acute and chronic heat stress on feed sorting behaviour of lactating dairy cows

Nutritional strategies to mitigate the negative effects of heat stress on animal welfare and productivity often involve changes in ration formulation. However, cattle commonly sort their ration in favour of certain components, and it is not clear how feed sorting responds to heat stress. This study investigated the association between heat stress and feed sorting behaviour. Lactating Holstein dairy cows (n = 32; parity = 2.8±1.2; mean±SD) were housed in a free stall barn and milked 3×/day. Cows were fed individually using the Calan Broadbent Feeding System and offered ad libitum access to a total mixed ration (containing on a dry matter basis: 3.3% ryegrass hay, 16.5% ryegrass baleage, 24.7% corn silage, 11.1% brewers grains, 19.7% ground corn, 19.8% concentrate and 4.9% protein/mineral supplement), provided 1×/day. Beginning at 186±60 days in milk, cows were exposed to either: heat stress conditions (HT; n = 15) (average temperature–humidity index: 77.6), or evaporative cooling (CL; n = 17), consisting of misters and fans over the freestall and feed bunks. Data were collected during a 4-day baseline period, and two 4-day experimental periods: starting at 10 days after implementing treatments (defined as acute heat stress for HT cows), and at 62 days after implementing treatments (defined as chronic heat stress for HT cows). Daily feed intake and physiological responses to heat stress (body temperature, respiration rate) were recorded. Samples of fresh and refused feed were collected daily from individual cows for particle size analysis. The particle size separator had three screens (19, 8 and 1.18 mm) and a bottom pan, resulting in 4 fractions (long, medium, short and fine particles). Feed sorting was calculated as the actual intake of each particle size fraction expressed as a percentage of the predicted intake of that fraction. During both heat stress periods, HT cows sorted for long particles more than CL cows (105.0% v. 100.6%; SE = 1.1). During acute heat stress, HT cows sorted to a greater extent than CL cows against medium and short particles, whereas sorting of these fractions did not differ during chronic heat stress. Body temperature and respiration rate were associated across treatments with the extent of sorting for long particles and against short particles during acute heat stress. These results suggest that feed sorting is particularly influenced during acute heat stress, and that sorting for longer particles may increase in heat stress.     

Review: welfare of dairy cows in continuously housed and pasture-based production systems

There is increasing interest in the use of continuous housing systems for dairy cows, with various reasons put forward to advocate such systems. However, the welfare of dairy cows is typically perceived to be better within pasture-based systems, although such judgements are often not scientifically based. The aim of this review was to interrogate the existing scientific literature to compare the welfare, including health, of dairy cows in continuously housed and pasture-based systems. Although summarising existing work, knowledge gaps and directions for future research are also identified. The scope of the review is broad, examining relevant topics under three main headings; health, behaviour and physiology. Regarding health, cows on pasture-based systems had lower levels of lameness, hoof pathologies, hock lesions, mastitis, uterine disease and mortality compared with cows on continuously housed systems. Pasture access also had benefits for dairy cow behaviour, in terms of grazing, improved lying/resting times and lower levels of aggression. Moreover, when given the choice between pasture and indoor housing, cows showed an overall preference for pasture, particularly at night. However, the review highlighted the need for a deeper understanding of cow preference and behaviour. Potential areas for concern within pasture-based systems included physiological indicators of more severe negative energy balance, and in some situations, the potential for compromised welfare with exposure to unpredictable weather conditions. In summary, the results from this review highlight that there remain considerable animal welfare benefits from incorporating pasture access into dairy production systems.