A feeding regimen that allows a smooth transition from milk to solid feed is vital for successful heifer-rearing programs. In the past, research efforts have focused on the development of feeding methods that allow early weaning, perhaps because the risk of disease is highest during the milk feeding stage. To encourage early intake of calf starter, conventional feeding programs have limited the supply of milk (often to 10% of BW at birth). However, dairy calves provided free access to milk will typically consume more than twice this amount. We critically review the available literature examining the relationship between milk feeding method, solid feed consumption, and rumen development in young dairy calves and identify areas where new work is required. We conclude that milk-fed dairy calves can safely ingest milk at approximately 20% of body weight (BW)/d, and greater milk consumption supports greater BW gain, improved feed efficiency, reduced incidence of disease, and greater opportunity to express natural behaviors, which in combination suggest improved welfare. Method of weaning greatly influences feed consumption, rumen development, and growth check in calves provided higher amounts of milk. Gradual weaning encourages starter intake during the preweaning period, and both weaning age and duration of weaning influence this consumption. Increased solid feed consumption during the weaning process contributes to rumen development, permitting higher starter intake and BW gain after weaning. Growth factors in milk may also enhance the growth and maturation of the gastrointestinal tract, but more research is required to understand the role of these factors. Greater nutrient supply through increased amount of milk appears to improve immune function and long-term performance of heifer calves; for example, reducing the age at first breeding and increasing first-lactation milk yield, but more research is needed to confirm these effects.

Metritis is a disease of particular concern after calving because of its profound negative effects on the reproductive performance of dairy cows. Cows at risk for metritis have shorter feeding times in the days before calving but prepartum dry matter intake (DMI) and water intake may also be useful in identifying cows at risk for this disease. Feeding, drinking, and intake measures may also be affected by social interactions among group-housed cows. The objective of this study, therefore, was to measure intake, feeding, drinking, and social behavior to determine which measures could identify cows at risk for metritis after calving. Feeding and drinking behavior and intake measures were collected from 101 Holstein dairy cows from 2 wk before until 3 wk after calving using an electronic monitoring system. Social behavior at the feed bunk was assessed from video recordings. Metritis severity was diagnosed based on daily rectal body temperature as well as condition of vaginal discharge that was assessed every 3 d after calving until d +21. In this study, 12% of cows were classified as severely metritic and 27% as mildly metritic. Prepartum feeding time and DMI were best able to identify cows at risk for metritis. Cows that developed severe metritis spent less time feeding and consumed less feed compared with healthy cows beginning 2 wk before the observation of clinical signs of infection. For every 10-min decrease in average daily feeding time during the week before calving, the odds of severe metritis increased by 1.72, and for every 1-kg decrease in DMI during this period, cows were nearly 3 times more likely to be diagnosed with this disorder. During the week before calving, cows that were later diagnosed with severe metritis had lower DMI and feeding times during the hours following fresh feed delivery. During this period these cows also engaged in fewer aggressive interactions at the feed bins compared with cows that remained healthy. This research is the first to show that social behavior may play an important role in transition cow health. Research is now required to determine how management should be changed to reduce or prevent illness in transition dairy cows.

The effects of high ambient temperatures on production animals, once thought to be limited to tropical areas, has extended into northern latitudes in response to the increasing global temperature. The number of days where the temperature-humidity index (THI) exceeds the comfort threshold (>72) is increasing in the northern United States, Canada, and Europe. Compounded by the increasing number of dairy animals and the intensification of production, heat stress has become one of the most important challenges facing the dairy industry today. The objectives of this review were to present an overview of the effects of heat stress on dairy cattle welfare and highlight important research gaps in the literature. We will also briefly discuss current heat abatement strategies, as well as the sustainability of future heat stress management. Heat stress has negative effects on the health and biological functioning of dairy cows through depressed milk production and reduced reproductive performance. Heat stress can also compromise the affective state of dairy cows by inducing feelings of hunger and thirst, and we have highlighted the need for research efforts to examine the potential relationship between heat stress, frustration, aggression, and pain. Little work has examined how heat stress affects an animal's natural coping behaviors, as well as how the animal's evolutionary adaptations for thermoregulation are managed in modern dairy systems. More research is needed to identify improved comprehensive cow-side measurements that can indicate real-time responses to elevated ambient temperatures and that could be incorporated into heat abatement management decisions.

Calves are born with a physically and metabolically underdeveloped rumen and initially rely on milk to meet nutrient demands for maintenance and growth. Initiation of solid feed consumption, acquisition of anaerobic microbes, establishment of rumen fermentation, expansion of rumen in volume, differentiation and growth of papillae, development of absorption and metabolic pathways, maturation of salivary apparatus and development of rumination behavior are all needed as the calf shifts from dependence on milk to solid feed. In nature and some production systems (e.g., most beef calves), young ruminants obtain nutrients from milk and fresh forages. In intensive dairying, calves are typically fed restricted amounts of milk and weaned onto starter feeds. Here we review the empirical work on the role of feeding and management during the transition from milk to solid feed in establishing the rumen ecosystem, rumen fermentation, rumen development, rumination behavior, and growth of dairy calves. In recent years, several studies have illustrated the benefits of feeding more milk and group rearing of dairy calves to take advantage of social facilitation (e.g., housing with peers or dam), and this review also examines the role of solid feed on rumen development and growth of calves fed large quantities of milk and reared under different housing situations. We conclude that the provision of high-starch and low-fiber starter feeds may negatively affect rumen development and that forage supplementation is beneficial for promoting development of the gut and rumination behavior in young calves. It is important to note that both the physical form of starter diets and their nutritional composition affect various aspects of development in calves. Further research is warranted to identify an optimal balance between physically effective fiber and readily degradable carbohydrates in starter diets to support development of a healthy gut and rumen, rumination behavior, and growth in young calves.

The dairy industry in the developed world has undergone profound changes over recent decades. In this paper, we present an overview of some of the most important recent changes in the dairy industry that affect health and welfare of dairy cows, as well as the science associated with these changes. Additionally, knowledge gaps are identified where research is needed to guide the dairy industry through changes that are occurring now or that we expect will occur in the future. The number of farms has decreased considerably, whereas herd size has increased. As a result, an increasing number of dairy farms depend on hired (nonfamily) labor. Regular professional communication and establishment of farm-specific protocols are essential to minimize human errors and ensure consistency of practices. Average milk production per cow has increased, partly because of improvements in nutrition and management but also because of genetic selection for milk production. Adoption of new technologies (e.g., automated calf feeders, cow activity monitors, and automated milking systems) is accelerating. However, utilization of the data and action lists that these systems generate for health and welfare of livestock is still largely unrealized, and more training of dairy farmers, their employees, and their advisors is necessary. Concurrently, to remain competitive and to preserve their social license to operate, farmers are increasingly required to adopt increased standards for food safety and biosecurity, become less reliant on the use of antimicrobials and hormones, and provide assurances regarding animal welfare. Partly because of increasing herd size but also in response to animal welfare regulations in some countries, the proportion of dairy herds housed in tiestalls has decreased considerably. Although in some countries access to pasture is regulated, in countries that traditionally practiced seasonal grazing, fewer farmers let their dairy cows graze in the summer. The proportion of organic dairy farms has increased globally and, given the pressure to decrease the use of antimicrobials and hormones, conventional farms may be able to learn from well-managed organic farms. The possibilities of using milk for disease diagnostics and monitoring are considerable, and dairy herd improvement associations will continue to expand the number of tests offered to diagnose diseases and pregnancy. Genetic and genomic selection for increased resistance to disease offers substantial potential but requires collection of additional phenotypic data. There is every expectation that changes in the dairy industry will be further accentuated and additional novel technologies and different management practices will be adopted in the future.