INTRODUCTION
Milk and milk replacer feeding strategies have been studied for many years.
Early studies focusing on levels of milk and milk replacer feeding were published over 40 years ago after the concept of using milk replacers had gained popularity.
Indeed in many species of animals there is research to study feeding levels and feed sources for the newborn or neonate and how this may affect later life issues, both during the growing period and the productive period of life.
The ‘conventional’ feeding program for calves in the U.S. is designed to encourage early intake of grain, stimulate rumen development, and facilitate weaning so that feed costs can be kept to a minimum.
This program provides approximately 1 gallon of liquid per day, usually in two feedings of 2 quarts each. When using milk replacer typically 1 to 1.25 pounds of powder is fed each day.
This feeding rate will meet the requirements for maintenance of a calf weighing 80 to 100 pounds under thermoneutral conditions.
Current feeding recommendations suggest that calves be fed 10 to 12% of their body weight, rather than a fixed volume of 1 gallon per day. In addition, milk or milk replacer amounts should be increased in cold weather, particularly for calves less than 3 weeks of age that are not consuming grain.
In recent years feeding strategies have been proposed that greatly increase the amount of milk or milk replacer fed to calves compared to conventional practices. These programs have been called by a variety of names including accelerated, enhanced, and intensified.
Numerous studies have documented the effects of these programs on calf growth during the preweaning period. More recently, studies have evaluated the long-term relationship between milk intake in dairy calves with modern genetics and milk production later in life. This review will focus on the effects of increased milk or milk replacer feeding on milk production.
We reviewed all of the worldwide literature and found four peer-reviewed publications relating calf milk replacer intake levels with future events such as age at calving and first lactation milk production. Each of the studies is a bit different and reports the data in somewhat differing ways, but they have a great deal of similarity. These will be reviewed in some detail.
In addition there have been three studies published in peer-reviewed journals that focus on increased feeding of liquid feeds to dairy calves, but in many aspects these studies show the differences between milk and milk replacer feeding in the dairy calf and interestingly all have been done in Israel. Since these studies utilize systems that are very different than what we in the US would consider ‘normal’ or ‘acceptable’ feed sources or practices, these studies will be reviewed in a separate section.
COMPARISON OF MILK REPLACER PROGRAMS
In a study by researchers from the animal science department at the University of Minnesota as well as Milk Products Inc. and Hubbard Feeds, 133 Holstein heifer calves from 3 farms were assigned to 5 treatments beginning at 3 days of age.
Calves were fed conventional milk replacer (20% protein, 20% fat, fed at 13.9% solids and 1.25 lbs of powder per day); acidified conventional milk replacer; intensive milk replacer (28% protein, 18% fat, 1.5 lbs of powder per day) fed at 16.7% solids; intensive milk replacer fed at 12.5% solids; or intensive milk replacer fed at 16.7% solids and at an increasing rate.
All calves on the first 4 treatments were fed twice daily through 35 days of age; milk replacer was reduced by half and calves were fed once daily from day 36 to weaning at 42 days.
Calves on the intensive, high solids, increasing feeding rate treatment were fed 1.5 lbs of powder per day from day 1 to 10 and 2.25 lbs of powder per day from day 11 to 42 in 2 equal feedings. On day 43 milk replacer was reduced by half and fed once daily until weaning at 49 days. All calves were fed free-choice starter; protein in the starter was 20% for conventional calves and 25% for calves fed intensive milk replacer. At 56 days of age calves were moved to group pens and fed grower rations; protein levels were 18% for conventionally fed calves and 21% for intensively fed calves. Diets fed during the later growing period and first lactation were similar across all groups.
No mention was made of the breeding protocol used in this study.
First lactation records were available for 95 of the animals that began the study. Milk replacer feeding program did not affect first-lactation performance (305-d (metabolisable energy(ME) milk yield averaged 28,916 lbs with 3.0% protein and 3.6% fat); however, heifers fed the intensive, high rate program calved almost a month (27.5 days) earlier than those fed conventional milk replacer (P =0.05).University researchers and feed industry personnel from the United Kingdom studied the impact of milk replacer feeding rate and protein concentration on animal performance through second lactation.
Holstein- Friesian calves with an average birth weight of 95 lbs began the study at 5 days of age. Calves were fed 1.32 or 2.64 lbs per day of milk replacer powder containing 21 or 27% crude protein and 17% fat until weaning at 56 days of age. All calves were housed in groups by treatment and fed via automated feeders. Water and 22% protein calf starter were available free-choice during the milk-feeding period.
After weaning, heifer calves remained in treatment groups through 12 weeks of age. All animals were offered the same diet from weaning through the remainder of the experiment. Heifers were bred after reaching 13.5 months of age and 695 lbs of body weight. Milk production data were collected for 81 heifers’ first and 66 cows’ second lactation. Neither age (24 months) nor body weight (1,116 lbs) at first calving was affected by the milk replacer feeding program. Milk production during first (49 lbs/d, 3.3% protein, 3.9% fat) and second lactation (54 lbs/d, 3.2% protein, 3.9% fat) was also similar regardless of treatment (based on 305-day production).
