Growth and body composition of calves fed three milk replacer levels
Feeding increased milk replacer can be beneficial depending on fat and protein percent, but if daily gains exceed 1 kg that can cause undue fattening.
By Al KertzI reviewed briefly some principles of body composition and growth (Kertz, 2023). Below is a preamble to my Feedstuffs article related to this subject area (Bartlett et al., 2024). My major professor at Cornell University, J.T. (Tom) Reid, published the classic review (Reid et al., 1955) that established some key elements in this area:
There is an inverse relationship between body water and fat. Thus, fattening is largely a replacement of water by fat.
The percentages of water, protein and mineral approach constancy in the fat-free body of animals after “chemical maturity” is attained.
Carbohydrates only account for about 0.5% of the body, so it can be ignored in longer-term studies.
Age is highly correlated with the percent of fat-free body components, and this was found to be a curvilinear relationship.
Some of the key cattle studies cited in that review were done in the 1910s and 1930s at the University of Missouri by Henry Waters and F.B. Mumford, for whom two buildings on campus are named. Then, Samuel Brody did his prodigious studies that culminated in his formidable 1964 classic book Bioenergetics and Growth. That was the main reason why a major symposium was held there in May 1967 on “Body Composition in Animals and Man.” Its findings are so pertinent to this day that it is still available as a download at the National Academies Press website.
As I was a dually enrolled undergraduate and graduate student at the University of Missouri at that time, I then met my future Cornell University major professor, who was the main organizer and speaker at that conference.
Several years later, I became part of a major research project at Cornell University in the growth and development of cattle. We used two breeds (Angus and Holstein), three sexes (bulls, steers and heifers), two levels of intakes (ad libitum and 70% of that level) and four body weight points (a 400 lb. baseline, 600 lb., 800 lb. and 1,000 lb. intervals). All animals were slaughtered, and detailed body composition was measured by both physical dissection and chemical analyses.
Other data measured included intake, daily gain and the single diet digestibilities. We also did specialized assays of muscle and adipose/fat growth, along with insulin and growth hormones. This study was replicated and involved graduate students from Chile, Colombia, Canada and Mali West Africa. I served as the project coordinator. References are Fortin et al., 1980 and 1981, and Kertz et al.,1982.
Part of this study at the University of Illinois (Bartlett et al., 2024) was previously reported (Bartlett et al., 2006). Calves were part of a larger experiment as described in Bartlett, 2001. Portions of the experiment have been published previously (Bartlett et al., 2006). Male Holstein calves were purchased from an Illinois dealer at less than one week of age. Groups of calves were delivered on May 27, July 22 and Sept. 17, 1999.
Calves were housed individually in hutches, which were placed on 15-20 cm of crushed rock, so no bedding was used in order to avoid consumption of organic material that could confound results. The next day, calves were fed whole, nonsalable milk at 10% of body weight. They remained on this diet for 14 days to allow for adjustment. Water was available at all times, but no dry feed was offered. Protocol is primarily described below as directly copied from the text because of its complexity and for readers’ convenience:
“Following the 14-day adjustment period, calves were stratified from highest to lowest body weight and randomly assigned to either an initial composition (baseline) group or to one of 12 experimental treatments. Eleven calves were killed for baseline measurements (2, 5 and 4 in groups 1 to 3, respectively) and 74 remained on their respective diets for 5 [weeks] before slaughter. Data from all 11 baseline calves were pooled and used to calculate starting body composition in treatment calves. Three of the 12 treatments were designed to address the current objectives, and only data for those treatments are reported here. Investigators were not blinded to treatments. To determine the effects of increased nutrient intake on growth and body composition, calves were fed a milk replacer at three different rates: 1.25%, 1.75% or 2.25% of body weight (DM basis), adjusted weekly (n = 6 per treatment for the 1.25% and 1.75% groups, n = 8 for the 2.25% of BW group).”
Calves were fed a whey protein-based milk replacer (MR) containing 24.8% crude protein (CP), 18.9% fat, 49.2% lactose, 7.2% ash and 5.1 Mcal/kg gross energy (GE), reconstituted to 12.5% solids with warm tap water. Calves fed at 1.25% and 1.75% of body weight were fed twice daily, whereas calves fed at 2.25% of body weight were fed three times daily. Corresponding liquid feeding rates (as fed) were 10%, 14% and 18% of body weight. Calves were weighed once weekly, and the amount of DM offered was adjusted weekly to maintain the desired feeding rates. Calf withers height, body length and heart girth were measured once weekly. Calves were monitored several times daily, and all observations concerning health were recorded. Fecal scores were assigned and recorded once daily. Blood samples were collected once weekly via jugular venipuncture at approximately 0700 hour, which was before the morning feeding.
Body composition procedures
All calves were humanely euthanized at the University of Illinois Meat Science Laboratory using captive bolt stunning, followed by exsanguination. Eleven calves were slaughtered for initial body composition data following the 14-day adjustment period. The remaining calves were slaughtered five weeks later. Calves were weighed before slaughter, which was approximately 17 hours after the last feeding; this weight was considered to represent shrunk body weight.
Following the exsanguination, blood was collected and the weight recorded. The hide and viscera were removed. The body was separated into three fractions: head, hide, feet and tail (HHFT); viscera, and carcass. The gastrointestinal tract (GIT) was removed and weighed. Digesta was removed from the GIT by rinsing the stomach and intestines thoroughly with water. The empty GIT was then reweighed, and the amount of digesta in the GIT at the time of slaughter was determined as the difference in weight between the full GIT and the empty GIT. Individual weights were recorded for the kidneys, liver and heart; all internal organs were then pooled to form the visceral fraction. The fractions were refrigerated overnight and processed the following day.
The HHFT and carcass were ground twice through a whole carcass grinder (model 801 GP15, Autio Co. Inc., Astoria, Ore.) fitted with a 1.3 cm plate and then were subsampled. The visceral fraction was ground twice through a grinder and then subsampled. The subsamples were frozen and then reground twice through a Butcher Boy grinder using a smaller die (3 mm). Subsamples were frozen (about 20°C) for later analyses, and another subsample was lyophilized.
We assumed that the variation in HHFT composition between calves would be insignificant and that diet would have little influence on HHFT composition. The HHFT fraction was extremely difficult to grind; therefore, HHFT composites were made. A HHFT composite was created for each day that calves were slaughtered. All HHFT from calves used to determine initial body composition were composited, and five HHFT from the treatment calves were composited, thereby creating three initial and three final HHFT samples. Nutrient intakes (Table 1) were linearly (P < 0.001) increased with increasing milk replacer feeding levels as a percentage of body weight.
Data in Table 2 show:
Linear increases (P < 0.03 to 0.001) in final body weight, daily gain, heart girth and body length and gain-to-feed ratio with increasing milk replacer (MR) feeding levels.
The middle feeding level of 1.75% of body weight resulted in 1.54 lb. daily weight gain, which is appropriate for the first two months of Holstein dairy calves for the goal of doubling birth weight. But 2.27 lb. daily gain [in the 2.25% feeding level] is on the verge of fattening.
However, withers height increase was not linear (P < 0.49) with increasing MR feeding levels. That is because the growing time from 14 days to 49 days of growth was too short, since withers height increases slower than body weight. In the classic report of Kertz et al. (1998), withers height increased about 2 in. per month during the first six months of life. So, in the 25 days of this study, withers height might be expected to increase by about 0.8 in. Thus, in this study, treatment differences would be small and quite variable at a standard error of means of 0.55 in. with only six calves per treatment.
There are many linear relationships for shrunk body weight and other body compartments, but that is expected just because of increased body weights with increased milk replacer feeding levels. So, let’s look at the composition of that body in Table 3.
Data in Table 3 show:
The percentage of water decreases as percentage of fat increases, in accordance with what was indicated at the beginning of this article (Reid et al., 1955).
Protein and ash proportions changed little.
Body energy concentration increased with increased milk replacer feeding levels and with increasing body fat percent.
A similar picture resulted when looking at the composition of empty body weight (EBW).
Glucose, insulin and IGF-1 increased with increasing feeding level. IGF-1 is noted to integrate growth, maintenance and repair, along with function of the immune system. This is likely in response to the increased feeding and nutrition level, as were increased glucose and insulin, too. Fecal scores were similar among treatments, but there was a “loosening” with increased feeding level — also seen in on-farm situations.
Studies with growing dairy and beef animals have shown that daily gains of about 1 kg (2.2 lb.) is the maximum for protein deposition. Above that daily gain, undue fattening is likely for dairy heifers. In this study, 1 kg daily gain was the result for feeding milk replacer at 2.25% of body weight. Fat percent increased linearly from a baseline of 3.7 to 7.5% on the 2.25% of body weigh feeding level (Table 3). The milk replacer fed in this study was about 25% CP and 19% fat on a dry matter basis.
In the study by Tikofsky et al. (2001), similar male calves as in this study were fed to gain 1.3 lb. daily. They were fed milk replacers with 28% protein, but fat percent varied from 15 to 31%. With that increasing fat percentage, body composition fat increased from 8.5 to 11.0%. Those fat percentages are much greater than the greatest of 7.5% in this study.
View our interview with Dr. Al Kertz on this research.
The Bottom Line
Increased feeding of milk replacer can be beneficial depending on fat and protein percent. But if daily gains exceed 1 kg (2.2 lb.), that can cause undue fattening. In this study and that of Tikofsky et al. (2001), no calf starter was fed in order to avoid confounding results and interpretations. That is often the major variable in calf feeding programs (Kertz, 2023).
References
Bartlett, K.S. 2001. Interactions of protein and energy supply from milk replacers on growth and body composition of dairy calves. MS Thesis, University of Illinois, Urbana, Ill.
Bartlett, K.S., F.K. McKeith, M J. Vandehaar, G.E. Dahl and J.K. Drackley. 2006. Growth and body composition of dairy calves fed milk replacers containing different amounts of protein at two feeding rates. J. Anim. Sci. 84:1454-1467.
Bartlett, K.S., F.K. McKeith, R.A. Molano, M.E. Van Amburgh, J. VandeHaar, G.E. Dahl and J.K. Drackley. 2024. Growth and body composition of dairy calves fed only milk replacer at 3 intakes. J. Dairy Sci. 107:7842-7850.
Fortin, A., S. Simpfendorfer, J.T. Reid, H.J. Ayala, R. Anrique and A.F. Kertz. 1980. Effect of level of energy intake and influence of breed and sex on the chemical composition of cattle. J. Anim. Sci. 51:604-613.
Fortin, A., J.T. Reid, S. Simpfendorfer, H.J. Ayala, R. Anrique, A.F. Kertz, A.M. Maiga, D.W. Sim and G.H. Wellington. 1981. Chemical composition and carcass specific gravity in cattle: effect of level of energy intake and influence of breed and sex. Can. J. Anim. Sci. 61:871-882.
Kertz, A.F., J.T. Reid, G.H. Wellington, H.J. Ayala, S. Simpfendorfer, A.M. Maiga and A. Fortin. 1982. Growth and development of cattle as related to breed, sex and level of intake. 1. Plasma, insulin and growth hormone. 2. Characterization of the chemical development and lipogenic activity of subcutaneous, perirenal and omental adipose tissue sites. 3. Growth and development of the liver as related to body weight, intake, chemical composition, DNA and RNA and lipogenic activity. 4. Growth and development of biceps femoris, longissimus and triceps brachii muscles as related to total muscle weight, chemical composition and DNA and RNA content. Search: Agriculture. Ithaca, N.Y.: Cornell Univ. Agr. Exp. Sta. No. 23, 32 pp.
Kertz, A.F., B.A. Barton and L.F. Reutzel. 1998. Relative efficiencies of wither height and body weight increase from birth until first calving in Holstein cattle. J. Dairy Sci. 81:1479-1482.
Kertz, A.F. Dairy Calf and Heifer Feeding and Management — Some Key Concepts and Practices. Outskirts Press, July 31, 2019, 166 pages. https://outskirtspress.com/dairycalfandheiferfeedingandmanagement.
Kertz, A.F. Fat and body composition matter long run. Hoard’s Dairyman, Sep. 25, 2023. p. 512-513.
Kertz, A.F. PERSPECTIVE AND COMMENTARY: Dairy calf feeding and nutrition major variables and subsequent performance. Appl. Anim. Sci. 39:449-455.
Reid, J.T., G.H. Wellington and H.O. Dunn. 1955. Some relationships among the major chemical components of the bovine body and their application to nutritional investigations. J. Dairy Sci. 38:1341-1359.
