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Cow turnover is a part of every modern dairy. Herd replacements present the opportunity to improve genetics and increase production. It is important to raise calves that both assure the opportunity to become a contributing part of the herd and to do so in a manner that maximizes the number of days a cow spends in production (lactation) versus growth to first calving and dry periods.
Multiple studies have shown that reducing the age of first calving from 24 to 25 months down to 22.5 to 23.5 improves lifetime profitability. Data interpreted from Changhee Do et al. demonstrates how lifetime profitability peaks around a first calving age of 23 months (Figure 1). Thereafter, as age to first calving increases, the net return per cow decreases.
Figure 1. Days to first calving effects upon lifetime profitability.
Source: Changhee Do et al., 2013.
Maximizing cow potential starts early
In order for profitability to be improved with earlier first calving age, heifers must reach that age in a condition that allows good milk production and –just as in later lactating cows— should not be overly heavy or light in weight.
Age is less important than body weight and height at the time of first breeding. In Holsteins the recommendation is weight around 350 kg and a height of approximately 120 cm. It is important that the growth be in both frame size and in lean muscle growth rather than adipose tissue.
Dairy cattle breeds obviously carry less muscle than do beef or dual-purpose breeds. In part we have selected them to maximize milk rather than muscle: maintaining more muscle than needed would represent a loss in efficiency. However, it is equally important that we raise our heifers to provide adequate muscle. In dairy cows the skeletal muscle system not only represents a method of movement but also acts as a reservoir of nutrients. Particularly in early lactation when feed intake does not meet the needs of the cow, muscle protein is used to not only provide amino acid for protein production but also the carbon backbone for production of glucose through gluconeogenesis. (For more on negative energy balance in dairy cows, see Science & Solutions Issue 17)
Currently there are a number of calf-rearing programs proposed to increase this early growth. Programs that maximize this growth and wean calves on less expensive dry feeds provide for better long-term growth. Increased average daily gain (ADG) pre-weaning can increase subsequent milk production, as shown in Table 1.
Table 1. Predicted differences in TDM residual milk (kg) for 1st, 2nd, and 3rd lactation as well as cumulative milk from 1st through 3rd lactation as a function of pre-weaning average daily gain and energy intake over predicted maintenance for the Cornell herd.
Source: M. E. Van Amburgh, et al., Cornell University, New York 2014.
Calf rearing requires attention to details to reduce morbidity and mortality among calves. One of the keys to success is getting calves to eat consistently and convert from consuming milk to consuming dry feed, i.e. calf starter. Feed consumption and health are well correlated. Calves that eat more tend to be healthier and healthier calves tend to eat more. Regardless of which one may precede the other, the goal is the same. Along these lines antibiotics have often been included in milk replacers. However, consumers in many places have voiced strong concern about sub-therapeutic antibiotics in dairy and livestock production. In a growing number of countries the use of antibiotic growth promoters has been banned—in part reflecting subsequent greater antibiotic-resistance in bacteria.
Ways to improve growth
Fortunately today we have other options to help maintain health, increase intake and improve performance. Phytogenic feed additives derived from plant extract have proven to be an effective part of a calf-rearing program. Research conducted at the University of Minnesota demonstrated that calves receiving calf milk replacer (CMR) containing Digestarom® P.E.P. performed equal to or better than that containing medication (Figure 2). In addition to increased body weight, calves receiving only Digestarom® P.E.P. also had significantly (P<0.05) improved feed conversion rate over non-medicated feeds and a numeric improvement over medicated feeds. Calves receiving Digestarom® P.E.P. milk replacer had reduced medication costs vs. calves receiving either non-medicated or medicated feed.
Figure 2. Comparison of non-medicated, medicated (neomycin/oxytetracycline) and Digestarom® P.E.P. in calf milk replacers.
Source: Chester-Jones, et al., 2010.
Additionally, Digestarom® Milk and Digestarom® Calf, for application in either milk or calf starter, respectively, have both been demonstrated to improve calf feed intake and performance. In a study conducted by a major milk replacer company in the United States, Digestrom® Milk improved the performance of calves fed both a 20% protein/20% fat diet and a 28% protein/20% fat product, as shown in Figure 3. The average of the two is a weight gain improvement of 2.85 kg. Based on the data from Cornell this would suggest a 154 kg improvement in milk production through the first 3 lactations.
Figure 3. Increased weight gain from the inclusion of Digestrom® Milk over a 42-day feeding period using to milk replacer formulations.
In a study conducted with Digestrom® Milk and Digestarom® Calf conducted in Austria calves demonstrated an improved growth rate of 100 g per day. If such results were translated in dairy calves the increased milk production through 3 lactations would be 228 kg of milk.
Early calf growth is important for long-term profitability through a combination of improving the calf physiologically to support subsequent lactations and by increasing the number of lifetime days in lactation. Digestrom® Milk and Digestrom® Calf can help improve growth that can result in increased milk production.