Answer provided by Noah Litherland, assistant professor of dairy cattle nutrition at the University of Minnesota.
Q: How do I manage first-calf heifers in the weeks prior to calving? (Along with some other questions related to first-calf heifers.)
A: Our goal for a successful primiparous-heifer program should be to reduce the number of metabolic, psychological, and pathogenic hurdles during the transition period. Calving and initiation of lactation are two unavoidable hurdles. Our focus should be to tear down additional hurdles through adaptive nutrition and behavioral management prior to calving.
- Avoid over-conditioning heifers in late gestation to reduce calving problems and to help avoid low postpartum DMI.
- Try to adapt behavior and social structure prior to calving, since this should reduce stress at calving.
- Avoid feeding anionic salts to primiparous cows.
- It may be advantageous to transport primiparous cows from the grower to the owner six to eight weeks prior to expected calving date to adapt behavior and minimize heifers calving early.
Should we focus on controlling energy intake in first-calf heifers?
Often, primiparous cows are moved from the heifer grower and placed in the far-off dry cow group to adapt them to new surroundings, expose them to social interactions with older cows, and to feed an appropriate diet. Moderate-energy or controlled-energy diets based on wheat straw and silage are offered at an ad libitum rate, but do not allow cows to greatly over-consume energy (Beever et al., 2006; Dann et al., 2006; Janovick-Guretzky et al., 2006). Moderate- energy diets for mature dry cows have been implemented with success and are being adopted by producers.
Are moderate-energy diets appropriate for primiparous cows?
Primiparous cows exhibit negative energy balance in early lactation similar to that of multiparous cows (Lin et al., 1984). Primiparous cows produce less milk compared to multiparous cows, but may be at risk for similar severity of negative energy balance after calving (Cavestany et al., 2005; Wathes et al., 2007).
Work examining the role of energy intake during the dry period has been limited in primiparous cows. Researchers in Wisconsin found that primiparous cows fed a more moderate-energy diet (59.7 percent TDN) prepartum had higher DMI postpartum than heifers fed higher-energy (69.3 percent TDN) (Grummer et al., 1995). Higher-energy feeding prepartum did not improve milk yield or milk composition (Grummer et al., 1995). Heifers fed the higher-energy diet prepartum had higher concentrations of blood non-esterified fatty acids (NEFA), ß-hydroxy butyrate (BHBA) and tended to have higher concentrations of liver triglycerides (Grummer et al., 1995). Heifers fed excessive energy prior to calving tended to have lower DMI postpartum than those fed a high-forage, moderate-energy diet or those fed in restricted amounts (Janovick Guretzky, 2006).
Field experience suggests that heifers consuming excessive energy prior to calving have more difficulty calving. Additionally, excessive body fat mobilization may reduce energy intake postpartum and predispose heifers to metabolic disorders. Hoffman et al. (1996) determined that feeding pregnant first-calf heifers low-energy, high-fiber forages may help in controlling energy intake and assist in minimizing over-conditioning at calving.
Finally, be aware of cold weather effects on energy requirements in these growing and pregnant heifers. Cold weather conditions may warrant higher energy intake in some situations.
Advantages in behavioral adaptations for first-calf heifers
In addition to the physiological and metabolic changes associated with calving and the initiation of lactation, primiparous cows must adapt to co-mingling with older, socially dominant cows, learn to use head locks and free-stalls, become accustomed to increased handling by humans, and adjust to the milking routine. Separate feeding and management of primiparous and multiparous cows is warranted (Grant 2007; Daniels et al., 2008), but is often not practical, especially on smaller herds.
According to the NRC (2001), primiparous cows consume less feed and in a different pattern (peaking later) than multiparous cows. Additionally, it is believed that primiparous cows are usually more timid and occupy a lower rank in the social herd hierarchy (Wierenga, 1990). Interesting data from Spain showed total eating time was longer when primiparous cows were housed with multiparous cows; however, primiparous cows housed alone had almost one more meal per day than did those housed with multiparous cows (Bach et al., 2006). Feeding area was limited to one feeder per 1.8 cows; however, more than 50 percent of the feeders at time of feeding were occupied by primiparous cows, suggesting they were not intimidated by multiparous cows (Bach et al., 2006). Housing multiparous and primiparous cows together may offer advantages in exposing heifers to intensified competition prior to calving as well as assumption of learned behaviors.
Two producers in the upper Midwest that I recently visited with have interesting philosophies on feeding behavior in close-up heifers and cows. One producer purposefully overcrowds the close-up group to increase competition at the feed bunk and purportedly stimulate intake. Data published by Bach et al. (2006) seem to support this theory, although results might not be the same in all situations. Another producer on a large dairy constantly mixes pens of dry cows to reduce the group’s desire to develop a strong social hierarchy. The mixing of dry-cow pens seemingly reduces negative social interactions and helps fresh cows acclimate to herdmates in the fresh-cow pen.
Future research should focus on the impact of nutrition and behavior in first-calf heifers on subsequent success in the weeks after calving.