Longer calving interval resulted in heifers with greater body weight and lower milk

In a pioneering research study, scientists have established relationship between calving interval and its impact on the offspring's health, milk production in their first 100 days of first lactation and other important factors.

Extending the time before inseminating dairy cows voluntarily could reduce how often they give birth, aiming to choose better times for insemination when cows are less likely to have fertility issues. Researchers wanted to see how this affects the health and milk production of calves born from cows with different waiting periods before insemination and different lengths of time between calving events.

They studied Holstein Friesian dairy cows, totaling 154 (41 first-time mothers, 113 experienced mothers). The cows were grouped by factors like how much milk they produced and their somatic cell count, then randomly assigned waiting periods of 50, 125, or 200 days before insemination. They focused on female calves (62 total) born to cows with different lengths of time between calving events.

They found that the length of time between calving events didn't affect the birth weight of the calves. However, from birth until they were weaned, calves born to cows with shorter times between calving events had higher levels of a substance called plasma nonesterified fatty acids compared to calves born to cows with longer times between calving events. These shorter intervals also led to higher levels of certain antibodies in the calves before they were weaned.

After weaning until the calves themselves gave birth for the first time, those born to cows with shorter intervals between calving events tended to have higher levels of plasma nonesterified fatty acids than those born to cows with longer intervals.

During the first 100 days after giving birth for the first time, calves born to cows with longer intervals between calving events tended to have lower levels of a substance called plasma IGF_1 and produced less milk that was adjusted for fat and protein content compared to calves born to cows with shorter intervals. However, these effects were not consistent across all groups with different lengths of time between calving events.

In summary, extending the time between calving events in dairy cows did not affect the birth weight of their calves or their body weight during the period before they were weaned or raised. However, calves born to cows with longer intervals between calving events had less of certain antibodies and lower levels of a specific substance in their blood before weaning. During the first lactation period of these calves, those born to cows with longer intervals between calving events tended to have lower levels of another substance in their blood and produced less milk with adjusted fat and protein content compared to calves born to cows with shorter intervals between calving events.

Summary

In conclusion, calves born from dams with an extended calving interval differ in natural antibodies, body weight, and milk performance across different periods from birth until the first 100 DIM. More differences among CInt groups in immune variables were observed before weaning, and more in body weight, and milk production variables occurred after calving. A longer calving interval in dams, resulted in heifer calves with lower IgG and IgM levels against keyhole limpet hemocyanin (KLH) and lower plasma Non esterified Fatty acid (NEFA )concentration during the first 12 weeks of life. While during the first 100 DIM ( Days in milk )  of the offspring’s first lactation, a longer calving interval in dams resulted in heifers with greater body weight and lower milk production. This is one of the first studies that evaluated the effects of dam’s calving interval on offspring’s performance. Although we found some consequences of CInt in terms of immunity during early life and milk production during later life, results need to be confirmed in further studies.