The Effects of Dry Period Versus Continuous Lactation on Metabolic Status and Performance in Periparturient Cows

Abstract

It has been argued that dairy cows with a high genetic milk production potential can maintain high milk production even with total omission of the dry period. Further, when omitting the dry period, cows are believed to experience fewer metabolic changes during the transition from late gestation to early lactation compared with cows having a traditional dry period. The performance and metabolic response to omission of the dry period for cows with an expected peak milk yield higher than 45 kg/d were studied in 28 Holstein dairy cows. The cows were followed in late gestation and in the subsequent 5 wk of early lactation. Fourteen cows were milked through late gestation (CM) and another 14 dairy cows underwent a 7-wk dry period (DRY). In the early lactation period, the cows had the same dry matter (DM) intake but cows in the CM group had a 22% reduction in milk yield compared with the cows in the DRY group. At calving, the experimental groups had the same average body weight and body condition score and there were no significant differences in body weight and body condition score changes in early lactation. However, the cows in the CM group compared with the cows in the DRY group had a higher plasma concentration of glucose and insulin and a lower plasma concentration of nonesterified fatty acids and beta-hydroxybutyrate in the following 5 wk of early lactation. Furthermore, the cows in the CM group had lower liver triacylglycerol concentration and higher liver glycogen concentration in the following early lactation. It is concluded that, even in dairy cows with an expected peak milk yield above 45 kg/d, omission of the dry period results in a relatively high reduction in milk yield in the following early lactation. Furthermore, these cows are in less metabolic imbalance in the following early lactation.

Effects of continuous lactation and short dry periods on mammary function and animal health

“…Similar to fat and protein content, the lactose content was increased during the last 2 months of gestation in CM cows (Remond et al, 1997a). However, in another study, the weekly content of lactose was decreased from week 5 to week 0 prepartum (Andersen et al, 2005). In two studies by our laboratory, no change in lactose concentration of milk was detected during late gestation .…”

“…Remond et al (1992 and1997a) claimed that the ratio of casein/total protein was decreased when milk yield was reduced during late gestation in CM cows (,6 kg/day). In another study, the weekly content of milk protein was reported to be increased from week 5 to immediately before parturition in cows with eliminated dry periods (Andersen et al, 2005). Milk protein content was increased during the entire late gestation in CM glands and it was maximal at 1 to 2 weeks before parturition .…”

“…Andersen et al (2005) showed that weekly fat content of milk was increased from week 5 to week 0 at prepartum in CM cows. Annen et al (2008) reported no change in milk fat content during the last 7 weeks of gestation.…”

“…Although some studies have reported that omitting the dry period did not have an impact on the milk production of the next lactation either without using bovine rbST in dairy cows (Remond and Bonnefoy, 1997) or using bovine somatotropin (bST) in multiparous cows (Annen et al, 2004a), in most studies it has resulted in production losses of 10% to 40% in the subsequent lactation (Andersen et al, 2005;Fitzgerald et al, 2007).…”

“…The changes of milk protein percentage in the subsequent lactation after modifying the length of the dry period have been variable. The protein percentage during the following lactation was reported to be increased (Annen et al, 2004a (primiparous cows); Andersen et al, 2005;Watters et al, 2008) or unaffected (Annen et al, 2004a (multiparous cows) andPezeshki et al, 2008) following SDP or CM. Greater milk protein percentage in cows with shortened or eliminated dry periods may be explained by reduced milk yield in these cows (dilution effect) or improved energy balance, and thereby sparing amino acids and energy for protein synthesis (Remond et al, 1997a).…”