Discipline: performance; Keywords: body condition, disease, fertility, culling
Below par post-calving health has a negative effect on the performance and survival of dairy cows and occurrence of uterine, metabolic and other health disorders which are risk factors for lower subsequent fertility and milk yield, and higher risk of culling. The interrelationship between loss in body condition score (BCS) and disease prevalence is however complex and establishing cause and effect associations is challenging. Increased risk of milk fever, ketosis, fatty liver, metritis, digestive disorders and mastitis in cows with greater loss of BCS after calving has been shown. Also, high energy mobilizing cows have been shown to be less able to overcome metabolic challenges during the early post-calving period. The objective of the study of Dr D. Manríquez and colleagues was to better understand the effect of BCS by assessing the influence of different levels of BCS change between 5 and 40 days in milk (DIM) on fertility [defined as resumption of ovarian cycling, pregnancy at first AI, pregnancy loss at 60 days of gestation, pregnancy at 150 DIM (P150) and pregnancy at 305 DIM (P305)], average daily milk within the first 90 DIM (M90), and live culling or death after 40 DIM in cows diagnosed with reproductive disorders (REP: dystocia, twins, retained fetal membranes, metritis, and clinical endometritis), other health disorders (OTH: subclinical ketosis, left displaced abomasum, lameness, clinical mastitis, and respiratory disease), or healthy with no disease events within 40 DIM. The paper of Dr Manríquez and colleagues was published in the Journal of Dairy Science, Volume 104 of 2021, page 12785 to 12799, using the title: Effect of body condition change and health status during early lactation on performance and survival of Holstein cows.
Their data included lactation information from 11733 cows calving between November and October in 16 herds across four geographical regions in the United States. The cows were evaluated for BCS at 5 DIM (BCS5) and at 40 DIM (BCS40) and the difference between BCS40 and BCS5 was classified as excessive loss of BCS (EL = more than 0.75), moderate loss (ML = −0.5 to −0.25), no change (NC = 0), or gain in BCS (GN = more than 0.25).
The odds (likelihood) of resumption of ovarian cycling in GN, NC, and ML cows were 1.94, 1.59 and 1.27 times greater than the odds of ovarian cycling in EL cows, respectively. The odds of pregnancy at 150 DIM (P150) in GN cows were 1.61 times greater than the odds of P150 in EL cows. Cows with REP or OTH disorders had smaller odds of ovarian cycling compared with healthy cows with no disease events cows (REP = 0.65 and OTH: OR = 0.79). For pregnancy outcomes, REP cows had smaller odds of pregnancy at the first artificial insemination compared with healthy cows with no disease events (0.70). Similarly, REP cows had smaller odds of being diagnosed pregnant by 150 and 305 DIM compared with healthy cows with no disease events (P150 = 0.73; P305 = 0.58). Overall, average daily milk within the first 90 DIM was greater in EL (39.5 kg per day) and ML (38.9 kg per day) cows than in NC (37.8 kg per day) and GN (36.2 kg per day) cows. On the other hand, average daily milk within the first 90 DIM was lower in REP (37.0 kg per day) cows compared with OTH (38.7 } kg per day) and healthy cows with no disease events (38.6 kg per day).
In conclusion: Both a change in BCS and health status measured within 40 DIM influenced subsequent cow performance and survival. In general terms, excessive loss of BCS and reproductive diseases decreased reproductive performance and survival compared with other changes in BCS categories and health groups. Furthermore, excessive loss of BCS during the early post-calving period (40 DIM) was characterized as having higher milk yield. The magnitude of the changes in BCS and health statuses of early lactation cows should therefore be considered when assessing subsequent performance and survival.