Assessment of the impacts of different factors on the occurrence of negative energy balance in Iranian dairy cows using a logistic generalised linear model

Feed intake of genetically high-producing cows decreases before parturition and, as a result, negative energy balance (NEB) is occurred. Negative energy balance is a part of normal physiology in the early lactation. However, this phenomenon has usually serious negative influences on production and health of dairy cows. The objective of the present research was to estimate the effects of some factors affecting the occurrence of negative energy balance in Iranian dairy cows.
Material and The data comprised 784,532 test day records belonging to 93,259 first-parity cows in 660 herds and calved between 2003 and 2013 were used. To investigate the probability of negative energy balance occurrence, a logistic generalized linear model using GLIMMIX of SAS statistical software was fitted to the data. In the model, factors of province (10 provinces), lactation stage (10 months), production season, first calving age (25 months) , sperm type of the sire (Iranian, Canadian and American), calving year (2003-2013), somatic cell count (SCC) in daily milk yield (200000), cow genotype (grade up to Holstein, purebred Holstein), milk yield at test day (covariable), within-herd variation for milk yield (high, low), and two-way interaction between stage of lactation and season of production were included. Using fat and protein content of test day milk records in each month of lactation, and with respect to threshold point of 0.12, binary dependent variable (0 and 1 codes for non-occurrence and occurrence of NEB, respectively) was defined.
All included factors, except first calving age, had significant effects on the occurrence of NEB (P200,000 as compared to the cows with SCC More utilisation of American sperms (along with providing nutrient requirements of high-producing cows), appropriate nutrition management in winter, optimized utilization of upgrade Holstein cows in breeding schemes, more attention to the cows at freshening, uniformity of milk production over the herd, and also providing suitable health and sanitation are useful recommendations to reduce NEB.