The relationship between body condition and the inter calving period in milking cow - a two year study

Abstract

The aim of this work was to evaluate, in French beef breeds relationships which exist between body condition of cows in the winter period and success in reproduction measured by the duration between two successive calving periods (CI). A total of 57 herds were studied in 12 departments, 9 representing Charolais regions and 3 representing Limousin regions. 15 techniciens were trained for the study. Individual measurements, which were taken from 2338 cows in the first year and 2378 cows in the second year, mainly concerned body condition (scores at the beginning and at the end of the stalling period), together with calving date and conditions. The initial average score was 2.33 for the Charolais group and slightly superior (+ 0.2 point ; p < 0.01) for the Limousine breed. The scores attributed to primiparous cows were higher than those for the multiparous cows (+ 0.3 point). Thin females which scored 1.5, or less, represented 8.8 % of Charolais cattle and 13.8 % of Limousine cattle. The average loss of scores throughout winter appeared very small, only 0.33 point for the totality of the Charolais sample and 0.23 for the Limousine cattle. This loss of condition corresponds to a mobilisation of body reserves in the order of 20 kg during the winter period. However, a relationship exists between the variation in condition during winter and initial condition. If the cows have a greater fat content at the beginning of winter then they loose more fat during the winter period. Multiparous thin cows which scored less than 2.0 in November-December increasedtheir score by 0.8 point during winter for each point less scored in the initial period. Conversely, those which scored more than 2.5 lost 0.3 point for each additional condition score point. No variation was found for an initial score of 1.8. During the two year study period, the average CI in multiparous cows was 364 days for both breeds. It was approximately 3 weeks greater in primiparous cows. Advancing the calving date by 5 days results in a subsequent prolongation of 2 days of the CI in primiparous cattle and by 1 day in multiparous cattle, without any noticable difference between the two breeds. CI depends on the score at the beginning of winter for primiparous cattle and/or young cows which calve early, up to mid-February. For a score of slightly less than 2.5 points, CI increases by close to 30 days for each point less ; from 3.5 to 2.5 points it decreases by 10 days and for greater than 3.5 points, body condition is no longer important as other factors take priority. CI of multiparous cows depends on both the score at the end of winter and the degree in the loss of condition, that is to say their feed assessment. When calving dates are retarded to the end of March from January, the score effect falls to below a threshold which decreases from 3.0 to 1.5. For each decrease of one point, CI increases from 5 to 15 days, and to an even greater extent when the feed assessment is poor and the cow is young. These observed thresholds and variations should be confirmed by other studies of this type under different environmental conditions.