Work

Exploring how milk production, body weight and body condition dynamics affect reproductive success after artificial insemination in dairy goats

Year: 2024

Type: article

Abstract: In the context of agroecological transition, breeding females with good reproductive ability, and therefore an increased number of successive lactations, is of great interest for farmers. This implies to better understand the variability of reproductive success, based on the dynamic interplay of biological functions such as body reserves, lactation, and reproduction. The objective of the study was to assess the relationship between artificial insemination (AI) success and phenotypic lactation curves used as proxies of biological functions. Data came from two French experimental farms breeding Alpine and Saanen goats. Milk yield (MY), body weight (BW) and sternal body condition score (BCS_S) data were recorded over the period 1996-2021. These time series data, at the lactation scale, were fitted with different models adapted to the data frequency to characterize their dynamics and further determine clusters of profiles. This overall methodological approach allowed the characterization of each phenotypic lactation curve (MY, BW and BCS_S) with three levels of increasing details: cluster membership, synthetic indicators and model parameters. According to data availability and these different levels of detail, three different data subsets were considered to investigate the link between phenotypic lactation curves and reproductive success. The first data set contained 638 lactations that had all information for MY, for BW and for BCS_S. The second data set contained 1359 lactations that had all information for MY and BW. The third data set was split into data sets that contained 1731 lactations for MY and 795 lactations for BCS_S. Mixed logistic regression with year as a random effect were performed to analyze the relationship between AI success and (1) cluster of phenotypic lactation curves membership, (2) synthetic indicators of phenotypic lactation curves (3) parameters of the fitted model to individual phenotypic lactation curves. Goats were inseminated 208.1 ± 11.0 days after kidding and fertility at AI was 67.1 ± 0.5 %. Among known factors affecting AI success, only parity and lactation stage at AI were related to AI (p<0.05). For primiparous, AI success was affected by MY clusters (p<0.05). For multiparous, MY clusters and BCS_S clusters were not related to AI success. Moreover, AI success was affected by some synthetic indicators such as: persistency (p<0.001) and repletion speed of BW (p<0.001). These three complementary approaches on MY showed that the shape of the lactation curve played more on AI success than the level of milk production.

Source: Theriogenology

DOI: 10.1016/j.theriogenology.2024.12.005

Authors: N. Gafsi, O. Martin, F. Bidan, B. Grimard, L. Puillet