Relationship between average daily gain of heifers at various stages of rearing and milk production in the first and second lactation
Year: 2026
Type: article
Abstract: The study aimed to determine whether ADG of Holstein heifers at various stages of rearing affects first and second lactation performance. Data on BW of heifers were obtained from 3 independent dairy operators (operators A, B and C) and used to calculate ADG from birth until weaning (all operators), from weaning until 180 d of age (all operators), from 181 until 360 d of age (operators A and C), and from 361 until 410 d of age (operator A). Datasets included: 1,583 records for the first and 1,290 records for the second lactation for operator A; 886 records for the first and 664 records the second lactation for operator B; and 1,190 records for the first and 675 records for the second lactation for operator C. Subsequently, BW records were used to calculate ADG for each phase of rearing and used in a 2-step data analysis. In the first step, ADG was regressed against the first and second 305-d lactation milk yield, first and second 305-d lactation protein yield, and first and second 305-d lactation fat yield to test for a linear and quadratic relationship between those variables. In the second step, a statistical model was built that evaluated the linear and quadratic impact of ADG, year and season of birth, year and season of calving, calving age, and dam parity (primi- or multiparous) on first and second 305-d lactation milk, protein, and fat yield. In both steps of analysis, pedigree data were used to correct phenotypic values for genetic effect. With increasing ADG preweaning (step 1), the 305-d milk yield in first lactation increased linearly for operator A and C but not for operator B, whereas 305-d milk yield in the second lactation increased quadratically for operator A, linearly for operator C but no association was found for operator B. With increasing ADG from weaning until 180 d of age, the 305-d milk yield in first lactation increased linearly for all 3 operators, whereas in second lactation it increased linearly for operator B and C, but not for operator A. With increasing ADG from 181 until 360 d of age, the 305-d milk yield in the first lactation decreased linearly for operator A but no association was found for operator C. With increasing ADG from 361 until 410 d of age (operator A), the 305-d milk yield in the first lactation decreased linearly. When other effects were included in the statistical model (step 2), the association of ADG with 305-d milk yield in the first and second lactation found in step 1 of analysis often changed. This change included direction or shape of the relationship or its significance. Although some associations remained significant, the large variability around estimates suggests a substantial influence of effects that were unaccounted for in the analysis. Moreover, although with increasing ADG the 305-d milk yield increased, milk component yield in some instances decreased, or no association could be found. In summary, the relationship between ADG of heifers at different stages of growth and future milk and milk component yield differed substantially between operators, being either linear (both positive and negative), curvilinear, or not significant, which makes coming to clear conclusions difficult.
Source: Journal of Dairy Science
Language: English
Subfield: Genetics
Domain: Life Sciences
SDG: Zero hunger
Open Access status: gold
Estimated APC paid: $3,500
OpenAlex ID: W7148725613