Optimal Age at First Calving in Pasture-Based Dairy Systems

Abstract

The age at first calving (AFC) is one of the most used indicators to evaluate the efficiency of rearing systems in dairy herds. The objective of the present study was to evaluate the association between AFC and different parameters of productive and reproductive efficiency in dairy cows of Holstein and Jersey breeds and their crosses, reared under pasture-based conditions. A retrospective longitudinal study was carried out with information on the performance of 77,311 cows with birth and culling dates between 1990 and 2016 from 654 specialized dairy herds located in mid and high-altitude regions of Costa Rica. Cows were classified into five classes according to their age in months at first calving (≤24, 25–27, 28–30, 31–33, ≥34). A generalized linear mixed model was used to assess the effect of AFC and breed factors on milk production (first lactation, lifetime total, and per day of life), open period (first calving and lifetime total), and herd life. The mean AFC was 29.5, 29.1, and 28.0 months for Holstein, Holstein × Jersey, and Jersey, respectively. The AFC was significantly associated (p < 0.01) with all the variables evaluated. Cows with AFC ≤ 24 presented a higher (p < 0.01) milk production (total lifetime and per day of life), as well as a longer herd life, compared to cows in classes of AFC > 28 m. The reduction in AFC contributes to a significant increase in the production and reproduction efficiency of pasture-based dairy herds. This effect was consistent across the three breed groups.

Lifetime milk production of Holstein cattle in the humid tropics compared to Holstein‐Gyr and Holstein‐Brahman crosses

“…Under these conditions, calving-conception intervals are above 140 days (Vargas-Leitón & José Romero-Zúñiga, 2010). This is consistent with the estimated reduction of 0.4% in the pregnancy rate at first service observed during the last three decades for the Holstein cattle (Vargas-Leitón et al, 2023). Likewise, a decrease of 0.4 kg in daily milk yield for each 1% increase in the Temperature Humidity Index (THI) has been reported locally for Holsteins (Ruiz-Jaramillo et al, 2019).…”

“…However, selection for milk production per cow has resulted in a higher proportion of nutrient intake directed towards production at the expense of maintaining an adequate energy balance, thus negatively affecting animal health and fertility (Madalena, 2008). In contrast, under semi-intensive pasture-based production systems common in tropical and subtropical regions, the performance of specialized dairy cattle suffers from several adverse factors, such as high temperature and humidity, variability in diet composition, long walks on hilly roads, and increased exposure to pests and infectious diseases (Vargas-Leitón et al, 2023).…”

The Season and Decade of Birth Affect Dairy Cow Longevity

“…In this sense, it is relevant to highlight that the use of high volumes of data from Dairy Herd Improvement Databases to calculate longevity metrics is not easily found in the literature. To our knowledge, it only has been used in the Latin American context by Cedeño and Vargas [13] for LPL and Vargas-Leiton et al for AFC [21] and, for the first time in South America, in this study for HL and LPL.…”