Seasonal variations in milk production and fertility in Holstein cows in dairy herds located in the desert

Abstract

The objective of this study was to evaluate annual seasonal trends in milk production and fertility in Holstein cows. Between 8 and 15 dairy herds were analyzed annually in the Comarca Lagunera region of Mexico during the period 2002–2022. In this region, the average daily ambient temperature exceeds 33°C during the summer. Records were obtained at the end of the month in each herd using commercial software. Milk production is the daily average in liters per cow for each month, and fertility is the percentage of pregnant cows at first AI. Generalized Estimating Equations were used, with inter- and intra-subject effects (herd, year, month, and interaction) with a normal distribution with an identity link function and the first-order autoregressive correlation structure. In addition, a simple linear regression model was applied with year as a covariate and a generalized linear model was used to evaluate monthly variations. Milk production and fertility showed seasonal variations; In the summer (June-August), minimum values were recorded for milk production (95% CI: 28.2-28.9 L/cow/day) and fertility (95% CI: 18.4-19.9%). In the winter (December-February), milk production registered maximum values (95% CI: 31.3-32.1 L/cow/day) and fertility increased (95% CI: 34.8-36.3%). Fertility increased in winter. Integrated dairy herd management and genetics influenced the increases in milk production and fertility.