Feed Efficiency and Physiological Parameters of Holstein and Crossbred Holstein × Simmental Cows.

This study aimed to compare the feed efficiency (FE) and physiological parameters of Holstein and crossbred Holstein × Simmental cows in a confinement system during winter and summer. The study was conducted in a dairy farm in southern Brazil by including a total of 48 multiparous cows. The cows were studied for 21 days in two periods, summer and winter, and their daily dry matter intake (DMI), milk yield (MY), rectal temperature (RT), respiratory rate (RR), body weight, and body condition score were recorded. An analysis of variance was conducted using the SAS statistical package. The results showed that crossbred Holstein × Simmental cows have a similar FE as Holstein cows in a high-production system (1.83 × 1.81 kg DMI/kg MY, respectively), and they can achieve the same production levels as purebred Holstein cows (43.8 vs. 44.5 milk/cow/day). Our findings indicated a difference for the period as both genetic groups achieved higher FE in winter than in summer (1.98 vs. 1.67 DMI/kg MY, respectively). In addition, we found evidence that crossbred cows are better at dissipating body heat during heat-stress situations, as they have higher RR in summer compared to purebred cows, while Holstein cows have higher RT in summer afternoons than crossbred cows. Therefore, using crossbred Holstein × Simmental cows is an alternative for high-production systems.

Rumination time, activity index, and productive performance of Holstein and crossbred Holstein × jersey cows exposed to different temperature-humidity indexes.

The aim of this study was to evaluate the rumination time, activity index, milk yield (MY), physicochemical milk characteristics, and physiological indicators of pure Holstein (H) and first (F1- ½ Holstein × Jersey) and second-generation (R1- ¾ Holstein × » Jersey) of crossbred cows in a pasture-based system under the influence of different temperature-humidity indexes (THI). Twenty-two multiparous cows (H = 7, F1 = 5, and R1 = 10) were evaluated throughout 1-year period. Daily information on rumination time and activity index was obtained using the software HealthyCow24® and the daily THI was determined from data logger information. Weekly, MY, physicochemical milk characteristics, body weight, body condition score, and physiological indicators were evaluated. THI were grouped into six classes from safe (< 68) to emergency (≥ 84). Variance analyses were performed. There was no interaction between the genetic group and THI classes for any trait. The rumination time was longer for crossbred R1 and F1 cows than for Holstein cows. The activity index increased, and rumination time decreased as the THI classes increased. There was no difference in MY between the genetic groups, but crossbred cows showed higher milk fat and protein content. Our study indicated that the high THI increases the activity index and decreases the rumination time, MY, and the physicochemical quality of milk, BW, BCS, RF, and RT of the three genetic groups (H, F1, and R1).

Evaluation of an electronic system for monitoring dairy cow rumination in a grazing-based system.

This research aimed to compare the rumination time estimated by an electronic monitoring system with direct visual observations of the rumination of dairy cows in a grazing-based system. Also, it aimed to estimate the agreement between different time intervals of the direct visual observations. To that end, we have observed twelve lactating cows for 16 h a day for 11 days. Then, we compared the data provided by the HealthyCow24® software with the visual observations to use as reference. After that, we estimated the Pearson's correlation coefficients, the linear regression, and the Bland-Altman plot by using the SAS software. Results showed that the rumination data estimated by the HealthyCow24® software and the visual observations were highly correlated (0.81; P < 0.0001). In the Bland-Altman analysis, we observed that the average of the standard deviations between the visual observation and the electronic monitoring system was - 2.14 min during a 2-h period. The upper limit (95%) was 30.61 min/2 h and the lower limit (95%) was - 34.88 min/2 h. Moreover, visual observations at intervals of up to 15 min were correlated with the data estimated by the electronic monitoring system and observed at 5-min intervals. In conclusion, the Allflex SCR electronic monitoring system is efficient in measuring the rumination time of grazing cows. Also, direct visual observations with intervals no longer than 15 min are reliable when used for evaluating the behavior of cows without losing data accuracy.

Reproductive and productive performance, udder health, and conformation traits of purebred Holstein, F1, and R1 crossbred Holstein × Simmental cows.

The objective of this study was to compare the reproductive performance, milk yield and composition, and udder health and conformation traits of Holstein (Ho), F1, and R1 crossbred Ho × Simmental (Sim) cows. Three commercial dairy farms in south Brazil were used as the research units. All farms held Ho, F1, and R1 crossbred Ho × Sim (¾ Ho × » Sim and ¾ Sim × » Ho) cows. The collection of milk samples and evaluation of udder conformation traits occurred during four visits to each farm. In addition to the actively collected data, retrospective reproduction records of the farms served as the basis for the statistical analysis using analysis of variance models using SAS. The F1 crossbred Ho × Sim cows and ¾ Sim (first rotational crossbreeding generation = R1 using Sim semen) cows had a shorter calving interval and calving to first service interval compared to the Ho cows (P < 0.0001). Milk yield did not differ among the genetic groups except for R1 (¾ Sim) that produced approximately 10% less milk than the other groups (P = 0.0245). Fat plus protein yield and somatic cell score did not differ among the genetic groups. Ho cows had shallower udders (P < 0.0001) and a higher udder clearance (P < 0.0001) than the other groups. F1 and R1 crossbred Ho × Sim cows had shorter reproduction intervals than purebred Ho cows. Although udder conformation traits lacked high-quality scores in crossbred cows, somatic cell scores reached the same level as in purebred Ho cows.