Effect of Temperature-Humidity-Index on Milk Performances of Local Born Holstein Dairy Cows Under Saharan Climate

The objective is to study the effect of heat stress on milk yield (MY) relative to milking records (n=18178) of native Holsteins (n=187), in the region of Ghardaia, according to periods of HS, using the temperature-humidity index (THI). With THI >72 during 07 months in the study area, which significantly (P<0.001) decrease the MY (-15.5% corresponding to 21.73 kg). Also, calving periods led to a significant drop (P < 0.001) in overall MY (7030.35 kg) of the order of (-14.6%), and over the lactation length (353.43 d), which explains 41% of the variations in MY. In addition, the non-significant effect (P=0.212) of the lactation range on the increase in MY, moreover, the lactation length shows a non-significant (P = 0.108) decrease (-4.68%) during heat stress (HS). Furthermore, the significant effect (P <0.001) of the interaction (Milking frequency × THI) on MY, when THI variates from < 74 to > 84, with regression of (-16.82% and -08.82%) of the MF (2X and 3X), respectively. Again, the NH cow is less sensitive to hyperthermia, so THI explains only 2% of the variation in MY levels. Thus, NH in arid regions have the ability to acclimatize to Saharan environmental conditions.

Effect of the Milking Frequency on the Concentrations of Ammonia and Greenhouse Gases within an Open Dairy Barn in hot Climate Conditions

Knowledge of how different management strategies affect gas production from livestock buildings can be helpful for emission predicting purposes and for defining mitigation strategies. The objective of this study was to statistically assess whether and how measured concentrations of ammonia (NH3), methane (CH4) and carbon dioxide (CO2) were influenced by milking frequency. Concentrations of gases were measured continuously by using infrared photoacoustic spectroscopy in the breeding environment of an open dairy barn located in Sicily in hot climate conditions. Data were acquired by specific in-field experiments carried out in 2016 and 2018, when milking sessions occurred twice a day (2MSs) and three times a day (3MSs), respectively. The number of the milking cows was 64 in both 2MSs and 3MSs. The results showed that concentrations of NH3, CH4 and CO2 were statistically influenced by the number of milking sessions. From 2MSs to 3MSs, NH3 concentrations were enhanced (P < 0.001) due to the higher cow’s activity. Conversely, gas concentrations of CH4 and CO2 were lower for 3MSs compared to those for 2MSs due to the effect of the different feeding frequency. Overall, the milking frequency influenced barn management and cow behaviour by modifying the level of gas concentrations in the barn environment.

Genetic Parameters Estimation of Milking Traits in Polish Holstein-Friesians Based on Automatic Milking System Data

The automatic milking system (AMS) provides a large amount of information characterizing the course of each milking cow, which is not available in the conventional system. The aim of our study was to estimate heritability and genetic correlations for milk yield (MY), milking frequency (MF), and speed (MS) for 1713 Polish Holstein-Friesian primiparous cows milked in barns with an AMS. Daily heritability indicators estimated using second-order Legendre polynomials and Random Regression Models showed high variation during lactation, ranging 0.131–0.345 for MY, 0.153–0.322 for MF, and 0.336–0.493 for MS. The rates of genetic correlation between traits ranged: 0.561–0.929 for MY-MF, (−0.255)−0.090 for MF-MS, (−0.174)−0.020 for MY-MS. It is possible to carry out effective selection for milking speed, which provides an opportunity to increase the number of cows per milking robot, and thus increase the profitability of production in the herd. The results proved that selection for milk yield and daily milking frequency is also feasible. The research showed a high, positive genetic correlation between milking frequency and milk yield, which allows us to conclude that preferring breeding cows with a natural tendency to frequent visits to the milking robot should indirectly improve the genetic basis of milking.