Bias of Calf Sex on Milk Yield and Fat Yield in Holstein Crossbreed Cows

Effects of assisted calving and retained fetal membranes on milk production in the smallholder farming system

The impact of assisted calving, retained fetal membranes (RFM) and calf sex on milk production in small-scale dairy systems remains unknown. This study evaluated their impact on early lactation milk production and standardized 305-day yield (305MY) using 279 lactation records from 23 farms over 18 months. Variables analyzed included assisted calving, RFM, calf sex, and lactation number, with milk production at 30 days and 305MY as response variables. General Linear Models were used for statistical analysis, with significance at P < 0.05, and trends at P < 0.1. Lactation number significantly affected early lactation milk production (P = 0.023), with RFM showing a trend toward significance (P = 0.078). Cows without RFM produced 21.8 ± 0.8 kg/day, while those with RFM produced 18.6 ± 1.7 kg/day. Assisted calving significantly affected 305MY (P < 0.05), with cows not requiring assistance having higher yields compared to those needing assistance. Interactions between assisted calving and lactation number (P = 0.099), as well as RFM and calf sex (P = 0.060), approached significance. In cows that did not require assisted calving, no significant differences in 305MY were found based on lactation number (P ≥ 0.05). However, in cows that required assisted calving, significant differences in 305MY (P < 0.05) were observed between first and third or higher lactations, with second-lactation cows having average values. Additionally, cows without RFM that gave birth to female calves had higher 305MY compared to cows with RFM or those that gave birth to male calves with RFM or without RFM. In conclusion, RFM reduces early lactation milk production by approximately 3.2 kg/day, and assisted calving impacts 305MY by about 1,069 kg/lactation.

The effect of two mineral-vitamin premixes on the blood biochemical parameters, milk yield and composition of Holstein-Friesian cows in Kazakhstan

The aim of this study was to determine the effect of two mineral-vitamin premixes on the health status (blood biochemical parameters), milk yield and composition of Holstein-Friesian (HF) cows in Kazakhstan. The study was performed on Holstein-Friesian cows kept on the Bek Plus dairy farm in the village of Korzhynkol, Fyodorovsky District, Kostanay Region. Forty primiparous cows, selected from the herd, were divided by the analogue method into two groups: a control group (C) and an experimental group (E) of 20 animals each. The diets fed to group E cows were supplemented with LI-R 18 PRO and PANTO® Mineral R-77 Premium mineral-vitamin premixes. The premixes positively affected cow productivity and blood biochemical parameters, whose values were higher in group E than in group C. Higher levels of glucose, albumins and globulins exerted a beneficial influence on the health status of cows. No cases of lameness or metabolic diseases were recorded in group E. The yields of milk, protein and fat were higher in group E than in group C. Dietary supplementation with two premixes had no significant effect on the chemical composition of milk, including the values of the following parameters: somatic cell count (SCC), dry matter (DM), lactose (L se ), casein (C in ), acidity (A ty ), lactic acid (LA), density (D ty ) , free fatty acids (FFAs), glucose (G se ) and urea (U ea ).

Genetic Parameters for Functional Longevity, Type Traits, and Production in the Serbian Holstein

In this study, the authors focused on the evaluation of the genetic parameters of longevity, milk yield traits, and type traits in dairy cattle populations in the Republic of Serbia. The total dataset used consisted of production records and pedigree data for 32,512 Holstein cows that calved from 1981 to 2015. The animal model was applied to determine the variance and covariance components and genetic parameters of the analyzed traits by applying the restricted maximum likelihood (REML) approach and using the programs VCE6 and PEST. The heritability of longevity traits was estimated using the Survival Kit V6.0 software package. Variance and covariance were estimated for five production traits: milk yield (MY), fat yield (FY), protein yield (PY), milk fat content (MC), and protein content (PC), and three longevity traits: length of productive life (LPL), lifetime milk yield (LMY), and the number of lactations achieved (NL) as well as for 18 standard type traits. Heritabilities for the milk, fat, and protein yield traits were 0.20 (MY), 0.15 (FY), and 0.19 (PY), respectively. The estimated coefficients of heritability for the longevity traits were higher when using the Weibull proportional hazards model compared to the traditional linear methods and ranged from 0.08 for NL to 0.10 for LPL. Heritability values for the type traits varied from a low of 0.10 (RLSsv-rear legs set-side view) to medium values of 0.32 (ST-stature). Genetic correlations were found between MY and the following longevity traits: LPL, LMY, and NL with values of -0.18, -0.11, and -0.09, respectively. Genetic correlations were found between MY and a number of linear type traits and varied from 0.02 (between MY and RUH-rear udder height) to 0.28 (between MY and FUA-fore udder attachment). Genetic correlations between the 18 investigated type traits ranged from -0.33 between TL (top line) and RTP (rear teats position) to 0.71 between AN (angularity) and RUH (rear udder height). Genetic correlations between most linear type traits and longevity traits (LPL, LMY, and NL) were generally negative and very low. The highest positive genetic correlation was found between UD and LPL (r_xy = 0.38).