The objective of this study was to investigate the effect of milking frequency (two times daily vs. three times daily) on the 305-d lactation milk, fat and protein yield and fat and protein percentage of Holstein dairy cows in Morocco. Data analyzed were 31400 records collected between 2009 and 2016 on 14272 cows raised in 194 herds. The frequency of milking had significant effects (P<0.05) on 305-d milk, fat and protein yield as well as fat percentage. The milk, fat and protein yield and fat percentage were higher by 265.1 kg, 13.3 kg, 5.8 kg, and 0.3 g/kg, respectively, i.e. 3,79%, 4.78%, 2.40%, and 0.75%, respectively, for cows milked thrice than those milked twice daily. However, the frequency of milking did not influence protein percentage (P>0.05). The interaction between parity and milking frequency was not significant (P>0.05) for any studied trait. Based on the results of this study, it can be concluded that increasing milking frequency increased milk, fat and protein yield as well as fat percentage regardless of parity. However, the additional milk yield obtained might not compensate for the cost of the labor generated by the extra milking. Manuscript profile

The study aimed to determine factors affecting the dry period length and effect of dry days on milk yield, milk composition and lactation length in the next lactation of dairy cows. Data used for analysis included 7264 lactation records collected from 2012 to 2016 on 4737 Holstein cows raised in 152 herds. The statistical model used to determine the factors influencing the dry period length showed that multiparous cows had a dry period 3.7 days longer than primiparous cows, and cows that calved from October to February had a dry period 2.5 days shorter than that of cows calved from March to September. The mixed model used to evaluate the influence of dry period on milk yield, milk composition and lactation length showed that the dry period influenced significantly milk yield and composition in the next 305 d lactation, but not the lactation length (P>0.05). Milk, fat and protein yields in the subsequent lactation were maximized with a 41 to 60-d dry period, whereas dry periods less than 20 d result in very pronounced losses in subsequent lactation yield. Fat and protein percentages were highest with the dry period classes greater than 80-d and less or equal than 20 d, respectively. The interaction between parity and dry length period was not significant (P>0.05) for any studied trait, indicating that dry days effects on milk yield and composition were consistent across lactations. It was concluded that dry period of 40 to 80 dry days does provide maximal performance in Holstein cows. Manuscript profile

The objective of this study was to determine the relationship between body weight (BW) and heart girth (HG) in Sardi and Timahdite sheep in order to develop a prediction equation of BW from HG. The data used for this study included 476 records on BW and HG (227 in Sardi and 249 in Timahdite) collected on males and females of different ages in 33 private farms. The BW and the HG averaged 34.8 ± 21.2 kg and 74.0 ± 16.3 cm, respectively in Sardi and 39.2 ± 22.7 kg and 78.4 ± 16.4 cm, respectively in Timahdite. Correlation coefficients between BW and HG were 0.958 in Sardi and 0.944 in Timahdite indicating a strong relationship between the two variables. Six predictive models for BW were fitted to the data; simple linear regression, polynomial quadratic and cubic regressions and three non-linear regressions (Gompertz, allometric and Mitscherlich). These models were used for the pooled data (regardless of breed and sex), separately for all the animals of a breed regardless of sex (breed-specific) and separately for males and females irrespective of breed (sex-specific). To determine the best fitted regression model, coefficient of determination (R2 or Pseudo-R2), residual mean square (MSE) and Akaike information criterion (AIC) were used. The six models fitted the dataset well since their R2 or Pseudo- R2 varied from 0.892 to 0.969. Nevertheless, based on the previous selection criteria, it seemed that the polynomial cubic model was the best and the allometric model should be discarded. Extreme observations of the three best models were checked using studentized residuals and an absolute value greater than two standard deviations implies considerable deviation. Once the outliers discarded, the best models were run on the clean dataset and compared. Thus, for the pooled data, Sardi breed and females, the Mitscherlich model was appropriate, whereas for Timahdite breed and males, cubic and Gompertz models, respectively were the best. Therefore, a tape measure was developed for each animal category in order to assist livestock farmers in managing their sheep better. Manuscript profile

The objectives of this study were to describe lactation curves for milk yield and composition using the Wood’s model and to estimate lactation curve characteristics. Data including 202 283 test-day records belonging to 27 108 first three lactations of Holstein cows recorded from 2012 to 2016 in a total of 193 herds were analyzed for milk yield, fat, protein, lactose, total solids (TS) and solids not fat (SNF) contents, as well as milk urea nitrogen (MUN) concentration and somatic cell score (SCS). The lactation curve and lactation parameters of interest were intercept (a) and curve shape (b and c) of the lactation curves, as well as the peak production (ym), the day at peak (tm) and persistency. The test-day averages milk yield, fat, protein, lactose, TS and SNF contents, as well as MUN and SCS were 24.4 ± 7.87 kg/day, 3.57 ± 0.78%, 3.04 ± 0.35%, 4.88 ± 0.26%, 12.2 ± 1.02%, 8.73 ± 0.39%, 15.8 ± 7.12 mg/dL and 4.37 ± 1.84 units, respectively. Standard lactation curve was the most frequent shape for milk yield (63.9%), lactose content (46.7%) and MUN (42.4%), while reversed standard was the most common shape for fat, protein, TS and SNF contents (59.4, 57.3, 57.8 and 54.0%, respectively) and for SCS (43.2%). The milk yield increased from calving to peak production of 28.2 kg/day that occurred 61 days from parturition and then decreased regularly to dry-off with a persistency of 6.87. The peak for lactose content and MUN concentration of 4.95% and 17.3 mg/dL, respectively was reached at lactation days 105 and 115 post-calving, respectively. Estimated minimum for fat, protein, TS, SNF percentages and SCS was attained at lactation days 100, 69, 83, 68 and 95, respectively with values 3.26%, 2.78%, 11.7%, 8.16% and 3.92, respectively. It was concluded that the knowledge of lactation curves for studied traits will help to improve herd management and to increase production. Manuscript profile