Authors : C. Darej, N. Moujahed, H. Hammami, A. Gillon and N. Gengler
Abstract: Lactation curve traits were determined for Holstein-Friesian cows in five dairy bovine farms in Tunisia two public farms and three Cooperative Units of Agricultural Production (UCPA) using Wood’s incomplete gamma function to lactation records by non-linear regression in 1967 model. A total of 49950 test day records during the period between 1997 and 2007 were used in the analysis. Six types of basal ration were identified in these farms (distributed during 1 month minimum) on the base of the roughages used in the basal ration (R1: Concentrate (CC) + Dry Forages (DF)+Silage (S); R2: CC+DF+S+Sugar Beet Pulp (SBP); R3: CC+DF+S+Summer Green Forages (SGF) R4: CC+DF+S+Spring Green Forages (SPGF); R5: CC+DF+S+SPGF+SP; R6: CC+DF+S+SPGF. The parameters of Wood model (a is the estimation of initial milk yield, b and c are respectively the increasing and the decreasing slopes of the curve) were estimated. The model included herd x year, herd x month, DIM x age x season of calving as fixed effects, herd x test day as random effect and random regression coefficients for animal herd x parity, herd x year, herd x year and ration effects which were defined as modified quadratic Legendre coefficients. Results suggested peak milk yield increased from 18.7-20.92 kg and 22.92, respectively from the first lactation to the second and the third. However, the highest persistency was observed in the first lactation. The R2 type rations including the sugar beet pulp, presented late peak milk and allowed high peak milk yield production while this ration allows a low persistency.
C. Darej, N. Moujahed, H. Hammami, A. Gillon and N. Gengler, 2012. Influence of Types of Ration on Modeling of Lactation Curves in Tunisia. Research Journal of Dairy Sciences, 6: 8-14.