Trends in calving ages and calving intervals for Iranian Holsteins in Fars province,southern Iran

Purpose  

To determine trends in calving ages and calving interval as measures of reproductive performance in Iranian Holsteins in Fars province, southern Iran during 2000–2005.     

Effect of dietary digestible lysine level on growth performance,blood metabolites and meat quality of broilers 23–38 days of age

This study was done to evaluate the effects of different dietary digestible lysine (dig Lys) levels on growth performance, blood metabolites, carcass and breast yield, and breast meat quality of broilers 23–38 days of age. Three hundred 23-day-old Cobb-500 male broiler chickens were allocated to a completely randomized design with five treatments (finisher diet containing 0.88%, 0.94%, 1.00%, 1.06% and 1.12% dig Lys) and six replicates of 10 birds each. Feed intake (FI) was not affected by different dietary dig Lys levels. Weight gain (WG) linearly increased and feed conversion ratio (FCR) linearly decreased with an increasing dietary dig Lys levels. With increasing dietary dig Lys levels, carcass and breast yield and breast meat hue angle (h^*) linearly increased, but abdominal fat decreased quadratically, whereas breast meat lightness (L^*) and ether extract composition linearly decreased. Dietary dig Lys levels did not show any significant effect on serum metabolites, breast meat cooking loss and water holding capacity. Based on the linear broken-line regression models, the weight gain, feed conversion ratio and breast yield were optimized when dietary dig Lys levels were 0.95%, 1.01% and 1.02% respectively. It is concluded that Lys requirements vary according to what productive parameter is taken for optimization. A minimum of 1.02% dig Lys concentration in the finisher diet is suggested to optimize breast yield, feed efficiency and performance in broiler chickens.