1. Since high concentrations of zinc are associated with reduced crop yields, environmental concerns are emerging regarding zinc accumulation in areas where poultry production is prevalent. This study investigates growth performance and zinc utilisation during the life cycle of broilers when diets were supplemented with various concentrations of zinc from two different sources. 2. A total of 740 Cobb 500 1-d-old male broiler chicks was randomly distributed into 88 battery cages. Excreta were collected over a 48-h period on d 10, 17, 24, 31, 38, and 45 to measure zinc excretion on a dry matter basis. 3. During the 45-d experimental period, broilers were given a maize-soybean meal basal diet (30 mg/kg zinc) supplemented with 0, 20, 40, and 80 mg/kg of zinc from zinc sulphate, Availa Zn amino acid complex, or an equal combination of zinc sulphate and Availa Zn amino acid complex. 4. Progressive additions of zinc to the basal diet significantly increased body weight gain of broilers, but did not affect feed conversion or mortality. Optimum body weight gain was achieved at 80 mg/kg supplemental zinc, which exceeds the NRC recommendations of 40 mg/kg. 5. During each excreta collection period, increased supplemental zinc concentrations significantly increased zinc excretion. However, the zinc source did not influence zinc utilisation. 6. As compared with zinc sulphate supplementation, the cumulative zinc excretion data indicate that adding zinc to the basal diet in the form of Availa Zn amino acid complex decreased zinc excretion.
Broiler breeder hens are typically provided a restricted amount of feed once a day. This feed is rapidly consumed; therefore, the hens fast for an extended period of time before their next feeding. In the current research, the effects on reproductive performance of implementing a twice-a-day vs. a once-a-day feeding program after photostimulation were investigated. Pullets and cockerels were reared on a skip-a-day feeding program. Pullets were weighed at 20 wk of age and then distributed into 30 laying pens such that each pen had a similar BW distribution. Each individual laying pen consisted of 35 hens and 4 roosters. At 21 wk of age, the birds were photostimulated for reproduction and 15 of the laying pens were placed on a once-a-day feeding schedule, whereas the other 15 pens were placed on a twice-a-day feeding schedule. The total amount of feed provided per day to all the laying pens was the same. Birds fed once a day received all their feed at 0630 h, whereas birds fed twice a day received 60% of their total feed allotment at 0630 h and the other 40% at 1500 h. Even though both treatment groups began egg production at the end of wk 23, birds fed twice a day laid more (P < or = 0.05) eggs through 42 wk of age than those fed once a day. Additionally, the average egg weight for the entire production period, which lasted until the birds were 60 wk of age, was greater for hens fed twice a day. Overall BW uniformity for the entire experiment was significantly better for hens fed twice a day vs. once a day. However, cumulative mortality was significantly higher for hens fed twice a day than for those fed once a day. The results indicate that feeding broiler breeder hens twice a day after photostimulation may enhance reproductive performance during the early lay period.
1. Environmental accumulation of zinc and copper is becoming a concern in areas having intensive animal production. This study examined performance and excretion of broiler chicks given diets supplemented with graded concentrations of zinc and copper from three different sources. 2. Two experiments were conducted, each utilising 570 1-d-old chicks. In Experiment 1, chicks were given diets containing supplemental zinc concentrations from 40 to 120 mg/kg supplied as zinc sulphate, a zinc amino acid complex (Availa Zn), or a combination of zinc sulphate and Availa Zn with each contributing one-half of the total supplemental zinc. In Experiment 2, broiler chicks were given diets with graded concentrations of supplemental copper ranging from 4 to 12 mg/kg from copper sulphate, a copper amino acid complex (Availa Cu), or a combination of copper sulphate and Availa Cu with each contributing one-half of the total supplemental copper. 3. During the 17-d experimental period, mineral concentration or source did not influence body weight, feed conversion, or the incidence of mortality from 1 to 17 d. 4. Decreasing dietary zinc concentration from 120 to 40 mg/kg reduced zinc excretion by 50%. 5. Copper excretion was decreased by 35% as supplemental copper was reduced from 12 to 4 mg/kg. 6. Reducing dietary zinc and copper concentrations can potentially decrease the accumulation of heavy metals in the environment without compromising bird performance.
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