A feeding study evaluated whether standard broiler diets prepared with grain derived from Syngenta Seeds NK Brand Bacillus thuringiensis (Bt) Corn hybrids had any adverse effects on male or female broiler chickens. Four kinds of corn grain were used in this study: (1) grain from the Bt-expressing field corn hybrid N7070Bt, (2) grain from the N7070Bt hybrid that had been sprayed with Liberty brand herbicide (glufosinate) according to manufacturer's instructions (N7070Bt + Liberty), (3) grain from standard N7070 (non-Bt isoline of N707OBt) grain, and (4) a lot of North Carolina grown grain from the 2000 growing season (NC2000). The amino acid balance for the four lots of corn was similar relative to their crude protein content; however, the NC2000 corn had higher protein content. Diets with the higher protein NC2000 season corn were amended with a combination of sand, ground cardboard (Solka Floc), and poultry fat so that the metabolizable energy and crude protein content of the diluted diets would be similar to that of the isoline and transgenic diets. Growth of broilers was excellent with males being significantly heavier than females (2,497 g vs. 2,103 g) at 42 d of age. BW of live birds at 42 d was within 26 g for the three treatment groups fed corn that was from the same genetic background, i.e., the two Bt transgenic groups (N7070Bt, N7070Bt + Liberty), and the non-Bt N7070 isoline corn group, while BW for the NC2000 group was significantly lower by 93 g. There was no overall corn source effect on feed conversion ratio (FCR) among the isoline and transgenic corn sources to 42 d of age, but FCR was poorer for broilers consuming the commercial NC2000 corn. There was no overall effect of corn source on survivability to 42 d. Carcass analysis at 48 d demonstrated no differences in percentage carcass yield due to corn source among males and females. The transgenic N7070Bt and N7070Bt + Liberty hybrid diets supported excellent broiler chicken growth with mortality and FCR that were similar to that supported by the N7070 isoline control and better than rates from the commercial NC2000 corn without significant differences among treatment groups in carcass yield. It was clear that the transgenic corn had no deleterious or unintended effects on production traits of broiler chickens in this study.

Commercial-level sow replacement rates were investigated for a 10-yr planning horizon using a stochastic life-cycle swine production model. A three-tiered breeding structure was modeled for the production of market hogs in a three-breed static crossing scheme. Growth and reproductive traits of individual pigs were simulated using genetic, environmental, and economic parameters. Culling was after a maximum of 1, 5, or 10 parities in commercial levels within 1- and 5-parity nucleus and 1-, 5-, and 10-parity multiplier combinations. Yearly changes and average phenotypic levels were computed for pig and sow performance and economic measures. For growth traits, greater commercial level response was for systems with higher sow replacement rates, 110 to 115% of lowest response. Phenotypic changes in net returns ranged from $.85 to 1.01 x pig-1 x yr-1. Average growth performances were highest for systems with greatest genetic trend. Highest kilograms.sow-1 x year-1 finished was for 10-parity commercial alternatives. System differences in total costs and returns per pig resulted primarily from differences in replacement costs. Removal of the gilt system from analyses often reduced ranges among systems for economic measures by more than 70%. Systems with the lowest commercial replacement rates were most profitable. Within these systems, those with higher genetic change had highest net returns. For high replacement rates, no more than 175% of market value could be paid for gilts, but with lower sow replacement rates commercial units could justify as much as 450%.

Sow replacement rates in a three-tiered breeding structure were investigated for a 10-yr planning horizon using a stochastic life-cycle swine production model. Market hogs were produced in a three-breed static crossing program and marketed on a liveweight basis. Growth and reproductive traits of individual pigs were simulated using genetic, environmental, and economic parameters. Sows were culled after a maximum of 1, 5, or 10 parities. Systems were defined by maximum sow age at culling and included combinations of 1- and 5-parity nucleus and 1-, 5-, and 10-parity multiplier and commercial tiers. Economic response to index selection was considerable for all culling alternatives with yearly increases in system profits ranging from $1.06 to 1.44 for each commercial hog marketed. When sows were culled after one parity in nucleus, multiplier, and commercial tiers, respectively (1,1,1), annual changes in net returns and all cost measures were 40 to 50% larger than responses in systems with lower sow replacement rates. Based on 10-yr averages for net returns, systems with low multiplier- and commercial-level replacement rates were more profitable than systems with higher replacement rates. The most profitable system (5,10,10) differed from the least profitable system (1,1,1) by more than $10 per pig, but when the (1,1,1) system was excluded, the range was only $3 per pig. The system with lowest replacement rates supported 3,388 more multiplier and 34,151 more commercial sows from a 750-sow nucleus level than the (1,1,1) system. Output from the two extremes differed by > 664,000 commercial market hogs sold.(ABSTRACT TRUNCATED AT 250 WORDS)