L. Mejia

Dietary influence of digestible lysine concentration on Cobb 500 hen broiler breeder reproductive performance.

A study was conducted to examine the reproductive parameters of Cobb 500 broiler breeder hens fed 2 different types of diets varying in digestible lysine concentration. In total, 240 Cobb 500 broiler breeder pullets were placed in individual cages and given experimental diets from 35 to 45 wk of age. Treatments 1 and 2 were diets formulated using only commercially available feed ingredients and consisted of digestible lysine intakes of 1,200 (IDL) and 1,010 mg/hen per day (ID). Treatments 3 and 4 consisted of semipurified diets with the inclusion of l-glutamic acid to maintain isonitrogenous conditions with digestible lysine intakes of 1,010 (SPL) and 600 mg/hen per day (SP). Hens fed the SPL and SP diets had lower hen-day egg production than hens fed the ID diet, with hens receiving the IDL diet yielding intermediate values. Hens fed the SP diet had the lowest (P < 0.05) egg weight, but no differences were observed among dietary treatments for egg specific gravity. Fertility and hatchability of eggs set were lowest (P < 0.05) for hens fed the SPL dietary treatment. No differences were observed for early and middle embryonic mortality, contaminated, or pipped eggs. Late embryonic mortality was observed to be higher (P < 0.05) in hens fed the SP diet. A decrease in the daily intake of digestible lysine appeared to improve broiler breeder reproductive performance when hens were fed a semipurified diet. In contrast, the same effect was not observed when hens were fed a standard industry-type diet that contained less lysine.

Evaluation of carryover effects of dietary lysine intake by Cobb 500 broiler breeder hens

Two experiments were conducted to examine the progeny performance of broiler breeder (BB) hens fed diets differing in digestible lysine (dLys). A total of 240 Cobb 500 BB pullets and 40 cockerels, 20 wk of age, were used for each of 2 experiments. In experiment 1, treatment diets were fed from 35 to 45 wk of age. Treatment 1 and 2 diets were formulated with common feed ingredients and BB had dLys daily intakes of 1,200 (IDL-1,200) and 1,010 mg/hen per d (ID-1,010), respectively. Treatments 3 and 4 were composed of semipurified diets formulated to dLys intakes of 1,010 (SPL-1,010) and 600 mg/hen per d (SP-600), respectively. In experiment 1, chick weight at hatch was lower (P < 0.05) for those that came from the SP-600 and SPL-1,010-fed hens, but 42 and 56 d BW was similar for all treatments. Improvements (P < 0.10) in feed conversion ratio were seen at 42 and 56 d for chicks from ID-1,010-fed hens compared with IDL-1,200 hens. For experiment 2, diets were fed to BB hens from 24 to 42 wk of age. Treatment 1 was composed of corn-soybean meal and formulated to a dLys intake of 1,000 mg/hen per d (CS-1,000). Treatments 2, 3, and 4 had inclusion of 25% distillers dried grains with solubles (DDGS) with dLys intake levels of 1,000 (DDGS-1,000), 800 (DDGS-800), and 600 (DDGS-600) mg/hen per d, respectively. Progeny performance was evaluated from eggs collected at wk 26, 31, and 36. Chick hatch weight was similar for all 3 hatches. Chicks from 26-wk-old BB hens and fed DDGS-600 diets resulted in lower (P < 0.05) BW, carcass weight, and breast weight, and higher (P < 0.05) back half (drumsticks and thighs) yield, at 42 d of age. Growout studies performed on eggs laid during wk 31 and 36 revealed no effect on growth or carcass parameters. In conclusion, the results from experiments 1 and 2 may not be comparable, and therefore, the impact on progeny performance needs to be further evaluated.