Influence of nutritional factors on productivity and egg quality in commercial brown laying hens

Resumen

The general aim of this PhD Thesis was to study the influence of different nutritional factors on the productivity and egg quality of commercial brown laying hens. The influence of methionine (MET), linoleic acid (LIN), and supplemental fat (SFAT), Ca level and source, and cereal type, and mean particle size (MPS) of the cereal, were studied. To reach these goals, three experiments (four trials) were carried out. In experiment 1, 2 trials were conducted to study the effect of reducing the MET (0.36 vs. 0.31%), LIN (1.60 vs. 1.12%), and SFAT (3.0 vs. 1.1%) content of isoenergetic diets on productive performance and egg quality of brown egg-laying hens late in the production cycle. There were 8 treatments arranged factorially (2x2x2) with 6 replicates of 20 hens per treatment (Hy-Line, from 59 to 70 wk of age in trial 1 and Lohmann, from 56 to 75 wk of age in trial 2). Except for SFAT, dietary treatment had little effect on laying hen performance and egg quality. The only effect observed of a reduction in MET content on hen performance was the decrease in the percentage of large and extra large eggs (79.8 vs. 85.9%; P < 0.05) from 60 to 67 wk of age in trial 2. A decrease in the level of SFAT reduced egg production (79.3 vs. 77.0%; P < 0.05), egg weight (66.3 vs. 64.9g; P < 0.001), egg mass (52.5 vs. 49.8 g/d; P < 0.001), feed conversion ratio (2.26 vs. 2.36 kg feed/kg eggs; P < 0.001), and percentage of extra large eggs (13.1 vs. 8.2%; P < 0.05) in trial 1 but no significant differences were detected in trial 2. Reducing the LIN content of the diet from 1.60 to 1.12% did not affect any trait in any of the two trials. We conclude that reducing the level of SFAT from 3.0 to 1.1% might decrease productivity and reduced slightly the commercial value of eggs. However, a reduction of the MET level from 0.36 to 0.31% and of LIN from 1.60 to 1.12% did not affect any trait in hens late in the production cycle. Eggshell quality was not affected by any of the dietary treatments. In experiment 2, a total of 1,152 Lohmann Brown laying hens was used to study the influence of level (3.5 and 4.0%) and source (coded FIN, COA, and OYS) of Ca of the diet on productive performance, egg quality, and tibiae characteristics from 58 to 73 wk of age. The FIN diet contained all the calcium carbonate as fine limestone (LIM). In the COA and OYS diets, 40% of the fine LIM was substituted by either coarse LIM or oyster shell. Each treatment was replicated 8 times (24 hens). Productive performance and egg quality traits were recorded every 4 wk and tibiae characteristics and shell quality traits were determined at 73 wk of age. An increase in Ca intake from 4.08 to 4.64 g/hen/d improved egg production (71.2 vs. 74.9%; P < 0.001), egg mass (49.0 vs. 51.4 g; P < 0.05), and feed conversion ratio (2.43 vs. 2.30 kg feed/kg egg; P < 0.001). Also, an increase in Ca intake improved shell weight (9.98 vs. 10.20%; P < 0.05), shell thickness (0.342 vs. 0.351 mm; P < 0.01), and shell density (82.0 vs. 83.8 mg/cm2; P < 0.001). Source of Ca had no effect on productive performance, tibiae characteristics, or egg quality except for shell density that was higher for hens fed COA than for hens fed FIN with hens fed OYS being intermediate (81.9 vs. 84.0 vs. 82.7 mg/cm2, respectively; P < 0.05). It is concluded that brown egg-laying hens in late phase of production require more than 3.5% Ca in the diet (4.08 g Ca/hen/d) and that the substitution of 40% of fine LIM by coarse LIM or oyster shell does not affect productive performance and has little impact on shell quality and tibiae characteristics. In the experiment 3, a total of 960 Lohmann Brown laying hens was used to study the effect of the main cereal of the diet and mean particle size (MPS) of the cereal on productive performance and egg quality from 20 to 48 wk of age. The experimental design was completely at random with 6 treatments arranged factorially with 2 cereals (corn vs. hard wheat) and 3 MPS of the cereal (hammer milled to pass through a 6-, 8- or 10-mm screen). Each treatment was replicated 8 times (20 hens per replicate). All diets were formulated to be isonutritive and contained 50% of either corn or hard wheat. Productive traits were recorded every 4 wk and egg quality was measured at 48 wk of age. The only significant effect detected was for feed intake (P < 0.05) that was greater for hens fed coarse ground cereals (10-mm) than for lens fed medium and fine ground cereals (8- or 6-mm). Also, hens fed corn had higher proportion of large and extra large eggs (> 63 g) from 45 to 48 weeks of age than hens fed hard wheat (84.5 vs. 79.4%; P < 0.05) but no differences were detected in any other period. Dietary treatment did not affect :he percentage of broken and shell-less and dirty eggs, percentage of shell, yolk, or albumen of the egg, or albumen and shell quality. We conclude that neither type of cereal nor MPS affected productive performance or egg quality of young brown hens, except for feed intake that increased with the coarser particle size.