The influence of AME(n) concentration of the diet on productive performance and egg quality traits was studied in Hy-Line brown egg-laying hens differing in initial BW from 24 to 59 wk of age. Eight treatments were arranged factorially with 4 diets varying in energy content (2,650, 2,750, 2,850, and 2,950 kcal of AME(n)/kg) and 2 initial BW of the hens (1,733 vs. 1,606 g). Each treatment was replicated 5 times (13 hens per replicate), and all diets had similar nutrient content per unit of energy. No interactions between energy content of the diet and initial BW of the hens were detected for any trait. An increase in energy concentration of the diet increased (linear, P < 0.05; quadratic P < 0.05) egg production, egg mass, energy efficiency (kcal of AME(n)/g of egg), and BW gain (P < 0.05) but decreased ADFI (linear, P < 0.001) and feed conversion ratio per kilogram of eggs (linear, P < 0.01; quadratic P < 0.01). An increase in energy content of the diet reduced Haugh units and the proportion of shell in the egg (P < 0.01). Feed intake (114.6 vs. 111.1 g/hen per day), AME(n) intake (321 vs. 311 kcal/hen per day), egg weight (64.2 vs. 63.0 g), and egg mass (58.5 vs. 57.0 g) were higher for the heavier than for the lighter hens (P < 0.01), but feed conversion ratio per kilogram of eggs and energy efficiency were not affected. Eggs from the heavier hens had a higher proportion of yolk and lower proportion of albumen (P < 0.01) and shell (P < 0.05) than eggs from the lighter hens. Consequently, the yolk-to-albumen ratio was higher (P < 0.001) for the heavier hens. It is concluded that brown egg-laying hens respond with increases in egg production and egg mass to increases in AME(n) concentration of the diet up to 2,850 kcal/kg. Heavy hens had higher feed intake and produced heavier eggs and more egg mass than light hens. However, feed and energy efficiency were better for the lighter hens.

White striping (WS) is a major problem affecting the broiler industry. Fillets affected by this myopathy present pathologies that compromise the quality of the meat, and most importantly, make the fillets more prone to rejection by the consumer. The exact etiology is still unknown, which is why a metabolomics analysis was performed on breast samples of broilers. The overall objective was to identify biological pathways involved in the pathogenesis of WS. The analysis was performed on a total of 51 muscle samples and distinction was made between normal (n = 19), moderately affected (n = 24) and severely affected (n = 8) breast fillets. Samples were analyzed using gas chromatographic mass spectral analysis and liquid chromatography quadrupole time-of-flight mass spectrometry. Data were subsequently standardized, normalized and analyzed using various multivariate statistical procedures. Metabolomics allowed for the identification of several pathways that were altered in white striped breast fillets. The tricarboxylic acid cycle exhibited opposing directionalities. This is described in literature as the backflux and enables the TCA cycle to produce high-energy phosphates through matrix-level phosphorylation and, therefore, produce energy under conditions of hypoxia. Mitochondrial fatty acid oxidation was limited due to disturbances in especially cis-5–14:1 carnitine (log2 FC of 2, P < 0.01). Because of this, accumulation of harmful fatty acids took place, especially long-chain ones, which damages cell structures. Conversion of arginine to citrulline increased presumably to produce nitric oxide, which enhances blood flow under conditions of hypoxia. Nitric oxide however also increases oxidative damage. Increases in taurine (log2 FC of 1.2, P < 0.05) suggests stabilization of the sarcolemma under hypoxic conditions. Lastly, organic osmolytes (sorbitol, taurine, and alanine) increased (P < 0.05) in severely affected birds; likely this disrupts cell volume maintenance. Based on the results of this study, hypoxia was the most likely cause/initiator of WS in broilers. We speculate that birds suffering from WS have a vascular support system in muscle that is borderline adequate to support growth, but triggers like activity results in local hypoxia that damages tissue.

The effects of fiber inclusion, feed form, and energy concentration of the diet on the growth performance of pullets from hatching to 5 wk age were studied in 2 experiments. In Experiment 1, there was a control diet based on cereals and soybean meal, and 6 extra diets that included 2 or 4% of cereal straw, sugar beet pulp (SBP), or sunflower hulls (SFHs) at the expense (wt/wt) of the whole control diet. From hatching to 5 wk age fiber inclusion increased (P<0.05) ADG and ADFI, and improved (P<0.05) energy efficiency (EnE; kcal AMEn/g ADG), but body weight (BW) uniformity was not affected. Pullets fed SFH tended to have higher ADG than pullets fed SBP (P=0.072) with pullets fed straw being intermediate. The feed conversion ratio (FCR) was better (P<0.05) with 2% than with 4% fiber inclusion. In Experiment 2, 10 diets were arranged as a 2×5 factorial with 2 feed forms (mash vs. crumbles) and 5 levels of AMEn (2,850, 2,900, 2,950, 3,000, and 3,050 kcal/kg). Pullets fed crumbles were heavier and had better FCR than pullets fed mash (P<0.001). An increase in the energy content of the crumble diets reduced ADFI and improved FCR linearly, but no effects were detected with the mash diets (P<0.01 and P<0.05 for the interactions). Feeding crumbles tended to improve BW uniformity at 5 wk age (P=0.077) but no effects were detected with increases in energy concentration of the diet. In summary, the inclusion of moderate amounts of fiber in the diet improves pullet performance from hatching to 5 wk age. The response of pullets to increases in energy content of the diet depends on feed form with a decrease in feed intake when fed crumbles but no changes when fed mash. Feeding crumbles might be preferred to feeding mash in pullets from hatching to 5 wk age.

A trial was conducted to study the influence of CP and fat content of the diet on performance and egg quality traits of brown egg-laying hens from 22 to 50 wk of age. The experiment was conducted as a completely randomized design with 8 treatments arranged factorially with 4 diets and 2 initial BW of the hens (1,592 vs. 1,860 g). Three of these diets differed in the CP content (16.5, 17.5, and 18.5%) and included 1.8% added fat. The fourth diet also had 18.5% CP but was supplemented with 3.6% fat instead of 1.8% fat. Each treatment was replicated 4 times, and the experimental unit consisted of 21 hens allocated into groups of 7 in 3 adjacent cages. All diets were isocaloric (2,750 kcal of AME/kg) and met the recommendations of brown egg-laying hens for digestible Arg, Ile, Lys, Met, Thr, Trp, TSAA, and Val. Productive performance and egg quality were recorded by replicate every 28 d. For the entire experimental period, diet did not affect any of the productive performance traits studied, but the heavier hens had higher ADFI (120.6 vs. 113.9 g; P < 0.001), egg production (92.5 vs. 89.8%; P < 0.01), and egg weight (64.9 vs. 62.4 g; P < 0.001) than the lighter hens. Initial BW did not affect feed conversion per kilogram of eggs or hen mortality, but BW gain was higher (289 vs. 233 g; P < 0.01) and feed conversion ratio per dozen of eggs was better (1.52 vs. 1.57; P < 0.01) for the lighter than for the heavier hens. None of the egg quality variables studied was affected by dietary treatment or initial BW of the hens. It is concluded that brown egg-laying hens, irrespective of their initial BW, do not need more than 16.5% CP to maximize egg production, provided that the diet meets the requirements for key indispensable amino acids. Heavier hens produce more eggs that are larger than lighter hens but feed efficiency per kilogram of eggs is not affected.

The influence of the main cereal and type of supplemental fat in the diet on productive performance and egg quality of the eggs was studied in 756 brown-egg laying hens from 22 to 54 wk of age. The experiment was conducted as a completely randomized design with 9 treatments arranged factorially, with 3 cereals (dented corn, soft wheat, and barley) and 3 types of fat (soy oil, acidulated vegetable soapstocks, and lard). Each treatment was replicated 4 times (21 hens/replicate). All diets were formulated to have similar nutrient content, except for linoleic acid, which ranged from 0.8 to 3.4% depending on the combination of cereal and fat source used. This approach allows for the estimation of the minimum level of linoleic acid in the diets that maximizes egg weight. Productive performance and egg-quality traits were recorded every 28 d, and the BW of the hens was measured individually at the beginning and at the end of the experiment. No significant interactions between main factors were detected for any of the variables studied. Egg production, egg weight, and egg mass were not affected by dietary treatment. Body weight gain was higher (P < 0.05) for hens fed corn or wheat than for hens fed barley, and also higher for hens fed lard than for hens fed soy oil or acidulated vegetable soapstocks. Egg quality was not influenced by dietary treatment, except for yolk color, which was greater (P < 0.001) for hens fed corn than for hens fed wheat or barley, and greater for hens fed lard than for hens fed soy oil or acidulated vegetable soapstocks. We concluded that brown-egg laying hens do not need more than 1.0% of linoleic acid in their diet (1.16 g/hen per d) to maximize egg production and egg size. The 3 cereals and the 3 fat sources tested can replace each other in the diet provided that the linoleic acid requirements to maximize egg size are met.

a b s t r a c tThe influence of method of grinding of the cereal of the diet on production and egg quality was studied in 420 Hy-line brown egg-laying hens. The design was completely randomized with six treatments arranged as a 3 × 2 factorial with three cereals (barley, dented maize and soft wheat) and two grinding procedures (hammer mill vs. roller mill). Each treatment was replicated seven times and the experimental unit was an enriched cage with ten hens. Production was recorded every four weeks from 24 to 59 weeks of age and egg quality was measured at 40 and 56 weeks of age. For the entire experiment, feed intake was higher in hens fed wheat or maize than in hens fed barley (110.8 and 110.7 vs. 109.7 g/d; P = 0.014) but most of the differences were observed when the cereal was roller milled (P = 0.009 for the interaction). Also, egg production was similar for the three diets when the cereal was hammer milled but tended to be lower for the barley than for the wheat or maize diets when the cereal was roller milled (P = 0.09 for the interaction). None of the other productive or egg quality traits was affected by dietary treatment. We conclude that roller mills are useful to grind low fiber cereals, such as maize or wheat. However, the use of the roller mill might not be adequate when barley is the main cereal in diets for egg-laying hens.

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The general aim of this PhD Thesis was to study the influence of different nutritional factors and management on the productivity and egg quality of comercial Brown laying hens. The factor studied were: 1) The effect of the main cereal and type of fat of the diet;2) The effect of crude protein and fat content of the diet; 3) The effect of energy concentration of the diet; 4) The effect of initial body weight of the hens at the onset of lay period.