ABSTRACT The objective of this study was to assess the effect of ambient temperature (T) and feeding time (FT) on eggshell thickness (ST) and egg weight (EW) of broiler breeder hens. Thirty 44-week-old Ross 308 broiler breeder hens were randomly distributed into six environmentally controlled chambers and kept in individual cages. Three thermal treatments were applied: 20 ºC (T1), cyclic 20-30 ºC (30 °C between 1000 h and 1800 h) (T2), and 30 ºC (T3). Birds received 180 g of commercial breeder food at 0730 h (FT1) or 1530 h (FT2). There were two replications per treatment and egg collection was performed for seven days. The eggs from the birds at T1 and T2 fed at 1530 h (T1FT2 and T2FT2 respectively) were significantly heavier than those laid by hens at the same T when fed in the morning (T1FT1 and T2FT1); eggs from T1FT1 and T2FT1 were heavier than the eggs from T3, but there were no significant differences between them. Both T and FT had significant effects on ST, but no significant interactions were found. Birds fed at 1530 h had the highest ST, whilst birds at T3 showed the lowest. Birds on T2 produced the thickest shells due to a higher ST in birds fed at 1530 h. Birds fed at 1530 h consumed their food between 1800 h and 2030 h, resulting in a higher dietary Ca2 + available during shell mineralization. The effect of FT and biphasic T treatments on ST in feed restricted broiler breeders should be interpreted considering the length of the high T phase to the actual food consumption time.

This experiment compared fertility of male broiler breeders with different crude protein (CP) intakes from diets containing 9.7%, 11.7% and 13% CP from 27 to 60 weeks of age (in two phases) and in a different group of birds from 52 to 60 weeks of age. This was to assess fertility of males with different CP intakes, as well as comparing fertility in older birds having been fed different protein intakes throughout production to those on a commercial ration for most of production. Sperm concentration and sperm mobility were assessed, as well as the number of points of hydrolysis in the inner-perivitelline membrane of eggs from commercial egg-type hybrids after insemination, which was used to predict egg fertility. There was no response to CP intake observed in sperm concentration or sperm mobility at any age. A positive effect of CP intake was observed in egg fertility towards the end of the production phase. While broiler breeder producers make use of separate sex feeding, the female ration is often fed to males in the appropriate amounts to achieve growth according to the target for males. However because it would be cheaper to include less CP in the ration, the effect of CP on breeder fertility is important. This experiment showed that reducing CP to 117 g/kg in male broiler breeder rations fed throughout the production phase had minimal negative effects on sperm quality, however, increasing CP intake towards the end of production may positively impact egg fertility.

The objective of the trial reported here was to determine whether breast meat yield would improve in broilers reared on short daylengths if higher levels of dietary protein were fed. To that end, 3200 Ross 308 International broilers were reared to 35 d in eight light-tight rooms, each room being divided into four pens which were populated with 100 feather-sexed male or female chicks. The lighting treatments used were 12, 16, 20 and 24 h light/d, and four balanced protein levels, being 0.85, 1.00, 1.15 and 1.30 of the Aviagen amino acid recommendations, were fed. At 35 d, three birds from each pen were sacrificed for measurement, individually, of physical and chemical characteristics. Body weight gain to 35 d was unaffected by both dietary protein content and light. FCE increased with dietary protein content to day 21. Feed intake to day 35 was not influenced by light or by dietary protein content. Birds on 24 h had a higher mortality compared with those on the three other lighting programmes, which did not differ from one another. Body protein content increased with both daylength and dietary protein content whereas body lipid content was influenced (decreased) only by dietary protein. Breast meat yield from birds reared on 12 h was not improved when these birds were fed high protein feeds whereas yields were increased in birds on the three longer daylengths used when feed protein was increased. The decreased breast meat yield in broilers given short daylengths is therefore not the consequence of a shortage of dietary protein.

Spring-hatched broiler breeders housed in non-lightproof facilities are frequently maintained on long daylengths to prevent precocity, but controlled-feeding and delayed dissipation of photorefractoriness retard sexual maturation. Trials were conducted to determine the appropriate growth for birds maintained on 14-h photoperiods, and to compare responses with naturally increasing and decreasing daylengths. Birds maintained on 14-h photoperiods matured about 5 d earlier and produced 2 more eggs to 60 weeks for each 10-d advance in age at 2.1 kg. However, despite requiring 0.2 kg less feed to reach 2.1 kg, accelerating growth resulted in 0.5 kg more feed being consumed to sexual maturity. The accelerated-growth birds produced more eggs that were too small for hatching and more double-yolked eggs during the early weeks of production. The data suggest that profitability is maximised when constant-14-h birds reach 2.1 kg at about 18-19 weeks. There were no significant differences in maturity between conventionally-grown birds given increasing or decreasing daylengths or those held on 14-h photoperiods, though there was a tendency for the constant 14-h birds to have later maturity, to produce 6-7 fewer eggs to 60 weeks, and to consume more feed per egg, resulting in a lower economic margin than naturally lighted birds. The wisdom of rearing Spring-hatched broiler breeders on long photoperiods to avoid precocity is therefore questionable. Birds allowed faster growth, generally matured about three weeks earlier than conventionally-grown birds, but matured five weeks earlier when given an increasing lighting regimen that started from 10 h rather than 11 h.

Two trials were conducted to investigate the effects of growth manipulation and early photostimulation on age at sexual maturity and, in one trial, subsequent laying performance, in broiler breeders. In the first trial, the possibility of reducing the age at sexual maturity, using early photostimulation and increasing the growth rate to achieve 2100 g at 15 weeks, was assessed. Sexual maturity was advanced by 15 d and the total number of eggs laid to 60 weeks, on a hen.week basis, was reduced significantly, by six. Mean egg weight was unaffected, but the number of unsettable eggs was increased by 2.6. Using 12 h rather than 16-h daylengths during the laying period resulted in a significant increase (7) in number of eggs laid. In the second trial, birds were transferred from 8 to 16-h daylengths at 10, 11, 12, 14, 16 or 18 weeks to determine the age at which they were able to dissipate photorefractoriness, and become photosensitive. Short-day controls were maintained on 8-h daylengths throughout. Birds were grown to achieve 2100 g at either 15 or 20 weeks. No interaction occurred between age at photostimulation and body weight. Because broiler breeders exhibit photorefractoriness, the earliest age at which the pullets responded to photostimulation was 14 weeks, so no advantage would be gained in terms of advancing sexual maturity by photostimulating earlier than this age. However, whilst some further advance in sexual maturity may be achieved by rearing the birds on a faster growth curve this would only be profitable through the advantages of being able to use one rearing unit to service three, instead of two, laying farms.

The objective of this study was the evaluation of the use of different measures as predictors of breast weight. Thirty-two Anak chicks and 32 Ross chicks were used for the experiment 1. They were randomly sampled from two populations of 400 broilers of each genotype. A slaughter followed by dissection of commercial cuts was done at 53 days old. The following weights were recorded: live weight (PV), eviscerated carcass (PC), and breast (Pch). Proportions to live weight were also used (%PC, %Pch). Breast height and length were measured with calipers previously to the slaughter. Differences between genotypes were found for PV, PC, %PC, Pch and %Pch (p< 0.05). The Ross broilers were heavier than the Anak ones, as theirs carcasses, breasts and proportions were higher. Pch was high correlated with PV, and the calipers measurements did not improve the prediction of Pch and %Pch. Sixty INTA-Campero broilers, randomly sampled from 100, were used for the experiment 2 up to 69 days old. At that age in vivo calipers measures were taken from the length and height of the breast, and ultrasound was used for depth of breast measure. The measured characters at slaughter were the same as those of the experiment 1. An appropriate prediction of Pch was obtained using PV, breast length and breast depth (R²=0,75). The elimination of the ultrasound measurement did not reduce the model fit in an important way (R²=0,725).

El objetivo del presente trabajo fue evaluar la utilización de distintas mediciones como predictores del peso de la pechuga. En la experiencia 1 se utilizaron 32 pollos Anak y 32 pollos Ross, muestreados al azar de dos lotes de 400 animales de cada genotipo. A los 53 dias de edad se realizó la faena y una disección de cortes comerciales. Se tomaron los siguientes pesos: peso vivo (PV), de la canal (PC) y de la pechuga (Pch). Se calculó para el análisis la proporción de cada uno sobre el peso vivo (%PC y %Pch). También se midieron el largo y el ancho de la pechuga con calibre. Se observaron diferencias entre genotipos para PV, PC, %PC, Pch y %Pch (p <0,05). Los animales de la línea Ross resultaron más pesados que los Anak, así coma su carcasa, pechuga y proporciones resultaron mayores. La Pch se correlacionó alta y positivamente con el PV. Ninguna de las mediciones con calibre in vivo significó un aumento de consideración en la precisión de la predicción de Pch. En la experiencia 2 se utilizaron 60 pollos INTA-Camperos, muestreados al azar de un lote de 100 animales. A los 69 días de edad se realizaron mediciones in vivo del largo y ancho de la pechuga con calibre, y de la profundidad por ultrasonido previo a la faena, midiéndose los mismos parámetros que en la anterior experiencia. La correlación entre PV y la Pch fue alta y positiva, pero media a baja con las mediciones con calibre. Se obtuvo una buena predicción de Pch (R²=0,75) a partir del peso vivo, del largo y de la profundidad de pechuga. La eliminación de la medición ecográfica no redujo el ajuste del modelo de manera significativa (R²=0,725).