LAYING AND PHYSICAL CHARACTERISTICS OF SHAVER BROWN AND NERA BLACK HENS IN HOT HUMID ENVIRONMENT
A total of one hundred and fifty Shaver brown and Nera black hens in their 14th week of lay were used in a study conducted to determine the laying and physical characteristics of Shaver brown and Nera black hens under humid tropical environment. Hens were housed individually in separate cages. The hens were supplied water ad libitum and fed layers mash containing 16.5% crude protein and 2650 kcal/kg of metabolizable energy for 10 weeks. The hens were also divided into three classes based on their laying performance as follows: good layers, intermediate layers and poor layers and their physical conditions appraised. Temperature readings were taken 3-hourly at time intervals of 0900h, 1200h, 1500h, and 1800h using a standard air thermometer and the mean daily temperatures noted. The climatic data taken during the period of the experiment showed that the study area had the natural day-length of 13 to 14 hours; mean maximum weekly indoor and outdoor temperatures of 27.90C to 29.20C and 26.80C to 30.50C, respectively; mean minimum weekly indoor and outdoor temperatures of 20.50C to 22.30C and 20.00C to 23.600C, respectively; relative humidity of 73.1% to 76.6% and mean total monthly rainfall of 781.33mm. Results showed that the peak of lay was between 0700h and 0800h and declined gradually throughout late afternoon hours until no egg was laid between 1700h and 1800h. For Shaver brown hens, about 86.24% and 13.76% of the eggs were laid in the morning and afternoon hours respectively, while 88.75% and 11.25% of the eggs were laid in the morning and afternoon hours respectively, for Nera black hens. Mean egg weight of 70.05g±1.07 and 70.10g±0.92 for eggs laid between r0600h and 0700h for Shaver brown and Nera black hens, respectively were the heaviest (P<0.05) of all the mean egg weights observed in all oviposition intervals. For Shaver brown hens, first eggs laid in a clutch were significantly greater (P<0.05) than subsequent eggs laid in a clutch, while the first eggs in a clutch for Nera black were greater than other eggs in the clutch, although the differences were not significant (P>0.05). Hens with the longest clutches and shortest number of pause days produced the greatest number of eggs. The total number of pause days observed were 1410 and 1329 for Shaver brown and Nera black hens, respectively. Observations made on physical characteristics of the hens revealed that good layers had smooth combs and wattles, moist and enlarged vents with flexible pubic bone, soft abdomen and worn out feathers. Intermediate layers had similar features with good layers except that the eye rings, beaks and shanks were slightly bleached. Poor layers had dry combs and wattles, tight and hard abdomen and closed pubic bones. The Effect of ambient temperature on performance parameters showed that for Shaver brown hens, hen day egg production, average daily feed intake, egg shell weight, egg shape index, albumin height, yolk height, yolk height and Haugh units were significantly reduced (P<0.05) with increasing temperatures. All performance parameters measured for Nera black hens were significantly reduced (P<0.05) with increasing temperatures. Likewise, there was significant interaction (P<0.05) of strain and temperature on average daily feed intake and yolk height. The results of the present study indicate that although heat stress had effect on performance, Shaver brown and Nera black hens are adapted to humid tropical environment and can lay 86.24% and 88.75% eggs, respectively in the morning hours, with overall production rate of 66.43% and 68.36% respectively, for Shaver brown and Nera black hens.