Scielo RSS <![CDATA[South African Journal of Animal Science]]> vol. 39 num. 1 lang. es <![CDATA[SciELO Logo]]> <![CDATA[<b>Supplementary heat requirements when brooding tom turkey poults</b>]]> In this study, the supplementary heat required when brooding turkey poults in winter and summer in the Kahramanmaras region of Turkey was determined using a heat and humidity balance method for a naturally ventilated house with a capacity of 6500 tom turkey poults. In the calculation of heat and humidity balance, temperature values, sensible heat and moisture production of tom turkey poults were taken from the American Society of Agricultural Engineers (ASAE) standards for corresponding turkey poult weights, and outside long term (1980 - 2005) monthly average temperatures were obtained from a local climate station. The coldest and warmest crucial months were determined as January (6.5 °C) and August (29.2 °C), respectively. When brooding was initiated in the first week of January, supplementary heat was needed for the subsequent five weeks, being 32937, 27028, 21721, 9476 and 5400 W per week, respectively. When brooding started in the first week of August, poults needed only 5544 W supplementary heat. However, tom turkey poults would nevertheless benefit from supplementary heat during this period because they are not yet fully feathered and the digestive system has not yet fully developed. <![CDATA[<b>Milk production potential of two ryegrass cultivars with different total non-structural carbohydrate contents</b>]]> The aim of the study was to compare a new Italian ryegrass (Lolium multiflorum) cultivar (Enhancer), bred to contain a high total non-structural carbohydrate content, with the cultivar, Dargle, in terms of dry matter (DM) production, nutritional value, carrying capacity and milk production. The ryegrass cultivars were sown (25 kg/ha) under supplementary irrigation in a randomized block design (7 blocks with 2 paddocks, 4.5 ha/treatment) on the 2nd May 2001 (year 1) and the 15th March 2002 (year 2) on an Estcourt soil type. Nitrogen was applied at 56 kg N/ha after each grazing. Grazing started on 26 June 2001 and the grazing cycle varied from 24 to 28 days. Pasture yield was estimated with a rising plate pasture meter. Forty Jersey cows from 50 to 150 days in milk were randomly allocated to one of the two treatments. The experimental period started on 22 August 2001 and consisted of an adaptation period of 15 days followed by a measurement period of 75 days. Pasture was allocated at 10 kg DM/cow/day above 30 mm. Cows were weighed and condition scored on two consecutive days at 14:00 at the start and the end of the experimental period. Milk production was recorded daily and milk composition was determined every 14 days. All cows were fed a flat rate of 3.6 kg DM of a dairy concentrate (120 g crude protein (CP)/kg DM, 11.5 MJ ME/kg DM) per day. The concentrate was fed in two equal portions during milking at 06:00 and 15:00. The total production of Enhancer was higher at 8438 and 9084 kg DM/ha in 2001 and 2002, respectively, compared to 7570 and 7694 kg DM/ha of Dargle. The DM and total non-structural carbohydrate content of Enhancer was higher than Dargle in 2001 but not in 2002. In 2002 the CP content of Enhancer was lower than that of Dargle. Enhancer increased 4% fat corrected milk production by 1.3 and 1.4 kg/cow/day in 2001 and 2002, respectively, and DM intake by 1.1 and 0.88 kg/cow/day compared to Dargle. The total milk production per hectare of Enhancer was 1499 kg and 2277 kg higher during 2001 and 2002, respectively, compared to Dargle. Enhancer, a high sugar Italian ryegrass, demonstrated good potential to increase milk production. <![CDATA[<b>Estimation of sustained peak yield interval of dairy cattle lactation curves using a broken-line regression approach</b>]]> A broken-line regression model with three straight lines and two breakpoints was used to estimate the sustained peak yield of the lactation curve. A sample of 1548 lactation records of 425 Holstein-Friesian cows was provided by the Research and Application Farm of the Agriculture Faculty of Çukurova University in Adana, Turkey. A total of 13463 test-day milk yields (kg/day), recorded once a month with electronic identification and automatic milking recording systems, between November 1994 and January 2006, were used. The data was classified as first, second, third, fourth, fifth, sixth and seventh parity, and included 4105, 3238, 2495, 1800, 1113, 641 and 71 test-day records, respectively. Times (days) at the beginning and end of sustained peak yield per parity were 73.9 - 160.2, 70.6 - 131.9, 70.8 - 130.7, 71.0 - 130.3, 71.3 - 130.4, 71.2 - 128.2 and 71.1 - 129.8, respectively. The peak yields of lactation curves were 19.1 kg/d, 21.8 kg/d, 23.8 kg/d, 24.2 kg/d, 24.2 kg/d 24.4 kg/d and 21.3 kg/d, and days in milk (DIM) at peak yields of lactation curves per parity were 126, 103, 102, 104, 106, 103 and 104, respectively. Persistency values (days) and total lactation milk yields (kg/lactation) per parity were 86.4, 61.3, 59.9, 59.3, 59.1, 57.0, 58.7 and 4852.2, 5105.7, 5503.5, 5503.7, 5449.3, 5416.3, 4802.4, respectively. Results showed that the first parity had a lactation curve with the lowest milk yield at peak that reached the peak point at the latest time (DIM) after parturition, but the largest interval between the beginning and end of the sustained peak yield among all parities. This means that the cows in the first lactation were more persistent than those in the later lactations. <![CDATA[<b>Effect of qualitative feed restriction on energy metabolism and nitrogen retention in sheep</b>]]> Periodic restrictions in feed quality and quantity is an important phenomenon in regions where animal production should bridge the gap between periods of forage production separated by a dry season. Eighteen Swifter male lambs, weaned at the age of ca. three months, were used to quantify effects of feed quality restriction and realimentation on changes in energy and nitrogen metabolism. The diet consisted of grass straw (17 MJ of gross energy [GE] and 46 g crude protein [CP] per kg dry matter [DM]) on an ad libitum basis and 35 g/kg0.75/d mixed concentrates (16.5 MJ of GE and 173 g CP per kg DM). At the age of ca. 3.5 months the animals were randomly divided into six blocks, based on live weight, according to a randomized complete block design. Within each block, the animals were randomly assigned to two restricted treatments (R1 and R2) and an unrestricted control (C) treatment. Treatments R1 and R2 were subjected to feed quality restriction by withholding the concentrate for 3 and 4.5 months, respectively. A modified linear model was developed to study the effects of restriction and realimentation. The comparison between treatments was made by analyzing the data of the R1 and R2 animals as deviations from the control animal in each block. During the restriction period, restricted animals lost weight and showed negative energy (EB) and nitrogen balances (NB), whereas their intake of low quality roughage increased significantly. During the realimentation period (5 and 6 months for the R1 and R2 animal, respectively), the R1 and R2 animals grew significantly faster than the control animals. The realimented animals persisted in ingesting significantly more low quality roughage and their EB and NB were significantly greater that those of the control animals. The R2 animals needed a longer period of realimentation because of a longer period of restriction. The expression of compensatory growth was mainly related to a sustained higher grass straw (low quality roughage) intake during the realimentation periods, and a significantly greater efficiency of metabolizable energy intake. The maintenance requirement of realimented animals was significantly lower only during the initial stages of realimentation compared with the controls. It seemed as if a three months feed restriction period in weaned sheep was better than 4.5 months. <![CDATA[<b>Effects of season and regulated photoperiod on the reproductive performance of sows</b>]]> Reproductive performance of experimental commercial Dalland sows (n = 87) maintained under a constant photoperiod (10 h light and 14 h darkness) and control sows (n = 187) maintained under natural daylight length (10.4 h light in winter and 13.4 h light in summer) were compared. In early summer 4.1% of experimental sows returned to oestrus compared to 20.8% of the control sows. In late summer 9.1% of experimental sows returned to oestrus compared to 21.9% of the control sows. Reduced photoperiod improved the farrowing rate of experimental sows in the early summer breeding compared to the control group (95.4% and 81.3%, respectively). With winter breeding there was a small proportion of sows that returned to service in both groups (7.9% and 8.9%) while the farrowing rate was high in both groups (93.9% and 91.0% in the experimental and control groups, respectively). Litter sizes derived from early summer services were 11.4 and 11.6 for the experimental and control groups, respectively, while winter services led to litter sizes of 11.6 and 12.4 whereas in late summer services, regulated photoperiod had improved the litter size of the experimental group (12.3) compared to the control group (11.2). <![CDATA[<b>Analysis of stayability in South African Angus cattle using a threshold model</b>]]> The objectives of the study were to estimate genetic parameters for stayability in the South African Angus cattle and to compare the sire and animal threshold models. Data and pedigree information were obtained from the Integrated Registration and Genetic Information System of South Africa. Stayability was defined as a probability that a cow remained in the herd until four (STAY4), five (STAY5), six (STAY6), seven (STAY7) and eight years of age (STAY8), given that she was a dam. Cows that were in the herd by a specific age were assigned a "1" or a "0", otherwise. The proportions of successful stayability were 0.63, 0.57, 0.49, 0.42, and 0.37 for STAY4, STAY5, STAY6, STAY7 and STAY8, respectively. Estimates of genetic parameters were obtained from sire and animal threshold models using AIREML algorithm. The model included the fixed effect of contemporary group and random effects of sire or animal genetic effect and the residual. Heritability estimates from the sire model were 0.26 ± 0.08, 0.26 ± 0.09, 0.30 ± 0.09, 0.24 ± 0.10 and 0.27 ± 0.11 for STAY4, STAY5, STAY6, STAY7 and STAY8, respectively. Corresponding estimates from the animal model were 0.20 ± 0.11, 0.20 ± 0.11, 0.20 ± 0.12, 0.18 ± 0.13 and 0.20 ± 0.14. Estimates from the sire and animal models were consistent. Results from the current study indicate that direct selection for stayability could be effective. However, the long generation interval required to obtain accurate estimates of genetic merit may slow genetic progress for stayability at older ages. <![CDATA[<b>Genetic diversity and relationships among indigenous Mozambican cattle breeds</b>]]> Three indigenous Mozambican cattle breeds, namely the Angone, Landim and Bovino de Tete were characterized using six proteins, 13 autosomal microsatellite loci and one Y-specific microsatellite locus (INRA124). The Mashona breed from Zimbabwe was also studied to elucidate the origin of the Bovino de Tete cattle. Expected mean heterozygosity ranged from 0.46 - 0.50 in the proteins and from 0.66 - 0.69 in the microsatellites. Population genetic variability was relatively high when compared to other African breeds. Only 4.5% of the total genetic variation could be attributed to the differences among the breeds. D A genetic distances and principal component analysis suggest that Mozambican breeds occupy an intermediate position between Indian Zebu and African taurine cattle. The genetic contribution from Indian Zebu, estimated by mR and average percentage of Zebu diagnostic alleles, was highest in the Angone breed and lowest in the Landim breed. The indicine Y-specific allele was fixed in the Angone breed (classified as Zebu), was found in 62% of the Bovino de Tete breed and was absent in the Landim breed (classified as Sanga). The hybrid nature of these breeds was also revealed by using an admixture model to infer population structure. Cluster analysis correctly assigned individuals to their rightful populations with probabilities ranging from 0.96 to 0.98, using prior population information. The results support the hypothesis of the Bovino de Tete cattle being a result of crossbreeding between Sanga and Zebu breeds. This study presents the first extensive information on the genetic diversity and relationships among Mozambican cattle breeds and with other breeds from different continents. <![CDATA[<b>Genetic parameter estimation of 16-month live weight and objectively measured wool traits in the Tygerhoek Merino flock</b>]]> Genetic evaluation systems require the accurate estimation of genetic parameters. The genetic, phenotypic and environmental parameters for live weight and objectively measured wool traits were estimated for a South African Merino flock. Records of the Tygerhoek Merino resource flock were used to estimate these parameters. The database consisted of records of 4 495 animals, the progeny of 449 sires and 1 831 dams born in the period 1989 to 2004. The pedigree records used have been collected between 1969 and 2004. Direct heritability estimates (h²a) for 16-month live weight (LW) and objectively measured wool traits ranged from 0.20 for staple strength (SS) to 0.68 for fibre diameter (FD). Maternal heritability estimates ranged from 0.05 for LW and FD, to 0.10 for clean fleece weight (CFW). The proportion of the total phenotypic variance due to the maternal permanent environment variance (c2pe) amounted to 5% for fleece weights. The genetic correlation between animal effects for LW, greasy fleece weight (GFW) and CFW were -0.28, -0.65 and -0.70 respectively. The genetic correlation between LW and CFW was positive, but low at 0.14. The other important genetic correlations among the wool traits ranged from low to high, and were variable in sign ((for GFW with CFW (0.87) and with staple length (SL - 0.18); CFW with clean yield (CY - 0.33) and with SL (0.29); FD with CY (-0.09), with SL (0.15), with SS (0.40) and with standard deviation of FD (SDFD - 0.38): CY with SL (0.33) and with SDFD (0.10); SS with coefficient of variation of FD (CVFD - -0.57) and with SDFD (-0.28); CVFD with SDFD (0.87)). These results suggested that worthwhile responses in the objectively measured traits can be achieved through direct and indirect selection. <![CDATA[<b>Genetic analysis of test day milk yields of brown swiss cattle raised at Konuklar State Farm in Turkey, using MTDFREML</b>]]> A total of 3696 Test Day Milk Yield (TDMY) records of Brown Swiss cows raised at Konuklar State Farm in the Konya Province of Turkey were used for estimating phenotypic and genetic parameters for TDMY. The phenotypic and genetic parameters were estimated by an MTDFREML programme using a Single Trait Animal Model (STAM). The model included additive direct effects, maternal permanent environment and errors as random effects, parity, year and season of calving as fixed effects, and days in milk (DIM) as a covariate. Genetic parameters and breeding values for TDMY in kg were estimated. The TDMY least square mean was estimated as 15.64 ± 5.82 kg, and the direct heritability (h²a), maternal heritability (h²m) and the repeatability (r) of TDMY were calculated as being 0.28 ± 0.09, 0.04 ± 0.54 and 0.31 ± 0.01, respectively. The effects of parity and year-season of calving on TDMY were significant. <![CDATA[<b>Genetic parameter estimates for functional herd life for the South African Jersey breed using a multiple trait linear model</b>]]> Longevity reflects the ability of a cow to avoid being culled for low production, low fertility or illness. Longevity can be used in breeding programmes if genetic parameters are known. Various measures are used for longevity. In this study survival in each of the first three lactations was analysed. Survival was denoted by a 1 if a cow survived, and 0 otherwise. The primary objective of the current study was to estimate genetic parameters for functional herd life. The secondary objective was to compare estimates of genetic parameters from the linear sire and animal models. Data and pedigree records on purebred Jersey cows that participated in National Milk Recording and Improvement Scheme of South Africa were used to estimate genetic parameters. A total of 181 269 cow records from 636 herds recorded over 16 years were available for analysis. Estimates of genetic parameters for herd life were obtained using REML procedures fitting three-trait (first three lactations as separate traits) linear animal and sire models. Heritability estimates (0.02 to 0.03) from the animal and sire models were somewhat similar for all lactations. However, heritability estimates for lactations 2 and 3 were slightly higher with the sire model compared to the animal model. The genetic correlation between lactations 1 and 2 from both the sire and animal models was higher than that between lactations 2 and 3. Genetic correlations from the sire model ranged from 0.68 to 0.99, compared to 0.76 to 0.99 from the animal model. Results from the current study suggest that genetic variation exists for functional herd life to allow for genetic improvement through selection. The moderate positive genetic correlation between survival in the first and third lactation suggest that early selection for functional herd life is feasible. <![CDATA[<b>Single nucleotide polymorphisms in the 5'-flanking region of the prolactin gene and the association with reproduction traits in geese</b>]]> Prolactin (PRL), a polypeptide hormone synthesized and secreted by the animal's anterior pituitary gland, plays an important role in the regulation of mammalian lactation and avian reproduction. Considering the significant association between single nucleotide polymorphisms (SNPs) in the 5'-flanking region of PRL and reproduction traits in the chicken, the objective of this study was to screen for SNP in the 5'-proximal region of PRL in geese and to evaluate the association between SNP and reproduction traits in geese. Chinese Wan-xi White geese (n = 200) and European Rhine geese (n = 80) were used for phenotyping. SNP was screened by comparing sequences of PCR products, and the single-stranded conformational polymorphism (SSCP) protocol was adopted for genotyping. Three SNPs (A-401G, G-268A and T-266A) in the 5'-proximal region of goose PRL were identified in both breeds. Statistical analysis suggested that the genotype AA characterized by A-401, G-268 and T-266 had a positive genetic effect on egg production. Therefore, these polymorphisms have the potential to be utilized in molecular breeding for egg production in geese.