Scielo RSS <![CDATA[South African Journal of Animal Science]]> vol. 43 num. 4 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[<b>Use of theoretical efficiencies of protein and fat synthesis to calculate energy requirements for growth in ruminants</b>]]> The main objection against conventional net energy systems is that owing to variation in gain composition and the different energy contents of protein and fat, the efficiency of energy gain cannot be regarded as a growth constant. The present approach shows that the separate accommodation of protein and fat in predicting ruminant nutritional requirements can easily be achieved, since growth energy retention efficiency can be replaced by protein and fat synthesis efficiencies, together with an augmentation of maintenance with the cost of protein turnover. The synthesis efficiency of protein (kPS) is taken to be kPS = (qL/qM)(6/7), with 6/7 the synthesis efficiency of protein, qL the metabolizability of the diet at an arbitrary level (L) of intake and qM the metabolizability of the diet at maintenance. The correction (qL/qM) allows for the usual evaluation of ruminant diets at the maintenance level of intake. The synthesis efficiency of fat from fermentation of digestible fibre is kFF = 1.018qM or kFF = 1.287k g, without the necessity of adjustment by qL/qM, since evaluation of metabolizability at maintenance is incorporated in the relationship between kFF and qM and where kg denotes growth energy efficiency. Maintenance estimated from fasting heat production or intake at zero energy retention should be augmented by the cost of protein turnover from (PB/6) - (qL/qM,) with PB/6 = 102.7 kJ/kg (FW)0.75 per day for cattle and PB/6 = 78.1 kJ/kg (FW)0.75 per day for sheep, where PB denotes protein breakdown and FW fasted body mass. Alternatively, with knowledge of the degree of protein maturity, body protein turnover can be incorporated in a theoretically derived estimate of protein retention efficiency. The effective energy system can also be improved by employing theoretical protein retention and fat synthesis efficiencies or by equivalently replacing protein retention efficiency by protein synthesis efficiency in conjunction with the augmentation of maintenance heat production by the cost of protein turnover. A comparison between average growth energy efficiencies shows excellent agreement between estimates of the present theory and those of the UK Agricultural Research Council (ARC) and the US California Net Energy System (CNES), with degrees of maturity together with protein and fat gain ratios that seem typical of original experimental conditions. This implies that the present approach should do at least as well as the ARC or CNES, but can be expected to do better with reasonable accuracy in estimating the degree of protein maturity or maintenance augmentation and the composition of energy gain. The relationship between conventional growth energy efficiency and the synthesis efficiency of fat from digestible fibre allows the accumulated information of net energy systems to be transferable to the new methodology. <![CDATA[<b>Nutrient intake, digestibility and nitrogen retention in indigenous goats fed on <i>Acacia nilotica</i> fruits treated for condensed tannins</b>]]> Polyethylene glycol (PEG 4000), Browse PlusTM (BP), wood ash (WA) and boiling water were evaluated as tannin deactivation methods on tannins in Acacia nilotica fruits. Twenty four Matebele goats of mean body mass, 38.7 ± 3.12 kg, were used in a digestibility and nitrogen balance trial. A completely randomized design was used, and the initial weight was used as a covariate in data analysis. The goats were randomly allocated to the treatments and were fed for 28 days on a basal diet of hay and A. nilotica fruits treated with PEG (MW 4000), BP, WA or boiling water. Acacia nilotica fruits had 4.39% catechin equivalents of condensed tannins, thus the amount of PEG, BP and WA used to treat the fruits was 1.5 parts per part of condensed tannin in the fruits. It was hypothesized that treating the fruits would deactivate the tannins in them and increase intake, digestibility and nitrogen retention. Treating the fruits for condensed tannins had no effect on hay and fruit intake. None of the treatments had an effect on the apparent digestibility of dry matter, organic matter, neutral and acid detergent fibre and nitrogen retention in the goats. The goats that were fed on the boiled fruits had a negative N retention of -1.03 g/day. It was concluded that none of the detannification methods improved feed intake, apparent nutrient digestibility and nitrogen retention. It is recommended that each detannification method should be tested on different types of tannins and at different concentrations before totally dismissing the treatments as not useful. <![CDATA[<b>Genetic diversity of four protected indigenous chicken breeds in China using microsatellite markers</b>]]> The genetic diversity of four protected indigenous chicken breeds was evaluated with 25 microsatellite markers. Polymorphism information content (PIC), heterozygosity with the estimator of genetic differentiation F ST and Nei's genetic distance were evaluated. The results showed that these four protected local chicken populations showed high levels of diversity. The proportion of inter-population subdivision among the four protected local chicken populations was 16.0%. The average heterozygosity was 0.514, 0.581, 0.567 and 0.589 in Dongan, Xuefeng black-bone, Xianghuang and Taoyuan chickens, respectively, while the average PIC estimates were 0.455, 0.581, 0.557 and 0.576. A phylogenetic tree was constructed using genetic distance and the neighbour-joining method. Its topology reflects the general pattern of genetic differentiation among the four chicken breeds. The results also showed high genetic diversity and genetic variation among all the breeds. The information about the four local breeds estimated by microsatellite analysis may be useful as an initial guide for the effective conservation of chicken genetic diversity and developing conservation strategies. <![CDATA[<b>Effect of a natural versus a synthetic antioxidant, and sex and age on the redox profile in the blood of growing turkeys</b>]]> An investigation was conducted with turkeys during the spring-summer seasons of 2008 to 2011. Each season the turkeys were allocated to three treatments. The control received a standard compound feed. In the second treatment, a natural feed additive, consisting of 5% extracted polyphenols from Cynara scolymus, was included in the diet, and the third consisted of a synthetic antioxidant mixture containing 17% butylhydroxytoluene (BHT), 6% propyl gallate, 2.4% etoxyquin and 25% citric acid. Blood samples were collected from the brachial vein, and antioxidative parameters were measured in the plasma. The males in the study had a significantly higher concentration of peroxides, malondialdehyde and vitamin C in their plasma than the females. The plasma concentration of low-molecular antioxidants, as well as the activity of the antioxidative enzymes, decreased with the age of the birds. The inclusion of the natural and synthetic feed additives to the diet increased the levels of the ferric-reducing ability of plasma and of vitamin C in turkeys. <![CDATA[<b>Genetic relationship between growth and carcass traits in Large White pigs</b>]]> Genetic relationships between growth and carcass traits in South African Large White pigs were estimated. Genetic parameters for growth and carcass traits were generated using a maternal effects model in ASREML. Data analysed were on 13 703 pigs from 28 herds tested between 1990 and 2007, and 4 128 carcasses from 21 herds evaluated between 1993 and 2007. The traits included in the study were backfat thickness (BFAT), test period weight gain (TPG), lifetime weight gain (LTG), test period feed conversion ratio (FCR), age at slaughter (AGES), lean percentage (LEAN), drip-free lean percentage (DLEAN), drip loss percentage (DRIP), carcass length (CRLTH), dressing percentage (DRESS), eye muscle area (AREA) and carcass fat (CFAT). Heritability estimates for growth traits ranged from 0.24 ± 0.03 for FCR to 0.45 ± 0.04 for BFAT, while those for carcass traits ranged from 0.14 ± 0.06 for DRIP to 0.55 ± 0.0.08 for AREA. Maternal genetic effects were significant in most traits, and were negatively correlated with direct heritabilities. Genetic correlations among growth traits ranged from -0.14 ± 0.08 between BFAT and LTG to -0.99 ± 0.01 between TPG and FCR, and LTG and AGES. For carcass traits, genetic correlations ranged from -0.02 ± 0.20 between DRIP and CRLTH to 0.99 ± 0.01 between LEAN and DLEAN. There is substantial genetic variation in growth and carcass traits; hence faster genetic improvement may be achieved through selection. Growth performance and carcass characteristics can be improved through selection for reduced backfat thickness and increased daily weight gain. <![CDATA[<b>Association of polymorphism in Exon 3 of toll-like receptor 4 gene with somatic cell score and milk production traits in Holstein dairy cows of Iran</b>]]> Mastitis is a complex inflammatory disease of the mammary gland that is caused by the invasion of pathogens. This leads to reduced synthetic capacity, compositional changes and increased somatic cell counts (SCC) in milk. Toll-like receptor 4 (TLR4) is a cell surface receptor that recognizes lipopolysaccharides (LPS) of gram-negative bacteria. Its role in pathogen recognition and the subsequent immune response and differential expression of the gene during mastitis have prompted the investigation of TLR4 gene as a candidate to improve mastitis resistance in dairy cattle. The aim of this study was to analyse the possible association of a single nucleotide polymorphism (SNP) in putative co-receptor-binding region 2 (T4CRBR2) of the TLR4 gene with somatic cell score (SCS) and milk-related traits in 408 Iranian Holstein cows. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique was performed for genotyping. The effect of the genotype on the traits of interest was analysed using the general linear model (GLM) procedure of SAS software. The B allele frequency was 0.634 and the distribution of genotypes was not in Hardy-Weinberg equilibrium in the overall population. The B allele of the SNP was associated with higher 305-day milk yield and breeding value for milk yield, and lower fat percentage and lower SCS, as compared with allele A. The association between TLR4 polymorphism with SCS and milk production traits reported in this study suggests that this SNP has the potential to be used as a marker for selection, based on molecular information. <![CDATA[<b>Assessing the genetic diversity of five Tanzanian chicken ecotypes using molecular tools</b>]]> The study aimed to evaluate the genetic diversity of Tanzanian chicken populations through phylogenetic relationship, and to trace the history of Tanzanian indigenous chickens. Five ecotypes of Tanzanian local chickens (Ching'wekwe, Kuchi, Morogoro-medium, Pemba and Unguja) from eight regions were studied. Diversity was assessed based on morphological measurements and 29 microsatellite markers recommended by ISAG/FAO advisory group on animal genetic diversity. A principal component analysis (PCA) of morphological measures distinguished individuals most by body sizes and body weight. Morogoro Medium, Pemba and Unguja were grouped together, while Ching'wekwe stood out because of their disproportionate short shanks and ulna bones. Kuchi formed an independent group owing to their comparably long body sizes. Microsatellite analysis revealed three clusters of Tanzanian chicken populations. These clusters encompassed i) Morogoro-medium and Ching'wekwe from Eastern and Central Zones ii) Unguja and Pemba from Zanzibar Islands and iii) Kuchi from Lake Zone regions, which formed an independent cluster. Sequence polymorphism of D-loop region was analysed to disclose the likely maternal origin of Tanzanian chickens. According to reference mtDNA haplotypes, the Tanzanian chickens that were sampled encompass two haplogroups of different genealogical origin. From haplotype network analysis, Tanzanian chickens probably originated on the Indian subcontinent and in Southeast Asia. The majority of Kuchi chickens clustered in a single haplogroup, which was previously found in Shamo game birds sampled from Shikoku Island of Japan in the Kõchi Prefecture. Analysis of phenotypic and molecular data, as well as the linguistic similarity of the breed names, suggests a recent introduction of the Kuchi breed to Tanzania. <![CDATA[<b>Intestinal digestibility of enriched-protein fodders measured by mobile bag incubated with or without pepsin-HCl and three-step techniques</b>]]> Ruminal, intestinal and total tract digestibility of dry matter (DM) and crude protein (CP) of leucaena (Leucaena leucocephala), Madras thorn (Pithecellobium dulce) and moringa (Moringa oleifera) fodders were measured in this study, using nylon bag and mobile bag techniques. Three cattle were fitted with permanent rumen and duodenal cannulae. Intestinal digestibility was measured using the mobile nylon bag (MNB) technique with or without incubation in a pepsin-HCl solution, and a three-step in vitro technique. The rate of ruminal disappearances of DM and CP, and the potential degradation of CP from nylon bags of both Madras thorn and moringa fodders were significantly higher than that for leucaena fodder. Potential degradation (A+B) values of CP were 45.6%, 54.2% and 52.8% for leucaena, Madras thorn and moringa fodders, respectively. Average DM and CP digestibility in the intestine and total tract for both Madras thorn and moringa fodders were significantly higher than for leucaena fodder. Average digestibility of DM and CP in the intestine and total tract measured using MNB without pepsin-HCl solution was significantly lower than with pepsin-HCl and with the three-step methods. These data suggest that the results of in vivo and in vitro methods for estimating intestinal digestibility are similar, though in all methods the incubation in a pepsin-HCl solution is necessary.