Scielo RSS <![CDATA[South African Journal of Animal Science]]> vol. 38 num. 2 lang. en <![CDATA[SciELO Logo]]> <![CDATA[<b>Threonine and lysine requirements for maintenance in chickens</b>]]> In order to describe the response of broiler breeder hens to dietary amino acids and to develop an effective model for the precise feeding of these birds after sexual maturity, accurate estimates of the amounts of each amino acid required for maintenance and egg production are needed. The maintenance requirement for threonine and lysine were estimated in two different experiments by measuring the nitrogen balance of adult male cockerels. Measured amounts of a diet first-limiting in threonine or lysine were fed by intubation each day for 4 d to give a range of intakes (unbalanced series) of from 0 to 239 mg threonine/kg or 0 to 40 mg lysine/kg body weight. To confirm that threonine or lysine was first-limiting and that the response obtained was to threonine or lysine and not to protein, a second series of diets was used (balanced series) in which synthetic threonine or lysine was added to each diet in the unbalanced series. A nitrogen-free diet containing energy, vitamins and minerals was made available ad libitum during the balance period, to ensure that the birds remained in positive energy balance. The balance period was three days and excreta were collected in colostomy bags (threonine) or in trays (lysine) during that time. The nitrogen content of the excreta was determined on dried homogenised samples. The resultant linear regression equations describing the effect of threonine or lysine intakes on nitrogen retention were: N retention = -230.4 (± 27.6) + 4.134 (± 0.274) I (R² = 91.9) and N retention = -256.8 (± 37.7) + 6.89 (± 1.37) I (R² = 70.8), respectively, where I is the intake of threonine or lysine in mg/kg body weight day. The threonine and lysine required to maintain the body at zero nitrogen retention was therefore estimated to be 56 and 37 mg/kg body weight day, respectively. <![CDATA[<b>Sprout selection and performance of goats fed <i>Acacia karroo</i> coppices in the false thornveld of the Eastern Cape, South Africa</b>]]> Acacia karroo Hayne is the dominant invading species in semi-arid savannas of South Africa and is an ecological threat of our modern era. This study investigated the preference and intake rates by goats when fed A. karroo coppice sprouts of different basal diameter sizes, viz. 3 mm, 4 mm and 5 mm. A study was also conducted to determine the digestibility and performance of goats when fed A. karroo coppices and commercial feed pellets. Nitrogen content varied among the sprout sizes. The larger sprouts had the highest nitrogen content, but the acid detergent fibre, neutral detergent fibre and hemicellulose did not differ among sprout sizes. There were no significant differences in preference of the different sprout sizes. Intake rate of the sprout sizes was significantly different; small sprouts were consumed at the highest intake rate compared to medium size sprouts, but not compared to the larger sprouts. Nguni goats had higher bite rates compared to Boer goats. However, intake rates of the Boer goats and the Nguni goats were not significantly different. Goats fed A. karroo had a higher average daily gain compared to the goats fed the pellets. Average daily gain differed between the two goat breeds. Apparent digestibility of dry matter and crude protein for A. karroo and pellets also differed. It is concluded that both Boer and Nguni goats have the potential to utilize smaller A. karroo sprouts. These animals can therefore potentially be used to control bush encroachment. <![CDATA[<b>Effects of dietary oil sources on egg quality, fatty acid composition of eggs and blood lipids in laying quail</b>]]> This study was performed to investigate the effects of different oils in the diets of laying quail on their performance, egg quality, serum lipids and fatty acid composition of egg yolk. One hundred and ninety two 12-wk old Japanese quail were allocated to eight groups with two replicates containing 12 quail each. They were fed for 10 weeks on diets containing 4% oil from different sources, viz. either sunflower, sesame, cottonseed, olive, hazelnut, maize, soyabean or fish oil. The dietary oils affected egg weight and its specific gravity, the egg yolk index and the Haugh unit but had no effect on live weight of the birds, eggshell thickness and albumen index. The highest egg weights were recorded in the groups fed olive and sunflower oil. Eggs from the soyabean oil group had the highest specific gravity. Serum triglyceride concentrations were lower in the birds receiving diets containing sunflower and hazelnut oil than in the other treatments. Serum total cholesterol levels were higher in the groups fed hazelnut and cottonseed oil than in those receiving the other oils. Serum low density lipoprotein (LDL) levels were lower in the groups fed soyabean and olive oil than the other oil sources. The results of this study demonstrated that olive oil improved egg weight and egg shell quality compared to the other oils tested; fish and soyabean oil increased the omega-3 fatty acid level of egg yolk, and soyabean oil had positive effects on serum lipid concentrations. Incorporation of these oils into the diets of Japanese quail may have practical value in manipulating egg yolk quality. <![CDATA[<b>Cloning and SNP screening of the TLR4 gene and the association between its polymorphism and somatic cell score in dairy cattle</b>]]> Toll-like receptor 4 (TLR4) is a cell-surface receptor that activates innate and adaptive immune responses. Recognizing a broad class of pathogen-associated molecular patterns (PAMPs), TLR4 is implicated as a receptor mediating cellular activation in response to bacterial lipopolysaccharide (LPS), a cell-wall component of gram-negative bacteria, which is the principal PAMP of TLR4. TLR4 is a candidate gene for resistance to a large number of diseases. Human models, in particular, suggest TLR4 to be a candidate gene associated with resistance to sepsis, immunodeficiencies, atherosclerosis and asthma. In this study the bovine TLR4 mRNA and genomic DNA were sequenced and their gene structures were determined through alignment of the genomic DNA sequence to the mRNA sequence. Its mRNA sequence consisted of a 2526-bp open reading frame (ORF) flanked by a 470-bp 5'-untranslated region (UTR) and a 743-bp 3'-UTR; and its genomic DNA is 11,013-bp in length and includes the three exons and two introns. Thirty-one single nucleotide polymorphisms (SNPs) were detected by sequencing polymerase chain reaction (PCR) products from 15 cattle, consisting of five randomly selected individuals from Chinese Simmental, Holstein and Sanhe cattle breeds each. Sixteen of these SNPs were in coding regions (cSNP). However, the 3'-untranslated region was comparatively conservative and no SNP was found in it. The SNP (g.8664C>T) found in the Toll IL-1 receptor (TIR) domain of the bovine TLR4 gene leads to amino acid substitution from Thr (C allele) to Ile (T allele). Three hundred and ninety seven cows from Chinese Simmental, Holstein and Sanhe cattle breeds were genotyped for SNP (g.8664C>T) using the method of created restriction site PCR together with restriction fragment length polymorphism (RFLP) by Hinf I. An association study between the SNP and somatic cell score (SCS) in the three breeds showed that the SCS of individuals with a CC genotype was significantly lower than that of the TT genotype. <![CDATA[<b>Heritability estimates and correlations between production and reproductive traits in Lori-Bakhtiari sheep in Iran</b>]]> Heritablities and correlations were estimated between lamb body weight at different ages and reproductive traits in the Lori-Bakhtiari sheep breed. Data and pedigree information for Lori-Bakhtiari sheep used in this study were 5826 records of body weight of lambs from 240 sires and 1627 dams, and 5741 records of reproductive traits from 1797 ewes collected from 1989 to 2006 from a Lori-Bakhtiari flock at the Shooli station in Shahrekord. The lamb traits investigated were weights at birth (BWT), weaning (WWT) and at six months of age (WT6). The reproductive traits were conception rate (CR), litter size at birth per ewe lambing (LSB/EL), litter size at weaning per ewe lambing (LSW/EL), litter size at birth per ewe exposed to a ram (LSB/EE), litter size at weaning per ewe exposed (LSW/EE), total litter weight at birth per ewe lambing (TLWB/EL), total litter weight at weaning per ewe lambing (TLWW/EL), total litter weight at birth per ewe exposed (TLWB/EE) and total litter weight at weaning per ewe exposed (TLWW/EE). (Co)Variance components and genetic parameters were estimated using the restricted maximum likelihood procedure applying three multi-trait animal models. The estimates of direct heritability for lamb body weights were 0.31 ± 0.02 at birth, 0.10 ± 0.02 at weaning and 0.19 ± 0.02 at six months of age, and estimates of maternal heritability were 0.22 ± 0.02, 0.16 ± 0.02 and 0.04 ± 0.02, respectively. The estimates of heritability for reproductive traits varied from 0.02 ± 0.01 for CR to 0.23 ± 0.01 for TLWB/EL, and repeatability estimates for reproductive traits ranged from 0.11 for CR to 0.28 for LSB. Genetic correlations among lamb body weight and various reproductive traits were positive and varied from 0.06 to 0.98. Phenotypic correlations were lower than genetic correlations (0.01 to 0.20). The estimates of genetic correlations between lamb body weight with CR and litter size at birth and at weaning were low to moderate, while those between lamb body weight with TLBW and TLWW per ewe lambing and per ewe exposed were positive and very high. Thus, lamb body weight at weaning or at six months of age could be considered as selection criteria to indirectly improve reproductive traits in Lori-Bakhtiari sheep because the heritability of lamb body weight was more than that of reproductive traits and can be measured at an early stage in the life of the animal. <![CDATA[<b>Estimates of genetic parameters and effect of inbreeding on milk yield and composition in South African Jersey cows</b>]]> The effect of inbreeding on the 305-d yields of milk, fat and protein, and the percentages of fat and protein in the first three lactations was estimated using records on the South African Jersey cows that participated in the National Dairy Animal Improvement Scheme. Inbreeding coefficients were estimated using the entire pedigree records of the Jersey breed and ranged from 0 to 42%. Data were analyzed using a repeatability animal model. The statistical model included the fixed effects of herd-year-season, age of the cow at calving, calving interval, inbreeding as a discrete or continuous variable and random effects of direct additive genetic, permanent environment of the cow and the residual effects. The multitrait derivative-free REML algorithm was used to obtain estimates of the variance components, ratios and empirical best linear unbiased estimates of the effects of inbreeding. Estimates of heritability were 0.26 (±0.009), 0.19 (±0.008), 0.23 (±0.008), 0.39 (±0.009), and 0.53 (±0.009) for milk, fat and protein yields and fat and protein percent, respectively. Corresponding estimates of the ratio of permanent environmental effect of the cow to total phenotypic variance were 0.20 (±0.008), 0.18 (±0.007), 0.21 (±0.007), 0.14 (±0.008) and 0.13 (±0.008). The regression coefficients for yields (kg) of milk, fat and protein were -15.42 (±1.13), -0.64 (±0.05), and -0.59 (±0.04), and 0.0011 (±0.0005) and 0.0003 (±0.0003) for percent (%) of fat and protein for each 1% increase in inbreeding, respectively. These results provide evidence of inbreeding depression for milk yield and composition traits in the South African Jersey population. <![CDATA[<b>Results of 23 years of selection for post-weaning weight in a Caracu beef herd</b>]]> Data from 1 698 animals belonging to an experimental Caracu herd were analysed with the objective of calculating the population selection differentials, generation intervals, effective size and inbreeding coefficients, and to estimate the direct and correlated responses for growth traits after 23 years of selection for post-weaning weight. The following traits were analysed: birth weight (BW), weaning weight corrected to 210 days of age (W210), weight corrected to 378 days for the males (W378), weight corrected to 550 days for the females (W550) and hip height for the males (HGTm) at the end of a feedlot test, and for the females (HGTf) at 550 days of age. The sire (W378) and dam (W550) weighted selection differentials for post-weaning weight were 1.10 and 0.28 standard deviation units and generation intervals 5.2 and 6.2 years, respectively. Mean inbreeding coefficient increased in the last five years, from 0.49 to 1.95%. The heritability estimates were 0.38, 0.27, 0.36, 0.37, 0.35 and 0.41 for BW, W210, W378, W550, HGTm and HGTf, respectively. The annual genetic trend estimates were 0.98 ± 0.17 kg/year for W378 and 0.27 ± 0.15 kg/year for W550. The estimates for the correlated responses to selection were 0.08 ± 0.02 kg/year for BW, 0.48 ± 0.11 kg/year for W210, 0.06 ± 0.02 cm/year for HGTm and 0.02 ± 0.02 cm/year for HGTf. These results confirmed that direct selection for post-weaning weight based on individual performance was relatively effective in achieving progress in all the growth traits. <![CDATA[<b>Effect of sage extract <i>(Salvia officinalis)</i> on growth performance, blood parameters, oxidative stress and DNA damage in partridges</b>]]> This study was performed to evaluate the effect of different doses of sage extract on the growth and blood parameters, oxidative stress and DNA damage in partridges. In total, 252 day-old partridges (Alectoris chukar) were used. The birds were divided into four groups: 0.1% flavomycin was included in the diet of the control group (I) while 2.5, 5.0 and 7.5 mL sage extract/kg were included in the diets of treatment groups II, III and IV, respectively. At the end of the experiment no significant differences between treatments were observed in live weight, live weight gain, feed consumption, feed conversion ratio, carcass weight and survival rate. In addition, blood analyses indicated that the differences between groups in the amounts of plasma cholesterol, triglyceride high density lipoprotein (HDL), very low density lipoprotein (VLDL) and alkaline phosphates (ALP) were not significantly different. Furthermore, treatments did not affect total sulphydryl (SH) and lipid hydroperoxide (LOOH) concentrations, total antioxidant response or the total oxidant status (TOS). However, sage extract significantly decreased DNA damage in a linear, dose-dependent manner whilst the antibiotic, flavomycin, elevated the oxidative stress index (OSI) and resulted in DNA damage. It was concluded that supplementing sage extract in the partridge diet at the doses studied does not lead to a negative effect on the growth performance of these birds. <![CDATA[<b>The effect of constant photoperiod on testis weight and the use of comb area to predict testis weights in broiler breeders males</b>]]> From the literature, it is evident that broiler breeder pullets exhibit photorefractoriness, and while it is assumed that male broiler breeders respond in a similar manner to females, it would be beneficial to determine if this is the case. This would enable lighting programmes to be designed that will ensure maximum fertility of both males and females. Male broiler breeders were housed in light-tight rooms and given constant photoperiods of 8, 10, 12, 14, 16 or 18 h/d. One or two birds were sampled from each room weekly from 71 to 232 d, and the remaining birds at 467 d, and testis weights measured. There was no significant difference between left and right testis weights, so the average was used in the analyses. Digital images of the head were recorded prior to slaughter and of four birds in each room weekly. The area of the comb was measured using image analysis software. The relationship between comb area and average testis weight was determined by regression analysis, with a logistic curve being best at fitting the data. A positive, significant relationship was observed with 69% of the variance in average testis weight being accounted for by comb area. Thus, comb area could provide a reasonable, non-invasive technique to assess fertility. At 165 d, average testis weights showed strong evidence that males exhibit juvenile photorefractoriness in a manner similar to females. Males on shorter photoperiods matured faster than those on photoperiods of 14 h and longer. As the birds aged, the effects of photorefractoriness wore off, but at the end of the experiment adult photorefractoriness was again evident, with birds on 14 h and longer having smaller average testis weights, and therefore, no longer responding to the stimulatory photoperiod. <![CDATA[<b>Mapping QTL for fatty acid composition that segregates between the Japanese black and Limousin cattle breeds</b>]]> The objective of this study was to search for quantitative trait loci (QTL) that segregate between Japanese Black and Limousin cattle breeds and affect relative amounts of saturated (SFA), mono-unsaturated (MUFA) and poly-unsaturated (PUFA) fatty acids. Six F1 Japanese Black-Limousin cross bulls were joined with 121 F1 females over a three-year period to produce 328 F2 progeny. Calves, aged from 450 to 641 d (average 561 d), were harvested using standard industry procedures. After aging, 2.54 cm thick steaks were cut from the posterior end of the wholesale rib, frozen at -20 °C, and held for determination of fatty acid composition. Percentages of the individual fatty acids were classified into percentages of SFA, MUFA and PUFA. Two hundred seventeen microsatellite markers covering the 29 bovine autosomes were assayed and QTL were identified by least squares regression. Genome-wise significant QTL with additive effects on SFA (-0.61 ± 0.19%), MUFA (0.93 ± 0.19%) and PUFA (-0.52 ± 0.11%) were observed near the centromere of BTA2. Also observed were five QTL indicative of dominance effects on: MUFA (BTA9, 119 cM, -1.87 ± 0.72%; BTA22, 47 cM, 1.85 ± 0.60%) and PUFA (BTA9, 54 cM, -1.49 ± 0.42%; BTA10, 38 cM, 1.20 ± 0.35%; and BTA15, 14 cM, 1.11 ± 0.36%). Based on these results, we conclude that it may be possible to improve the healthfulness of beef by manipulating fatty acid composition using genetic markers and appropriate crossbreeding systems. <![CDATA[<b>Leptin gene polymorphism in Indian Sahiwal cattle by single strand conformation polymorphism (SSCP)</b>]]> Leptin, a 16-Kilo dalton protein produced by the obesity (ob) gene, plays an important role in the regulation of feed intake, energy metabolism, growth and reproduction in cattle. The genetic variation of the leptin gene in Sahiwal cattle (Bos indicus) was investigated using an optimized non-radioactive polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis of 13 amplified fragments covering almost the entire gene. Twenty-eight SSCP band patterns were detected from 10 of these fragments in a sample of 202 Sahiwal cattle. Polymorphisms were detected in the samples, indicating that Sahiwal cattle have high genetic variability in the entire leptin gene. This result opens interesting prospects for future breeding programmes and conservation strategies. These leptin gene variants can be sequenced and screened in the entire population to develop single nucleotide polymorphisms (SNPs) for association studies with different productive and reproductive performances and marker assisted selection.