Scielo RSS <![CDATA[South African Journal of Animal Science]]> http://www.scielo.org.za/rss.php?pid=0375-158920090002&lang=en vol. 39 num. 2 lang. en <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>Long-term selection experiment with Afrikaner cattle 1</b>: <b>Environmental factors affecting calf growth traits</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0375-15892009000200001&lng=en&nrm=iso&tlng=en A selection and line x environment interaction study with grade Afrikaner cattle was established in 1956 at Matopos Research Station, Zimbabwe. Two selection lines of 100 cows each were reared in different management environments. The non-supplemented (NS) line relied on the range throughout the year and was mated to calve with the onset of the rains (December to February). The supplemented (S) line was offered protein-rich supplements during the dry season and mated to calve prior to the onset of the rains (October to December). In 1976 lines were sub-divided into four lines with 75 cows each, where one sub-line remained within each environment as a control; the remaining sub-lines were interchanged between environments. Bulls were selected on weaning weight within control lines, while replacement heifers were selected on weight at mating within sub-line. Data collected over a 40-year period (1958 to 1997) were analyzed. There were no line differences, however, productivity in the S environment was superior compared with the NS environment. While there were no environment differences in birth weight, calves born early in the S environment were estimated to be 90 kg (33%) heavier at 18 months than calves born late in the NS environment. The performance of calf growth from birth to 18 months in this study has emphasized the importance of matching animal physiological status with seasonal changes in the sub-tropics. The effect of previous lactation status (PLS) increased from 1.2 ± 0.13 kg at birth to 7 ± 0.6 kg at 205 days of age, a difference that persisted to 18 months (5 ± 0.9 kg). Given the significant and consistent detrimental effects of PLS on calf growth, it is recommended that this effect be considered in routine evaluations. <![CDATA[<b>Long-term selection experiment with Afrikaner cattle 2</b>: <b>Genetic parameters and genotype x environment interaction for calf growth traits</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0375-15892009000200002&lng=en&nrm=iso&tlng=en A selection and line x environment interaction study with grade Afrikaner cattle was established in 1956 at Matopos Research Station, Zimbabwe. Two selection lines of 100 cows each were reared in different management environments. The non-supplemented (NS) line relied on the range throughout the year and was mated to calve with the onset of the rains (December to February). The supplemented (S) line was offered protein-rich supplements during the dry season and mated to calve prior to the onset of the rains (October to December). In 1976, lines were sub-divided into 75 cows each, where one sub-line remained within each environment as a control; the remaining sub-lines were interchanged between environments. Bulls were selected on weaning weight within control lines, while replacement heifers were selected on weight at mating within sub-line. Data recorded over approximately six generations of selection (40 years) was analyzed. The direct heritability estimates were moderate for birth weight (0.4), but low (0.1 to 0.2) for the other traits, similarly maternal heritabilities were low (0.1 to 0.2). Permanent environmental effects due to dam were moderate (0.3) for weights at 205 days, weaning and at 12 months, and was still an important effect at 18 months. Relatively large negative (-0.4) direct-maternal genetic correlations were indicated for weaning and yearling weights. There were indications that all post-weaning weight traits evaluated were closely related giving rise to their joint inclusion in joint multivariate analysis. There were no indications of line x environment interactions, however, interaction of sire x year was important for all the traits highlighting the tremendous year to year variations experienced in the sub-tropics. There is a need to evaluate selection for genotypic stability, particularly for the more extensive farming environments. <![CDATA[<b>Long-term selection experiment with Afrikaner cattle 3</b>: <b>Selection applied and response in calf growth traits</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0375-15892009000200003&lng=en&nrm=iso&tlng=en A selection and line x environment interaction study with grade Afrikaner cattle was established in 1956 at Matopos Research Station, Zimbabwe. Two selection lines of 100 cows each were reared in different management environments. The non-supplemented (NS) line relied on the range throughout the year and was mated to calve with the onset of the rains (December to February). The supplemented (S) line was offered protein-rich supplements during the dry season and mated to calve prior to the onset of the rains (October to December). In 1976, after approximately two generations of selection, lines were sub-divided into 75 cows each, where one sub-line remained within each environment as a control; the remaining sub-lines were interchanged between environments. Bulls were selected on weaning weight within control lines, while replacement heifers were selected on weight at mating within sub-line. Data recorded over approximately six generations of selection (40 years) were analyzed. The average age of sires and dams at the time of birth of their progeny was 5.9 and 7.5 years respectively in the pre-crossover phase and was reduced to 4.4 and 6.5 years respectively in the post-crossover phase. The rate of inbreeding across lines and environments was 1.2%/generation. The cumulative selection differential trends for both the S and NS lines for adjusted weaning weight plotted against generation number were very low, relatively linear and greater for the S line (0.10 s.d./year) compared with the NS line (0.08 s.d./year). Direct and correlated responses were uniformly low, approximating 1% of the trait mean per generation, and indicating that considerable attention was given to secondary characters. These results concur with general findings of effective direct and correlated responses of weight traits to individual selection. <![CDATA[<b>Long-term selection experiment with Afrikaner cattle 4</b>: <b>Cow fertility and calf survival</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0375-15892009000200004&lng=en&nrm=iso&tlng=en A selection and line x environment interaction study with grade Afrikaner cattle was established in 1956 at the Matopos Research Station, Zimbabwe. Two selection lines of 100 cows each were reared in different management environments. The non-supplemented (NS) line relied on the range throughout the year and was mated to calve with the onset of the rains (December to February). The supplemented (S) line was offered protein-rich supplements during the dry season and mated to calve prior to the onset of the rains (October to December). In 1976, after approximately two generations of selection, lines were sub-divided into 75 cows each, where one sub-line remained within each environment as a control; the remaining sub-lines were interchanged between environments. Bulls were selected on weaning weight within control lines, while replacement heifers were selected on weight at mating within sub-line. Data recorded over six generations of selection (40 years) were analyzed. The average incidence of calving success (the presence or absence of a calf) was 68%. Heritability and repeatability (in parenthesis) estimates for calving success and calving date were 0.08 ± 0.02 (0.10 ± 0.02) and 0.09 ± 0.02 (0.17 ± 0.02), respectively. Favourable genetic trends were shown (-0.8 ± 0.09 days/generation for calving date). Correlation estimates of sires' EBV between measures of fertility and growth were all unfavourable. A significant interaction was manifested for calving success and was due to the markedly poorer performance (10 percentage units) of the S line cows in the NS environment. The interaction serves to reinforce the commonly held principle that cattle, and in particular breeding cows, be reared in a similar environment in which selection takes place advocating antagonistic selection (upwards selection in a poor environment). Calf losses within the first 24 h of birth and pre-weaning were 3.8% and 8%, with heritability estimates of 0.15 ± 0.07 and 0.07 ± 0.03, respectively. It is recommended that fertility and calf survival be included in routine breed evaluations. There is a need to implement data collection strategies to ensure that all calving activities are comprehensively recorded. <![CDATA[<b><i>In vitro</i></b><b> biological activity of tannins from <i>Acacia</i> and other tree fruits</b>: <b>Correlations with colorimetric and gravimetric phenolic assays</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0375-15892009000200005&lng=en&nrm=iso&tlng=en This study was designed to investigate impact of tannins on in vitro ruminal fermentation parameters as well as relationships between concentration and in vitro biological activity of tannins present in tree fruits. Dry and mature fruits of known phenolic content harvested from Acacia nilotica, A. erubescens, A. erioloba, A. sieberiana, Piliostigima thonningii and Dichrostachys cinerea tree species were fermented with rumen fluid in vitro with or without polyethylene glycol (PEG). Correlation between in vitro biological activity and phenolic concentration was determined. Polyethylene glycol inclusion increased cumulative gas production from all fruit substrates. The largest increase (225%) after 48 h incubation was observed in D. cinerea fruits while the least (12.7%) increase was observed in A. erubescens fruits. Organic matter degradability (48 h) was increased by PEG inclusion for all tree species except A. erubescens and P. thonningii. For D. cinerea fruits, colorimetric assays were poorly correlated to increases in gas production due to PEG treatment. Ytterbium precipitable phenolics (YbPh) were also poorly correlated with response to PEG for A. erioloba and P. thonningii fruits. However, YbPh were strongly and positively correlated to the increase in cumulative gas production due to PEG for A. erubescens and A. nilotica. Folin-Ciocalteau assayed phenolics (SPh) were not correlated to response to PEG in P. thonningii and A. sieberiana. It was concluded that the PEG effect on in vitro fermentation was closely related to some measures of phenolic concentration but the relationships varied with tree species. <![CDATA[<b>Effects of novel feed additives in wheat based diets on performance, carcass and intestinal tract characteristics of quail</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0375-15892009000200006&lng=en&nrm=iso&tlng=en The present study was conducted to investigate the effects of the supplementation of an antibiotic growth promoter or novel feed additives with or without a xylanase-based enzyme complex to wheat-based diets on the growth performance, carcass yields and quality and intestinal characteristics (length of the total and small intestine, pH and viscosity of digesta, microflora) of Japanese quail. Eight hundred and forty day-old male quail chicks were randomly assigned to 14 groups of similar mean weight each of which included three replicates of 20 quail. The control group received a wheat-soyabean meal basal diet. In the treatment groups, the basal diet was supplemented with one of the following: an antibiotic, oregano essential oil, cinnamon essential oil, oregano essential oil plus cinnamon essential oil, a probiotic, a mannanoligosaccharide, and the same diets plus an enzyme. During the 35-d growth period there were no significant differences in body weight gain (BWG), feed intake (FI) or feed conversion ratio (FCR) of quail between dietary treatments. The use of oregano essential oil plus cinnamon essential oil or mannanoligosaccharide without the enzyme complex in the quail diets decreased plasma total cholesterol level compared to the control diet. The dietary supplementation of AGP, oregano essential oil, cinnamon essential oil, oregano essential oil plus cinnamon essential oil without the enzyme complex decreased plasma triglyceride levels compared with the control diet. When oregano essential oil, cinnamon essential oil, oregano oil plus cinnamon oil, a probiotic or a mannanoligosaccharide with an enzyme complex were used in a wheat based quail diet, the intestinal viscosity was significantly decreased compared to the control diet. Although the use of essential oils in combination with the enzyme complex, a probiotic and a mannanoligosaccharide with or without the enzyme complex in the wheat based diet significantly reduced the intestinal viscosity compared to the control diet, these treatments negatively decreased plasma total cholesterol and triglyceride. <![CDATA[<b>Investigation of effects of three candidate genes on leg action and fat deposition traits in pigs</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0375-15892009000200007&lng=en&nrm=iso&tlng=en Data from 188 sows were used in the current study to examine the effects of high mobility group AT-hook1 (HMGA1), transcription factor 7-like-2 (TCF7L2) and insulin-like growth factor binding protein 3 (IGFBP3) genes on leg action and fat deposition traits, and further to explore the possible relationships between these genes on both traits. The candidate genes used in the study are known for their roles in fat deposition and growth. Overall leg action was scored on a scale of 1 (good movement) to 9 (leg weakness). Fatness traits included 10th rib backfat (BF10), adjusted 10th rib backfat to 125 kg (adjBF10) and last rib backfat (last BF), measured by ultrasonic imaging approach. The association analyses between single nucleotide polymorphisms (SNPs) and traits were performed using PROC MIXED procedures of SAS. The results showed that the associations between HMGA1, TCF7L2 and IGFBP3 genotypes with fat deposition traits were mostly suggestive in this limited data set. Leg action was also suggestively associated with IGFBP3 gene effects but was not associated with HMGA1 and TCF7L2 genes. Thus, IGFBP3 AA homozygote individuals tended to have had better movements (5.40), and were fatter when compared to GG homozygotes (5.84). The results from this study suggest a possible association between the IGFBP3 gene effects on both leg action and fatness. Therefore, further studies must be carried out in several populations, and using larger data to demonstrate these results conclusively. <![CDATA[<b>Apparent and true amino acid digestibility of artemia meal in broiler chicks</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0375-15892009000200008&lng=en&nrm=iso&tlng=en In order to determine the amino acid digestibility of artemia meal, five-week old male broiler chicks were given a semi-purified diet in which artemia meal was the sole source of protein. Apparent amino acid digestibility values of the assay diet, using ileal and excreta contents, were calculated using chromic oxide as indigestible marker. True digestibility values were calculated using endogenous output determined by feeding a nitrogen-free diet. The results showed that in determination of apparent amino acid digestibility of excreta, serine had the lowest (0.80) and methionine the highest (0.92) digestibility, while glycine had the lowest (0.88) and arginine and leucine the highest (0.95) apparent ileal digestibility. In measuring true excreta and ileal amino acid digestibility, alanine and glycine had the lowest (0.90 and 0.93) and methionine the highest (0.96 and 0.99) digestibility, respectively. In general, the site of measurement had no effect on apparent or true amino acid digestibility of artemia meal. <![CDATA[<b>Estimation of growth curve parameters in Konya Merino sheep</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0375-15892009000200009&lng=en&nrm=iso&tlng=en The objective of this study was to determine the fitness of Quadratic, Cubic, Gompertz and Logistic functions to the growth curves of Konya Merino lambs obtained by using monthly records of live weight from birth to 480 days of age. The models were evaluated according to determination coefficient (R²), mean square prediction errors (MSPE) and Durbin Watson (DW) statistics. The R² values of the models ranged from 0.96 to 0.99 for females and from 0.96 to 0.99 for males. The Cubic model gave the best R² value of 0.99 in females, while the Logistic model gave the lowest R² value of 0.96 in females. The results indicated that the Quadratic and Gompertz models showed the best fit to growth of Konya Merino ewe lambs by having higher R² values, lower MSPE and non autocorrelation. By using these models live weights at later ages could be predicted from early partial live weight data. Further studies should be carried out on growth curve characteristics at later ages including adult age.