Scielo RSS <![CDATA[South African Journal of Animal Science]]> vol. 45 num. 1 lang. es <![CDATA[SciELO Logo]]> <![CDATA[<b>Dietary effect of silage type and combination with camelina seed on milk fatty acid profile and antioxidant capacity of sheep milk</b>]]> The present study sought to quantify the differences between maize-based (MS) and grass-silage-based (GS) diets in terms of their effect on the milk yield, milk fatty acid composition and antioxidant capacity in dairy ewes, and to test the hypothesis that it is possible to improve yield, fatty acid (FA) composition and antioxidant capacity by supplementing diet with camelina seed (Cs). Experimental diets consisted of a 2 x 2 factorial arrangement of type of silage (GS vs. MS) and camelina seed (-Cs vs. +Cs). Feeding the MS diets increased net energy for lactation (NE L) intake, raw milk yield and fat, protein and lactose yields. Feeding +Cs increased energy corrected milk (ECM), milk fat content and fat yield. Maize silage consumption is associated with an increased proportion of hypercholesterolemic fatty acids (HFA) and a higher value of the atherogenicity index. However, an MS diet led to an increased share of t11-C18:1 and c9,t11-conjugated linoleic acid (CLA) in milk. Milk FA profile in ewes fed GS diet was of higher quality for human beings owing to higher concentrations of α-linolenic acid and a lower content of HFA. Supplementing with camelina seed resulted in a higher concentration of t11-C18:1, c9,t11-CLA and C18:3n-3 in milk fat. The trolox equivalent antioxidant capacity (TEAC) value of milk was higher in milk from MS-fed ewes compared with that of their counterparts fed GS. Dietary supplementation with camelina seed increased the oxidative stability of milk samples. These results suggest that grass-silage-based diet supplemented with camelina seed results in milk of better quality for human consumption. <![CDATA[<b>The effect of breed on fatty acid composition of subcutaneous adipose tissues in fat-tailed sheep under identical feeding conditions</b>]]> A study was conducted to evaluate the fatty acid (FA) profile of subcutaneous adipose tissue and tailfat of two fat-tailed sheep breeds under identical feeding conditions. Twelve male lambs from two breeds, Sanjabi (n = 6), weighing 23.3 ± 0.48 kg, and Mehraban (n = 6), weighing 26.1 ± 2.14 kg, were used in this investigation. All animals were weighed and slaughtered at the end of a 90-day fattening period and FA composition of subcutaneous adipose tissue and tailfat was determined. Significant breed differences in total FA, total polyunsaturated fatty acid (PUFA) and n-6PUFA contents were observed in the subcutaneous adipose tissue, but not in the tailfat. Breed differences were observed in the conjugated linoleic acid (CLA) content of subcutaneous adipose tissue, with higher levels in Sanjabi than in Mehraban lambs. Linoleic and α-linolenic acid of subcutaneous adipose were significantly higher in the Sanjabi breed than in the Mehraban breed. Thus, adipose tissue from fat-tailed Sanjabi lamb has a higher proportion of health-promoting linoleic and α-linolenic acids, unsaturated fatty acids (UFA) and CLA, suggesting that the Sanjabi breed could be used for producing healthier lamb products. <![CDATA[<b>An exploratory analysis to determine the impact of fixed effects and to establish genetic parameters across six types of ostrich feathers</b>]]> After a decline in value, ostrich feathers have again become an important part of the income of ostrich producers. Between 22586 and 22753 feather weights, as well as length and width measurements, were obtained from feathers harvested annually during the resting period from a pair-bred ostrich flock maintained at Oudtshoorn Research Farm from 2001 to 2012. The flock consisted mostly of the South African Black (SAB) genotype, but birds from the Zimbabwean Blue (ZB) and Kenyan Redneck (KR) strains were also introduced to study strain effects, as well as the effect of crossbreeding between these genotypes (ZB x SAB; SAB x ZB; KR x SAB; SAB x KR). The feathers were sorted into six feather-type categories, namely floss, short hard body feathers, long hard body feathers, tail feathers, white plumes and short body floss. White plumes had the highest average feather length (AFL), average feather width (AFWD) and square-root-transformed feather weight (SRFW) at 66.2 ± 0.38 cm, 21.2 ± 0.23 cm and 13.66 ± 0.17 g, respectively. A significant decline in AFL took place from 2001 and 2012 (40.0 ± 0.25 cm and 38.7 ± 0.56 cm, respectively), while AFWD stayed fairly constant. Feather weights were higher for males than females resulting in a 24% higher geometric mean for backtransformed feather weights (GMFW) for males relative to females. SAB birds outperformed ZB and KR birds for AFL, AFWD and SRFW. Crosses were intermediate and sometimes comparable with the SAB genotype. Except for long hard body plumes, the weights for all the feather types were higher for the purebred SAB breeders compared with purebred ZB and KR breeders. Heritability estimates of AFL, AFWD and SRFW across the six feather categories were low to moderate at 0.080 ± 0.012, 0.044 ± 0.009 and 0.116 ± 0.017, respectively. The animal permanent environmental effect for the feather traits was lower in magnitude and ranged between 0.025 ± 0.008 for AFL and 0.041 ± 0.012 cm for SRFW. Direct genetic correlations of feather dimensions with SRFW were moderate to high at 0.287 ± 0.117 with AFL and 0.614 ± 0.072 with AFWD. The present results indicate that feather quantity can be improved by genetic selection in ostriches, and further studies should be conducted. <![CDATA[<b>Fatty acid profile and health lipid indices in the raw milk of Simmental and Holstein-Friesian cows from an organic farm</b>]]> The aim of this study was to compare the health-related fatty acid (FA) profiles and health lipid indices in the raw milk of Simmental and Holstein-Friesian cows from an organic farm. The milk from Simmental cows had a significantly higher content of C12:0, C16:1cis9, C17:1trans9, C18:2cis9,12 (LA), C18:3cis9,12,15 (LNA), C20:1cis9, C20:4cis5,8,11,14, n-6 PUFA, total polyunsaturated fatty acids (PUFAs) and unsaturated fatty acids (UFAs), and a lower content of C15:0, C18:0, C20:0, C22:0 and conjugated linoleic acid (CLA) in the total content of FA than the milk of Holstein-Friesian cows. The PUFA/SFA and UFA/saturated fatty acid (SFA) ratios in the milk from Simmental cows were significantly higher, whereas the thrombogenic index and the LA/LNA ratio were significantly lower compared with the milk of Holstein-Friesian cows. <![CDATA[<b>The effect of dietary protein on breast meat yield of broilers reared on different daylengths</b>]]> The objective of the trial reported here was to determine whether breast meat yield would improve in broilers reared on short daylengths if higher levels of dietary protein were fed. To that end, 3200 Ross 308 International broilers were reared to 35 d in eight light-tight rooms, each room being divided into four pens which were populated with 100 feather-sexed male or female chicks. The lighting treatments used were 12, 16, 20 and 24 h light/d, and four balanced protein levels, being 0.85, 1.00, 1.15 and 1.30 of the Aviagen amino acid recommendations, were fed. At 35 d, three birds from each pen were sacrificed for measurement, individually, of physical and chemical characteristics. Body weight gain to 35 d was unaffected by both dietary protein content and light. FCE increased with dietary protein content to day 21. Feed intake to day 35 was not influenced by light or by dietary protein content. Birds on 24 h had a higher mortality compared with those on the three other lighting programmes, which did not differ from one another. Body protein content increased with both daylength and dietary protein content whereas body lipid content was influenced (decreased) only by dietary protein. Breast meat yield from birds reared on 12 h was not improved when these birds were fed high protein feeds whereas yields were increased in birds on the three longer daylengths used when feed protein was increased. The decreased breast meat yield in broilers given short daylengths is therefore not the consequence of a shortage of dietary protein. <![CDATA[<b>Effects of <i>Rhus coriaria </i>on nutrient composition, thiobarbituric acid reactive substances and colour of thigh meat in heat-stressed broilers</b>]]> Heat stress negatively affects the meat quality in broiler chickens, as indicated by lipid peroxidation. The aim of this study was to investigate the effects of 0.0, 2.5, 5.0 and 10 g sumac fruit powder/kg of the diet, along with 100 mg α-tocopherol acetate (AT)/kg as antioxidants, on meat characteristics of broilers under heat stress conditions. Consumption of 5.0 g sumac/kg decreased the thiobarbituric acid reactive substance (TBARS) concentration in thigh meat. The thigh meat pH increased only as a result of AT consumption. Dietary inclusion of both AT and 10 g sumac/kg decreased the fat content of the meat. None of the meat colour indices, lightness (L*), redness (a*) and yellowness (b*), was affected by dietary treatments. It was concluded that dietary sumac consumption improved the TBARS and pH, and decreased thigh meat fat in broilers under heat stress.