Scielo RSS <![CDATA[Revista Brasileira de Zootecnia]]> vol. 47 num. lang. es <![CDATA[SciELO Logo]]> <![CDATA[Development and reproductive performance of Hereford heifers of different frame sizes up to mating at 14-15 months of age]]> ABSTRACT Body development and reproductive performance of a hundred forty-two 14 to 15-month-old heifers, classified at weaning according to frame size as small, medium, and large, were evaluated. The parameters evaluated were: body weight, hip height, body condition score, weight gain, ovarian activity, and pregnancy rate. At weaning, body weight and hip height were significantly different among frame scores, (small – 133.0 kg, 92.2 cm; medium – 158.5 kg, 96.6 cm; and large – 185.2 kg; 100.2 cm). After weaning, heifers grazed together on natural pastures during the autumn and on ryegrass (Lolium multiflorum La.) during the winter and spring. Frame score differences remained until the beginning of the breeding season (BS), starting on average at 14 months of age. Weight gain between weaning and the beginning of BS was not different among frame scores (0.740 kg/day, on average). Body weights at the beginning of the BS were significantly different, of 255.7 kg (53.3% of the mature weight) for small heifers, 285.0 kg (59.4%) for medium heifers, and 307.6 kg (64.1%) for large heifers. Ovarian activity at the beginning of the BS was not different among the three groups. The average weight gain values during the BS of 0.492, 0.472, and 0.421 kg/day for small, medium, and large heifers, respectively, were significantly different. Pregnancy rates were not different among groups (small, 71.4%; medium, 76.4%; and large, 76.5%). Frame score did not influence the reproductive performance of heifers, but the small and medium heifers conceived 29 and 20 days earlier, respectively, than the large heifers. <![CDATA[Protein and mRNA expression of gonadotropin-releasing hormone receptor in yaks during estrus]]> ABSTRACT To demonstrate the role of gonadotropin-releasing hormone (GnRH) in yaks (Bos grunniens), we characterized the expression of gonadotropin-releasing hormone receptor (GnRHR) mRNA and protein. The level of GnRHR mRNA in the hypothalamus was higher than that in the pineal gland, pituitary gland, and ovary during estrus. Immunofluorescence analysis showed that GnRHR was expressed in the pinealocyte, synaptic ribbon, and synaptic spherules of the pineal gland and that melatonin interacts with GnRHR via nerve fibers. In the hypothalamus, GnRHR was expressed in the magnocellular neurons and parvocellular neurons. In the pituitary gland, GnRHR was expressed in acidophilic cells and basophilic cells. In the ovary, GnRHR was present in the ovarian follicle and Leydig cells. Gonadotropin-releasing hormone receptor is located in the pineal gland, hypothalamus, pituitary, and gonad during estrus of yaks and is mainly expressed in the hypothalamus and ovaries during the estrus period. <![CDATA[Individual responses of growing pigs to threonine intake]]> ABSTRACT A nitrogen balance test was performed to evaluate the individual responses of growing pigs to threonine intake. Eight commercial barrows were used (body weight ranging from 15 to 20 kg). A dose-response study was performed, in which the threonine supply increased in seven equidistant steps (the seven dietary threonine levels ranged from 50 to 120% of the requirements) every three days for each pig. The levels of all other amino acids were 20% higher than the tested amino acid. Nitrogen retention as a function of threonine intake was calculated per individual and per group (NLIN and NLMixed, respectively) using a linear plateau model. The highest break point value was 42.42 g of threonine intake (the most demanding individual), whereas the lowest value was 34.16 g (the least demanding individual), corresponding to a difference of 19%. In terms of N retention, the highest plateau value was 66.71 g and the lowest was 49.48 g, with a difference of 25%. There was no significant correlation between slope and plateau values or between slope and break point values. When using the model in which all parameters were random effects, the variations in threonine intake and nitrogen retention were 1.68±1.30 and 0.01±0.10 g, respectively, and no variance in the slope of the curve was detected. The average daily threonine intake values for the maximum response obtained in the group, as calculated by the NLIN and NLMixed procedures, were 13.96 and 14.02 g/day, respectively. The threonine intake for the maximum N retention between individuals ranged from 34.16 to 42.42 g, corresponding to a difference of 19%. The current recommended intake to optimize N retention is 14.02 g/day. The group responses obtained by the NLMixed procedures are very similar to those estimated by the NLIN procedure (all individuals). <![CDATA[Effect of linseed oil sediment in the diet of pigs on the growth performance and fatty acid profile of meat]]> ABSTRACT The objective of this investigation was to examine the influence of dietary linseed oil sediment on the growth performance and fatty acid composition in the muscle tissue of pigs. Sixty-eight crossbred Swedish Yorkshire × Norwegian Landrace pigs were allocated to two trials with two different levels of linseed oil sediment. Twenty-four pigs in Trial 1 were allotted into control 1 and experimental 1, of 12 animals each, and forty-four pigs in Trial 2 were allotted into control 2 and experimental 2, of 22 animals each. In both treatments, control and experimental groups were formed by animals analogous by origin, gender, weight, and condition score. Control pigs were fed identical diets ad libitum in both trials. The treated pigs were fed the same diet as control pigs, but vegetable oil was replaced by linseed oil sediment at a rate of 25 g kg−1 (experimental group 1) in Trial 1 and 50 g kg−1 (experimental group 2) in Trial 2. The results indicated that in both trials, vegetable oil replacement for linseed oil sediment had no significant influence on the growth rate of pigs, though a tendency was observed for a more rapid daily gain. Addition of linseed oil sediment to the diets increased the content of n-3 α-linolenic (C18:3n-3), eicosatrienoic (C20:3n-3), and eicosapentaenoic (C20:5n-3) acids and total n-3 polyunsaturated fatty acids (PUFA) and decreased the C18:2n-6/C18:3n-3 and n-6:n-3 ratios and the thrombogenic index of meat. Moreover, the addition of 50 g kg−1 linseed oil sediment resulted in higher content of docosapentaenoic (C22:5n-3) fatty acid, total PUFA, and PUFA:SFA ratio. Supplementation of pig diets with linseed oil sediment increases the content of α-linolenic, eicosatrienoic, eicosapentaenoic, and docosapentaenoic fatty acids and total content of n-3 polyunsaturated fatty acids and have a positive effect by improving the polyunsaturated fatty acids:saturated fatty acids and n-6:n-3 fatty acid ratios in meat.