Influence of Palm Kernel Meal Inclusion and Exogenous Enzyme Supplementation on Growth Performance, Energy Utilization, and Nutrient Digestibility in Young Broilers

The objective of the present study was to investigate the influence of palm kernel meal (PKM) inclusion and exogenous enzyme supplementation on growth performance, nitrogen-corrected apparent metabolizable energy (AMEn), coefficient of apparent ileal digestibility (CAID) and total tract retention of nutrients in young broilers fed corn-based diets. Four inclusion levels of PKM (no PKM [PKM0], 8% [PKM8], 16% [PKM16], and 24% [PKM24]) and two enzyme additions were evaluated in a 4×2 factorial arrangement of treatments. A total of 384, one-d-old male broilers (Ross 308) were individually weighed and allocated to 48 cages (eight broilers/cage), and cages were randomly assigned to eight dietary treatments. Results indicated that the inclusion of 8% and 16% PKM increased (p<0.05) the weight gain compared to the PKM0 diet. Birds fed the PKM8 diets had the highest (p<0.05) feed intake. Weight gain and feed intake were severely reduced (p<0.05) by feeding the PKM24 diet. Enzyme supplementation increased weight gain (p<0.05), independent of PKM inclusion level. In PKM0 and PKM8 diets, enzyme addition significantly (p<0.05) lowered feed conversion ratio (FCR); whereas enzyme addition had no effect on FCR of birds fed PKM16 and PKM24 diets. In PKM0 and PKM16 diets, enzyme addition significantly (p<0.05) increased CAID of nitrogen and energy but had no effect in the PKM8 and PKM24 diets. Inclusion of PKM into the basal diet, irrespective of inclusion level, enhanced (p<0.05) starch and fat digestibility. Inclusion of PKM at 16% and 24% resulted in similar CAID of neutral detergent fiber (NDF) but higher (p<0.05) than that of the PKM0 and PKM8 diets. Enzyme addition, regardless of the level of PKM inclusion, significantly (p<0.05) increased CAID of NDF. There was a significant (p<0.05) decrease in AMEn with PKM inclusion of 24%. The present data suggest that inclusion of PKM in broiler diets could be optimized if PKM-containing diets are formulated based on digestible amino acid contents and supplemented with exogenous enzymes. If amino acid digestibility and AME of PKM considered in the formulation, it can be included in broiler diets up to 16% with no deleterious effects on growth performance.

A sex difference in the cortisol response to tail docking and ACTH develops between 1 and 8 weeks of age in lambs

It is important to understand factors that may influence responses to stress, as these factors may also influence vulnerability to pathologies that can develop when stress responses are excessive or prolonged. It is clear that, in adults, the sex of an individual can influence the cortisol response to stress in a stressor specific manner. Nevertheless, the stage of development at which these sex differences emerge is unknown. We tested the hypothesis that there are sex differences in the cortisol response to tail docking and ACTH in lambs of 1 and 8 weeks of age. We also established cortisol responses in males when tail docking was imposed alone and in combination with castration at these ages. In experiment 1, 1 and 8 week old male and female lambs were subjected to sham handling, tail docking or, in males, a combination of tail docking and castration. In experiment 2, we administered ACTH (1.0 IU/kg) to male and female lambs at 1 and 8 weeks of age. There were significant cortisol responses to all treatments at both ages. Sex differences in the cortisol responses to tail docking and ACTH developed between 1 and 8 weeks of age, with females having greater responses than males. The data suggest that the mechanism for the sex difference in response to tail docking may involve the adrenal glands. At both ages, in males, the cortisol response to the combined treatment of tail docking and castration was significantly greater than that for tail docking alone.

Effects of dietary lipid type on muscle fatty acid composition, carcass leanness, and meat toughness in lambs

Isonitrogenous amounts of two protein sources differing in rumen degradation rate and in lipid composition were fed to sheep with or without a rapidly fermentable cereal grain. The effects on intake, carcass leanness, and muscle fatty acid (FA) composition were examined. Thirty-eight crossbred wether lambs (9 mo, 35 to 48 kg) were allocated by stratified randomization to six treatment groups: 1) basal diet of alfalfa hay:oat hay (20:80) ad libitum = basal; 2) basal + lupin (358 g DM/d) = lupin; 3) basal + fish meal (168 g DM/d) = fish meal; 4) basal + barley (358 g DM/d) = barley; 5) basal + barley + lupin (179 + 179 g DM/d) = barley/lupin; or 6) basal + barley + fish meal (179 + 84 g DM/d) = barley/ fish meal. Lambs were fed individually. Dietary treatments were imposed for 8 wk, and the supplements were offered at 2-d intervals. Daily feed intake and weekly BW of lambs were recorded. At the end of the feeding period lambs were slaughtered after an overnight fast. Hot carcass weight (HCW) and fat depth (GR; total fat and muscle tissue depth at 12th rib, 110 mm from midline) were recorded. At 24 h postmortem samples of longissimus thoracis (LT) and longissimus lumborum (LL) muscles were taken from chilled (4 degrees C) carcasses for the assessment of FA composition and meat tenderness, respectively. Lambs fed lupin or fish meal with or without barley had heavier slaughter weights (P < 0.004) and HCW (P < 0.001) than lambs fed basal or barley when initial BW was included as a covariate. The lupin diet also resulted in heavier carcasses (P < 0.05) than the fish meal or barley/fish meal diets. With GR as an indicator, fish meal and barley/ fish meal diets produced leaner carcasses (P < 0.01) than lupin and barley/lupin lambs. Long-chain n-3 FA content [20:5n-3 (P < 0.001), 22:5n-3 (P < 0.003), and 22:6n-3 (P < 0.001)] in the LT muscle were substantially higher with the fish meal and barley/fish meal diets, whereas muscle total n-6 FA was increased (P < 0.003) by lupin and barley/lupin compared with all other diets. Thus, increased muscle long-chain n-3 FA content occurred without an increase in fatness measured as GR, whereas increased muscle n-6 FA content was associated with an increase in carcass fatness. Under these circumstances, a reduction in carcass fatness had no effect on meat tenderness measured as Warner-Bratzler shear force.

Ontogenic and nutritional changes in circulating insulin-like growth factor (IGF)-I, IGF-II and IGF-binding proteins in growing ewe and ram lambs

The ontogeny of the IGF endocrine system was investigated in 15 young lambs before and after weaning at 62 days of age. Before weaning, plasma IGF-I concentrations were higher in rams than ewes, and plasma concentrations of IGF-II and IGF-binding protein-3 (IGFBP-3) also tended to be higher in rams than in ewes. Feed intake of ewes and rams was restricted after weaning to remove sex differences in feed intake. Plasma concentrations of IGF-I and IGFBP-3 did not differ between rams and ewes at 100 days of age, but plasma IGF-II was higher in rams than in ewes at this time. Since circulating concentrations of GH were higher in rams than in ewes at 100 days of age, this implies that the restricted feed intake blocked the IGF-I and IGFBP-3 responses to GH. We conclude that sex differences in circulating IGF-I and IGFBP-3 concentrations in the growing lamb alter with age, and are not present when nutrition is restricted.

GH, GH-releasing factor and somatostatin in the growing lamb: sex differences and mechanisms for sex differences

Factors contributing to sex differences in the somatotrophic axis were investigated in growing lambs. In the first experiment, circulating patterns of GH in venous blood, pituitary content of GH and GH mRNA, and median eminence (ME) contents of GH-releasing factor (GRF) and somatostatin (SRIF) were characterized in prepubertal ram and ewe lambs which were pair-fed to remove sex differences in feed intake. Mean and baseline plasma GH concentrations, GH pulse amplitude, and integrated plasma GH were greater in ram lambs than in ewe lambs, but GH interpulse interval did not differ between sexes. The pituitary GH content and ME contents of GRF and SRIF were greater in rams than in ewes, but steady-state levels of mRNA for GH in the pituitary gland did not differ between sexes. A second experiment investigated sex effects on the levels of SRIF in hypophysial portal blood, and found that these did not differ between sexes. We concluded that the presence of sexually dimorphic patterns of GH secretion in the growing lamb is independent of feed-intake differences between sexes. The lack of sex differences in circulating patterns of SRIF in portal plasma implies that there may be a difference in GRF secretion which may produce sexually dimorphic patterns of GH secretion in lamb.

Sexual dimorphism of circulating somatotropin, insulin-like growth factor I and II, insulin-like growth factor binding proteins, and insulin: relationships to growth rate and carcass characteristics in growing lambs

The effects of sex and age on patterns of circulating somatotropin (ST) concentration and plasma IGF-I, IGF-II, insulin, and IGF binding protein-3 (IGFBP-3) were studied in ram, wether, and ewe lambs (n = 7 or 8) sampled at mean ages of 81 (I1) and 158 d (I2). Between 81 and 158 d of age, rams grew more rapidly than wethers (P < .01), and wethers grew more rapidly than ewes (P < .01). The sex differences in growth were reflected in empty body weight at slaughter: rams > wethers > ewes (P < .05). Mean plasma ST concentrations, ST pulse amplitude, and integrated plasma ST concentrations were greater (P < .05) in rams than in ewes at I1 and I2. Characteristics of the ST plasma profile in wethers were generally intermediate between those of rams and ewes. The interpulse interval was greater in ewes than in wethers at I2. The IGF-I and IGFBP-3 concentrations were greater in rams than in ewes at both sampling times. Plasma IGF-II was greater in ewes than in rams at I2. Mean plasma ST was approximately two thirds less at I2 than at I1 regardless of sex. Mean plasma ST and IGF-I at both ages were positively correlated with growth. Mean plasma ST at I2 was negatively correlated with fatness at slaughter. Sex and age significantly affected patterns of circulating ST and concentrations of IGF-I and IGFBP-3 in prepubertal growing lambs, under conditions for which growth rates and composition were also sexually dimorphic.

Acute prenatal androgen treatment increases birth weights and growth rates in lambs

One hundred seventy-four Border Leicester x Merino ewes were mated to Romney Marsh rams. The ewes were randomly allocated to either an untreated control group or to one of four treatment groups. The treated groups were defined by the time (days postcoitus) of acute prenatal androgen treatment (APAT). The selected treatment times were 30, 40, 50, and 60 d postcoitus. Acute prenatal androgen treatment involved a single 2-mL i.m. injection of 100 mg/mL testosterone propionate. The statistical analysis of all measured parameters was performed using an analysis of variance via a general linear model. Postnatal plasma testosterone concentrations were not affected by treatment (P > .05). The time of treatment affected the observed responses to APAT (P < .05). Acute prenatal androgen treatment increased birth weight, ADG, and live weight and altered wool growth, plasma insulin levels, and ano-genital distance (P < .05).

Effects of growth hormone-releasing factors and cottonseed meal on hormones and metabolites in plasma from lambs fed lucerne chaff ad libitum

This study was part of an experiment on the effects of cottonseed meal (CSM) and growth hormone-releasing factor (GRF) on growth in lambs fed lucerne chaff. Forty-eight crossbred lambs were fed lucerne chaff ad libitum, alone or with a cottonseed meal supplement (CSM; 300 g/day). Eight lambs from each group were injected twice daily with recombinant or synthetic GRF (rGRF and sGRF respectively; 30 8g per kg body weight/day) or excipient only for 28 or 30 days. Jugular blood samples were obtained on days 0, 7, 14, 21 and 28. On day 29, blood samples were taken from selected lambs (n = 2/group) at 0, 20, 40, 60, 80, 100, 120, 160 and 240 min after injection. Supplementation of lucerne chaff with CSM generally increased glucose and urea concentrations in plasma, reflecting improved energy and protein status. However, concentrations of growth hormone, insulin-like growth factor-1 and insulin were unaffected by CSM, as were plasma proteins, triacylglycerols and non-esterified fatty acids. Injection of rGRF and sGRF stimulated secretion of growth hormone (GH), insulin-like growth factor-1 (IGF-1) and insulin. Peak GH concentrations (20 min) following injection of GRF appeared to be higher in lambs fed CSM than in those receiving lucerne chaff alone. In contrast, maximal concentrations of IGF-1 were seen after 14 days of treatment. These changes were accompanied by increased plasma glucose, with no changes in triacylglycerols, non-esterified fatty acids and protein. Plasma urea was reduced by GRF, indicating that amino acids were diverted away from catabolism towards protein synthesis. These two sources of GRF were very similar in their endocrine and metabolic effects. This confirms similar observations regarding their effects on growth performance and carcass composition.

Changes in the maternal body and feto-placental growth following various lengths of feed restriction during mid-pregnancy in sheep

The impact of maternal feed restriction during pregnancy on components of the maternal body and feto-placental growth was investigated to assess its influence on lamb birth weight. Single-bearing ewes were well-fed for the duration of pregnancy or feed restricted between the 30th and 96th, 50th and 96th or 75th and 96th day of pregnancy. Well-fed ewes increased in liveweight between the 30th and 96th day of pregnancy (48 g/day), while ewes feed restricted between the 30th and 96th, 50th and 96th and 75th and 96th day of pregnancy lost 55, 87 and 203 g/day respectively. Maternal fat deposits and muscle tissue of feed restricted ewes at the 96th day of pregnancy were less than for well-fed ewes. Placental weight was lower (P < 0.05) in ewes feed restricted between the 30th and 96th day of pregnancy, but not in ewes feed restricted between the 50th and 96th or the 75th and 96th day of pregnancy. Re-feeding ewes at the 96th day of pregnancy following feed restriction between the 30th and 96th day of pregnancy was associated with muscle tissue deposition during late pregnancy, while well-fed ewes depleted both fat deposits and muscle tissue during lat pregnancy. Lamb birthweight was not significantly affected by feed restriction during mid-pregnancy, despite various rates of depletion and repletion of maternal body reserves, and different patterns of placental growth.

Maternal undernutrition during mid-pregnancy in sheep. Placental size and its relationship to calcium transfer during late pregnancy

The aim of the present experiment was to determine the relationship between placental and fetal weight after placental growth had been retarded by maternal undernutrition. Placental weight and fetal weight were measured in single-lamb-bearing ewes which were well-fed throughout pregnancy, or severely undernourished between the 30th and 96th day of pregnancy. Placental transfer of calcium and whole-body metabolism of both glucose and Ca were measured during late pregnancy. The change in fleece-adjusted live weight between the 30th and 96th day of pregnancy was 99 (SE 9.8) and -146 (SE 9.6) g/d for the well-fed and undernourished ewes respectively. The condition score of well-fed ewes did not significantly change between the 96th (2.9 (SE 0.08)) and 140th (3.0(SE 0.13)) day of pregnancy, while it increased from 1.6 (SE 0.15) to 2.3 (SE 0.11) for the previously undernourished group. Undernutrition caused an increase (P less than 0.01) in placental weight measured on the 96th (21%) and 140th (30%) day of pregnancy. In contrast fetal growth was not significantly affected by maternal undernutrition. While the voluntary dry matter intakes (g/d) of previously undernourished ewes after the 97th day of pregnancy were higher than for their well-fed counterparts, there was no significant difference between whole-body glucose or Ca metabolism, or the placental transfer of Ca measured during late pregnancy. This experiment confirms earlier reports of an increase in placental weight as a result of maternal undernutrition during mid-pregnancy; but the factors causing and the functional significance of this response have not been identified. Contrary to earlier proposals, placental weight per se did not limit fetal growth during late pregnancy. It is hypothesized that a combination of factors originating from maternal, placental and fetal sources act together to regulate growth of the fetus.