Energy requirements for maintenance and growth of early-weaned Dorper crossbred male lambs

A Dynamic Tool to Describe Lamb Growth and Its Use as a Decision Support System

A dynamic model has been developed to simulate aspects of feedlot lamb growth and body composition, including energy and protein requirements, growth rate, composition of gain, and body mass. Model inputs include initial body mass (kg), standard final mass (kg), age (days), and dietary energy concentration (Mcal·kg-1). The model was assessed as a decision support tool using a dataset of 564 individual measures of final body mass and diet energy. The simulations provide graphical and numerical descriptions of nutrient requirements, composition of gain, and estimates of animal performance over time. The model is accurate and precise, with a root mean squared error of 7.79% of the observed final body mass and a coefficient of determination of 0.89 when simulating the same variable. The model can be used as a reliable decision support tool to estimate final body mass and the days on feed required to reach a certain final mass with precision and accuracy. Moreover, the dynamic model can also serve as a learning tool to illustrate practical principles of animal nutrition, nutrient requirement relationships, and body composition changes. This model holds the potential to enhance livestock management practices and assist producers in making informed decisions about feedlot lamb production.

Energy and Protein Requirements of Growing Lambs in Colombian Highlands

Determining the nutritional requirements of lambs is necessary to formulate balanced rations and contribute to sustainable sheep production systems. However, limited information is available regarding the nutritional requirements of growing lambs in the Colombian highlands. Twenty-two Romney Marsh males were used. Initially, four lambs were slaughtered at 20 kg body weight (BW). The remaining 18 lambs were distributed into two groups, according to BW (light: 20 BW and heavy: 30 kg BW). Lambs were randomly allocated into one of three different nutritional schemes, according to voluntary intake (no restriction, and 25 and 50% restriction). All the animals received a totally mixed ration. When a voluntary-fed lamb gained 10 kg BW, the two other lambs restricted to 25 and 50% were slaughtered and dissected into components to determine protein and gross energy concentration. Energy and protein accumulation were analyzed through regression analysis. The net energy for maintenance was 82.3 kcal/kg BW0.75, while the energy efficiencies for maintenance and gain were 0.72 and 0.29, respectively. Crude protein for maintenance was 1.78 g/kg BW0.75, and the nitrogen efficiencies for maintenance and gain were 0.41 and 0.27, respectively. The maintenance requirement of energy was greater, while protein was similarly related to values reported in the literature; however, the efficiency of energy and protein use was lower in growing lambs. These results suggested that estimating energy and nitrogen requirements for growing lambs must be adjusted in Colombian highland conditions.

Performance, biochemical and physiological parameters of Dorper × Santa Ines lambs fed with three levels of metabolizable energy

This study aimed to evaluate the performance and the blood biochemical and physiological parameters of Dorper × Santa Ines lambs receiving three levels of metabolizable energy (ME). A completely randomized design with three treatments (ME levels) and eight replicates (lambs) was used. Twenty-four non-castrated male lambs of four months of age and 21.07 ± 3.91 kg body weight (BW) received a diet composed of 40% Tifton 85 hay and 60% concentrate feed, on a dry matter basis. The amount of feed supplied was adjusted to meet 115, 201, and 288 kcal ME per kg of metabolic weight (MW = BW^0.75) daily. Average daily gain and the intake of dry matter (g/day and % BW^0.75/day), nutrients, and energy increased linearly (P < 0.001) with ME level. The dry matter intake relative to BW (% BW/day) and feed conversion ratio showed quadratic responses (P < 0.05) to ME level. Serum creatinine decreased linearly (P = 0.038), whereas plasma glucose increased linearly (P = 0.045) with ME level. Serum urea presented a high variation (standard error range = ±1.98-6.07 mg/dL) in response to 288 kcal/kg^0.75/day of ME supply, and did not stabilize during the trial. Respiratory rate increased linearly (P < 0.001) with ME level at each time of day (morning/afternoon), but with higher intensity in the afternoon. Heart rate and rectal temperature increased linearly (P < 0.001) with ME level. Given that the range of ME level simulated a restricted-to-ad libitum ME intake, the best response in terms of feed efficiency can be obtained with 252 kcal/kg^0.75/day of ME supply, which probably reflects the best balance of metabolic and physiological parameters. Thus, in order to achieve high productive performance in tropical environments, feedlot lambs should be fed with high-concentrate diets.

Estimation of the net energy and protein requirements for maintenance of male arctic foxes (Alopex lagopus) during the growth period1,2

The maintenance requirements of net energy and net protein were assumed to represent the most accurate and important values totally for the animal's utilization. The objective of this experiment was to determine the net energy and net protein requirements for maintenance of growing arctic foxes. The experiments was evaluated using regression models estimated from data collected by means of indirect calorimetry, nitrogen balance trials, and digestion and metabolism experiments. Thirty-six growing arctic foxes (3 487 ± 261.7 g) at the age of 85 days were randomly assigned to four groups with 9 animals in each group. Arctic foxes were fed a complete formula diet at four intake levels (100%, or 80%, 60%, and 40% of feed requirements) from 24 July 2017 to 23 September 2017. Arctic foxes in each treatment were kept individually in respiration chambers after 1-d adaptation at day 2 for a 3-d balance trial and then at day 5 followed by a 3-d fasting period. The metabolizable energy intake (MEI), heat production in the fed state (HP), and retained energy (RE) of arctic foxes significantly decreased (P < 0.01) as the feed intake level decreased. Fasting heat production (FHP) of arctic foxes was not influenced by feed intake level (P > 0.05). The metabolizable energy maintenance requirement (MEm) and net energy maintenance requirement (NEm) estimated from the linear relationship between RE and MEI were 230 and 217 kJ/kg of body weight BW0.75/d, respectively. The MEm and NEm estimated by logarithmic regression of HP on MEI were 225 and 209 kJ/kg BW0.75/d, respectively. The net N maintenance requirement (NNm) and net protein maintenance requirement (NPm) estimated from the linear relationship between retained nitrogen (RN) and daily nitrogen intake (NI) were 179.6 mg/kg BW0.75/d and 1.123 g/kg BW0.75/d, respectively. It is concluded that NEm and NPm values obtained fill the net energy and protein requirements shortage, and provide the basic data for establishing the standard of nutrition demand of breeding arctic foxes in China.

Growth performance, nutrient digestibility, and slaughter traits of male fattening lambs under different feeding standards

This study compared the growth performance, nutrient utilization, and slaughter traits of Dorper crossbred male lambs fed as per the established nutrition recommendations for sheep, with an aim to verify the efficacy of different feeding standards. A total of 576 lambs (4 months of age, 28.3 ± 0.86 kg BW) were randomly allotted to 3 treatments with 12 replicates per treatment (16 lambs per replicate). The lambs were fed diets formulated according to the following 3 nutritional systems: the nutrient requirements of Dorper crossbred lambs established by Chinese Academy of Agricultural Sciences (CAAS), NRC (National Research Council), (2007), and AFRC (Agricultural and Food Research Council) (1993). The experiment lasted for 81 d. Feed intake was recorded every 3 days, and lambs were weighed every 20 days. Digestibility trials were conducted with 6 lambs each group from d 42 to 53 and d 70 to 81. At the end of the experiment, 10 lambs randomly chosen from each group were sacrificed to determine the carcass traits and meat quality. The results indicated that the lambs in the NRC group had the highest dry matter intake (DMI), followed by those in the AFRC and CAAS groups (P < 0.05). The average daily gain, carcass weight, and dressing percentage were higher for lambs in the CAAS group than those in the NRC group (P < 0.05). The lambs in the CAAS group had the lowest feed conversion ratio, followed by those in the AFRC and NRC groups (P < 0.05). The apparent digestibility of DM was higher for the lambs in the CAAS group than those in the NRC group (P < 0.05). Water losing rate, as well as the lightness (L*), redness (a*), and yellowness (b*) values of the longissimus thoracis were not different among groups (P > 0.05). In conclusion, Dorper crossbred lambs fed diets formulated according to the CAAS recommendations exhibited superior growth performance than those fed diets formulated according to the American or British feeding standards.

Prediction of methane emission from sheep based on data measured in vivo from open-circuit respiratory studies

Objective

The current study analysed the relationships between methane (CH₄) output from animal and dietary factors.

Methods

The dataset was obtained from 159 Dorper×thin-tailed Han lambs from our seven studies, and CH₄ production and energy metabolism data were measured in vivo by an open-circuit respiratory method. All lambs were confined indoors and fed pelleted diet during the whole experimental period in all studies. Data from two-thirds of lambs were used to develop linear and multiple regressions to describe the relationship between CH₄ emission and dietary variables, and data from the remaining one third of lambs were used to validate the established models.

Results

CH₄ emission (g/d) was positively related to dry matter intake (DMI) and gross energy intake (GEI) (p<0.001). CH₄ energy/GEI was negatively related to metabolizable energy/gross energy and metabolizable energy/digestible energy (p<0.001). Using DMI to predict CH₄ emission (g/d) resulted in a coefficient of determination (R²) of 0.80. Using GEI, digestible energy intake, and metabolizable energy intake predict CH₄ energy/GEI resulted in a R² of 0.92.

Conclusion

the prediction equations established in the current study are useful to develop appropriate feeding and management strategies to mitigate CH₄ emissions from sheep.

Influence of dietary supplementation with Bacillus licheniformis and Saccharomyces cerevisiae as alternatives to monensin on growth performance, antioxidant, immunity, ruminal fermentation and microbial diversity of fattening lambs

Alternatives to antibiotics for improving productivity and maintaining the health of livestock health are urgently needed. The scope of this research was conducted to investigate the effects of two alternatives (Bacillus licheniformis and Saccharomyces cerevisiae) to monensin on growth performance, antioxidant capacity, immunity, ruminal fermentation and microbial diversity of fattening lambs. One hundred and sixty Dorper × Thin-tailed Han sheep (32 ± 3.45 kg BW) were randomly assigned into 5 treatments of n = 32 lambs/group. Lambs in the control group were fed a basal diet (NC) while the other four treatments were fed basal diets supplemented with monensin (PC), Bacillus licheniformis (BL), Saccharomyces cerevisiae (SC), and the combination of Bacillus licheniformis and Saccharomyces cerevisiae with protease (BS), respectively. The experiment lasted for 66 d. Feed intake was recorded every 2 d and lambs were weighed every 20 d. Ten lambs from each group were slaughtered at the end of the trial, and samples of serum and rumen fluid were collected. The results indicated that the dietary regimen did not affect the dry matter intake (DMI). The average daily gain (ADG) of BS treatment was significantly higher than NC group (P < 0.05). Compared with the NC treatment, the other four supplementation treatments increased the concentration of growth hormone (GH), insulin-like growth factor I (IGF-I) and insulin (INS) (P < 0.05). The malondialdehyde (MDA) and total antioxidant capacity (TAOC) showed no significant difference among the 5 treatments while the activity of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) of BS group was significantly increased (P < 0.05). The supplementation regimen decreased the concentration of ammonia Nitrogen (NH3-N) and increased the content of microbial crude proteins (MCP) (P < 0.05). The supplementation of antibiotics and probiotics reduced the concentrations of acetate and increased the concentrations of propionate (P < 0.05). The supplementation treatments increased the relative abundance of Lentisphaerae, Fibrobacteres and Tenericutes at the phylum level, whereas at the genus level, they increased the relative abundance of Fibrobacter (P < 0.05). Overall, this study confirmed the facilitating effect of B. licheniformis, S. cerevisiae and their compounds on growth performance, improve the antioxidant capacity and immune function, and beneficially manipulate ruminal fermentation and microbial diversity of fatting lambs.

Net protein and metabolizable protein requirements for maintenance and growth of early-weaned Dorper crossbred male lambs

Background

Dorper is an important breed for meat purpose and widely used in the livestock industry of the world. However, the protein requirement of Dorper crossbred has not been investigated. The current paper reports the net protein (NP) and metabolizable protein (MP) requirements of Dorper crossbred ram lambs from 20 to 35 kg BW.

Methods

Thirty-five Dorper × thin-tailed Han crossbred lambs weaned at approximately 50 d of age (20.3 ± 2.15 kg of BW) were used. Seven lambs of 25 kg BW were slaughtered as the baseline animals at the start of the trial. An intermediate group of seven randomly selected lambs fed ad libitum was slaughtered at 28.6 kg BW. The remaining 21 lambs were randomly divided into three levels of dry matter intake: ad libitum or 70% or 40% of ad libitum intake. Those lambs were slaughtered when the lambs fed ad libitum reached 35 kg BW. Total body N and N retention were measured.

Results

The daily NP and MP requirements for maintenance were 1.89 and 4.52 g/kg metabolic shrunk BW (SBW^0.75). The partial efficiency of MP utilization for maintenance was 0.42. The NP requirement for growth ranged from 12.1 to 43.5 g/d, for the lambs gaining 100 to 350 g/d, and the partial efficiency of MP utilization for growth was 0.86.

Conclusions

The NP and MP requirements for the maintenance and growth of Dorper crossbred male lambs were lower than the recommendations of American and British nutritional systems.

Effect of different feeding regimens on energy and protein utilization and partitioning for maintenance and growth in pre-weaned lambs reared artificially

Estimation of metabolizable energy (ME) requirement for maintenance (ME) and growth (ME) in pre-weaned lambs have been limited to milk-only fed lambs. This study aimed to determine energy and nitrogen metabolisability of milk and pellets when fed together, compare the growth and chemical body composition of lambs fed varying levels of pellets in addition to milk, and to estimate ME, ME, and the CP:ME ratio requirements for growth. The study included 32 twin-born Romney-cross ram lambs. Four lambs were slaughtered at 24 h post-partum to estimate initial body composition and the remaining 28 were assigned to 1 of 4 treatment groups of 7. Group 1 was fed milk replacer (MR) only; group 2 was fed MR and allowed ad libitum access to pellets; groups 3 and 4 were offered 30% and 60%, respectively of the average pellet intake of the ad libitum group the previous day while being fed MR. Milk replacer was fed as a proportion of the lamb's live weight (LW). Lambs from each treatment were placed in metabolic cages at 17 kg LW for 4 d to allow for total fecal and urine collection. All lambs were slaughtered at 18 kg LW. The ADG, ADG:ME ratio, stomach and liver weight, and rumen papillae lengths increased ( < 0.05) with increasing pellet intake. Increasing daily ME intake increased ( < 0.05) both daily energy and protein deposition but had no effect ( > 0.05) on fat deposition. However, the total chemical body composition was unaffected ( > 0.05) by dietary treatment. Digestibility of energy and N decreased ( < 0.05) with increasing ME intake. Percent energy and N retained for growth were 96% vs. 71% and 72% vs. 30% for milk and pellets, respectively. The ME and ME values obtained were 0.40 MJ ME/kg LW·d and 13.8 MJ ME/kg ADG, respectively. The CP:ME ratio of MR and pellet was 11.1 and 15.7, respectively. However, a simulation model suggested that lambs require a CP:ME ratio of 13.1 at 5 kg and 10.9 at 18 kg LW, indicating that protein intake may be limiting to lamb growth in early life and in excess by 18 kg LW. In conclusion, increasing pellet intake was associated with decreased N retention. The inclusion of pellets, however, improved the efficiency of ME utilization for growth in pre-weaned lambs and was beneficial for rumen development. The ME was higher than previously recommended values and the CP:ME intake of lambs does not match their requirements which may warrant further studies.

Different dietary energy intake affects skeletal muscle development through an Akt-dependent pathway in Dorper × Small Thin-Tailed crossbred ewe lambs

The objective of this experiment was to investigate the mechanisms through which different levels of dietary energy affect postnatal skeletal muscle development in ewe lambs. Twelve Dorper × Small Thin-Tailed crossbred ewe lambs (100 d of age; 20 ± 0.5 kg BW) were selected randomly and divided into 2 groups in a completely randomized design. Animals were offered identical diets at 100% or 65% of ad libitum intake. Lambs were euthanized when BW in the ad libitum group reached 35 kg and the semitendinosus muscle was sampled. Final BW and skeletal muscle weight were decreased (P < 0.01) by feed restriction. Both muscle fiber size distribution and myofibril cross-sectional area were altered by feed restriction. Insulin-like growth factor 1 (IGF-1) messenger RNA (mRNA) content was decreased (P < 0.05) when lambs were underfed, whereas no difference for IGF-2 mRNA expression was observed (P > 0.05). Feed restriction altered phosphor-Akt protein abundance (P < 0.01). Moreover, the mammalian target of rapamycin (mTOR) pathway was inhibited by feed restriction, which was associated with decreased phosphor-mTOR, phosphorylated eukaryotic initiation factor 4E binding protein 1 (phosphor-4EBP1), and phosphorylated ribosomal protein S6 kinase (phosphor-S6K). Both mRNA expression of myostatin and its protein content were elevated in feed-restricted ewe lambs (P < 0.05). In addition, mRNA expression of both muscle RING finger 1 and muscle atrophy F-box was increased when ewe lambs were underfed. In summary, feed restriction in young growing ewe lambs attenuates skeletal muscle hypertrophy by inhibiting protein synthesis and increasing protein degradation, which may act through the Akt-dependent pathway.

Energy requirements of early-weaned Dorper cross-bred female lambs

The net and metabolizable energy (NE and ME) requirements of Dorper cross-bred female lambs with BWs of 20-35 kg were assessed in a comparative slaughter trial. Thirty-five Dorper × thin-tailed Han cross-bred female lambs weaned at ~50 days of age (20.3 ± 2.15 kg BW) were used. Seven randomly selected lambs were slaughtered at the start of the trial (baseline group). An intermediate group consisting of seven randomly selected lambs fed ad libitum was slaughtered when the lambs reached an average BW of 28.5 kg. The remaining 21 lambs were allotted randomly to three levels of dry matter intake: ad libitum or restricted to 70% or 40% of the ad libitum intake. All the lambs were slaughtered when the sheep fed ad libitum reached a BW of 35 kg. Total body energy, nitrogen, fat, ash and moisture content were determined. In a digestibility trial, an additional 15 Dorper × thin-tailed Han cross-bred female lambs (28.7 ± 1.75 kg BW) were housed in metabolism cages and used in a completely randomized design experiment to evaluate the ME value of the diet at the three feed intake levels. The maintenance requirements for NE and ME were 245.5 and 380.3 kJ/kg metabolic shrunk body weight (SBW^0.75 ) respectively. The partial efficiency of energy use for maintenance was 0.645. The NE requirements for growth ranged from 1.18 to 5.18 MJ/d for the lambs gaining 100-350 g/d from 20 to 35 kg BW. Partial efficiency of ME for growth was 0.44. In conclusion, the current study suggests that the NE requirement for maintenance and growth of Dorper early-weaned cross-bred female lambs is lower than the current AFRC and NRC recommendations.