Energy requirements for growth in male and female Saanen goats

Modeling Gastrointestinal Tract Wet Pool Size in Small Ruminants

The gastrointestinal tract (GIT) wet pool size (GITwps) refers to the total amount of wet contents in GIT, which in small ruminants can reach up to 19% of their body weight (BW). This study aimed to develop models to comprehensively predict GITwps in small ruminants using a meta-regression approach. A dataset was created based on 21 studies, comprising 750 individual records of sheep and goats. Various predictor variables, including BW, sex, breed, species, intake level, physiological states, stages and types of pregnancy, dry matter intake, and neutral detergent fiber intake (NDFI), were initially analyzed through simple linear regression. Subsequently, the variables were fitted using natural logarithm transformations, considering the random effect of the study and residual error, employing a supervised forward selection procedure. Overall, no significant relationship between GITwps and BW (p = 0.326) was observed for animals fed a milk-based diet. However, a strong negative linear relationship (p < 0.001) was found for animals on a solid diet, with the level of restriction influencing GITwps only at the intercept. Furthermore, the prediction of GITwps was independent of sex and influenced by species in cases where individuals were fed ad libitum. Pregnant females showed a noticeable reduction in GITwps, which was more pronounced in cases of multiple pregnancies, regardless of species (p < 0.01). The composition of the diet was found to be the primary factor affecting the modulation of GITwps, with NDFI able to override the species effect (p < 0.0001). Overall, this study sheds light on the factors influencing GITwps in small ruminants, providing valuable insights into their digestive processes and nutritional requirements.

Determination of Maintenance Energy Requirements for Fattening Castrated Korean Black Goats (Capra hircus coreanae)

Simple Summary

The energy required for fattening castrated Korean black goats was estimated using the correlation between metabolic energy intake per dietary body weight and average daily gain per dietary body weight. The Y-axis intercept value was the metabolic energy requirement for maintaining the lives of the fattening Korean black goats. It was calculated to be 108.76 kcal/kg BW^0.75 (p < 0.05, r² = 0.6036).

Abstract

Twelve adult (10 months old) castrated Korean black goats, with an average initial body weight of 24.98 ± 3.7 kg, were used in this experiment to determine their maintenance energy requirements. Dry matter intakes (g/d, p = 0.945) were not affected by energy levels, but metabolic energy intake (kcal/d, p < 0.002) and average daily gain (g/d, p < 0.001) were significantly increased at higher energy levels. Nutrient digestibility was similar in the treatments, but crude fat digestibility increased with the addition of protective fat powder (p = 0.001). The energy required for fattening the castrated Korean black goats was estimated using the correlation between metabolic energy intake per dietary body weight and average daily gain per dietary body weight. The Y-axis intercept value was calculated to be 108.76 kcal/kg BW^0.75 (p < 0.05, r² = 0.6036), which was the metabolic energy requirement for maintaining the lives of the fattening Korean black goats. The estimated energy requirements of the black goat can improve specification techniques, such as the energy level and the amount of feed supply required for domestic black goats.

Genotype effects on energy and protein requirements in growing male goats

Goat genotype may alter the net energy and protein requirements for maintenance (NEm and NPm, respectively) and weight gain (NEg and NPg).This study was designed to investigate and quantify the effect of goat type on NEm, NPm, NEg and NPg, and quantify the net requirements for energy and protein for dairy, meat and indigenous growing male goats. For that, comparative slaughter studies were gathered and a meta-analytical approach was used. Two distinct databases were organized: one composed of 233 individual records from 11 studies of meat (n = 81), dairy (n = 97) and indigenous (n = 55) growing male goats weighing from 4.50 to 51.0 kg, to depict NEm and NPm; and another database composed of 239 individual records from nine studies of meat (n = 87), dairy (n = 97) and indigenous (n = 55) growing male goats weighing from 4.30 to 51.0 kg, to depict NEg and NPg. Our findings showed that NEm of meat goats was 8.5% greater (336 ± 10.8 kJ/kg0.75 of empty BW; EBW) than dairy and indigenous goats (310 ± 8.20 kJ/kg0.75 EBW; P < 0.05). Whereas, NPm was not affected by goat type (1.92 ± 0.239 g/kg EBW; P = 0.91). The NPg was 185.1 ± 1.82 g/kg of EBW gain for goats weighing 5 kg BW and 192.5 ± 4.33 g/kg of EBW gain for goats weighing 45 kg BW, and thus did not change across goat type (P = 0.12). On the other hand, NEg increased from 7.29 ± 0.191 to 11.9 ± 0.386 MJ/kg of EBW in male dairy goats, and from 7.32 ± 0.144 to 15.7 ± 0.537 MJ/kg of EBW in meat and indigenous growing male goats weighing between 5 and 45 kg BW. When body protein was used as a predictor in the allometric equation instead of EBW seeking to account for the degree of maturity, goat type differences disappeared; however, this predictor showed a high variation among individuals. In conclusion, energy and protein requirements for gain in distinct goat types reflect on body composition differences. Future research should focus on better understanding the maturity degree and its consequences in the energy requirement of growing male goats and better depict the goat type effect on it, as well as on the efficiency of utilization.

Can maintenance intake reduce production costs without compromising the reproductive performance in bucks?

Excessive intake of nutrients can result in decreases in the reproductive efficiency of goat bucks and increase production costs in goat e nterprises. In this study, the aim was to compare the reproductive features of young bucks fed diets for maintenance of growth or were fed ad libitum. Ten bucks were used (n = 5/group), with a completely randomized design. Blood and semen were collected from each animal every 2 weeks for nine collections. Semen was frozen and later analyzed using flow cytometry to compare reactive oxygen species, plasma membrane integrity, acrosome integrity, and membrane lipid peroxidation. Body condition score, sexual behavior, testicular biometry and histomorphometry of the testis, as well as oxidative enzymes and carbonylated proteins, were also evaluated. Animals fed ad libitum had a greater body condition score (3.32 + 0.08 × 2.88 + 0.05), sperm volume (0.68 + 0.04 × 0.52 + 0.03 mL), and testis circumference (25.2 + 0.21 × 24.5 + 0.24 cm) and volume (121 + 5.83 × 107 + 4.38 cm³, left testicle; 116 + 5.26 × 100 + 3.75 cm³, right testicle). Ejaculates of the bucks fed diets to maintain growth rate had a larger number of minor and total sperm morphology defects. There were no differences in testosterone concentrations and sexual behavior. In conclusion, there can be feeding for growth rate maintenance instead of ad libitum feeding, for the reduction in production costs of young bucks without compromising semen quality and reproductive functions.

Energy requirements and efficiency of energy utilization in growing dairy goats of different sexes

The aim of this study was to investigate the effects of sex on the requirements for maintenance and efficiency of energy utilization in growing Saanen goats. A database from 7 comparative slaughter studies that included 238 Saanen goats was gathered to provide information for the development of prediction equations of energy requirements for maintenance and efficiency of energy utilization. The experimental design provided different levels of metabolizable energy intake (MEI) and empty body weight (EBW). The data were analyzed so that sex (e.g., intact males, castrated males, and females; n = 98, 80, and 60, respectively) was a fixed effect, and blocks nested in the studies and goat sex were random effects. For the development of linear and nonlinear equations, we used the MIXED and NLMIXED procedures in SAS (SAS Institute Inc., Cary, NC). Nonlinear regression equations were developed to predict heat production (HP, kcal/kg^0.75 of EBW; dependent variable) from MEI (kcal/kg^0.75 of EBW; independent variable). Using the comparative slaughter technique, the net energy requirement for maintenance (NE_M) was calculated as the value of HP at MEI equal to zero. Additionally, NE_M was evaluated based on the degree of maturity. The metabolizable energy requirement for maintenance was calculated as the value at which HP is equal to MEI. Efficiency of ME utilization for maintenance (k_m) was calculated as the ratio between NE_M and the metabolizable energy requirement for maintenance. Efficiency of energy utilization for growth (k_g) was assumed to be the slope of the linear regression of retained energy (RE) on MEI above the maintenance stage (model intercept equal to 0). Efficiencies of RE as protein (k_p) and as fat (k_f) were calculated using the multiple linear regression of MEI above the maintenance (model intercept equal to 0) on RE as protein and as fat, respectively. Sex affected NE_M (75.0 ± 1.76 kcal/kg^0.75 of EBW for males and 63.6 ± 2.89 kcal/kg^0.75 of EBW for females) and sex did not affect k_m (0.63). In contrast, sex no longer affected NE_M when degree of maturity was considered on its estimation. The k_g was different between sexes (0.31 for castrated males and females, and 0.26 for intact males), but k_p (0.21) and k_f (0.80) were similar between sexes. These results may be useful for improving robustness of the energy requirement recommendations for dairy goats.

Applying the California net energy system to growing goats

The aim of this review is to describe the main findings of studies carried out during the last decades applying the California net energy system (CNES) in goats. This review also highlights the strengths and pitfalls while using CNES in studies with goats, as well as provides future perspectives on energy requirements of goats. The nonlinear relationship between heat production and metabolizable energy intake was used to estimate net energy requirements for maintenance (NE_m). Our studies showed that NE_m of intact and castrated male Saanen goats were approximately 15% greater than female Saanen goats. Similarly, NE_m of meat goats (i.e., >50% Boer) was 8.5% greater than NE_m of dairy and indigenous goats. The first partial derivative of allometric equations using empty body weight (EBW) as independent variable and body energy as dependent variable was used to estimate net energy requirements for gain (NE_g). In this matter, female Saanen goats had greater NE_g than males; also, castrated males had greater NE_g than intact males. This means that females have more body fat than males when evaluated at a given EBW or that degree of maturity affects NE_g. Our preliminary results showed that indigenous goats had NE_g 14% and 27.5% greater than meat and dairy goats, respectively. Sex and genotype also affect the efficiency of energy use for growth. The present study suggests that losses in urine and methane in goats are lower than previously reported for bovine and sheep, resulting in greater metabolizable energy:digestible energy ratio (i.e., 0.87 to 0.90). It was demonstrated that the CNES successfully works for goats and that the use of comparative slaughter technique enhances the understanding of energy partition in this species, allowing the development of models applied specifically to goat. However, these models require their evaluation in real-world conditions, permitting continuous adjustments.

Body composition, protein and energy efficiencies, and requirements for growth of F1 Boer × Saanen goat kids

We conducted a study in which body composition, energy and protein requirements, and efficiency of MP and ME were determined in F1 Boer × Saanen goat kids of 5 to 25 kg BW by using the comparative slaughter technique. Two experiments were performed: Exp. 1 estimated the maintenance requirements of kids from 15 to 25 kg BW, and Exp. 2 estimated the gain requirements of kids from 5 to 25 kg BW. In Exp. 1, 28 intact male F1 Boer × Saanen goat kids were utilized, with 7 kids slaughtered (BW of 15.0 ± 0.35 kg) at the onset for estimation of initial body composition and the remaining 21 kids assigned to a randomized block design. Within each block, kids were subjected to 3 levels of feed intake treatments (ad libitum [100%] or restricted to 70% or 40% ad libitum). All kids in each block were slaughtered when the animals fed ad libitum reached 25 kg BW. The NE, ME for maintenance, and partial efficiency of use of ME for NE were 321.6 kJ/kg BW, 525.9 kJ/kg BW, and 0.61, respectively. The net protein and MP for maintenance were 2.43 g/kg of BW and 4.41 g/kg of BW, respectively; thus, the estimated partial efficiency of MP for maintenance was 0.55. In Exp. 2, 32 intact male F1 Boer × Saanen goat kids were distributed in a completely randomized design and slaughtered at 5.6 ± 0.85 kg BW ( = 6), 10.0 ± 0.35 kg BW ( = 6), 15.3 ± 0.52 kg BW ( = 7), 20.4 ± 0.66 kg BW ( = 6), and 25 ± 0.46 kg BW ( = 7). Body composition was then fitted to allometric equations. Body fat composition increased from 37 to 114 g/kg empty BW (EBW; < 0.001), and body protein composition decreased by 10% (from 203.2 to 180.6 g/kg EBW; < 0.001) when kids grew from 5 to 25 kg BW. The NE increased by approximately 60% (from 7.2 to 11.5 MJ/kg of empty BW gain [EWG]; < 0.001), and the net protein for gain decreased by 10% (from 186 to 166 g/kg of EWG; < 0.001). The partial efficiency of the utilization of ME to NE for growth was 0.32 ( < 0.0001), and the partial efficiencies of the utilization of ME for the synthesis of protein and fat were 0.19 and 0.59 ( < 0.011), respectively. These results demonstrate that the protein and energy maintenance requirements in young crossbred goat kids are greater than values reported previously in feeding system studies. In addition, their requirements for gain depend on body composition and are driven by efficiencies of deposition.