Twenty-four lactating and 13 nonlactating Alpine goats were used to determine effects of stage of lactation and dietary concentrate level on energy utilization. Diets comprising 60 or 20% concentrate ...(60%C and 20%C, respectively) were consumed ad libitum by lactating animals and at a level of intake near maintenance by nonlactating animals. Measurement periods were d 25 to 31 (early), 87 to 94 (mid), and 176 to 183 (late) of lactation. Eleven observations were made in early and mid lactation for each diet, and 8 and 7 were made in late lactation for the 60%C and 20%C diets, respectively. Efficiency of metabolizable energy (ME) use for maintenance (66.9, 71.4, and 61.1% for early, mid, and late lactation, respectively) and the maintenance ME requirement (479, 449, and 521 kJ/kg of BW0.75 for early, mid, and late lactation, respectively) determined with nonlactating animals differed among stages of lactation. The efficiency of ME use for maintenance was similar between diets, but the maintenance requirement tended to be greater for the 60%C than for the 20%C diet (504 vs. 463 kJ/kg of BW0.75). The latter difference may have involved greater ME intake for the 60%C diet, resulting in a slightly greater difference between ME intake and total heat energy for the 60%C compared with the 20%C diet (11 vs. −8 kJ/kg of BW0.75). Intake of ME by lactating goats was greater for the 60%C than for the 20%C diet (18.6 vs. 16.3 MJ/d). Recovered energy in lactation from mobilized tissue tended to be greater for the 60%C than for the 20%C diet (8.44 vs. 6.55 MJ/d) and differed among stages of lactation (2.60, 1.59, and 1.13 MJ/d in early, mid, and late lactation, respectively). Recovered energy in tissue gain was similar among stages of lactation and between diets and was not different from 0. Efficiency of use of dietary ME for lactation differed among stages of lactation (59.5, 51.9, and 65.4% for early, mid, and late lactation, respectively) and tended to be greater for the 60%C than for the 20%C diet (64.2 vs. 54.9%). The efficiency of use of dietary ME for maintenance and lactation was similar among stages of lactation and was greater for the 60%C compared with the 20%C diet (64.3 vs. 60.9%). Predicted milk yield from National Research Council requirements was reasonably accurate. In conclusion, using data of nonlactating goats to study energy utilization for maintenance in lactation has limitations. Efficiency of energy use by lactating dairy goats consuming diets high in concentrate appears greater than that by goats consuming diets low in concentrate. Despite differences in nutrient requirement expressions, observations of this study support National Research Council recommendations of energy requirements of lactating dairy goats.
Thirty-six lactating Alpine does were used to determine effects of stage of lactation and level of feed intake on energy utilization. Twelve does were assigned to measurement periods in early, mid, ...and late lactation (wk 5, 13, and 27, respectively). For 6 does of each group, after ad libitum consumption of a 60% concentrate diet, feed intake was restricted to near the metabolizable energy (ME) requirement for maintenance (MEm) for 8 d followed by fasting for 4 d. For other does, fasting immediately followed ad libitum consumption. Intake of ME was similar among stages of lactation with ad libitum intake (22.1, 22.1, and 19.8kJ/d in early, mid, and late lactation, respectively). The efficiency of ME use for maintenance determined with does fed near MEm averaged 81%. Fasting heat energy was greater for ad libitum consumption than for near MEm consumption 368 vs. 326kJ/kg of body weight (BW)0.75 and was numerically lowest among stages in late lactation with near MEm intake (334, 350, and 295kJ/kg of BW0.75 in early, mid, and late lactation, respectively) and ad libitum consumption (386, 384, and 333kJ/kg of BW0.75 in early, mid, and late lactation, respectively). The efficiency of use of dietary ME for lactation was greater for consumption near MEm than for consumption ad libitum (67.9 vs. 58.6%) and with ad libitum consumption tended to decrease with advancing stage of lactation (63.9, 57.3, and 54.5% for early, mid, and late lactation, respectively). Estimated MEm was greater for ad libitum intake than for near MEm intake and was lowest during late lactation (429, 432, and 358kJ/kg of BW0.75 for near MEm intake and 494, 471, and 399kJ/kg of BW0.75 for ad libitum intake in early, mid, and late lactation, respectively). However, because of increasing BW as the experiment progressed, MEm (MJ/d) was similar among stages of lactation with both levels of intake. The efficiency of ME use for maintenance and lactation was similar among stages of lactation and greater with near MEm intake than ad libitum intake (77.1 vs. 67.7%). In conclusion, the MEm requirement (kJ/kg of BW0.75) of does in late lactation was less than in early and mid lactation. A marked effect of restricted feed intake subsequent to ad libitum consumption on estimates of efficiency of energy use for maintenance and lactation was observed compared with use of nonlactating animals. Level of feed intake can have substantial effect on estimates of energy utilization by lactating dairy goats.
Eight Boer (75%) x Spanish (BS) and 8 Spanish (S) wethers (155 ± 8 d of age and 19.2 ± 2.3 kg of BW initially) were used in a replicated crossover design with a 2 x 2 factorial arrangement of ...treatments to determine effects of genotype, diet quality, and time of day on energy expenditure (EE), heart rate (HR), and EE:HR with ad libitum, near maintenance, and fasting levels of feed intake. Diets were 65% concentrate or coarsely ground alfalfa hay. Energy expenditure was ranked (P < 0.05) ad libitum > maintenance > fasting (500, 390, and 270 kJ/kg of metabolic BW). Heart rate did not differ between genotypes when fasting and with maintenance intake, but was greater (P < 0.05) for S than for BS when intake was ad libitum (BS: 55, 71, and 92; S: 52, 72, and 100 beats/min for fasting, maintenance, and ad libitum, respectively, SEM = 2.0). There was an interaction in EE:HR (P < 0.05) between level of feed intake and genotype (BS: 5.31, 5.59, and 5.00; S: 5.07, 5.57, and 5.22 kJ/kg of metabolic BW:beat/min for ad libitum, maintenance, and fasting, respectively, SEM = 0.13), without an effect of diet. The effect of time on EE, HR, and EE:HR differed among levels of intake (P < 0.05). General patterns of change in EE and HR as time of day advanced did not differ, but increases near meals followed by decreases were of slightly greater magnitude for maintenance than for ad libitum intake. The ratio of EE:HR was greater for the maintenance level of feed intake than for ad libitum intake at most times. These results indicate similar potential for use of HR to predict EE of different genotypes of growing meat goats and that establishing EE:HR with different diets or levels of intake may not be crucial. Magnitudes of difference among hours suggest that when EE:HR is used to predict EE of confined goats from full-day measurement of HR, EE:HR should be determined over an extended period of time, such as 24 h.
Twenty-three Boer (75%)×Spanish (25%) multiparous does, eight with ruminal cannula, grazed grass/legume pastures in different stages of production. Four cannulated and eight non-cannulated does were ...confined in a building at night and had pasture access from approximately 07:00 to 19:00h (Night); other animals had continual pasture access (Past). Data collection periods 15days in length were in late gestation (L-G; 137±5.2days), early lactation (E-L; 43±2.1days), late lactation (L-L; 97±1.1days), the dry period (Dry), and early gestation (L-G; 65±5.9days). Most does had a litter size of 2, and kids were weaned at 118±1.0days. Ingesta collected from cannulated does after rumen-evacuation averaged 19.9, 12.5, 14.7, 13.4, and 19.9% CP (SE=0.59) and 50.8, 59.2, 63.1, 61.4, and 38.1% NDF in L-G, E-L, L-L, Dry, and E-G, respectively; (SE=1.55). Kid ADG tended (P<0.08) to be greater for Past than for Night (138 vs. 118g; SE=7.4). Intake of ME (823 vs. 735kJ/kg BW0.75; SE=27.5) was greater for Night than for Past (P<0.05). There were treatment differences in time spent grazing (4.5 and 5.8h; SE=0.28) and resting (18.5 and 16.7h for Night and Past, respectively; SE=0.25). Energy expenditure (EE) was greater (P<0.05) for Past than for Night (754 vs. 687kJ/kg BW0.75; SE=14.5). Recovered energy (RE) in and EE for tissue gain were similar between treatments. RE in tissue gain was greatest among periods (P<0.05) in Dry (6, 0, 11, 113, and 22kJ/kg BW0.75 in L-G, E-L, L-L, Dry, and E-G, respectively; SE=8.5). RE of lactation from dietary ME was greater for Past vs. Night regardless of period (244 vs. 194kJ/kg BW0.75; SE=16.1). However, RE of lactation derived from mobilized tissue differed between treatments (P<0.05) in E-L but not L-L (54, 15, 175, and 11kJ/kg BW0.75 in Night/E-L, Night/L-L, Past/E-L, and Past/L-L, respectively; SE=16.0). EE associated with activity tended to be greater (P<0.07) for Past than for Night (243 vs. 202kJ/kg BW0.75; SE=14.4) and was greatest among periods in E-G (184, 219, 193, 176, and 343kJ/kg BW0.75 in L-G, E-L, L-L, Dry, and E-G, respectively; SE=22.7). In conclusion, ‘night-locking’ decreased activity EE to an extent less than the depression in MEI. The greatest impact of Night was in E-L, with reduced RE of lactation and a tendency for lower kid ADG.
Six Alpine (AL; 38.4
±
3.0
kg), Angora (AN; 23.1
±
2.7
kg), Boer (BO; 40.8
±
4.5
kg) and Spanish (SP; 33.6
±
2.2
kg) wethers (1.5 yr of age) were used to determine the effects of time of the day and ...potential interactions between time, genotype and diet quality on energy expenditure (EE), heart rate (HR) and EE:HR when fed near maintenance and fasting. The experiment consisted of four simultaneous crossovers, with 21
d for adaptation before measures. Diets were 60% concentrate (CON: 15% CP) and ground alfalfa hay (FOR: 23% CP), offered in two meals at 8:00 and 16:00
h. Energy expenditure was determined from O
2 consumption and production of CO
2 and CH
4 over 2-day periods in fed and fasting states (total 4-day fasting period). Fasting EE was higher during the day than night, with values generally highest at 16:00–17:00
h. Animal within breed affected EE, HR and EE:HR (
P
<
0.05). The diurnal pattern in EE varied with diet (
P
<
0.05), although total daily EE was not different between diets. Before the morning meal, there were a number of hours during which EE was greater for CON than for FOR. However, at both meals the rise in EE was considerably greater for FOR versus CON, lasting for 3–4
h. The same general pattern in HR was observed, although the period of time when there was a dietary difference after the afternoon meal was shorter. For both fed and fasted goats, EE:HR differed among hours of the day (
P
<
0.05). EE:HR tended (
P
<
0.09) to differ between diets (5.99 and 6.21 for CON and FOR, respectively) and to be affected (
P
<
0.09) by an interaction between breed and diet (AL: 5.84 and 6.38; AN: 5.91 and 5.73; BO: 6.05 and 6.58; and SP: 6.17 and 6.15
kJ/(kg BW
0.75
×
day):heart beats/min) for CON and FOR, respectively. In conclusion, for use of HR to predict EE by goats, it appears desirable to determine the ratio of EE:HR with a diet similar to that consumed during prediction and over an extended period of time.
Twelve mature Angora does were used in a replicated 3 x 3 Latin square to determine effects of feeding level on energy utilization. Fiber growth and change in tissue (nonfiber) mass were determined ...in the first 4 wk of 6-wk periods, preceded by 14 or 18 d of adaptation. Determination of ME intake and gas exchange measures occurred in wk 4, followed by feeding near maintenance, then fasting in wk 5 and 6 to determine the ME requirement for maintenance (MEm). A 60% concentrate diet was fed at levels to approximate 100, 125, and 150% of assumed MEm low, medium (med), and high, respectively. Digestibilities and diet ME/GE were not affected by treatment with different amounts of feed offered and subsequent intake near MEm. Heat energy during fasting (261, 241, and 259 kJ/kg of BW⁰.⁷⁵; SEM = 8.7) and efficiency of ME used for maintenance (71.6, 69.6, and 69.2%; SEM = 2.29) were similar among treatments, although MEm differed (P < 0.04) between med and high (365, 344, and 377 kJ/kg of BW⁰.⁷⁵ for low, med, and high, respectively; SEM = 10.3). Tissue gain was less (P < 0.01) for low than for the mean of med and high (MH; -0.6, 23.7, and 29.8 g/d), although clean fiber growth only tended (P < 0.09) to differ between low and MH (5.60, 6.57, and 7.36 g/d for low, med, and high, respectively; SEM = 0.621). Intake of ME was greater (P < 0.01) for MH than for low (6.87, 8.22, and 8.41 MJ/d for low, med, and high, respectively). Total heat energy was less (P < 0.02) for low vs. MH and tended (P < 0.07) to be greater for high than for med (6.03, 6.31, and 6.77 MJ/d); mobilized tissue energy was low but greater (P < 0.02) for low vs. MH (0.16, 0.01, and 0.04 MJ/d for low, med, and high, respectively). Efficiency of ME use for fiber growth was similar among treatments (17.2, 16.3, and 17.7% for low, med, and high, respectively; SEM = 1.61). In conclusion, efficiency of ME use for fiber growth was similar to the NRC recommendation regardless of feeding level, although MEm was decreased perhaps because of experimental conditions used. Energy appeared partitioned to fiber growth, but preferential usage was not complete possibly because energy metabolism for tissue accretion reached a plateau with the greatest feeding level.
Yearling Boer
×
Spanish goat wethers (40) were used to develop and compare body composition prediction equations for mature meat goats based on urea space (US) and body condition score (BCS). Before ...the experiment, one-half of the animals were managed to have high BW and BCS (1–5, with 1 being extremely thin and 5 very fat) and the others were managed to have low BW and BCS. During the 24-week experiment, initially fat wethers were fed to lose BW and BCS and initially thin wethers were fed to increase BW and BCS. BCS, US, and whole body chemical composition were determined after 0, 12, and 24
weeks. Mean, minimum, and maximum values were 42.1 (S.E.
=
1.12), 24.5, and 59.0
kg for shrunk BW; 3.0 (S.E.
=
0.11), 1.5, and 4.0 for BCS; 61.3 (S.E.
=
1.01), 53.7, and 76.5% for water; 20.2 (S.E.
=
1.11), 4.7, and 29.7% for fat; 15.6 (S.E.
=
0.19), 13.3, and 18.1% for protein; and 2.9 (S.E.
=
0.062), 2.2, and 3.7% for ash, respectively. For water, fat, and ash concentrations and mass, simplest equations explaining greatest variability (with independent variables of US, BCS, and (or) shrunk BW) based on BCS accounted for more variation than ones based on US, although in some cases differences were not large (i.e., water and ash concentrations and mass). Neither US nor BCS explained variability in protein concentration. Equations to predict protein mass based on shrunk BW and US or BCS were nearly identical in
R
2 and the root mean square error. A 1
unit change in BCS corresponded to change in full BW of 8.9
kg (full BW (kg)
=
17.902
+
(8.9087
×
BCS);
R
2
=
0.653), fat concentration of 7.54% (%fat
=
−5.076
+
(7.5361
×
BCS);
R
2
=
0.612), and energy concentration of 3.01
MJ/kg (energy (MJ/kg)
=
0.971
+
(3.0059
×
BCS);
R
2
=
0.615). In summary, BCS may be used as or more effectively to predict body composition of meat goats than US. The primary determinant of BCS, within the range of BCS observed in this experiment, was body fat content.
Boer goats (7/8 and 1/8 Spanish breed) were used to characterize effects of gender and age on the ME requirement for maintenance (MEm). There were eight animals of each gender, doelings, intact ...males, and wethers castrated at 2mo of age. Kids were weaned at 3.7mo and thereafter consumed a 50% concentrate pelleted diet ad libitum while in group pens at most times. Measurement periods consisted of three segments of 12, 10, and 4 days with consumption ad libitum and near MEm and while fasting, respectively. Maintenance segment measures began at 4.9, 7.8, 11.7, and 14.8 mo of age in periods 1, 2, 3, and 4, respectively. Feed intake data, feces and urine collections, and a calorimetry system were used to determine ME intake and heat energy (HE). The MEm estimate was based on fasting HE and the slope (km) of the regression of recovered energy (RE) against ME intake with intake near MEm and while fasting, and kg was RE with ad libitum intake relative to ME intake above MEm. BW (kg) during the maintenance segment was 20.6, 30.8, 46.5, and 57.1 for doelings, 25.9, 40.1, 67.3, and 76.9 for males, and 23.1, 35.1, 53.9, and 65.0 for wethers in periods 1, 2, 3, and 4, respectively (SE=1.85). km was similar among genders and periods (P>0.05%; 70.2%, 69.5%, and 69.7% for doelings, males, and wethers, respectively; SE=1.25). Fasting HE and MEm were affected by gender×period interactions (P<0.001). Fasting HE (kJ/kg BW0.75) was 277, 272, 281, and 281 for doelings, 288, 327, 334, and 398 for males, and 274, 303, 274, and 305 for wethers (SE=10.1); MEm (kJ/kg BW0.75) was 382, 390, 399, and 420 for doelings, 412, 469, 492, and 569 for males, and 384, 417, 426, and 439 for wethers in periods 1, 2, 3, and 4, respectively (SE=14.2). kg tended (P=0.067) to vary among genders (61.5%, 48.1%, and 52.7% for doelings, males, and wethers, respectively; SE=3.91). In conclusion, MEm was not greatly different between doelings and wethers and increased for both as the study progressed, whereas that for males was greater, with the difference increasing considerably as age rose.
•Ruminants use considerable energy for maintenance.•Many factors influence the maintenance energy requirement of goats.•Energy required for maintenance of Boer goats was similar for doelings and wethers.•The maintenance need of doelings and wethers increased slightly with aging to 15mo.•The maintenance need was greatest for males, particularly at 1 yr of age or older.
Yearling Boer x Spanish goat wethers were used to assess effects of initial body condition and subsequent level of feed intake on body composition. Before the experiment, 21 wethers were fed to ...achieve high body condition score (BCS; 1 to 5, with 1 = extremely thin and 5 = extremely fat) and BW (initially fat; I-F) and 21 were fed for low BCS and BW (initially thin; I-T). During the experiment, I-F wethers were fed low amounts of a pelletized diet and I-T wethers received high amounts. Harvest measures were determined before the experiment (week 0) and after 12 and 24 weeks, with seven animals per initial body condition and time. BCS in Experiment 1 was 3.8, 3.2, 2.6, 1.9, 2.8, and 3.5 (S.E. = 0.11) and live BW was 53.3, 46.2, 42.4, 36.6, 40.1, and 48.2 kg (S.E. = 2.03) for I-F:week 0, I-F:week 12, I-F:week 24, I-T:week 0, I-T:week 1, and I-T:week 2, respectively. There were substantial declines in mass of many internal organs with advancing time for I-F compared with relatively small change for I-T. Examples include the reticulo-rumen (1.03, 0.59, 0.52, 0.87, 0.78, and 0.73 kg; S.E. = 0.041), small intestine (0.59, 0.27, 0.23, 0.55, 0.33, and 0.36 kg; S.E. = 0.021), large intestine (0.40, 0.24, 0.24, 0.33, 0.33, and 0.26 kg; S.E. = 0.017), and liver (0.86, 0.45, 0.42, 0.56, 0.60, and 0.67 kg for I-F:week 0, I-F:week 12, I-F:week 24, I-T:week 0, I-T:week 12, and I-T:week 24, respectively; S.E. = 0.031). Conversely, change in internal or non-carcass fat mass was much greater for I-T versus I-F (5.7, 3.9, 2.8, 0.6, 2.5, and 5.1 kg for I-F-week 0, I-F-week 12, I-F-week 24, I-T-week 0, I-T-week 12, and I-T-week 24, respectively; S.E. = 0.33). Changes in carcass mass of protein (-5.9, -5.3, 7.0, and 5.8 g/day; S.E. = 0.89) and fat (-1.9, 0.2, 21.4, and 26.6 g/day; S.E. = 2.35) were greater (P < 0.05) for I-T versus I-F, as was also true for non-carcass protein (6.1, 0.0, 14.5, and 6.3 g/day; S.E. = 0.91) and fat (-16.3, -10.4, 13.6, and 26.3 g/day for I-F:weeks 1-12, I-F:weeks 1-24, I-T:weeks 1-12, and I-T:weeks 1-24, respectively; S.E. = 2.49). Based on energy concentrations in empty body tissue lost or gained in weeks 1-12 and 1-24 (14.8, 12.1, 19.9, and 26.4 MJ/kg for I-F:weeks 1-12, I-F:weeks 1-24, I-T:weeks 1-12, and I-T:weeks 1-24, respectively; S.E. = 2.13), the energy concentration in weeks 13-24 was 9.4 and 32.9 MJ/kg for I-F and I-T, respectively. In conclusion, the energy concentration in tissue mobilized or accreted by yearling meat goats within certain body condition ranges may not necessarily be the same and appears influenced by initial animal characteristics and subsequent feeding conditions.
Eight Boer (75%)
×
Spanish (BS) and eight Spanish (S) wether goats (155
±
8 days of age and 19.2
±
2.3
kg BW, initial) were used in a replicated crossover design experiment with a 2
×
2 factorial ...arrangement of treatments to determine the effects of genotype and diet quality on heat production with ad libitum, near maintenance and fasting levels of feed intake. Diets were 65% concentrate (CON 15% CP, DM basis) and coarsely ground alfalfa hay (FOR 23% CP). There were no significant interactions between genotype and diet. ME intake was similar between genotypes and greater (
P
<
0.05) for CON versus FOR both when intake was ad libitum (7.60 versus 5.43
MJ/day) and near maintenance (4.31 versus 4.09
MJ/day). DE concentration was greater (
P
<
0.05) for CON than for FOR with ad libitum (74.4 versus 55.5%) and restricted intake (77.0 versus 59.6%). Energy expenditure (EE), determined by respiration calorimetry, at all levels of intake was similar between genotypes. EE was greater (
P
<
0.05) for CON than for FOR at each of the three levels of intake, ad libitum (573 and 521
kJ/kg BW
0.75 while fasting), near maintenance (426 and 400
kJ/kg BW
0.75) and fasting (280 and 255
kJ/kg BW
0.75). Efficiencies of ME utilization for maintenance (
k
m) and gain (
k
g) and the ME requirement for maintenance (ME
m) were similar between genotypes.
k
m was similar between diets (0.705 and 0.690 for CON and FOR, respectively), although
k
g was greater (
P
<
0.05) for CON than for FOR (0.603 versus 0.387). ME
m was numerically greater (
P
<
0.17) for CON than for FOR (407 versus 379
kJ/kg BW
0.75), which may have involved higher ME intake with CON. In conclusion, under the conditions of this experiment energy requirements and efficiency of utilization were not different between growing Boer crossbred and Spanish goats regardless of diet quality.
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