Biomedical subjects

M J VandeHaar

Publications and source records attributed to M J VandeHaar.

17 recordsLinked to original sources

PubMed2006

Use of bovine somatotropin for increased skeletal and lean tissue growth of Holstein steers.

One hundred-sixty Holstein growing-finishing steers (initial BW of 185 kg) were blocked by BW to determine the effectiveness of long-term bovine somatotropin (bST) administration on lean, skeletal, and carcass measurements. Steers were randomly allocated to 4 treatments (10 steers/treatment) within a block (n = 4 blocks). Treatments were control, no bST (C-C); bST from d 0 to 182 (bST-C); bST from d 183 to slaughter (C-bST); and bST from d 0 to slaughter (bST-bST). Steers received a s.c. injection of placebo or bST at 14-d intervals. Doses were 320 mg of bST/injection from d 0 to 112 and 640 mg of bST/injection from d 113 to slaughter. The last treatment was administered 31 d before slaughter. Steers received a 14% CP (DM basis) diet from d 0 to 182 and 11.5% CP from d 183 to slaughter that consisted of dry, whole-shelled corn and a pelleted protein-mineral supplement. Steers were slaughtered when BW per block averaged 615 kg (d 325, 353, 367, and 381 for the 4 blocks, respectively). Thirty steers were removed from the study because of poor performance with respect to their pen mates, illness, lameness, death, incomplete castration, and incorrect treatment. Serum IGF-I concentrations increased 151% (P < 0.01) from d 7 through 35 in bST-treated steers compared with control steers. During the first 182 d, bST-C and bST-bST steers were heavier (P < 0.01) and had greater (P < 0.01) ADG, G:F, hip height, and hip height gain compared with C-C and C-bST steers. From d 183 to slaughter, C-bST steers had reduced (P < 0.05) daily DMI and greater G:F than bST-C steers. At final slaughter, C-bST and bST-bST steers had greater (P < 0.05) hip height than C-C steers. Noncarcass weight was increased and dressing percent reduced (P < 0.05) in C-bST and bST-bST steers compared with C-C steers. Quality grade was least (P < 0.05) in bST-bST carcasses compared with C-C, whereas bST-C and C-bST carcasses were intermediate. At final slaughter, steers receiving bST had greater (P < 0.05) carcass protein and water composition and lower (P < 0.05) carcass lipid and lipid accretion than C-C steers. Bovine somatotropin was effective in reducing carcass fat and increasing edible lean. Administering bST to young, lightweight steers increased skeletal growth and noncarcass weight without an increase in total carcass weight, but decreased carcass quality.

Animals↗

PubMed2006

Growth and body composition of dairy calves fed milk replacers containing different amounts of protein at two feeding rates.

Previous research has demonstrated that increasing the CP concentration from 16 to 26% in milk replacers fed to male preruminant dairy calves at 1.5% of BW (DM basis) daily resulted in increased ADG, G:F, and deposition of lean tissue. However, the effects of dietary CP would be expected to vary depending on ME intake. Here, male Holstein calves < 1 wk old were used to determine the effects of feeding rate and CP concentration of isocaloric, whey protein-based milk replacers on growth and body composition. After a 2-wk standardization period, calves were assigned randomly to an initial baseline group or to treatments in a 2 x 4 factorial arrangement of feeding rate (1.25 or 1.75% of BW daily, DM basis) and milk replacer CP concentration (14, 18, 22, or 26% of DM). No starter was offered, but calves had free access to water. After a 5-wk feeding period, calves were slaughtered and body composition was determined. Increasing the feeding rate increased (P < 0.05) ADG, G:F, empty-body gains of chemical components and energy, the percentage of fat in empty BW gain and in the final empty body, and concentrations of IGF-I and insulin in plasma. Increasing the feeding rate decreased (P < 0.01) percentages of water and protein in the empty body and decreased urea N in plasma. Increasing dietary CP concentration linearly increased (P < 0.05) ADG, body length, heart girth, and gains of water and protein but linearly decreased (P < 0.05) fat gain. As dietary CP increased, fat content in empty body gain decreased, and water and protein increased. Increasing CP concentration increased (quadratic, P < 0.02) G:F, with greatest efficiencies for calves fed 22% CP. Gross energetic efficiency (retained energy:intake energy) was greater (P < 0.05) for calves fed at 1.75% of BW daily. Efficiency of dietary protein use for protein gain was greater for calves fed at 1.75% of BW daily but was not affected by dietary CP. The ratio of protein gain to apparently digestible protein intake above maintenance decreased as dietary CP increased. Interactions (P < 0.05) of feeding rate and CP concentration for gains of water and protein indicated that when dietary CP was 26% the ME supply limited protein use by calves fed at 1.25% of BW daily. Body composition of preruminant calves can be markedly altered by manipulating the protein to energy ratio in milk replacers. These dietary effects on body composition and growth are not predicted by current NRC standards.

Animal Feed↗

PubMed2006

Major advances in nutrition: relevance to the sustainability of the dairy industry.

The typical cow has a maintenance requirement of about 10 Mcal of net energy for lactation (NEL) per day. Each kilogram of milk takes an additional 0.7 Mcal of NEL. Thus, the cow producing 45 kg of milk per day needs 4 times as much total energy as she needs for her maintenance requirement alone. The elite cow producing 90 kg/d needs 7 times as much total energy as she needs for maintenance alone. Consequently, the efficiency of using feed energy is much greater for the elite cow than it was for the cow of 100 yr ago consuming a diet of mostly forage. With increased productivity has come the need for fewer cows to produce milk on a per capita basis and increases in net income per cow. However, compared with energetic efficiency, the efficiency of using feed protein to make milk protein has not increased as dramatically, partly because cows are often fed protein in excess. This nitrogen waste is an environmental concern; N losses in manure contribute to water pollution and ammonia emissions from dairy farms. However, the complexities of protein nutrition and limitations in measuring feed N fractions make accurate specifications for feed protein fractions difficult. The economic risk of underfeeding protein is greater than the risk of overfeeding protein, so protein efficiency has not been maximized in the past, nor is it likely to be maximized in the near future. Most cows also are fed excess P, a notable contaminant of surface waters, but several recent studies have shown that feeding P above NRC recommendations has no utility for milk production or fertility. The goal of this article is to examine the impact of nutrition on productivity, efficiency, environmental sustainability, and profitability of the dairy industry.

Animal Nutritional Physiological Phenomena↗

PubMed2004

Effect of dietary energy and somatotropin on components of the somatotropic axis in Holstein heifers.

The somatotropic axis, consisting of growth hormone (GH), GH receptor (GHR), insulin-like growth factor (IGF)-I, IGF binding proteins (IGFBP), and IGF receptors, controls growth and mammary development in heifers. Manipulation of the axis with recombinant bovine somatotropin (rbST) improves heifer growth and reduces age at first calving. The effects of rbST are influenced by dietary energy through partially understood mechanisms. The objective was to characterize the somatotropic axis in Holstein heifers fed a diet for either low or high rate of gain and treated with or without rbST. Heifers (120 d of age) were assigned to one of 2 diets to gain either 0.8 kg/d (low, n = 18) or 1.2 kg/d (high, n = 20). Within each diet, half of the heifers (n = 9 for low and n = 10 for high) received daily rbST injections (25 microg/kg of body weight). Treatments and diets continued until slaughter (2 mo after puberty). Blood was collected 2x per week, and a frequent sampling window was performed 1 d before slaughter. Liver was collected at slaughter. Feeding a high diet or treating with rbST increased serum IGF-I and decreased serum IGFBP-2. The observed changes in serum IGF-I and IGFBP-2 were reflected in their respective liver mRNA amounts. Feeding a high diet decreased serum GH concentrations after rbST injection, but the stimulatory effect of rbST on serum IGF-I was nonetheless greater in high-diet heifers. The differential IGF-I response may be explained by greater GHR 1A in the liver of high-diet heifers. We conclude that a high-gain diet modifies the somatotropic axis in rbST-treated heifers by decreasing serum GH but increasing serum IGF-I after rbST treatment. Greater IGF-I (indicative of an increased GH response) may be a consequence of greater GHR 1A expression in the liver.

Animals↗

PubMed2002

Effect of dietary protein on prepubertal mammary development in rapidly growing dairy heifers.

The objective was to determine whether increased dietary protein would enhance mammary development in prepubertal heifers fed for rapid body growth (1.2 kg/d). Fifty-four Holstein heifers (weighing approximately 134 kg) were assigned to one of three treatments. Heifers were fed a total mixed ration with metabolizable energy at 2.85 Mcal/kg and metabolizable protein at low, standard, or high concentrations (37, 41, or 44 g/Mcal of metabolizable energy, respectively) from 3.5 mo of age until slaughter at approximately 46 d after puberty. Heifers fed low, standard, and high protein gained 1130, 1170, and 1180 g/d, respectively. Dietary protein did not affect age or weight of heifers at puberty or slaughter, withers height gain, or carcass composition. Average mammary parenchymal DNA content for heifers on diets of low, standard, and high protein was 595, 619, and 670 mg/100 kg of body weight, respectively, and was not significantly different. However, for heifers that attained puberty early, those fed low protein had 33% less parenchymal DNA than those fed high protein, even though their body growth and carcass composition were not compromised. We conclude that dietary protein does not have a major effect on mammary development of rapidly grown prepubertal heifers, provided the diet contains adequate protein for normal body growth. But we suggest that feeding low-protein diets increases the risk of impaired mammary development when heifers are fed for rapid growth and attain puberty early and that the new National Research Council guidelines for protein relative to energy seem adequate for optimal mammary development.

Aging↗

PubMed2002

Clinical responses to intramammary endotoxin infusion in dairy cows subjected to feed restriction.

Nonpregnant, midlactation primiparous Holstein cows were fed ad libitum (n = 12) or at 80% of maintenance energy requirements (n = 12) to determine whether feed restriction influences clinical response to endotoxin-induced mastitis. After 2 wk of ad libitum or restricted feeding, one mammary quarter per cow was infused with 100 microg of endotoxin. Within 3 to 6 h of intramammary infusion, endotoxin increased mean rectal temperature, heart rate, and milk somatic cell count and immunoglobulin (IgG) concentration; and decreased blood leukocyte count and rumen motility in both restricted and ad libitum-fed cows. Mean serum and milk tumor necrosis factor-alpha (TNF-alpha) concentrations showed only modest increases following endotoxin infusion. Restricted fed cows had slightly different acute fever responses and significantly increased heart and respiration rates than ad libitum fed cows. However, feed restriction did not influence mean total leukocyte count, rumen motility, serum TNF-a concentrations or milk IgG and TNF-alpha concentrations. Thus, results of this study suggest that energy balance does not significantly alter clinical symptoms following acute endotoxin-induced mastitis, at least in midlactation cows. As such, negative energy balance may not underlie the increases in severe coliform mastitis commonly observed in periparturient dairy cows.

Acute Disease↗

PubMed2002

Effect of protein level in prepartum diets on metabolism and performance of dairy cows.

Multigravid Holstein cows (n = 75) were used in a randomized block design to evaluate the effect of prepartum diets formulated to supply surplus energy and incremental concentrations of protein on the nutritional status of dairy cows at parturition. Cows were blocked according to expected calving date and assigned to one of five diets: 9.7, 11.7, 13.7, 14.7, and 16.2% crude protein (CP). Dietary treatments were initiated 28 d before expected calving date and fed until parturition. A common diet was fed postpartum. Dry matter intake and milk yield were recorded daily through 90 d postpartum. Increasing the protein concentration from 9.7 to 14.7% of dry matter during the last 28 d of gestation improved responses of cows during lactation. Increasing dietary protein up to 14.7% also increased milk yield response to recombinant bovine somatotropin (rbST) during the ninth week of lactation and yields of 305-d 2x mature equivalent milk, milk protein, and milk fat. Plasma aspartate aminotransferase tended to be highest in cows fed 13.7 and 14.7% CP prepartum, but decreased linearly postpartum in response to dietary protein levels. There were no treatment differences for plasma insulin-like growth factor-1 (IGF-1) at d 60 postpartum (before rbST provision), but IGF-1 on d 90 (after rbST provision) was higher in plasma of cows fed 14.7% CP than the other diets except 13.7% CP. Close-up diets containing 13.7% CP and surplus energy produced the most beneficial outcomes during the subsequent lactation.

Animals↗

PubMed2002

Short communication: relationship between body growth and mammary development in dairy heifers.

Our objective was to determine if prepubertal rate of body weight (BW) gain, independent of diet, was related to mammary development of dairy heifers. Data from two studies recently conducted at Michigan State University were used to identify factors, within a dietary treatment group, that would account for variation in first lactation milk production or amount of mammary parenchymal DNA at the time of puberty. Factors analyzed for variation in milk production during first lactation were: postpartum BW, prepubertal BW gain, gestational BW gain, postpartum BW gain, body condition score (BCS) at breeding, and BCS at calving. Factors analyzed for variation in mammary parenchymal DNA at puberty were: BW at slaughter, age at puberty, prepubertal BW gain and body protein and body fat content at slaughter. For both analyses, prepubertal BW gain did not account for any of the variation in mammary development. The only significant covariate for the milk production model (r2 = 0.44) was BCS at breeding. Similarly, the only significant covariate in the parenchymal DNA model (r2 = 0.22) was body fat content at slaughter. These results suggest that, within a dietary treatment, heifers that grow faster do not have impaired mammary development, and increased body fatness may be a better predictor of impaired mammary development than BW gain.

Adipose Tissue↗

PubMed2002

Evidence for a local effect of leptin in bovine mammary gland.

On average, high-energy diets promoting body growth rates above 1 kg/d before puberty impair mammary development by 15 to 20% in cattle. We hypothesized that leptin, a protein produced by adipocytes, mediates the inhibitory effect of high-energy diets on mammary development. Therefore, our objectives were to determine the effect of leptin on mammary epithelial cell proliferation, and the distribution of mRNA for two leptin receptor isoforms in prepubertal bovine mammary glands and other peripheral tissues. Addition of leptin to culture media containing either 5 ng/ml of insulin-like growth factor-I (IGF-I) or 1% fetal bovine serum decreased DNA synthesis of a bovine mammary epithelial cell line (MAC-T) in a dose-dependent manner. The minimal doses of leptin that decreased IGF-I- and fetal bovine serum-stimulated cell proliferation were 64 and 1 ng/ml, respectively. In addition, we determined that MAC-T cells and isolated bovine mammary epithelial cells express the long form of leptin receptor (Ob-Rb) mRNA. Ob-Rb mRNA was detected in all bovine tissues examined. In contrast with reports on other species, mRNA expression of the short form of leptin receptor (Ob-Ra) was detected only in bovine liver, pituitary body, and spleen. These results support the concept that leptin mediates the inhibitory effect of high-energy diets on mammary development.

Animals↗

PubMed2001

Negative energy balance does not decrease expression of leukocyte adhesion or antigen-presenting molecules in cattle.

Sixteen yearling Holstein steers were fed for 210 or 60% of maintenance requirements to impose positive or negative energy balance, respectively. Blood was collected and analyzed for serum concentration of nonesterified fatty acids (NEFA), and leukocytes were isolated and counted. Isolated leukocytes were then analyzed for expression of the adhesion molecules L-selectin (CD62L), Mac-1 (CD11b and CD18), and major histocompatability complex (MHC) class I and class II molecules with immunostaining and flow cytometric analysis. Negative energy balance increased the concentration of NEFA in serum (P < 0.0001). Expression of CD62L on neutrophils was increased 14% during negative energy balance (P = 0.03). Energy balance did not affect expression of CD62L on any other cell types or expression of CD11b or CD18. Negative energy balance did not affect MHC class I expression but resulted in a small but significant increase in the expression of MHC class II (P = 0.03). The results of this study provide little evidence that nutritionally created negative energy balance impairs expression of CD62L, CD11b, and CD18 or expression of MHC class I or MHC class II molecules by resting bovine blood leukocytes.

Animals↗

PubMed2000

Effects of altering dietary cation-anion difference on calcium and energy metabolism in peripartum cows.

Our objective was to determine the effects of varying dietary cation-anion differences (DCAD: meq[(Na + K) - (Cl + S)]/100 g of dry matter) in prepartum diets on Ca, energy, and endocrine status prepartum and postpartum. Holstein cows (n = 21) and heifers (n = 34) were fed diets with varying amounts of CaCl2, CaSO4, and MgSO4 to achieve a DCAD of +15 (control), 0, or -15 meq/100 g of dry matter for the last 24 d before expected calving. Dietary Ca concentration was increased (by CaCO3 supplementation) with decreasing DCAD. Plasma ionized Ca concentrations prepartum and at calving in both cows and heifers increased with reduced DCAD in the diet. At calving, plasma ionized Ca concentration was 3.67, 3.85, and 4.35 for cows and 4.44, 4.57, and 4.62 mg/dl for heifers fed diets containing +15, 0, and -15 DCAD, respectively. All heifers had normal concentrations of plasma ionized Ca (>4 mg/dl) at calving. Also at calving, plasma concentrations ofparathyroid hormone and calcitriol were less in cows and heifers fed diets containing reduced DCAD, but the plasma concentration of hydroxyproline was not affected by diet. Prepartum dry matter intake, energy balance, and body weight gains were lower and concentration of liver triglyceride was higher for heifers but not cows fed the -15 DCAD diet. Also, nonesterified fatty acids the last week prepartum were positively correlated with liver triglyceride for heifers but not cows. Feeding of anionic salts plus CaCO3 to reduce DCAD to -15 and increase Ca in prepartum diets prevents hypocalcemia at calving in cows, but decreases prepartum dry matter intake and increases the concentration of liver triglyceride in heifers. That heifers maintained calcium homeostasis at calving regardless of diet but ate less when fed the -15 DCAD diet suggests that they should not be fed anionic salts before calving.

Animals↗

PubMed1997

Effects of diet and bovine somatotropin on heifer growth and mammary development.

Forty Holstein heifers [body weight (BW) = 126 kg] were blocked by BW into groups of 4, and, within each block, heifers were randomly assigned to one of four treatments. Twenty heifers had ad libitum access to a diet formulated to produce a BW gain of 0.8 kg/d (control diet), and 20 heifers had ad libitum access to a diet formulated to produce a BW gain of 1.2 kg/d. (high diet). Half of the heifers fed each diet were injected daily with bovine somatotropin (bST; 25 micrograms/ kg of BW). The high diet increased daily BW gain as well as body condition score. Injection of bST also increased daily BW gain, but did not affect body condition score. The high diet reduced age at puberty by 58 d, but did not affect BW, withers height at puberty, or pelvic area at slaughter. Injection of bST had no effect on age at puberty, but increased BW, withers height at puberty, and pelvic area at slaughter. The high diet did not affect mammary parenchymal DNA, RNA, or the ratio of RNA to DNA. The injection of bST increased mammary parenchymal DNA, RNA, and the ratio of RNA to DNA. The high diet was more cost effective for rearing dairy heifers from 120 d of age to potential breeding size (> or = 363 kg of BW and postpubertal) than was the control diet. In conclusion, the high protein, high energy diet increased growth rate without detrimental effects on mammary development. Injection of bST increased BW, skeletal size, and mammary development.

Animals↗

PubMed1996

Effect of energy balance and somatotropin on insulin-like growth factor I in serum and on weight and progesterone of corpus luteum in heifers.

Holstein heifers (approximately 1 yr old) were fed to be in negative energy balance (n = 14; NEB) or positive energy balance (n = 15; PEB) during four estrous cycles. Each heifer was given PGF2 alpha to control the timing of fourth estrus. From 1 d after PGF2 alpha injection until 10 d after estrus, half of the heifers were injected daily with 14 mg of somatotropin (bST), and the corpus luteum (CL) was collected on d 10. Heifers in NEB had less IGF-I in serum (P < .01), smaller CL (P < .01), and less progesterone in CL (P < .01) than heifers in PEB. Exogenous bST increased (P < .01) IGF-I in serum, but this increase was greater in heifers in PEB than those in NEB (P < .01 for interaction of energy balance and bST). Nonetheless, bST did not alter weight or progesterone content of the CL in either energy balance group. In addition, serum IGF-I during the first 10 d after estrus was not correlated to luteal weight and only weakly correlated (r = .3) with luteal progesterone content. We conclude that exogenous bST given during luteal development does not alter growth or progesterone content of the CL in heifers. Reduced concentration of IGF-I in serum during luteal development does not account for suppressed luteal growth and progesterone synthesis of heifers in NEB.

Animals↗

PubMed1995

Long-term somatotropic and galactopoietic effects of a (1-30) ethyl amide analog of growth hormone-releasing factor.

Thirty-five lactating Holstein cows (165 +/- 8 DIM) received the following treatments for 96 d: uninfused controls; i.v. infusion of .9, 2.7, or 8.1 mg/d of Ile2, Ser8.28, Ala15, Leu27, Hse30-bovine growth hormone-releasing factor (1-30) ethyl amide; or i.v. infusion of 12 mg/d of recombinant Leu27, Hse45-bovine growth hormone-releasing factor (1-45) lactone. Concentrations of somatotropin in serum and SCM yield of cows infused with 1-30 releasing factor increased quadratically as the dose increased. Responses for somatotropin and SCM yield were quantitatively similar for cows infused with 2.7 and 8.1 mg of 1-30 or 12 mg of 1-45. While concurrently infused with the 1-30 or 1-45 as described, cows retained their ability to release somatotropin following an acute i.v. injection of 10 nmol/100 kg of BW of either growth hormone-releasing factor 1-30 or 1-45. Mean concentrations of IGF-I in serum increased similarly in magnitude for cows infused at all doses of 1-30 or 1-45. The 1-30 releasing factor generally increased IGF-binding protein-3, but had little effect on IGF-binding protein-2. The 1-45 releasing factor did not significantly affect either binding protein. Yield of SCM was correlated with serum concentrations of somatotropin, but not with IGF-I. Concentrations of NEFA in serum were elevated through 36 and 50 d in response to the highest doses of 1-30 and 1-45, respectively. Treatment did not affect DMI, BW, or body condition score.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Ration formulation using linear programming.

A combination spreadsheet-LP ration formulation program offers tremendous advantages for dairy nutritionists. The spreadsheet format provides the framework for flexibility in describing feeds and in formulating a realistic and practical ration. The LP module can solve for a complicated set of nutrient requirements to give a relatively well-balanced ration. This "first-cut" ration can then be reworked in the spreadsheet mode to meet the needs of the individual farm based on other biologic and management considerations.

Animal Feed↗

PubMed1991

Reduced serum concentrations of insulin-like growth factor-I (IGF-I) in protein-restricted growing rats are accompanied by reduced IGF-I mRNA levels in liver and skeletal muscle.

The serum concentration of insulin-like growth factor-I (IGF-I) is reduced in growing rats fed a low-protein diet, and this decrease is age-dependent, being more pronounced in younger animals. To determine whether this decrease in serum IGF-I is related to a decrease in IGF-I mRNA, growing female rats were given free access to either a 15% protein-sufficient or a 5% protein-deficient diet for 1 week. Protein restriction in 4-week-old rats decreased body weight gain by 44% (P less than 0.001 compared with 4-week controls), serum IGF-I concentration by 67% (P less than 0.001) and liver IGF-I mRNA abundance by 51% (P less than 0.001). During week 6, protein restriction for 1 week resulted in a 20% increase in food intake with no change in weight gain, a 38% reduction in serum IGF-I (P less than 0.001 compared with 6-week controls) and a 39% decrease in liver IGF-I mRNA (P less than 0.001). The serum IGF-I concentration was highly correlated (r = 0.80; P less than 0.001) with the hepatic IGF-I mRNA concentration. Skeletal muscle IGF-I mRNA abundance was also decreased significantly by protein restriction (37% at week 4, P less than 0.001, and 24% at week 6, P less than 0.01) and was closely correlated (r = 0.71; P less than 0.001) with body weight gain. Liver GH-binding protein and GH receptor mRNA abundance were reduced by 1 week of protein deprivation at week 6 but not at week 4.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Influence of alpha-ketoisocaproate on lamb growth, feed conversion, and carcass composition.

Four experiments were conducted to determine whether leucine's alpha-ketoacid, alpha-ketoisocaproate (KIC), would influence lamb growth, feed conversion, and carcass composition. In the first experiment, lambs were injected intraperitoneally with 3.5 g of Na-KIC per day. In the second experiment, KIC unprotected from rumen degradation was fed at a rate of 15 g per animal daily. In a third experiment, KIC, leucine, and isovalerate (IVA), protected from rumen degradation, were fed to growing lambs at a rate of 1 g per animal per day. Finally, a fourth experiment was conducted in which ruminally protected KIC was fed to growing lambs at a rate of 1 g per animal per day. Ketoisocaproate tended to increase ADG and decrease fat deposition in all four experiments. Ketoisocaproate increased ADG by 11 (P less than .09), 10 (P less than .05), 9, and 13% in 1 through 4, respectively, and feed efficiency improved 5, 9 (P less than .02), 5, and 5%, respectively. Fat thickness over the 12th rib decreased 28 (P less than .06), 11, 17 (P less than .04), and 5% in Exp. 1 through 4, and the perirenal fat depot also decreased 13, 5, 18, and 3%, respectively. In contrast, neither ruminally protected leucine nor IVA affected the growth of young lambs. Together these studies indicate that administration of KIC to growing lambs can increase weight gain and muscle growth while decreasing fat deposition.

Adipose Tissue↗