Effect of concentrate source and amount in diets on plasma hormone concentrations of prepubertal heifers

The effects of plane of nutrition and diet type on metabolic hormone concentrations, growth and milk production in high genetic merit dairy herd replacements

Seventy high genetic merit Holstein heifers were used in two experiments to investigate (1) the effects of plane of nutrition and diet type during the pre-pubertal period and (2) the effects of plane of nutrition during the post-pubertal period on metabolic hormone concentrations, growth and milk production. In experiment 1, treatment 1 and 2 heifers were given food to achieve a live-weight gain of 0·70 and 0·95 kg/day from 3 to 10 months of age on a grass silage based diet, while treatment 3 heifers were given food to achieve 0·95 kg/day on a barley straw/concentrate diet. During the pre-pubertal period, heifers reared on treatment 1 had significantly higher growth hormone(GH) concentrations (ng/ml per 1 h) than heifers reared on treatment 2 (P < 0·01) and had significantly lower insulin concentrations than heifers reared on treatment 3 (P < 0·01). Heifers reared on treatment 1 had significantly lower insulin-like growth factor 1 (IGF-1) concentrations than those reared on treatment 3 (P < 0·01). At 10 months of age heifers reared on treatment 1 were of lower condition score (P < 0·01) than those on treatment 2 and had a smaller heart girth diameter (P < 0·01) than those on treatments 2 and 3. During the first lactation, milk yield and composition produced by the heifers was not significantly affected by treatment. In experiment 2, treatment A heifers were given, from 14 to 24 months of age, a low plane of nutrition to allow a live-weight gain of 0·65 kg/day on a grass silage and grass based diet during the winter and summer periods respectively. Treatment B heifers were kept on a high plane of nutrition to allow a live-weight gain of 0·90 kg/day on the same forage along with concentrate supplementation. During the rearing period, GH and IGF-1 concentrations were not significantly affected by treatment. Treatment A heifers weighed less before calving (P < 0·05), had a lower condition score (P < 0·01), and had a smaller heart girth diameter (P < 0·01) than those on treatment B. During the first 10 weeks of lactation, heifers on treatment A had a higher silage dry matter intake and lost less weight (P < 0·05) than those on treatment B, however, by 20 weeks of lactation these effects had disappeared. Milk yield and composition during the first lactation were not significantly affected by treatment. Overall, the findings of experiments 1 and 2 did not show any beneficial effects of higher weights at first calving in high genetic merit Holsteins and therefore indicate that accelerated growth in the pre- or post-pubertal period may not be required.

Endogenous LPS alters liver GH/IGF system gene expression and plasma lipoprotein lipase in goats

Endotoxin lipopolysaccharide (LPS) affects the ruminant health and animal performance. The main purposes of this study were to investigate the potential effects of GH/IGF system and lipoprotein lipase (LPL) concentration on resistance the circulating LPS concentration increased in liver with high concentrate diet treatment. Non-lactating goats were randomly allocated to two groups: a high-concentrate diet (HCD) or a low-concentrate diet (LCD) in cross over design and the blood collection at different time points after feeding at the end of the experiment. The average rumen pH was significantly reduced (P<0.05), but the duration with pH was not more than 120 min in the HCD group. The plasma LPL concentration was significantly raised (P<0.05). However, from 2 h onwards, LPS concentration was significantly reduced (P<0.01) in the HCD group compared with LCD group. In addition, the plasma IGF1 concentration and the hepatic insulin-like growth factor-1 receptor (IGF1R) mRNA expression were markedly reduced (P<0.05). However, growth hormone (GH) secretion at 15, 30, and 45 min after feeding and growth hormone receptor (GHR) mRNA expression in the liver was significantly increased (P<0.05) in HCD group. The correlation analysis showed that the plasma LPL concentration was positively correlated with hepatic GHR mRNA expression (P<0.05). Conversely, the plasma LPS concentration was negatively correlated with LPL concentration (P<0.05). These findings reveal that alterations in GH/IGF system function in response to a high-concentrate diet are accompanied by corresponding changes in systemic LPL in non-lactating goats' liver in presence of endogenous LPS stress.

Effects of energy and protein restriction, followed by nutritional recovery on morphological development of the gastrointestinal tract of weaned kids

Effects of energy, protein, or both energy and protein restriction on gastrointestinal morphological development were investigated in 60 Liuyang Black kids, which were sourced from local farms and weaned at 28 d of age. Weaned kids were randomly assigned to receive 1 of 4 dietary treatments (15 kids per treatment), which consisted of adequate nutrient supply (CON), energy restriction (ER), protein restriction (PR), or energy and protein restriction (EPR). The entire experiment included adaptation period (0 to 6 d), nutritional restriction period (7 to 48 d), and recovery period (49 to 111 d). Three kids from each group were killed at d 48 and 111, and the rumen, duodenum, jejunum, and ileum were harvested. On d 48 (end of nutritional restriction), lengths of the duodenum (P = 0.005), jejunum (P = 0.003), and ileum (P = 0.003), and weights of the rumen (P = 0.004), duodenum (P = 0.006), jejunum (P = 0.006), and ileum (P = 0.004) of kids in ER, PR, and EPR were less than those of kids in CON. Compared with CON, PR decreased papillae width (P = 0.03) and surface area (P = 0.05) of the rumen epithelium, villus surface area (P = 0.05), and N concentration (P = 0.02) of the jejunum mucosa on d 48. Compared with CON, EPR decreased papillae height (P = 0.001), width (P = 0.001), and surface area (P = 0.003), N concentration (P = 0.01), and the ratio of N to DNA (P = 0.03) of the rumen epithelium. Compared with CON, EPR also decreased villus height (P = 0.01), width (P = 0.006), and surface area (P = 0.006), N concentration (P < 0.001), and the ratio of N to DNA (P < 0.001) of the jejunum mucosa on d 48. On d 111 (end of nutritional recovery), lengths of the duodenum (P = 0.001), jejunum (P = 0.001), and ileum (P = 0.001), weights of the rumen (P < 0.001), duodenum (P = 0.001), jejunum (P < 0.001), and ileum (P < 0.001) of kids in ER, PR, and EPR were still less than those of kids in CON; N concentrations of rumen epithelium of kids in PR (P = 0.01) and EPR (P = 0.001), and the ratio of N to DNA of jejunum mucosa of kids in EPR (P < 0.001) were greater than those of kids in CON. Results indicate that nutritional restriction of 6 wk can retard gastrointestinal morphological development for kids weaned at 28 d of age and retarded development remains evident, even after nutritional recovery of 9 wk.

Endocrine profiles of periparturient mares and their foals1

The aim of this study was to characterize concentrations of leptin, IGF-I, and thyroid stimulating hormone (TSH) in the blood serum of mares pre-and postpartum, in the milk serum of mares postpartum, and in the blood serum of their foals. Nine pregnant Quarter Horse mares and their offspring were used in this study. Once weekly between 1000 and 1200 h for 2 wk before their predicted parturition date, mares were weighed, assigned a BCS, and blood was sampled via jugular venipuncture. Within 2 h of parturition and before the foals nursed (d 0), blood samples were obtained from the mares and foals, and a milk sample was collected from the mares. Blood from the foals and blood and milk from the mares were collected again at 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 12, 19, 26, 33, and 61 d postpartum. Mares and foals also were weighed and assigned a BCS on d 0, 5, 12, 19, 26, 33, and 61. Additionally, on d 5, 33, and 61, ultrasound images of fat depth and area of the LM immediately cranial to and parallel with the last rib on the left side of the foals were measured to characterize changes in fat depth and LM area over time. There were no changes in mare blood concentrations TSH (P = 0.15), nor were there any changes in foal blood concentrations of leptin (P = 0.54) or TSH (P = 0.10) during the trial period. Mare blood concentrations of IGF-I tended to change over time (P = 0.07), whereas leptin changed over time (P < 0.001), initially decreasing and then remaining relatively stable after d 5. Foal blood concentrations of IGF-I increased initially, peaked at d 19, and stabilized thereafter (P < 0.001). Milk concentrations of leptin and TSH were greatest on d 0 and decreased over time (P < 0.007), reaching nadir concentrations at d 61. Milk concentrations of IGF-I also changed over time (P = 0.02), being greatest on d 0 and undetectable by d 12. There was no difference in BCS (P = 0.94) in mares over time, but there was a difference between pre- and postpartum BW (P < 0.001) due to foaling. However, no differences were detected in pre- (P = 0.70) or postpartum BW (P = 0.76) of mares over time. Mean ultrasonic fat depth and LM area increased (P < 0.04) as the foals aged, as did BCS and BW (P < 0.001). Recognizing changes in metabolic hormones surrounding the time of parturition in the mare and foal provides a basis for further determination of the role, if any, these hormones play in the milk, as well as in the neonate.

Exposure of pregnant dairy heifer to magnetic fields at 60 Hz and 30 µT

Thirty-two pregnant Holstein heifers weighing 499 +/- 45 kg, at 3.1 +/- .7 months of gestation and 21 +/- 2.0 months of age were confined and exposed to 30 microT magnetic fields (MFs) and a 12 h light/12 h dark light cycle. The heifers were divided into two replicates of 16 animals. Each replicate was divided into two groups of eight animals each, one group the non-exposed and the second, the exposed group. The animals were subjected to the different treatments for 4 weeks. After 4 weeks, the animals switched treatment, the exposed group becoming the non-exposed group and vice versa. Then the treatment continued for 4 more weeks. Catheters were inserted into the jugular vein, and blood samples were collected twice a week to estimate the concentration of progesterone (P4), melatonin (MLT), prolactin (PRL), and insulin-like growth factor 1 (IGF-1). Feed consumption was measured daily. The results indicated that exposure of pregnant heifers to MF similar to those encountered underneath a 735 kV high tension electrical power line for 20 h/day during a period of 4 weeks produces slight effects. This is evidenced by statistically significant higher body weight (1.2%), higher weekly body weight gain (30%), and decreases in the concentration of PRL (15%) and IGF-1 (4%) in blood serum. The absence of abnormal clinical signs and the absolute magnitude of the significant changes detected during MF exposure, make it plausible to preclude any major animal health hazard.

Effect of increasing energy and protein intake on body growth and carcass composition of heifer calves

The objective was to determine whether increased energy and protein intake between 2 and 14 wk of age would increase growth rates of heifer calves without fattening. At 2 wk of age, Holstein heifer calves were assigned to 1 of 4 treatments in a 2 x 2 factorial arrangement with 2 levels of protein and energy intake (moderate [M]; high [H]) in period 1 (2 to 8 wk of age) by 2 levels of protein and energy intake (low [L]; high [H]) in period 2 (8 to 14 wk of age) to produce similar initial BW for all 4 treatments. Treatments were ML, MH, HL, and HH, indicating moderate or high energy and protein intake during the first period and low or high intake during the second period. The M diet consisted of a standard milk replacer (21.3% CP, 21.3% fat) fed at 1.1% of BW on a DM basis and a 16.5% CP grain mix fed at restricted intake to promote 400 g of average daily gain (ADG), whereas the L diet consisted only of the grain mix. The H diet consisted of a high-protein milk replacer (30.3% CP, 15.9% fat) fed at 2% of BW on a DM basis and a 21.3% CP grain mix available ad libitum. Calves were weaned gradually from milk replacer by 7 wk and slaughtered at 8 (n = 11) or 14 wk of age (n = 41). In periods 1 and 2, ADG and the gain:feed ratio were greater for calves fed the H diet. Calves fed the H diet were taller after both periods 1 and 2. No difference was observed in carcass composition at 8 wk, but at 14 wk calves fed MH and HH had less water and more fat than calves fed ML and HL. Plasma IGF-I concentrations were greatest for calves fed the H diet during either period. Plasma leptin concentrations were increased in calves fed the H diet during period 1 from 4 to 6 wk of age. Increasing energy and protein intake from 2 to 8 wk and 8 to 14 wk of age increased BW, withers height, and gain:feed ratio. Calves fed the H diet from 8 to 14 wk of age had more body fat than calves fed the L diet. Increased energy and protein intake can increase the rate of body growth of heifer calves and potentially reduce rearing costs.

An energy-rich diet causes rumen papillae proliferation associated with more IGF type 1 receptors and increased plasma IGF-1 concentrations in young goats

We tested the hypothesis that the dietary energy-dependent alterations of the rumen papillae size are accompanied by corresponding changes in systemic insulin-like growth factor (IGF)-1 concentration and in rumen papillary IGF type 1 receptors (IGF-1R). Young male goats (n=24) were randomly allocated to two groups (n=12) and fed a high level (HL) metabolizable energy [1200 kJ/(kg(0.75).d)] or a low level (LL) [500 kJ/(kg(0.75).d)] diet for 42 d. The concentration of ruminal total SCFA did not differ between the groups, but the molar proportion of butyric acid was enhanced by 70% in the HL group (P<0.05). Both the length and width of the papillae were greater (P<0.05) in the HL group, and the surface was 50-100% larger (P<0.05) in the tissue sampled from the artrium ruminis, the ventral ruminal sac and the ventral blind sac. Transport of Na+ across the rumen epithelium, which is amiloride sensitive, was higher (P<0.05) in the HL than in the LL group. Furthermore, the plasma IGF-1 concentration was about twofold higher in the HL group (P<0.05), and the maximal rumen epithelial IGF-1R binding was also higher in the HL (P<0.05) than in the LL group. IGF-1R mRNA and IGF-1 mRNA were detected in rumen papillae; however, they were unaffected by dietary treatments. DNA synthesis and cell proliferation of cultured rumen epithelial cells were higher (P<0.05) after IGF-1 treatment (25 or 50 microg/L) compared with those in the medium without IGF-1. Thus dietary energy-dependent alterations of rumen morphology and function are accompanied by corresponding changes in systemic IGF-1 and ruminal IGF-1R.

Soyhulls as an alternative feed for lactating dairy cows: a review

Dairy producers use soyhulls, a byproduct of soybean processing, to replace either grain or forage in diets of lactating dairy cows. In view of the nutritional and economical value of soyhulls it is anticipated that this practice will continue to increase in popularity among nutritionists and producers of ruminant animals. This paper reviews information regarding the nutritional value of soyhulls and the effects of feeding this alternative feed on ruminal fermentation, nutrient digestion and utilization, and performance of dairy cows. Soyhulls can replace corn grain to supply about 30% of the dry matter (DM) in high-grain diets without negatively affecting either the fermentation or digestion of nutrients in the gastrointestinal tract or the performance of dairy cows. Additionally, data suggest that soyhulls might successfully replace forage to supply < or = 25% of the DM in diets of dairy cows when the supply of effective fiber, which includes a chemical and a physical component, remains adequate after including the hulls. However, caution should be exercised when data from different studies are extrapolated to practical situations because the response to feeding soyhulls appears to be largely affected by the type of carbohydrate being replaced by soyhulls; the amount, type, and physical form of the dietary forage; and the incidence of either negative or positive associative effects before and after the addition of soyhulls to the original diet. Unfortunately, the paucity of data from experiments in which soyhulls constituted more than 25 to 30% of the dietary DM restricts the ability to identify the maximum amount of soyhulls that can be used in diets of dairy cows. Information from studies in which > or = 25 to 30% of dietary DM supplied as either cereal grains or forages are replaced with soyhulls is needed to better understand and predict the production of dairy cows fed diets containing the hulls. This knowledge is essential for maximizing the use of soyhulls in diets for dairy cows.